Columbia  ^nitiersiitp 
inttjeCitpofi^etoiSorfe  ^'^'^ft 

COLLEGE  OF  PHYSICIANS 
AND   SURGEONS 


Reference  Library 

Given  by 


t^x-zv:u-^^^  f'^zsi 


fjzs 


TREATISE 


ON 


HUMAN   PHYSIOLOGY. 


FOR   THE    USE    OF 


STUDENTS  AND  PRACTITIONERS  OF  MEDICINE. 


BY 

HENRY  C.  CHAPMAN,  M.D., 

PnOFESSOR  OF  INSTITUTES  OF  MEDICINE  AND  MEDICAL  JURISPRUDENCE  IN  JEFFERSON  MEDICAL  COLLEGE 
PHILADELPHIA  ;    CHAIRMAN,  BOARD  OF  CURATORS,  ACADEMY  OF  NATURAL  SCIENCES  OF  PHILA- 
DELPHIA ;   MEMBER  OF  THE  COLLECJE  OF  PHYSICIANS,  OF  THE   ZOOLOGICAL  SOCIETY, 
PHILADELPHIA  ;   OF   THE    AMERICAN    PHILOSOPHICAL   SOCIETY,    AND   OF 
THE   AMERICAN   PHYSIOLOGICAL  SOCIETY. 


SECOND  EDITION. 


ILLUSTRATED    WITH    595    ENGRAVINGS. 


PHILADELPHIA: 

LEA   BROTHERS   &   CO 

189  9. 


Entered  according  to  Act  of  Congress  in  the  year  1899,  by 

LEA    BROTHERS   &   CO., 

In  the  C)ffice  of  the  Librarian  of  Congress  at  Washington.     All  riglits  reserved. 


C3G 


A 


TO 


MY  WIFE 


THIS  WORK  IS  AFFECTIOXATELY  DEDICATED 


AS  A  SMALL  ACKNOWLEDGMEXT  OF  THE  IXTEKEST  EVIXCED  AND 


ENCOURAGEMENT  EXTENDED  IN  ITS  COMPLETION, 


BY 


THE  AUTHOR. 


Digitized  by  the  Internet  Archive 

in  2010  with  funding  from 
Columbia  University  Libraries 


http://www.archive.org/details/treatiseonhumanpOOchap 


PREFACE  TO  SECOND  EDITION. 


In  submitting  a  revision  of  his  Treatise  on  Human  Physiology 
to  the  profession,  the  author  may  say  that  its  fundamental  plan 
remains  unchanged,  as  continued  experience  in  teaching  confirms 
his  belief  in  its  adaptation  to  the  needs  of  both  students  and  prac- 
titioners, two  classes  whose  demarcation  is  really  artificial. 

Aside  from  its  plan  the  book  has  been  recast.  The  recent  ad- 
vances in  our  knowledge  of  Physiology,  especially  of  Physiological 
Chemistry  and  of  functions  of  the  Xervous  System,  have  necessi- 
tated the  rewriting  of  a  great  part  of  the  work  and  the  addition 
of  new  illustrations.  The  author  has  endeavored  to  accommodate 
these  important  additions  without  an  increase  in  tlie  number  of 
pages,  by  the  most  careful  condensation  and  elimination  of  less 
important  matter,  and  he  trusts  that  his  efforts  to  make  the  work 
more  than  ever  useful  as  a  text-book  have  not  been  without  V)ene- 
ficial  results. 

It  need  hardly  be  said  that  the  additions  made  here  and  there 
to  the  bibliography  (ahvays  obtained  from  the  original  sources 
cpioted)  represent  but  a  selected  part  of  the  vast  Physiological 
literature  that  has  appeared  in  the  last  few  years,  but  it  is  hoped 
that  no  important  additions  to  our  knowledge  of  the  subject  have 
been  omitted. 

HEXRY  C.  CHAPMAX. 

Philadelphia,  April,  1899. 


PREFACE  TO  FIRST  EDITIOX. 


To  those  familiar  with  the  many  excellent  German,  French,  and 
English  treatises  upon  Physiology,  it  may  appear  strange  that  the 
author  should  feel  it  incumbent  upon  himself  to  offer  one  more  con- 
tribution upon  such  a  well-worn  theme.  The  experience,  however, 
of  the  past  eight  years,  as  Professor  of  the  Institutes  of  Medicine  or 
Physiology  in  the  Jefferson  Medical  College  of  Philadelphia,  has 
convinced  the  author  that  there  is  a  want  felt  by  students  and  prac- 
titioners of  medicine  for  a  systematic  work,  representing  the  exist- 
ing state  of  physiology  and  its  methods  of  investigation,  and  based 
upon  comparative  and  pathological  anatomy,  clinical  medicine, 
physics,  and  chemistry,  as  well  as  upon  experimental  research.  It 
is  the  hope  of  the  author  that  the  present  work,  embodying  essen- 
tially liis  teaching,  will  not  only  supply  such  a  want,  but  will  facili- 
tate and  stimulate  the  study  of  this  most  important  branch,  the 
institutes,  that  is  to  say,  the  foundation  of  all  rational  medicine. 
The  author  takes  much  pleasure  in  here  expressing  his  acknowl- 
edgments to  Dr.  A.  P.  Brubaker,  Demonstrator  of  Physiology  in 
the  Jefferson  ]\Iedical  College,  for  the  assistance  rendered  in  the 
performance  of  the  experimental  part  of  the  work  ;  to  Arthur  E. 
Brown,  Esq.,  Superintendent  of  the  Zoological  Garden,  of  Philadel- 
phia, for  the  many  facilities  and  courtesies  extended  in  the  dissec- 
tion of  the  rare  animals  that  have  died  at  the  Garden,  the  results  of 
which  are  frequently  made  use  of  in  the  work,  and  to  Dr.  I^awrence 
Wolff,  Demonstrator  of  Chemistry  in  the  Jefferson  Medical  College, 
for  the  favor  of  seeing  the  work  through  the  press. 

HEXRY  C.  CHAPMAN. 


CONTENTS. 


PAGE 

Introduction 17-2'; 


CHAPTER  I. 

GENERAL    STRUCTUKE    OF    THE   BODY,    PHYSICALLY    AND    CHEMICALLY. 

Organs  —  Tissues — Cells  —  Pi-oximate  Principles  of  Inorganic 
Origin — Water — Sodium  ("hloride — Potassium  Chloride — Cal- 
cium Phosphate — Calcium  Carbonate — Sodium  Cai-bouate         ,     28-i2 

CHAPTER  II. 

PROXIMATE    PRINCIPLES    OF    ORGANIC    ORIGIN. 

Carbohydrates — Sugars — Fats      .......     -13-56 

CHAPTER  III. 

PROXIMATE    PRINCIPLES    OF    THE   THIRD    CLASS. 

Proteids — Albuminoids — Amides — Amines — Alcohols — Ferments     57-68 

CHAPTER  IV. 

FOOD. 

Use  of  Food — Kinds  of  Food — ^Food  Stuffs — Hunger  and  Thirst 
— Mixed  Diet — Tea  and  Cofltee — Tobacco— Alcohol— Distilled 
Liquors — Wine — Malt  Lic^uors  ......     69-82 

CHAPTER  Y. 

DIGESTION. 

The  Teeth— Mastication— Enamel— Cement— Tooth  Pulp- 
Maxillary  Bones  and  Temporo-maxillary  Articulation — In- 
termaxillary Bone — Muscles  of  Mastication  .         .         .         83-94 

CHAPTER  YI. 

DIGESTION.— ( Continued. ) 
INSALIYATION    AND    DEGLlTlTloN. 

Insalivation — De2;lutition  .......       95-105 


10 


CONTENTS. 


CHAPTER  VII. 

DIG  ESTION.— ( ttH/(/«(e(/. ) 
GASTRIC   DIGESTION. 

Functiou  of  tlie  Stomaeli — Experiments  on  Digestion — Mucous 
Membrane  of  Stomach — Gastric  Glands — Gastric  Juice — 
Composition  of  Gastric  Juice — Action  of  Gastric  Juice  Upon 
Food 


lOG- 125 


CHAPTER  VIII. 

DIGESTION.  — (ro»//»»r'(/.) 
INTESTINAL  DIGESTION.     INTESTINAL  JUICE.     PANCREATIC  JUICE.      FUNC- 
TIONS   OF    LIVER.       GLYCOGEN.       BILE.       FECES.       DEFECATION. 

Intestinal  Juice — Pancreatic  Juice — Internal  Secretion  of  Pan- 
creas—The Bile — (Hycogen— The  Large  Intestine — The  Con- 
tents of  the  Large  Intestine — Defecation — Resume  of  Diges- 
tion             126-158 

CHAPTER  IX. 

ABSORPTION. 

Lacteals,  Thoracic  Duct,  etc.— Lymphatic  System— Lymph 
and  Chyle— Structure  of  Villi— Chyle— Venous  Absorption — 
Osmosis — Absorjttion  l>y  Stomach  and  Rectum — Conditions 
favoring  Absorpti(m — Resume  of  Absorption  .  .  .     159-178 

CHAPTER  X. 

THE    BLOOD, 

Physical  Characters  of  the  Blood — Quantity  of  Blood  in  Human 
Body — Red  Corpuscles — Diameter  of  Red  Blood  Corpuscles 
in  Vertebrates 17y-190> 

CHAPTER  XI. 

THE  BLO(  n).—(nmtinue(L ) 

White  Corpuscles— Structure  of  Solitary  and  Lymphatic  Glands 
—Structure  of  Spleen— Production  of  White  Corpuscles — 
Thyroid  Gland — Internal  Secretion  of  Thyroid  Gland —Thy- 
mus Gland- Blood  Plates 191-200 


CHAPTER  XII. 

THE  ISLOOD.— (rW//////»r-/.) 

Coagulaticm  of  the  Blood,  Theories  of 201-207 

CHAPTER  XIII. 

T H i;  B \A)()D.—{Omtiii iicd. ) 

Comijosition  of  tlie  Blood— Haemoglobin — Spectrum  Analysis- 
Gases  of  Blood— Salts  of  Blood — Composition  of  Corpuscles 
-Transfusion 208-22& 


CONTENTS.  11 

GET  AFTER  XI Y. 

CIRCL'LATIOX    OF    THE    BLOOD. 

The  Heart — Duration  of  Movements  of  Heart  ....     230-243 

CHAPTEK  XY. 

CIRCrLATION  OF  THE  BLOOD.— (r'o/(//H««rf.) 
THE    HEART. 

Cardiac  Imi)nlse — Cardiograph — \York  Done  by  the  Heart — 
Cause  of  Sounds  of  Heart — Conditions  Influencing  Action 
of  Heart — Cause  of  Heart's  Contraction — Stimuhis  to  Heait.     244-258 

CHAPTER  XVI. 

CTRCULATIOX  OF  THE  BU)0\).—{Oynt!nii,'f1.) 
THE    ARTERIES. 

Flow  of  Liquids  through  Tubes — Elasticity  and  Contractility  of 

Arteries — Dilatation  of  Arteries — Sphygmograph  .         .     259-274 

CHAPTER  XVII. 

CIRCULATION  OF  THE  m.OOD.— {Continued.) 
PRESSURE   AND   VELOCITY    OF   THE    BLOOD   IN   THE    ARTERIES. 

Pressure  of  Liquids — Hydrostatic  Paradox — Hydrostatic  Bel- 
lows— Blood  Pressure — Hannodynamonieter — Arterial  Pres- 
sure— Aortic  Pressure  —  Kymograph — Blood  Pressure  in 
Turtle  and  Frog — Manometers  —  Spring  Kymograph — 
Htemodromometer — Stromuhr — Hfemodromograph  —  Traces 
of  Pressure  and  Velocity  of  Blood  .....     275-310 

CHAPTER  XVIII. 

CIRCULATION  OF  THE  BLOOD.— (Cr/;«/fHwrf.) 
THE   CAPILLARIES. 

Structure  of  Capillaries — Capacity  of  Capillary  System — Phe- 
nomena of  Cajiillary  Circulation — Velocity  of  Blood  in 
Capillaries — Plethysmograph — Pressure  of  Blood  in  Capillar- 
ies— Capillary  Force      ........     311-325 

CHAPTER  XIX. 

CIRCULATION  OF  THE  mA)0\y.—{C<mcliuled.) 
THE  VEINS. 

Capacity  of  Venous  System — Venous  Pressure — Causes  of  Flow 
of  Blood  in  Veins — Rapidity  of  Circulation — Resume  of  the 
History  of  the  Discovery  of  the  Circulation  of  the  Blood        .     326-337 


12  CONTENTS. 

CHAPTER  XX. 

RESPIRATION. 

Respiration  in  luvertebrata — Structure  of  Larynx — Structure 
of  Trachea — Structure  of  Pleura — Intrapulinonary  and  Intra- 
thoracic pressure  .........     338-350 

CHAPTER  XXI. 

RESPIRATION.— ( Continued. ) 
MUSCLES    OF    RESPIRATION. 

Inspiration— Expiration — Types  of  Breathing  .         .         .     351-362 

CHAPTER  XXII. 

RESPIRATION.— ( ( '<,H/!„,ir,l. ) 
RESPIRATORY    MOVEMENTS   AS   STUDIED    15Y   THE    GRAPHIC    METHOD. 

Number  of  Resjjirations — Mechanical  Work  Performed  during 
Respiration — Breathing  Capacity — S])ironieter — Tension  of 
Gases  in  Blood  and  Ti.ssucs 363-383 

CHAPTER  XXIII. 

RESPIRATION.— (rVj»////»r'r/.) 
ABSORPTION    OF    OXYGEN — EXHALATION    OF    CARBON    DIOXIDE. 

Valentin  and  Brunner's  Apparatus  —  Hempel  Apparatus — 
Amount  of  Oxj^gen  Absorbed — Regnault's  Respiration  Ap- 
paratus— Carbon  Dioxide  Exhaled — Voit's  Respiration  Ap- 
paratus— Respiratory  Quotient — Ventilation — Asphyxia       .     884-412 

CHAPTER  XXIV. 

ANIMAL    HEAT. 

Influence  of  Age  and  Sex— Daily  Variations — Food — Muscular, 
Mental  and  Glandular  Action — Surrounding  Temperature — 
The  Calorimeter — Specific  Heat  of  Tissues — Heat  Produced 
in  Twenty-four  Hours — Heat  Value  of  Foods — Correlation 
of  Heat  and  Mechanical  Woik — Conditions  Influencing  Ex- 
penditure of  Heat — Influence  of  Baths  and  Clothing — Regu- 
lation of  Heat  Produced  and  Expended         ....     413-449 

CHAPTER   XXV. 

THE    KIDNEYS    AND    URINE. 

Structure  of  Kidney — Excretion  of  Urine — The  Urine — Constit- 
uents of  the  Urine — Determination  of  Urea — Influence  of 
Muscular  Exercise  on  the  Production  of  Urea — Hipi)uric  Acid 
— Formation  of  Alkaline  Urine      ......     450-475 


CONTENTS.  13 

CHAPTER  XXYI. 

STRUCTURE    OF    NERVOUS   SYSTEM. 

The  Neuron  Theory — Medullated  Nerve  Fibers — Axis-cylinder 
of  Nerves — Gelatinous  Nerve  Fibers — Peripheral  Distribu- 
tion of  Nerves— Composition  of  Nervous  System  .         .         .     476— 18-") 

CHAPTER  XXVII. 

XERVOUS  HYHTKyi— {Continued.) 
BATTERIES.        OHM'S    LAW.        INDUCTION    APPARATUS.        PENDULUM    MYO- 
GRAPH.      SPRING  MY'OGRAPH.       WHIPPE.       LATENT    PERIOD.       VELOCITY 
OF   NERVE    FORCE,    ETC. 

Polarization  —  Potential — Electro-motive  Force,  etc. — Resis- 
tance-box— Influence  of  Resistance^Induction  Apparatus — 
Unii^olar  Induction — Helmholtz's  Induction  xVpparatus — 
Traces  of  Muscular  Contraction — Marking  Lever — Pendulum 
Myograph — Rapidity  of  Transmission  of  Nerve  Force — 
Muscular  and  Nervous  Force         ......     486—51 1 

CHAPTER  XXVIII. 

NERVOUS  SYSTEM.— ( Vontinued.) 

GALVANOMETERS.  NON-POL  ARIZABLE  ELECTRODES.  ELECTRICAL  CUR- 
RENT. RESrSTANCE.  ELECTRO-MOTIVE  FORCE  OF  NERVE.  CAUSE  OF 
ELECTRICAL    CURRENT    OF    NERVE. 

Multipliei" — Scale  and  Lamp  for  Galvanometer — Wiedemann's 
Galvanometer — Telescope  and  Scale  for  Galvanometer — 
Capillary  Electrometer — Disposition  of  Diverting  Vessels — 
Physiological  Rheoscope — Electro-motive  Force — Resistance 
of  Nerve — Double  Dipolar  Molecules— Static  and  Dynamic 
Electricity 512-533 

CHAPTER  XXIX. 

NERVOUS  SYSTEM.— ( Con/inm-d. ) 
CURRENTS    OF    REST    AND   ACTION.        NEGATIVE     VARIATION.        ELECTRO- 

TONUS. 

Differential  Rheotome — Rheocord — Rate  of  Propagation  of 
Current  of  Action — Electrotonus — Effect  of  Strength  of 
Constant  Current — Ritter's  Law    ......     534-556 

CHAPTER   XXX. 

NERVOUS  SYSTEM.-  (ro«/(H««?.) 

THE    SPINAL    CORD,   ITS    STRUCTURE    AND    FUNCTIONS  AS  A  CONDUCTOR  OF 

MOTOR    AND    SENSORY    IMPULSES. 

Course  of  Nerve  Fibers — Medulla  Oblongata — Functions  of 
Anterior  and  Posterior  Roots — Degeneration  of  the  Nerve 
Fibers — Decussation  of  Nerve  Fibers — Distribution  of  Spinal 
Nerves         .......  .  .  .     557-577 


14  CONTENTS. 

CHAPTER  XXXI. 

XERVOrS  SYSTEM.— ( Coutiniied. ) 

Division  of  Labor  in  Animals  and  Man. — Reflex  Automatit-  and 

Nutritive  Functions  of  Spinal  Cord        .....     578-592 

CHAPTER  XXXII. 

NERVOUS  SYSTEM.— (row///u«-d.) 
THE  MEDULLARY'  NERVES. 

Third  Nerve  ;  Motor  Oculi  Communis — Fourth  Nerve  ;  Pa- 
theticus — Fifth  Nerve  ;  Trigeminal — Seventh  Nerve  ;  Portio 
Dura  or  Facial — Pars  intermedia — Ninth  Nerve  ;  Glosso- 
pharyngeal— Tenth  Nerve;  Pneumogastric — Eleventh  Nerve; 
Spinal  Accessory — Twelfth  Nerve;  Hypoglossal    .         .         .     593-645 

CHAPTER  XXXIII. 

NERVOUS  SYSTEM.  — (Co«///,!»-(7. ) 

THE    PONS    VAROLII.        CRURA    CEREBRI.        CORPORA   STRIATA.        THALAMI 

OPTICI.       CORPORA    QUADRIGEMINA.       CEREBELLUM. 

Pons  Varolii — Crura  Cerebri — Functions  of  Corpora  Striata— 

Thalami  Optici — Corpora  Quadrigemina — Cerebellum     .       .     646-658 

CHAPTER  XXXIV. 

NERVOUS  SYSTEM.— ( CoraC/nwerf. ) 
THE   CEREBRAL   HEMISPHERES. 

Cerebral  Fissures  and  Convolutions — Weight  of  Brain — Injury 
to  the  Cerebral  Hemispheres — Comparative  Development  of 
the  Brain — Localization  of  Functions — Aphasia — Sleej)  .     659-681 

CHAPTER  XXXV. 

NERVOUS  SYSTEM.— ( ConclwM. ) 
SYMPATHETIC   NERVOUS    SY'STEM. 

Sympathetic  Nerve — Cervical  Ganglia  and  Cardiac  Nerves — 
Lumbar  and  Sacral  Ganglia — Effects  of  Division  of  Cervical 
Sympathetic — Vaso-Motor  Nerves 682-695 

CHAPTER  XXXVI. 

THE  SKIN  AND  ITS  APPENDAGES.  SEBACEOUS,  MAMMARY  AND  SUDO- 
RIFEROUS CiLANDS.  PERSPIRATION.  TACTILE  AND  OTHER  FORMS  OF 
CUTANEOUS  SENSATION. 

The  Skin— The  Nails— The  Hairs— Sebaceous  Glands— Mam- 
mary Glands  and  Milk — Sudoriferous  Glands — Perspiration 
— Sense  of  Touch,  "Weight,  Temperature       ....     696-724 

CHAPTER  XXXVII. 

THE    NOSE    AND    OLFACTION.       THE    TONGUE    AND    GUSTATION. 

Olfaction — Gustation 725-733 


coy  TEXTS.  lo 

CHAPTER  XXXVIII. 

THE    EYE    AXD    VISIOX. 

The  Optic  Nerves — Visual  Center — The  Sclerotic  and  Cornea — 
The  Choroid — Ciliary  Processes — Ciliary  Muscle — The  Iris — 
The  Retina — The  Vitreous  Humor  and  Hyaloid  Tunic — The 
Crystalline  Lens — The  Aqueous  Humor — Intraocular  Pres- 
sure.      ...........     734-751 

CHAPTER  XXXIX. 

PHYSIOLOGICAL    OPTICS. 

Refraction — Cardinal  Points — Spherical  and  Chromatic  Aber- 
ration— Astigmatism — Myopia — Hypermetropia — Accommo- 
dation— Ophthalmoscope       .......     752-774 

CHAPTER  XL. 

BINOCITLAR    VISION'.       SENSATION    AND   PERCEPTION   OF    SIGHT.        PROTEC- 
TIVE  APPENDAGES   OF   THE    EYE. 

Binocular  Vision — Sensation  of  Sight — Perception  of  Sight — 

Protective  Appendages,  etc.,  of  the  Eye         ....     775-790 

CHAPTER  XLI. 

PHYSIOLOGICAL    ACOUSTICS. 

Intensity  of  Sound — Pitch  of  Sound — Qualitj^  of  Sound — Reso- 
nance         791-809 

CHAPTER  XLII. 

THE    LARYNX,    AND   THE   PRODUCTION    OF    THE   VOICE    AND  SPEECH. 

The  Larynx — Production  of  the  Voice — Speech         .         .         .     810-825 
CHAPTER  XLIII. 

THE    STRUCTURE    OF    THE    EAR.    AND   THE    SENSATION    OF    HEARING. 

The  Structure  and  Functions  of  the  External  Ear — The  Struc- 
ture and  Functions  of  the  Middle  Ear — Structure  and  Func- 
tions of  the  Internal  Ear — Auditory  Centre  .         .         .     826-848 

CHAPTER  XLIV. 

IRRITABILITY,    CONDUCTIVITY    AND    CONTRACTILITY    OF    MUSCLE. 

Structure  of  Muscle — Work  Done  by  Muscle — Action  of  Muscles 

as  Levers — Walking — Running       .....  849-S59 

CHAPTER  XLV. 

REPRODUCTION. 

Spontaneous  Generation  —  Fissiparous,  Gemmiparous,  and 
Sexual  Generation — Female  Generative  Apparatus — Corpus 
Luteum  of  Menstruation  and  Pregnancy — 3Ienstruation — 
The  Male  Generative  Apparatus 8G0-S75 


1  ()  CONTEXTS. 

CHAPTER    XLVI. 

REPRODUCTION.— (  Condmled. ) 

Impiegiiation  of  the  Ovum — Polar  Globules — Development  of 
Embryo — Formation  of  Blastodermic  Membranes — Develop- 
ment of  Primitive  Organs — Development  of  Amnion,  Allan- 
tois,  and  Umbilical  Vesicle — Development  of  the  Nervous 
System — Development  of  Alimentary  Canal  and  its  Append- 
ages^Development  of  the  Vascular  System — Development 
of  Respiratory  Organs — Development  of  the  Genito-urinary 
Organs — Development  of  Extremities — Develoj^ment  of  the 
Placenta         876-909 


PHYSIOLOGY. 


IXTRODUCTIOX. 

Physiology,  from  the  Greek  c'jm'  and  /.uyu-:,  literally  means  a 
discourse  on  Xature.  At  the  present  day,  however,  the  word  has 
not  such  an  extended  significance,  physiology  as  understood  by 
naturalists  and  physicians  meaning  the  study  of  the  functions  or 
uses  of  the  parts  of  which  living  beings  consist. 

The  word  parts  is  used  in  preference  to  that  of  structures,  in- 
asmuch as  there  are  beings  like  the  monera,  simple  masses  of  a 
jelly-like  substance  or  protoplasm,  which  are  so  structureless  and 
unorganized  that  great  difficulty  is  experienced  in  classifpng  them, 
it  being  questionable  whether  they  should  be  ranged  among  ])lants 
or  animals,  or  relegated  to  an  intermediate  kingdom,  the  "  Protis- 
tenreich "  of  Hteckel,^  or,  as  Huxley  -  expresses  it,  a  sort  of  a 
biological  "  no  man's  land."  Indeed  it  has  been  doubted  whether 
the  term  living  at  all  could  be  properly  applied  to  the  monera  in 
the  same  sense  in  which  that  word  is  used  in  reference  to  the  higher 
animals.  As  the  totality  of  the  functions  or  uses  of  the  parts, 
structures,  or  organs  of  which  living  beings  consist,  constitute  their 
life.  Physiology  may  be  defined  therefore  as  the  study  of  life  or  of 
function. 

Necessarily  from  the  definition,  Physiology  presupposes  a  knowl- 
edge of  anatomy  or  structure.  The  relation  of  the  two  may  be 
compared  to  the  study  of  a  clock  when  at  rest  and  when  going. 

The  anatomist  studies  the  form  and  relation  of  the  weights,  the 
pendulum,  the  hands,  etc.,  at  rest ;  the  physiologist,  the  fall  of  the 
weight,  the  swinging  of  the  pendulum,  the  movement  of  the  hands. 
Anatomy  is  the  statical,  physiology  the  dynamical,  part  of  biology. 

As  well  might  the  mechanician  hope  to  understand  the  move- 
ments of  the  clock  and  to  reaulate  it  without  a  knowledoe  of  the 
parts  composing  it,  as  for  the  physiologist  to  understand  the  motions 
of  the  living  body  without  a  previous  knowledge  of  its  structure. 

Anatomy  and  physiology  are  so  intimately  associated  that,  philo- 
sophically, they  should  be  studied  together ;  indeed,  to  separate 
them,  except  for  the  convenience  of  teaching,  is  highly  illogical. 

As  Hyrtl  ^  well  observes,  "  Anatomy,  unassociated  with  physiol- 

^  Generello  Morpliologie,  Bd.  2,  s.  xxii.     Berlin,  ISGli. 
^Physical  Basis  of  Life,  p.  129.     Lay  Sermons.     New  York,  1871. 
^  Lehrbuch  der  Anatoniie,  s.  18.     "Wien,  1881. 
2  17 


18  INTRODUCTION. 

ogy,  is  a  mindless  study  and  does  not  deserve  the  name  of  science. 
Can  one  study  the  arrangement  of  a  machine  without  any  reference 
to  its  object  ?  It  is  possible  simply  to  view  the  harmoniously  ar- 
ranged parts  of  a  whole,  simply  to  stare  at  it  without  reflection. 
The  anatomist  can  undertake  no  investigation  without  considering 
the  physiological  questions  involved.  The  paths  of  both  sciences 
meet  and  cross  each  other  in  so  many  places  that  there  arc  but  few 
divergent  points." 

In  beginning  the  study  of  any  su1)ject  not  only  is  it  indispensable 
that  the  object  of  the  investigation  should  be  clearly  defined,  but  it 
is  proper  that  relation  to  knowledge  in  general  should  be  pointed 
out. 

The  classification  of  the  sciences  has  been  a  vexed  one  from  the 
time  of  Bacon '  to  Comte."  This,  from  the  nature  of  things,  might 
have  been  expected ;  for  there  are  no  sharply  defined  lines  in 
nature ;  one  science  encroaches  so  upon  another  that  it  is  impossi- 
ble to  say  where  the  one  ends  and  the  other  begins.  All  classifica- 
tion, therefore,  must  be  imperfect.  The  following  one,  that  of 
Comte,  is  ojjcn  to  many  criticisms,  as  shown  in  the  masterly  essay 
of  Spencer.'* 


Classification 

of 
Knowledge 


(^  Mathematics. 
Astronomy. 

Physics. 


Chemistry.  ,  ^ 

Biology.  r/  ..1  f  Anatomy. 

o     •  1  Zoology.  -    T5,      .  1  -^ 

bociologv.  ^           ^•'  rhvsiology. 


Admitting  its  many  fiuilts,  we  make  use  of  it  here  on  account  of 
its  brevity  sim])ly  to  indicate  the  position  of  Physiology  relatively 
to  that  of  other  kinds  of  knowledge. 

It  will  be  seen,  from  the  table,  that  the  study  of  plants  and  ani- 
mals constitutes  the  sul)ject-matter  of  Biology. 

The  second  division  of  this  grand  science  comprehends  all  that  is 
known  of  the  structure,  functions,  habits,  geographical  and  geolog- 
ical distribution  of  animals  ;  therefore,  the  study  of  animal  functions 
or  animal  physiology  is  a  subdivision  of  Zoology.  In  the  same 
manner,  vegetal  ]ihysiology  forms  a  part  of  Botany.  Human  phy- 
siology, a  part  of  general  animal  physiology,  forms  the  subject  of 
this  work. 

If  the  sciences  are  studied  in  the  order  in  which  they  follow  each 
other  as  given  above,  then  the  inorganic  will  precede  the  organic-. 
This  is  the  logical  order  and  historically  the  one  in  which  they 
were,  generally  speaking,  cultivated,  for  the  phenomena  of  the  in- 
organic world  are  less  complex  and  more  easily  generalized  than 
those   of  the   organic,   and,  therefore,   more    readily    investigated. 

1  De  Augmentis  Scientiamm.  ^  Cours  de  Philosophic  Positive. 

'Genesis  of  Science.     Essays.     London,  1868. 


INTRODUCTIOX.  10 

Wherever  practicable,  the  historical  order  will  be  found  to  be  the 
best  cue  to  pursue  in  the  study  of  any  science  ;  indeed,  as  we  pro- 
ceed, it  will  be  seen  that  the  phenomena  of  physiology  depend  upon 
physical  and  chemical  laws,  and  that  probably,  with  the  advance  of 
knowledge,  the  whole  subject  will  be  treated  as  a  branch  of  molecu- 
lar physics — hence  the  indispensability  to  the  student  of  physiology 
of  a  knowledge  of  physical  and  chemical  science.  Ample  illustra- 
tions of  the  value  of  such  knowledge  'svill  be  given  when  the  special 
functions  are  considered.  The  special  senses  of  sight  and  hearing, 
for  example,  depend  for  their  successful  study  u])on  familiarity  with 
optics  and  acoustics  ;  the  investigation  of  the  circulation  is  a  ques- 
tion of  hydraulics  ;  that  of  secretion,  of  organic  chemistry. 

By  referring  to  the  classification  just  oifered,  it  will  be  observed 
that  Botany  comes  before  Zo<')logy  ;  where  practicable,  its  study 
should  precede  that  of  Zoology,  for  plants  serve  to  bridge  over,  to 
a  certain  extent,  the  gap  between  the  mineral  and  animal  worlds, 
and  at  diiferent  points  touch  the  confines  of  these  two  kingdoms. 
Further,  with  some  exce})tions,  plants  are  destitute  of  a  nervous 
system,  and  even  if  extended  investigation  should  show  that  their 
nervous  system  is  more  developed  than  now  it  is  supposed  to  be,  it 
would  exercise  a  small  influence  as  compared  with  that  of  the 
higher  animals.  Plants,  therefore,  oifer  a  favorable  opportunity  of 
examining  the  processes  of  nutrition  iminfluenced  by  the  nervous 
system. 

When  we  come  to  examine  the  circulation,  digestion,  etc.,  in 
man,  we  shall  see  that  these  functions  are  greatly  modified  by  the 
nervous  system  ;  hence  the  advantage  of  studying  nutrition  in  lower 
organizations  where  these  disturbing  elements  are  eliminated. 

Having  endeavored  to  define  the  object  of  our  study,  and  to  indi- 
cate its  limits  and  relation  to  knowledge  in  general,  let  us  now  con- 
sider the  different  methods  by  which  human  physiology  can  be 
investigated — and,  first,  a  great  deal  can  be  learned  of  the  functions 
of  the  human  body  by  careful  reflection  on  the  structure  of  the 
same.  Haller  ^  says  :  "  and  first  the  fabric  of  the  human  body  is 
to  be  learned,  whose  parts  are  almost  infinite.  Those  who  would 
study  physiology  separately  from  anatomy  certainly  seem  to  me, 
can  be  compared  with  mathematicians  who  undertake  to  express, 
by  calculation,  the  forces  and  functions  of  a  certain  machine  of 
which  they  have  learned  neither  disks,  wheels,  measures,  nor 
material.  Truly  I  am  persuaded  that  we  know  scarcely  anything 
of  physiology  unless  we  have  learned  it  through  anatomy." 

Undoubtedly,  the  functions  of  many  organs  might  be  inferred 
from  the  thorough  study  of  their  structure.  As  a  matter  of  history, 
the  demonstration  of  the  valves  in  the  veins  by  Fabricius  to  Harvey 
was  one  of  the  important  facts  that  first  suggested  to  the  latter  to 
investigate  the  flo\y  of  the  blood. 

1  Elementa  Plivsiologiae.     Lausanme,  MDCC'LVII.     Preface,  p.  1. 


'20  IXTHODUCTIOX. 

The  functions  of  certain  nerves  will  probably  1)e  never  definitely 
settled  until  anatomy  has  determined  whether  they  terminate  in 
muscle,  gland,  or  sensory  organs. 

Not  only,  however,  is  a  knowledge  of  general  descriptive  anatomy 
necessary,  but  it  is  indispensable  also  that  the  student  who  hopes  to 
cultivate  physiology  with  any  success,  must  have  a  thorough  train- 
ing in  histology,  or  the  science  which  has  for  its  object  the  study  of 
the  tissues. 

The  necessity  of  a  thorough  knowledge  of  structure,  in  order  to 
understand  function,  is  so  obvious  that  it  seems  superfluous  to  dwell 
further  upon  it.  Pathology  furnishes  valuable  data  to  the  student 
of  human  physiology.  Where  disease  is  restricted  to  one  organ, 
and  when  it  is  noticed  that  with  the  destructi(jn  of  the  tissues  com- 
posing it  a  particular  function  gradually  weakens  and  finally  dis- 
appears, it  is  a  logical  inference  that  the  loss  of  function  is  depend- 
ent upon  the  loss  of  structure.  In  this  way  the  uses  of  many  parts 
might  be  ascertained — hence,  the  importance  of  carefully  kept 
clinical  records  and  th(^rough  post-mortem  examination. 

Suppose,  for  example,  that,  associated  with  loss  or  want  of 
speech,  in  the  majority  of  instances  it  is  found,  after  death,  that  a 
particular  convolution  in  the  hemisphere  of  the  brain  is  either 
wanting,  undeveloped,  or  diseased — it  would  be  a  fair  conclusion 
that  the  feculty  of  speech  was  connected,  in  some  way,  with  this 
particular  convolution,  especially  if  it  was  clearly  shown  that  the 
facts  were  not  mere  coincidence,  but  bore  the  relation  of  cause  and 
effect.  Or  take  the  case  of  a  human  being  suddenly  paralyzed  upon 
one  side  of  the  body  both  with  reference  to  sensation  and  motion, 
and  post-mortem  examination  revealed  that  certain  parts  of  the 
opposite  side  of  the  brain  were  affected,  as  in  apoplexy,  for  example. 
It  would  be  natural  then,  to  consider  that  the  parts  affected  in  the 
one  side  of  the  brain  presided  over  the  opposite  side  of  the  body  and 
extremities — -or,  take  the  case  of  a  man  suddenly  stabbed  in  the 
back-bone,  the  instrument  penetrating  only  half-way  through  the 
spinal  cord,  and  the  patient  loses  voluntary  motion  on  the  side  of 
the  wound,  and  sensation  on  the  opposite  side — the  view  that  the 
sensory  fibers  decussate  in  the  cord,  and  the  motor  one  in  the 
medulla  would  )je  confirmed. 

While,  according  to  many  thinkers,  clinical  medicine  and  morbid 
anatomy  alone  will  not  furnish  data  sufficient  to  deduce  a  physiol- 
ogy and  a  rational  pathology,  undoubtedly  such  facts  as  the  above 
are  invalualjle  as  aids  in  throwing  light  upon  the  still  obscure  func- 
tions of  the  nervous  system  and  the  uses  of  other  structures  in  the 
human  body. 

The  admirable  observations  of  lieaumont  ^  and  Budge  ^  upon 
human  beings,  in  whom  the  stomach  and  intestine  had  been 
wounded  in  such  a  nuuiner  as  to  render  them  susceptible  of  experi- 

'  Exjieriraents  and  Observations.     Plattsburg,  1833. 
2  Virchow's  Archiv,  Bd.  xiv.,  s.  140. 


IXTEODUCTIOX.  21 

ment,  arc  illustrations  of  the  application  of  patliological  cases  to  the 
study  of  physiology. 

"When  the  vast  complexity  of  structure  exhibited  by  the  human 
organization  is  considered,  it  becomes  evident  that  any  investigation 
of  its  function,  however  extended,  if  it  be  confined  to  man  alone, 
can  lead  to  but  very  limited  results. 

Comparative  anatomy  has  shown,  however,  that  tlie  life  of  the 
animal  kingdom  is  a  grand  panorama,  each  fleeting  form,  as  it 
passes  before  the  view,  recalling  that  which  has  just  passed,  fore- 
shadowing that  which  is  to  come ;  the  simplest  of  living  beings,  so 
lowly  organized  and  transparent  that  their  entire  life  processes  can 
be  observed  by  the  microscope,  leading  througli  intermediate  forms 
to  higher  types  of  life,  closely  approaching  that  of  man  himself. 
With  the  development  of  additional  structures,  we  find  correspond- 
inglv  increased  functions,  and  infer  tliat  the  new  function  is  due  to 
the  new  structure. 

The  comparative  method  of  investigation  is  therefore  the  opjxjsite 
of  the  pathological  one,  by  which,  as  we  have  seen,  the  use  of  a 
structure  is  inferred  from  loss  of  function  dependent  upon  the  loss 
of  structure. 

In  the  hands  of  Harvey,  Hunter,  Cuvier,  ]Muller,  Milne  Ed- 
wards, Owen,  comparative  anatomy  has  proved  of  invaluable  service 
in  the  study  of  physiology. 

In  his  great  work,  Harvey^  states  "that  if  anatomists  had  given 
to  the  organization  of  the  inferior  animals  the  same  attention  that 
they  devote  to  the  structure  of  the  human  body,  the  question  of  the 
circulation  would  long  since  have  been  determined." 

Observations  upon  the  enlargement  of  the  collateral  vessels  in  the 
horns  of  the  deer  when  in  the  velvet  after  ligature  of  the  carotid, 
suggested  to  the  great  ])hysiological  surgeon,  John  Hunter,"  the  idea 
of  the  collateral  vessels  maintaining  the  circulation  in  the  thigh 
after  ligature  of  the  main  trunk. 

The  ligation  of  the  carotid  in  the  dog,'^  and  of  the  femoral  in  the 
same  animal,  done  ])y  Home  ^  at  the  suggestion  of  Hunter,  having 
further  convinced  the  latter  of  the  feasibility  of  ligation  as  a  cure 
for  aneurism.  Hunter  tied  the  femoral  artery  in  the  celebrated  case 
of  the  coachman  suffering  from  popliteal  aneurism  and  thereby  in- 
troduced a  most  capital  improvement  in  surgery .•" 

To  study  the  pliysiology  of  man  without  the  slightest  knowledge 
of  life  as  exhibited  in  the  lower  animals  is  as  if  one  would  attempt 
to  master  the  steam  engine  without  any  acquaintance  with  the  ele- 
mentary laws  of  heat  or  mechanics,  or  to  investigate  a  magnetic 
a])paratus  without  knoAving  anytliing  about  the  simple  facts  of  elec- 
tricity. 

'  De  Motu  Cordis,  p.  'A?,.     Frankfort,  1628. 

^  Works,  edited  by  Palmer,  vol.  iii.,  p.  201. 

^Ibid. ,  vol.  i.,  p.  444.  *Ibid.,  vol.  iii.,  p.  597. 

5  Experimental  I'liysiology,  p.  30.     Owen.     London,  1882. 


2  2  IXmOD  UCTION. 

As  the  study  of  comparative  anatomy,  in  its  application  to  human 
physiology,  at  the  present  day,  is  very  much  neglected,  it  may  not 
be  superfluous  to  ofler  a  few  instances  as  illustrations  of  the  impor- 
tance of  the  study  in  this  respect.  For  example,  from  the  fact  of 
the  bile  and  pancreatic  juice  passing  into  the  alimentary  canal  at 
the  same  point  in  man,  it  is  impossible  to  say  to  which  of  these 
fluids  the  changes  exhibited  after  their  mixture  Avith  the  food  are 
due. 

By  examining  the  rabbit  or  the  beaver,  however,  Ave  find  that 
the  opening  of  the  pancreatic  duct  into  the  intestine  is  situated 
twelve  inches  and  more  below  that  of  the  bile-duct.  Hence,  the 
different  changes  exhibited  by  the  food  as  it  is  successively  aflected 
by  these  secretions,  can  be  perfectly  observed  by  killing  a  rabbit  or 
l)eaver  in  full  digestion.  Indeed,  as  we  shall  see,  it  is  in  this  way 
the  emulsifying  power  of  the  pancreas  is  usually  demonstrated.^ 
Again,  tlie  question  as  to  whether  the  bile  is  a  secretion  or  an 
excretion  flnds  its  answer  in  the  structure  of  the  doris,^  a  little 
mollusk  in  which  the  liver  has  two  ducts,  one  of  which  carries  the 
bile  into  the  alimentary  canal,  where  it  mixes  with  the  food,  while 
the  other  removes  it  at  once  from  the  ])ody,  showing  that  the  bile, 
in  this  case  at  least,  is  l)oth  a  secretion  and  an  excretion. 

One  of  the  best  established  facts  in  physiology  is  that  the  intel- 
lectual faculties  depend  upon  the  development  of  the  brain,  both  in 
reference  to  quantity  and  to  quality.  This  is  well  seen  when  the 
l^rains  in  a  series  of  animals  are  compared  with  reference  to  their 
intelligence.  AVith  the  gradual  addition  of  certain  parts  of  the  brain 
there  is  a  corresponding  increase  in  mental  activity — and  in  this 
way,  to  a  considerable  extent,  the  functions  of  certain  parts  of  the 
brain  have  been  made  out. 

Embryology,  or  the  study  of  the  transitory  phases  through  which 
every  animal  ])asses  in  its  development  from  the  stage  of  the  Qgg  to 
that  of  the  adult,  and  which  might  be  called  the  comparative  anat- 
omy of  the  individual,  has  already  proved  to  be  of  service  in  throw- 
ing light  on  the  functions  of  the  human  V>ody,  and  which  the  future 
Avill,  no  doubt,  show  to  be  susceptible  of  even  a  wider  application 
than  is  made  of  it  at  present,  for  the  embryo  of  animals,  with  the 
exce])tion  of  the  loAvest,  consists  of  three  germinal  layers,  of  which 
the  upper  one  gives  rise  to  the  epidermis  and  central  nervous  system, 
the  lower  one  to  th(>  epithelium  of  the  alimentary  canal  and  its  ap- 
pendages, the  middle  one  to  bone,  muscle,  vessel,  etc.  These 
germinal  layers,  even  at  the  start,  can  be  readily  distinguished,  the 
cells  composing  them  being  diflerently  affected  by  physical  and 
chemical  agents.  Some  of  the  lower  animals,  for  example  the 
hydrozoa,  never  get  beyond  this  layered  stage,  the  inner  layer 
acting  as  stomach,  the  outer  as  skin.     If  a  tissue  in  the  adult  can 

'Bernard:  Pliysiolofjio  Exjierimentale,  Umw  ii.,  ]>.  179.     Paris,  ISoCJ. 
^('iivicr:  Mcinoires  Pour  Servir  a  I'Histoire  et  a  1' Anatomic  des  Mollusquez. 
Paris,  1.S17.     Mcnioire  sur  le  (ienre  Doi'is,  p.  16. 


INTRODUCTWX.  23 

be  shown  to  have  been  derived  from  one  of  these  layers  in  its 
embrvonic  stage  its  function  could  almost  be  predicted.  Indeed  the 
whole  modern  pathological  histology  is  an  application  of  this  view\ 
The  older  pathologists,  like  ^lorgagni/  confined  themselves  to  the 
study  of  the  organs  as  affected  by  disease. 

Bichat,'  in  investigating  the  tissues  of  which  the  organs  are  com- 
posed, created  histology  ;  Schleiden  ^  first  showed  that  vegetable 
tissues  consist  of  cells,  and  Schwann,*  following  his  lead,  applied 
Schleiden's  view  to  the  tissues  of  animals.  The  embryologists, 
Reichert,^  Kolliker,^  Remak,''  etc.,  then  proved  that  the  cells  com- 
posing the  tissues  were  the  modified  cells  of  the  original  mulberry 
mass  of  cells  into  which  the  Q^g  or  primitive  cell  segments.  The 
obvious  corollary  of  these  generalizations  followed  when  Virchow,^ 
Billroth,''  Paget,^"  Rindfleisch,'^  etc.,  shoAved  that  pathological 
structures  were  the  still  further  modified  cells  composing  the  tissues 
of  the  organ,  and  that  morbid  growths  were  really  physiological 
ones,  exhibiting  themselves  under  conditions  otherwise  than  nor- 
mal ;  while  with  the  development  of  teratology,  through  the  works 
of  Geoffrey  St.  Hilaire,^^  and  others,  the  explanation  of  the  produc- 
tion of  monsters  lusus  naturae  became  possible.  That  which  is 
pathological  at  one  stage  of  growth  was  shown  to  be  physiological 
at  another  ;  that  which  is  normal  in  one  animal  is  aljnormal  in 
another.  Gradually  the  strict  demarcation  between  physiology  and 
pathology  has  been  broken  do  Am,  and,  with  the  flision  of  the  two 
studies,  a  rational  pathology  and  rational  treatment  are  being  slowly 
developed. 

Notwithstanding  the  importance  of  a  knoAvledge  of  general 
physics  and  chemistry,  anatomy,  embryology,  and  pathology  in  the 
study  of  the  functions  of  the  human  body,  nevertheless,  the  study 
of  human  physiology  is  often  almost  entirely  based  on  experiments 
made  upon  living  animals  :  the  study  of  the  circulation  and  respira- 
tion by  means  of  the  graphic  method,  the  making  of  gastric  fistulte, 
the  introduction  into  the  system  of  an  animal  of  various  substances, 
toxic  and  narcotic,  the  removal  of  various  parts  of  the  nervous  sys- 
tem, are  examples  of  the  kind  of  work  often  exclusively  done  in 
physiological  laboratories. 

The  student  of  physiology,  however,  should  not  confine  himself 
to  the  experimental  methods,  however  invaluable  and  indispensable 
they  may  l)e  as  a  means  of  investigation,  but  should  avail  himself 
also,  as  far  as  possible,  of  the  other  methods  of  research  just  referred 
to,  studying  the  subject  from  all  the  different  points  of  view  possible 

'  De  Sedibus  Morbonim,  1761.  ^  Anatomie  (ienerale.  18<ll. 

^Miiller's  Archiv,  1838.  *  Mikroskopi<c-lie  Untersuchunofen,  1839. 

^Entvrickelung  in  Wirbelthiere,  1840.  ^  Entwickelunsr  der  Cephalopoden,  1844. 
'  EntAvickelung der  Wirbelthiere,  1852."    ^Cellular  Pathologic,  1854. 

9  Allgemeine  Pathologie,  1872.  '<>  Surgical  Patholog}-,  1870. 
"  PathologLsche  Anat(jmie,  1873. 

'^HLstoire  Generale  et  Particuliere  des  Anomalies  de  1' organization,  1837. 


24  INTRODUCTIOX. 

and  comparing  the  resnlts  obtained  by  the  various  methods  made 
use  of. 

As  objections  are  often  made  to  the  experimental  study  of  physi- 
ology, it  will  not,  it  is  hoped,  be  considered  superfluous  if  we,  for 
a  moment,  consider  some  of  the  most  important  of  those  usually 
advanced.  It  is  often  urged  as  an  objection  to  a  vivisection,  that 
the  pain  inflicted  so  disturbs  the  normal  condition  that  any  result 
as  to  the  function  of  a  part  determined  in  this  way  is  valueless  ;  the 
suiferino;  entailed  vitiatino;  anv  conclusion  as  to  the  healthv  function 
of  the  part  examined.  This  objection  is,  of  course,  not  made  if 
anaesthetics  are  used.  There  are,  however,  experiments  performed 
in  which  it  is  necessary  that  the  animal  should  be  in  the  full  pos- 
session of  its  foculties  and  which,  from  the  conditions  of  the  inves- 
tigations, make  the  use  of  anaesthetics  impossible.  As  regards  such 
investigations  it  may  be  said,  without  doubt,  that  animals  sufl'er  far 
less  from  the  pain  inflicted  in  a  vivisection  than  man  does  from  a 
similar  wound  due  to  an  accident  or  the  knife  of  the  surgeon.  This 
is  due  to  several  causes  ;  the  animal  is  in  ignorance  of  what  is  going 
to  be  done,  forgets  the  operation  almost  immediately,  his  nervous 
organization  is  less  susceptible  than  tliat  of  the  human  being,  and 
his  wounds  heal  up  more  quickly.  The  influence  of  pain,  though 
less  in  an  animal  than  man,  must  nevertheless  be  always  taken  into 
consideration. 

Whenever  the  vivisection  is  performed  without  an  anaesthetic,  the 
physiologist  ought  not  to  draw  any  conclusion  from  the  experiment 
until  the  animal  has  had  time  to  recover  from  the  effects  of  the 
shock,  hemorrliage,  etc.,  and  has  so  far  returned  to  his  normal 
condition  that  the  influence  of  pain,  if  any  still  exists,  is  so  small 
in  amount  that  it  cannot  be  considered  as  interfering  with  the  func- 
tion of  the  structure  examined.  It  is  evident,  therefore,  that  if  the 
physiologist  had  no  higher  motive,  selfishness  would  induce  him  to 
be  as  merciful  as  possible  and  to  eliminate,  so  far  as  he  is  able,  pain, 
as  a  possible  source  of  fallac}-  in  his  conclusions. 

The  animal,  both  during  and  after  vivisection,  should  be  treated 
just  as  a  patient  undergoing  an  operation  would  be  by  a  wise  sur- 
geon ;  the  object  in  both  cases  being  to  restore,  as  rapidly  as  pos- 
sible, the  physiological  conditions — the  conditions  of  health.  As 
an  illustration  of  what  has  just  been  said,  as  regards  the  amount  of 
permanent  disturbance  produced  in  an  animal  by  a  vivisection,  it 
may  be  mentioned  that  Blondlot's  jiointer  bitch,  in  which  a  gastric 
fistula  had  been  made,  was  used,  after  her  recovery,  by  her  master 
for  eight  years  in  the  field  for  hunting  purposes,  and  in  the  labora- 
tory for  obtaining  gastric  juice,  and  that  during  that  period  the  dog 
had  two  litters  of  pups. 

The  Canadiau,  St.  ]Martin,  on  whom  the  gastric  fistula  was 
caused  by  a  gunshot  wound,  producing  far  more  dangerous  effects 
than  the  vivisection  just  referred  to,  lived  to  be  eighty-four  years 
old,  enjoyed  good  health  all  his  life,  married  and  had  children,  per- 


INTRODUCTION.  25 

formed  the  duties  of  a  servant,  and  Mas  during  this  time  frequently 
of  inestimable  value  to  science,  as  affording  Dr.  Beaumont  and 
others  the  rare  opportunity  of  observing  gastric  digestion  in  man 
under  the  most  favorable  circumstances. 

One  might  as  well  object  that  the  pain  suffered  by  St.  Martin, 
after  the  explosion  of  the  gun,  vitiated  the  conclusions  drawn  by 
Beaumont,  as  to  object  to  the  conclusions  of  Blondlot  because  the 
making  of  a  gastric  fistula  in  a  dog  involved  the  giving  of  the  ani- 
mal pain.  A  far  more  important  objection  than  that  just  referred 
to  is  that,  as  animals  differ  very  much  in  their  organization,  con- 
clusions drawn  from  experiments  made  upon  one  kind  of  an  animal 
cannot  be  applied  to  another  kind  ;  digestion  in  a  dog,  for  example, 
not  being:  exactlv  the  same  as  in  a  man. 

It  is  undoubtedly  true  that,  while  frogs,  turtles,  pigeons,  rabbits, 
dogs,  horses,  etc.,  agree  anatomically  in  many  respects  with  each 
other  and  man,  they  disagree  to  such  an  extent  tliat  tlie  result  of 
experiments  made  upon  one  of  these  animals  is  often  utterly  inap- 
plicable to  the  other,  and  entirely  worthless  as  applied  to  man.  In- 
deed, the  most  striking  differences  in  the  effect  of  certain  substances 
are  observed  even  in  closely  allied  animals,  varieties  of  the  same 
species.  Thus  the  black  rhinoceros  feeds  upon  the  euphorbia,  which 
poisons  the  white  species ;  goats  and  lambs  avoid  most  of  the  so- 
lanaceous  plants  ;  the  ox  and  the  rabbit  will  eat  belladonna ;  the 
goat,  the  hemlock  ;  the  horse,  aconite. 

Such  differences  should  be  always  taken  into  consideration  when 
the  results  of  a  vivisection  upon  one  animal  are  to  be  applied  to  the 
determination  of  the  function  of  a  structure  in  another.  It  must 
be  always  proved  that  the  structure  and  functions  compared  are 
homologous.  Further,  a  careful  post-mortem  examination  should 
be  always  made  after  the  vivisection,  in  order  to  learn  exactly  what 
has  been  done,  to  show  that  no  structure  has  been  involved  which 
would  modify  the  results  except  the  one  examined.  It  is  the  neg- 
lect of  such  precautions,  the  indifference  to  the  infliction  of  pain, 
the  comparing  of  utterly  milike  conditions,  the  absence  of  the  test 
of  post-mortem  examination,  the  want  of  controlling  experiments, 
and  of  comparison  of  the  results  obtained  with  the  facts  of  pathol- 
ogy and  comparative  anatomy  that  has  brought  vivisection  into  the 
disrepute  in  which  it  is  held  at  the  present  day  by  many  even  edu- 
cated persons.  Crude  generalizations,  based  upon  imperfect  ex- 
periments ])erformed  upon  animals  illogically  applied  to  man,  have 
made  even  medical  men  doubt  altogether  of  the  efficiency  of  this 
method,  and  account  for  their  sympathizing  Avith  the  Avell-meaning, 
no  doubt,  but  ill-judged  efforts  to  suppress  experimental  investiga- 
tion altogether ;  and  yet  if  vivisection  should  be  banished  from  the 
laboratory,  the  physiologist  would  be  deprived  of  his  most  fertile 
methods  of  research.  The  history  of  physiology  proves  not  only 
the  importance  of  vivisection,  but  its  indispensability  as  a  means  of 
present  research.     Indeed,  it  is  no  exaggeration  to  say  that  there 


26  IXTEODVCTIOX. 

is  not  au  organ  in  the  animal  body  Avhose  functions  have  not  been 
learned,  in  part  at  least,  by  vivisections.  Let  us  illustrate  this 
statement  by  a  few  examples. 

Consider  the  history  of  the  circulation  of  the  blood,  and  we  shall 
see  that  every  important  advance  made  in  a  knowledge  of  the 
subject  was  due  to  a  vivisection.  Thus,  Galen  demonstrated 
by  vivisection  that  the  artery  contained  blood  and  not  air,  as  its 
et^^uology  would  indicate.  It  was  by  a  vivisection  that  Harvey 
proved  that  the  blood  flowed  from  the  heart  to  the  periphery 
through  the  arteries,  and  from  the  periphery  back  to  the  heart 
through  the  veins.  Finally,  it  was  through  a  vivisection  that 
Malpighi  saw,  for  the  first  time,  the  blood  actually  flowing  from 
the  arteries  into  the  veins  through  the  intermediate  vessels,  the 
capillaries.  One  of  the  most  important  discoveries  ever  made  in 
physiology,  that  of  the  functions  of  the  roots  of  the  spinal  nerves, 
that  the  anterior  are  motor  and  the  posterior  are  sensory,  was 
demonstrated  by  Majendie  upon  a  living  animal.  The  influence  of 
the  nervous  system  upon  the  heart,  so  far  as  is  known,  has  been  en- 
tirely learned  by  the  experimental  investigations  made  upon  ani- 
mals by  the  AVebers,  Yon  Bezold,  Ludwig,  Cyon,  etc.  The  beau- 
tiful investigations  of  Bernard  upon  the  salivary  glands,  the 
l)ancreas,  the  liver,  by  means  of  vivisections,  have  demonstrated 
certain  peculiarities  in  reference  to  the  secretion  of  these  organs, 
that  could  never  have  been  learned  by  any  other  method.  By 
means  of  vivisection  Brown-Sequard  showed  the  influence  of  the 
sympathetic  nerve  in  diminishing  the  calibre  of  the  ])lood  vessels, 
and  thence  discovered  the  vasomotor  nerves,  by  which  the  distri- 
bution of  the  l:)lood  to  the  tissues  is  regulated.  It  is  needless  to 
multiply  examples  of  the  imjjortance  of  vivisection  as  a  means  of 
research,  as  nearly  every  chapter  in  this  work  will  afford  such.  It 
must  not  be  forgotten,  however,  that  vivisection  is  but  one  means 
of  physiological  research,  and  that  however  important  may  be  the 
results  obtained  by  it,  the  latter,  as  already  mentioned,  should  be 
always  compared  with  such  facts  of  comparative  anatomy  and 
pathology  as  have  a  bearing  upon  the  function  investigated,  so  that 
so  far  as  possil^le  all  sources  of  fallacy  may  1)e  eliminated. 

To  those  fjimiliar  with  the  history  of  medicine  any  argument  to 
prove  the  importance  of  the  study  of  physiology  would  be  super- 
fluous. Physiology  has  always  been,  and  is  still,  the  corner- 
stone of  medicine.  The  doctrines  of  Hippocrates,  Galen,  Syden- 
ham, Bocrhaave,  Hiniter,  and  Virchow,  reflect  as  a  mirror  the 
physiology  of  the  day.  It  is  self-evident  that  to  understand  dis- 
ease and  its  cure  one  must  first  understand  health.  The  study  of 
physiology  must  precede  that  of  pathology  and  therapeutics.  Hand 
in  hand  they  advance  together,  the  progress  of  the  one  depending 
ujion  that  of  the  other.  There  is  no  better  illustration  of  the  truth 
of  this  view  of  the  dependence  of  pathology  and  therapeutics  upon 
physiology  than  ophthalmic  medicine,  the  most  developed  and  fin- 


IXTB  OD  LX'TIOX.  2  7 

ished  of  all  Ijrauclies  of  medicine,  whose  present  perfected  condi- 
tion is  entirely  due  to  the  comparatively  thorough  understanding  of 
the  structure  and  function  of  the  healthy  eye. 

On  the  other  hand,  diseases,  like  those  of  the  nervous  system,  are 
in  a  proportionally  backward  condition  owing  to  the  imperfect 
knowledge  of  the  normal  anatomy  and  physiology  of  the  parts  in- 
volved. 

Having  deiined  the  subject  of  physiology,  considered  the  methods 
by  which  it  is  studied,  and  its  importance  to 'medicine,  it  only  re- 
mains now  in  conclusion  to  indicate,  generally,  the  order  in  which 
the  study  will  be  pursued,  and  here  nature  ^^'ill  be  our  guide.  Our 
first  sensations  are  those  of  hunoer  and  thirst — hence  the  taking"  of 
food.  We  "vdll,  therefore,  after  describing  the  general  physical  and 
chemical  structure  of  the  body,  begin  Avitli  the  study  of  digestion 
and  absorption,  the  elaboration  of  the  food  into  the  blood,  and  its 
circulation  will  be  then  described,  the  consideration  of  excretion, 
animal  heat,  completing  the  study  of  nntrition. 

But  man  is  more  than  a  vegetable,  he  feels,  thinks,  moves.  Im- 
pressions of  the  outer  world  made  upon  his  nervous  system  awaken 
in  him  consciousness,  the  inner  world  of  mind.  Through  his 
nervous  system  man  not  only  becomes  aware  of  the  existence  of  an 
environment,  but  adjusts  his  actions  with  reference  to  it.  Finally, 
though  the  individual  perishes  in  the  reproduction  of  his  kind,  the 
race,  temporarily  at  least,  survives,  hence  the  study  of  development. 
We  will  begin,  therefore,  with  the  study  of  nutritir)n,  consider  next 
the  nervous  system,  concluding  with  an  account  of  reproduction. 


CHAPTER   I. 

GENERAL  STRUCTURE  OF  THE    BODY,   PHYSICALLY 
AND   CHEMICALLY. 

Before  taking  up  the  study  of  tlio  functions,  specifically,  it  will 
be  well  to  consider,  from  a  general  point  of  view,  of  what  the  human 
body  consists,  physically  and  chemically  speaking,  to  obtain  some 
general  knowledge  of  its  organization,  of  which  the  functions  are 
the  living  expression. 

As  is  known  to  every  one,  the  human  body,  like  that  of  a  do- 
mestic animal,  is  made  up  of  skin,  muscles,  bone  ;  of  various  viscera, 
such  as  the  heart,  lungs,  liver,  stomach  ;  of  nerves,  arteries,  etc. 

The  old  anatomists  busied  themselves  almost  entirely  with  the 
description  of  such  organs,  their  number,  size,  color,  relative  posi- 
tion, etc.  This  kind  of  study  may  be  said  to  have  culminated  in 
Cuvier,  who,  as  regards  the  exactness,  extent,  and  variety  of  his 
knowledge,  stands  without  a  rival  as  an  anatomist.  If,  however, 
any  one  organ  is  examined  somewhat  closely,  it  will  be  found  to  be 
far  from  homogeneous.  Thus  the  stomach  consists  of  several  tissues, 
mucous,  fibrous,  muscular,  etc.;  the  heart,  of  muscular,  connective, 
adipose,  nervous  tissue,  etc.  Such  tissues,  combined  in  greater  or 
less  proportions,  make  up  the  different  organs  of  which  the  body  is 
composed  ;  the  same  tissue,  for  example,  the  connective,  being  found 
in  different  organs,  just  as  the  substance  wood  may  be  applied  to 
making  a  chair,  sofa,  bed,  or  bookcase  furnishing  a  room. 

The  investigation  of  the  tissues,  the  creation  of,  histology,  is  due 
to  the  genius  of  Bichat.  If  now"  any  tissue  be  studied  in  detail,  it 
(;an  be  still  further  resolved  into  simpler  ultimate  physical  elements 
or  what  are  commonly  called  cells,  or  their  modifications.  This  last 
analysis  was  made  by  Schleiden  and  Schwann.  Through  the  prog- 
ress of  organic  chemistry  it  has  also  become  possible  to  state,  with 
tolerable  accuracy,  of  what  the  body  is  composed  chemically.  When 
the  analysis  is  a  proximate  one,  the  result  gives  such  principles  as 
water,  common  salt,  salts  of  lime ;  starch,  sugar,  fat ;  albumin, 
casein,  etc.  These  principles  exist  as  such  in  the  human  body,  and 
are  called  ])roximate  principles,  b("'ing  the  result  of  a  proximate 
analysis.  If  now  these  principles  be  analyzed,  they  will  be  found 
to  consist  of  hydrogen,  oxygen,  sodium,  chlorine,  carbon,  nitrogen, 
phosphorus,  etc.  In  this  way  it  is  shown  that  the  human  body 
consists,  ultimately,  of  the  ordinary  chemical  elements.  A  human 
being  then  consists,  ultimately,  of  myriads  of  cells  composed  of  the 
ordinary  chemical  elements.  Certain  cells  form  tissues,  certain  tis- 
sues act  together  as  organs,  and  the  organs  harmoniously  working 


GENERAL  STRUCTURE  OF  THE  BODY 


29 


together  constitute  a  living,  healthy  man.  The  chemical  elements 
composing  the  cells  also  act  in  concert,  as  proximate  principles.  A 
resume  of  the  above  physical  and  chemical  facts  may  be  seen  thrown 
together  synoptically  as  follows  : 


The  Human  Body  Consists 


PHYSICALLY 

of  Organs. 
The  organs  of  tissues. 
The  tissues  of  cells. 
The  cells  of  elements. 

Examples  of  Cells. 

1.  Cells  floating  in  a  liquid  :  blood 

corpuscles,  lymph  corpuscles. 

2.  Cells  in  layers  :  epidermis,  epi- 

thelium, enamel. 

3.  Cells  in  masses  :  adipose  tissue, 

medulla  of  hair. 

4.  Cells  imbedded  in  non-cellular 

substance  :  cartilage,  bone. 

5.  Cells  forming   fusiform    bands : 

unstriated  muscular  fiber. 
G.   Cells   transformed    into   tubes  : 

capillaries,  nerves,  dentine. 
7.   Cells  transformed  into  filaments: 

fibrous  tissue,  elastic  tissue. 

A  cell  may  consist,  in  its  wall,  of 
membrane  ;  in  its  contents,  of 
liquid  and  granules  ;  in  its  ap- 
pendages, of  filaments. 


CHEMICALLY 

of  Principles. 
The  principles  of  elements. 

Proximate  principles. 

of  1st  Class. 

Water,  sodium  chloride,  calcium 
phosphate,  sodium  carbonate, 
etc. 

of  •2d  Class. 
Starch,  sugar,  oils,  fats. 

of  3cl  Class. 

Albumin,  fibrinogen,  hsemoglobin, 
etc. 

Ultimate  Elements. 

Oxygen,  hydrogen,  carbon,  nitro- 
gen, chlorine,  phosphorus,  sul- 
phur, calcium,  sodium,  potas- 
sium, magnesium,  iron,  fluor- 
ine, iodine,  silicon. 


Let  us  now  take  up  somewhat  more  in  detail  what  is  known  of 
cells  and  proximate  princi])les.  A  cell  may  be  defined  as  the  ulti- 
mate elementary  living  unit,  a  mass  of  living  matter,  varying  from 
the  Tj-i-Q  mm.  to  |-  mm.  (-^ Jg-Q-th  to  the  y^-g-th  of  an  inch)  in  diameter. 
It  may  consist  of  a  cell  wall,  inclosing  cell  contents  of  a  liquid, 
semi-liquid,  or  granular  character.  The  granules  in  some  cells  are 
united,  according  to  many  histologists,  by  filaments  or  threads  ;  the 
cell  contents  consisting  then  of  a  network.  Often  among  the  cell 
contents  can  be  distinguished  a  still  smaller  cell,  the  nucleus,  and, 
within  this,  the  nucleolus.  Sometimes  the  cell  wall  is  elongated 
into  an  appendage,  a  cilia.  Great  diflcrence  still  prevails  among 
histologists,  etc.,  as  to  the  relative  importance  of  the  nucleus  and 
nucleolus  of  the  cell  contents  and  cell  Avail. 

According  to  some  observers,  the  all  important  element  in  cell 
life  is  the  nucleus,  Avhile  others  maintain  that  it  is  the  cell  contents. 
The  cell  wall  and  even  the  nucleus  are  regarded  by  some  as  the  cell 
contents  in  a  state  of  retrograde  metamorphosis. 

As  we  proceed  in  our  studies,  it  will  be  seen  that  there  are  cells, 


30 


CELLS. 


like  the  blood  corpuscles,  which  have  neither  nucleus  nor  cell  wall ; 
Further,  there  are  protoplasmic  beings,  like  the  monera,  of  which 
the  protamoeba  (Fig.  1)  is  an  example  which,  through  life,  never 
exhibit  either  nucleus  or  cell  wall.     Such  facts  prove  that  in  certain 

cases  at  least,  neither  the  nu- 
cleus  nor  cell  wall  is  an  indis- 
pensable element  to  the  life  of 
cells,  and  should  make  physi- 
ologists cautious  in  attributing 
])Ositive  functions  to  this  or 
that  element  of  a  cell.  In- 
deed, it  cannot  be  said  that  the 

Protamaba.     (H.eckel.)  Fig.    2. 

relative  significance  of  either 
nucleus,  nucleolus,  cell  wall, 
or  cell  centents,  is  as  yet  defi- 
nitely understood.  As  ex- 
amples of  cells,  attention  may 
be  called  to  those  lining  the 
uriniferous  tubules  of  the  kid- 
ney, to  the  cells  of  the  enamel, 
to  those  of  the  epithelium  of 
the  mouth  (Fig.  2),  of  the 
columnar  epithelium  of  the 
intestine,  to  the  multipolar 
cell  found  in  nervous  tissues, 
to  the  ciliated  epithelial  cells 

from    the    pulmonarv  mucous        Buccal  and  glandular  epithelium,   with  granular 
,  /T-i.        -v\  ''         11        1     matter  and  oil-globules ;  deposited  as  sediment  from 

membrane  (1^  Ig.   ■)),    to    blood    human  saliva.     (Dalton.) 


Fig.  .S. 


Fig.  4. 


Columnar  ciliated  epithelium  cells 
from  the  human  nasal  membrane: 
magnified  300  diameters.  (Quain  and 
.Shakpky.) 

cells  (Fig.  4),  to  unstriated 
muscular  fiber  cells. 

As  we  take  up  the  differ- 
ent organs,  the  cells  com- 
posing their  tissues  will  l)e 
described   more    in    detail  ; 


Human  blood-globules,  a.  Eed  globules,  seen  flat- 
wise, h.  Red  globules,  seen  edgewise,  c.  Whit© 
globule.     (Dalton.) 


GENERAL  STUUCTUEE  OF  THE  BODY. 


31 


so  the  above   example!^  will,    therefore,    suffice  for  the  pre.sent   in 
giving  a  general  idea  of  the  form  of  cells. 

While  there  is  still  some  doubt  as  to  the  exact  use  of  the  differ- 
ent parts  of  the  cells,  there  is  no  doubt  that  the  life  of  the  organ- 
ism resides  in  the  cells  composing  it.  Among  other  reasons  for 
supjiosing  so,  may  be  mentioned  the  fact  that  the  life  of  the  human 
being  begins  as  the  ovum,  a  cell,  and  that  the  tissues  of  the  em- 
bryo, out  of  which  are  built  up  the  organs  of  the  adult,  consist  of 
modified  cells,  the  lineal  descendants  of  this  primitive  cell  or  ovum, 
and  inheriting  its  life  characteristics,  the  life  of  the  organism  being 
the  resultant  of  the  lives  of  the  individual  cells  composing  it. 

The  independent  life  of  cells  is  well  seen  in  some  of  the  lower 
animals,  whose  blood  corpuscles  can  be  observed  actually  feeding 
upon  substances  artificially  introduced  into  the  circulation,  and  in 
the  embryonic  state  can  be  observed  dividing  and  subdividing,  and 
so  reproducing  themselves.  Gland  cells,  like  those  of  the  liver, 
kidney,  etc.,  in  taking  from  the  blood  the  materials  out  of  which 
their  respective  secretions  are  elaborated,  show  their  independent 
activities.  Pathological  processes  often  present  chances  for  observ- 
ing this  independent  cell  life,  in  the  wandering  of  the  white  and 
red  blood  cells  out  of  the  vessels,  in  the  rapid  proliferation  of  cells 
seen  in  the  development  of  various  morbid  growths,  etc.  The  pro- 
tozoa and  protophyta,  or  the  simplest  of  animals  and  plants,  how- 
ever, offer  the  most  favorable  opportunities  for  observing  the  life 
history  of  cells  ;  for  these  simple  beings  never 
get  beyond  the  one-cell  stage  of  life,  indeed 
neither  tissues  nor  organs  are  ever  developed 
in  them  in  the  same  sense  that  these  are  in  the 
higher  animals.  The  entire  life  cycle  of  these 
minute  plants  and  animals  can  be  often  fol- 
lowed under  the  microscope.  The  manner  in 
which  cells  take  food,  move  about,  their  mode 
of  reproduction — usually  through  simple  di- 
vision, though  sometimes  endogenously  and 
by  gemmation  and  conjugation — can  be  readily 
observed  by  an  examination  of  the  greenish 
matter  on  damp  bricks,  stones,  etc.,  consisting 
usually  of  palmoglea,  micrococcus,  or  the  green- 
ish film-like  spirogyra  seen  covering  the  ditches 
and  ponds  in  the  neighborhood  of  the  city,  and 
which  also  usually  contain  specimens  of  uni- 
cellular protozoa  paramcecium  (Fig.  5),  stentor, 
as  w^ell  as  desmidiaceae,  of  wdiich  Fig.  6  is  an  example.  These  re- 
searches, always  interesting  to  the  mere  microsco})ist  on  account  of 
the  beauty  of  the  vegetable  and  activity  of  the  animal  forms,  have 
a  deep  meaning  to  the  philosophical  physiologist.  For  it  is  reason- 
able to  suppose  that  the  life  of  man  or  the  higher  animals,  wdien  in 
the  one-cell  or  ovum  stage  (Fig.  7),  is  similar  to  that  of  these  beings 


/ 


Paramcecium  cainlatuiii 
a,  a.  Contractile  ^(-■Kll  -  }i 
Mouth.     (Carpemiu  ) 


32 


CELLS. 


which  pass  beyond  this  uniccllukir  stage.  Hence,  avc  may  con- 
clude that  the  human  ovum,  or  any  of  the  cells  descended  from  it, 
absorbs  and  assimilates  nutriment,  like  the  unicellular  beings  just 
referred  to.  The  segmentation  of  the  egg  in  the  higher  animals 
corresponds  also  to  the  division  of  the  cell  seen  in  the  reproduction 


Fig.  6. 


Fig. 


TRT^ 


Pediastrum  pertusum. 
(Carpenter.) 


Unman  ovum,  magnified  85  diam.    a.  Vitelline  membrane 

h.  Vitellus.    c.  Germinative  vesicle,    d.  Germinative 

spot.     (Dalton.) 


of  these  minute  beings,  the  manner  in  which  the  nucleus  divides 
first  into  tAvo  halves  and  the  cell  contents  or  protoplasm  constricts 
around  the  new  nuclei  being  essentially  the  same  in  both  cases  ;  the 
only  diflFerence  Ijeing,  as  Ave  shall  see  hereafter,  that  in  the  former 


Fig.  8. 


Division  of  the  yolk  of  Ascaris.    A,  B,  C  (from  Kolliker),  ovum  of  Ascaris  nigrovenosa ;  I)  and 
E,  that  of  Ascaris  acuminata  (from  Bagge).     (Quain  and  Sharpey.) 


the  new  cells  hold  together  and  are  transformed  into  tissue,  in  the 
latter  the  new  cells  are  scattered,  constituting  the  next  generation 
of  cells.  This  distinction  may  be  seen  by  comparing  the  segmenta- 
tion of  ascaris  (Fig.  8 )  with  the  reproduction  of  protococcus  through 
continued  subdivision  (Fig.  9).  In  either  case,  however,  the  life 
of  the  resultant  cells  is  that  inherited  by  them  from  the  parent  cell. 
The  cells  resulting  from  the  segmentation  of  the  mammalian  ovum 
or  Q^^  are  at  first  very  similar,  l)ut  soon  a  marked  difierence  between 
them  can  be  ob.served.  According  to  the  researches  of  A'^an  Bene- 
den  on  the  rabbit,  the  diiference  is  noticeable  even  in  the  two  first 
segmentation  cells.  However  this  may  l)e,  the  cells  soon  begin  to 
differ  in  size,  shape,  and  the  manner  in  which  they  arc  affected  by 
chemical  agents.     Some  dispose  themselves  so  as  to  form  the  epi- 


CELLS. 


33 


blast,  others  the  hypobhist,  and  between  these  two  layers  a  third 
appears,  the  mesoblast. 

The  modification  of  the  cells  and  the  fnrther  development  of 
these  three  layers  will  be  considered  when  we  take  up  the  subject  of 
reproduction.  It  will  be  seen  then  that  throuo;]i  the  processes  in- 
cidental to  development,  cells  often  lose  their  originally  round  form, 
becoming  sometimes  flattened  or  scale-like,  and  often  of  a  prismatic 
and  columnar  shape.  Sometimes  the  cells  float  free  in  a  liquid,  like 
the  blood  corpuscles  ;  or  they  may  arrange  themselves  in  layers,  like 
those  of  the  enamel ;  or  in  masses,  as  seen  in  the  medulla  of  hairs. 
They  may  be  imbedded  in  a  solid  non-cellular  matrix,  as  in  carti- 
lage.   Cells  are  sometimes  flattened  into  bands,  as  in  the  unstriated 


Fig.  9. 


Development  of  Protococcus  pluvialis.     (Caepentek.) 

muscular  fiber,  or  a  number  are,  through  the  dissolution  of  their 
adjacent  walls,  metamorphosed  into  tubes,  of  which  the  capillaries 
and  dentine  are  examples,  or  they  may  be  converted  into  fibrous 
tissue.  These  modifications  are  shown  synoptically  arranged  in 
the  table  giving  the  physical  constituents  of  the  body.  The  va- 
rious substances  elaborated  by  cells  in  diiferent  parts  of  the  adult 
economy  will  be  more  appropriately  considered  as  the  functions  of 
the  organs  are  taken  up.  It  will  be  seen  that  the  life  of  the  body 
is,  therefore,  the  resultant  life  of  the  cells  composing  it ;  that  the 
body  is  a  living  republic  of  cells. 

Let  us  now  return  to  the  chemical  composition  of  the  body,  or  of 
the  cells  of  which  it  consists.  We  have  seen  that  the  human  body 
consists  of  chemical  elements  acting  as  proximate  principles. 

A  proximate  principle  may  be  defined  as  a  principle,  simple  or 
compound,  which  exists  and  acts  as  such  in  the  human  body. 
Thus,  sodium  chloride  is  a  proximate  principle.  Neither  the  rare 
metal  sodium,  nor  the  offensive  greenish  gas  chlorine,  however,  are 
proximate  principles,  for  they  do  not  exist  or  act  as  such  in  the 
body.  Calcium  phosphate  is  an  example  of  a  proximate  principle  ; 
but  the  metal  calcium,  and  the  phosphoric  acid,  not  existing  or  act- 
ing separately,  as  calcium  and  phosphoric  acid,  in  the  body,  cannot 

3 


34  GENERAL  STRUCTURE  OF  THE  BODY. 

be  reo^arcled  as  proximate  principles.  The  purely  analytical  chemist 
would  resolve  such  proximate  principles  as  fat,  albumin,  into  their 
ultimate  elements,  carbon,  hydrogen,  oxygen,  nitrogen,  and  sidphur 
respectively.  The  physiological  chemist,  however,  Avould  study 
these  principles  without  further  decomposition,  investigating  the 
part  that  fat  and  albumin  play  as  such  in  the  economy  without  re- 
gard to  their  ultimate  chemical  composition. 

Proximate  Principles. 

Leaving  out  of  consideration  for  the  present  the  gases,  Avhich  can 
be  more  conveniently  treated  of  under  the  subject  of  the  blood,  the 
proximate  principles  can  be  divided,  for  convenience  of  description, 
into  those  of  inorganic  and  organic  origin,  the  latter  being  further 
subdivided  into  those  in  which  nitrogen  is  absent  and  those  in  which 
it  is  present. 

Proximate  Principles  of  the  First  Class,  or  those  of 
Inorganic  Origin. 

Substances.  Where  found. 

Water  ......  Universal. 

Sodium  chloride   ....  Universal,  except  enamel. 

Sodium  sulphate  ....  Universal,  except  milk. 

Sodium  phosphate         .         .         .  Universal. 

Sodium  carbonate  .         .         .  Blood,  saliva,  lymph. 

Potassium  chloride        .         .         .  Muscles,  blood,  saliva,  gastric  juice. 

Potassium  phosphate    .         .         .  Universal. 

Potassium  sulphate       .         .         .  Bile,  gastric  juice. 

Potassium  carbonate     .         .         .  Bones,  lymph. 

Calcium  chloride  ....  Bones. 

Calcium  fluoride  ....  Bones,  dentine,  enamel. 

Calcium  sulphate  .  .  .  Blood,  feces. 

Calcium  phosphate        .         .         .  Universal. 

Calcium  carbonate         .         .         .  Bones,  teeth,  cartilage. 

Magnesium  phosphate  .         .         .  Blood,  bone,  muscle. 

Iron Blood,  bile,  feces. 

Silicic  acid Hair,  urine. 

Iodine Thyroid  body. 

As  implied  in  the  definition,  tlic  principk's  of  this  class  are  in- 
organic in  origin,  being  found  in  the  rocks  forming  the  crust  of  the 
earth,  in  sea  water,  springs,  etc.,  and  are  crystallizable.  With  the 
exception  of  calcium  carbonate,  of  which  the  otoliths  of  the  ear  con- 
sist, they  are  combined  in  the  body  with  the  organic  principles. 
This  union  is  so  intimate  that  as  the  organic  principles  become 
effete,  and  are  eliminated,  the  inorganic  substances  are  cast  out  with 
them.  Some  of  these  substances  play  a  more  important  role  than 
others,  and  are  found  in  greater  or  less  quantities  in  the  economy. 

Let  us  consider  no^v  the  most  important  of  these  substances, 
where  they  occur,  and  their  principal  uses. 

Water,  H^O. — In  the  maintenance  of  life,  none  of  the  proximate 
principles,    Avhether  inorganic   or   organic,    surpass   in   importance 


WATER. 


35 


water.  When  it  is  learned,  liowever,  that  it  constitute.s  nearly  ()8 
per  cent,  by  weight  of  the  whole  body,  this  will  no  longer  be  a  snb- 
ject  of  surprise.  In  the  course  of  our  studies  wa  shall  find  that 
water  exists  in  all  parts  of  the  body  :  in  solids,  like  bone  and 
enamel  ;  in  fluids,  like  the  tears,  perspiration,  etc.  Its  uses  in  the 
economy  are  manifold.  It  gives  consistence  and  general  resiliency 
to  the  body,  pliability  to  tendons,  elasticity  to  cartilage,  resistance 
to  the  bones.  Various  substances,  like  articles  of  food  and  the 
effete  matters,  find  their  way  into  and  out  of  the  body  through  their 
solubility  in  water.  The  importance  of  water  is  at  once  seen  if  the 
system  is  deprived  of  it.  The  tissues  become  shrivelled  and  dried 
up  and  inflexible,  the  liquids  become  thick,  inspissated,  lose  their 
fluidity.  On  the  other  hand,  an  excess  of  water  gives  rise  to 
general  del)ility,  muscular  Aveakness,  dropsies,  etc. 

In  the  living  body  water  exists  as  "  water  of  composition  " — that 
is,  it  constitutes  an  integral  part  of  the  tissues.  The  water  is  not 
taken  up  by  the  tissues,  like  a  sponge,  but  really  forms  a  part  of 
its  substance,  the  union  l)eing  a  chemical  one. 


Ql'axtity  of  Water.' 


Substance. 

Enamel 

Epithelium 

Teeth 

Bones 

Tendons 

Cartilages  . 

Skin  . 

Liver . 

Muscles 

Ligaments  . 

Blood 


Parts  per  1000. 

2 

\         '.  37 

.  100 

.  130 

.  500 

.  550 

.  575 

.  618 

.  725 

.  768 

.  780 


Substance. 

Milk  . 
Chyle  . 
Bile 

Urine  . 
Lymph  . 
Saliva  . 
Gastric  juice  . 
Perspiration  . 
Tears  . 
Pulmonary  vapor 


Parts 


per  1000. 

.  887 

.  904 

.  905 

.  933 

.  960 

.  983 

.  984 

.  986 

.  990 

.  997 


The  relative  amount  of  water,  in  the  tissues,  is  regulated  by  the 
salts.  Thus,  when  water  is  added  to  the  blood,  the  corpuscles  be- 
come swollen,  and  finally  are  dissolved  away  ;  but  if  a  strong  solu- 
tion of  salt  be  added  instead,  the  corpuscles  lose  their  water  and 
shrivel  up.  Most  of  the  water  found  in  the  system  is  taken  in  as 
part  of  the  solid  and  fluid  articles  of  the  food.  As  we  shall  see 
hereafter,  however,  about  300  grammes  (4629  grains)  are  formed 
in  the  system  throuo-h  combustion  of  hvdroo-en.-  The  dailv  amount 
of  water  necessary  for  the  healthy  adult  is  estimated,  b}'  Dalton,^ 
at  about  2  kil.  (4.4  lbs.).  This,  of  course,  includes  the  water  en- 
tering into  the  solid  articles  of  food.  About  fifty-two  per  cent, 
of  the  water,  after  it  has  played  its  part  in  the  economy,  is  dis- 
charged by  the  skin  and  lungs,  the  rest  by  the  kidneys  and  with 
the  feces.     When,  however,  the  skin  is  not  active,  as  in  the  winter 

1  Robin  et  Yerdeil,  op.  cit. ,  p.  1 15. 

2  Dalton,  Phvsiologv,  1882,  p.  37. 
3 Op.  cit.,  p.  36. 


36  GENERAL  STBUCTURE  OF  THE  BODY. 

time,  then  the  kidneys  act  very  freely ;  in  the  summer  the  reverse 
is  the  case.  Diuretics  favor  the  one  set  of  emunctories,  diaphoretics 
the  other, 

Bv  o;kincino;  at  the  Table  it  may  be  seen  how  universally  water 
is  found  in  the  tissues,  and  its  relative  amount.  Thus,  while  we 
find  that  a  thousand  parts  of  pulmonary  vapor  contain  nine  hun- 
dred and  ninety -seven  parts  of  water,  it  Avill  be  seen  there  are  only 
two  parts  of  water  in  a  thousand  of  enamel,  and  that  a  substance, 
like  tendon,  so  different  from  either  of  those  just  mentioned,  is  half 
made  up  of  water.  The  great  importance  of  water  in  health,  and 
still  more  in  disease,  cannot  be  too  much  dwelt  u})on  by  the  physi- 
ologist and  practising  physician. 

Salts  of  Sodium. 

Sodium  Chloride,  XaCl, — Next  to  water,  common  salt  is  the  most 
important  of  the  inorganic  proximate  principles,  being  found,  like 
water,  almost  universally,  even  in  the  ovum.  With  the  exception 
of  the  enamel,  in  which  it  has  not  yet  been  discovered,  salt  is  found 
in  all  the  solids  and  fluids  of  the  body.  The  absolute  amount,  how- 
ever, has  not  yet  been  determined.  The  saltish  taste  of  the  tears 
and  ]>erspiration  is  due  to  the  presence  of  this  principle.  It  is 
found  in  the  largest  proportion  in  fluids. 

Quantity  of  Sodium  Chloride/ 

Substauce.  Parts  per  1000.     Substance.  Parts  per  1000. 

Blood 6.04  Saliva         ....     1.5 

Chyle    .....     5.3  Perspiration       .         ,         ,     3.4 

Lymph           ,         .         .         .4.1  Urine         ....     4.4 

Milk 0.8  Feces         .         .         .         .3.0 

Salt  is  introduced  into  the  system  through  the  different  articles 
of  animal  and  vegetable  food  which  always  contain  it ;  in  addition, 
salt  as  such  is  added  to  the  food  of  man  and  the  herbivora ;  the 
amount  contained  in  their  food  not  being  sufficient  for  the  wants 
of  the  economy.  Salt,  like  all  other  inorganic  principles,  passes 
ultimately  through  the  body,  and  is  carried  out  of  it  in  the  urine, 
feces,  perspiration,  etc. 

Recent  experiments  -  have  shown  that  the  excretion  of  sodium 
chloride  does  not  depend  simply  on  the  amount  ingested,  since  in 
some  cases  the  sodium  chloride  excreted  was  much  greater  for  sev- 
eral days  than  that  taken  as  food,  the  excess  being  supplied  by  the 
tissues. 

The  uses  of  salt  in  the  system  are  manifold.  Disintegration  of 
the  red  blood  corpuscles  is  prevented  through  the  presence  of 
salt.     A  solution  of  sodium  chloride  having  a  strength  of  0.6  per 

iK()l)in  et  Verdeil,  op.  cit.,  p.  76. 

2  Klein  und  \'eiTon,  Sitzungsbericlite  der  Wiener  Academie  ]S[ath.-Phv.s.  Klasse, 
1807,  s.  627. 


SALTS.  37 

cent.,  the  amount  in  which  it  is  present  in  the  blood,  is  often  called 
the  "  physiological  salt  solution  "  and  is  said  to  be  "  isotonic  "  to 
the  red  corpuscles  since  the  latter  retain  their  form  and  coloring 
matter  in  the  same.  The  phenomena  of  osmosis,  or  the  passage  of 
fluids  and  gases  through  animal  membranes,  are  greatly  modi- 
lied  by  the  amount  of  salt  present,  a  solution  of  salt  osmosing 
through  a  membrane  much  less  readily  than  pure  water.  Absorp- 
tion is  influenced  by  it.  It  increases  the  solubility  of  albumin  ; 
this  substance  lieing  less  quickly  coagulated  l\v  heat  in  a  solution 
of  sodium  chloride  than  in  water.  From  sodium  chloride  is  derived 
the  hydrochloric  acid  of  the  gastric  juice.  Salt  is  of  great  use  as  a 
condiment,  it  being  imp()ssil)le  to  support  life  on  food  without 
flavor,  however  good  the  latter  may  be  in  quantity  or  (|uality. 
Nutrition  is  undoubtedly  afl'ected  in  other  ways  by  salt,  as  yet  not 
perfectly  understood.  The  experiments  of  Boussingault  ^  upon 
bullocks,  and  of  Dailly  ^  upon  sheep,  showed  what  a  deleterious  ef- 
fect was  produced  in  their  general  appearance  when  these  animals 
were  deprived  of  salt.  It  is  well  known  how  the  wild  buflalo  is 
found  by  the  salt  licks  of  the  Xorthwest,  and  how  the  hunter  in 
Southern  Africa  avails  himself  of  his  knowledge  of  the  habits  of 
wild  animals  collecting  near  salt  springs,  to  kill  his  game.  Every 
one  is  familiar  with  the  fact  of  how  cattle  run  to  any  one  who  will 
give  them  salt.  It  is  said  that  fugitives  from  justice  will  often  risk 
capture  and  their  lives  to  obtain  salt.  Facts  like  the  above  show 
what  a  deep-seated  want  is  felt  1)y  man  and  beast  alike  when  de- 
prived of  salt. 

Sodium  Sulphate  (Xa.,SO^),  connnonly  called  Glauber  salts,  is 
found  in  the  blood  and  other  fluids  of  the  body.  It  is  introduced 
into  the  system  with  food  and  discharged  together  with  potassium 
sulphate  in  the  urine  in  the  condition  which  we  shall  see  hereafter 
is  known  as  "preformed  sulphuric  acid."  The  diarrhoea  that  sul- 
phate of  sodium  gives  rise  to  wlien  administered  in  purgative  doses 
is  probably  due  to  the  epithelial  cells  of  the  intestine  being  aflected 
in  such  a  manner  by  this,  as  by  other  laxatives,  as  to  prevent  the 
absorption  of  water.  Sodium  phosphate  exists  in  the  fluids  of  the 
economy,  the  blood  for  example,  both  as  monosodium  phosphate 
(XaH.,PO^)  and  disodium  phosphate  (Xa^HPO^).  These  salts  are 
taken  into  the  body  as  food  and  are  discharged  in  the  feces  and 
urine.  The  acidity  of  the  urine,  as  will  be  shown  when  that  excre- 
tion is  considered,  is  principally  due  to  the  monosodium  or  ])rimary 
acid  phosphate  (XaH.,PO^).  The  latter  osmoses  or  passes  through 
membranes  more  readily  than  the  disodium  or  secondary  sodium 
phosphate.  Sodium  carbonate  (XaCO^)  is  found  in  the  blood, 
lymph,  saliva,  pancreatic,  intestinal  juices,  etc.  It  is  ])roduced 
within  the  bodv  bv  the  oxidati(m  of  organic  sodium  salts,  or  is  in- 
troduced with  the  food.    To  the  existence  of  this  salt  the  alkalinity 

'  Chimie  Agricole,  p.  271.     Paris,  1834. 

2  Longet :  Traite  <le  Physiologie,  tome  i. ,  p.  76. 


.38  GENERAL  STRUCTURE  OF  THE  BODY. 

of  the  economy  is  principally  clue.  Its  importance  may  be  appre- 
ciated from  the  fact  that  carbon  dioxide  will  not  pass  from  the 
tissues  in  acidified  blood  and  that  death  can  be  prevented  in  an 
animal,  whose  blood  has  been  acidified  by  feedino;  with  acid,  by 
venous  injection  of  sodium  carbonate.  Through  reaction  with  the 
carbon  dioxide  given  by  the  tissues  to  the  blood  the  sodium  car- 
bonate, in  presence  of  water,  liecomes  sodium  bicarbonate  or  acid 
carbonate  (XaHCO,). 

■      Na^CO,  +  CO.^  +  H^O  =  XaHC03  +  NaHCO^ 

Through  the  further  action  of  acids  both  carbonates  give  up  their 
carbon  dioxide.  The  carbon  dioxide  set  free  is  usually  regarded 
as  being  of  advantage  mechanically  to  the  economy,  the  particles 
of  the  chyme,  for  example,  being  separated  ])y  it  and  rendered  more 
susceptible  to  the  action  of  the  intestiual  juice  in  the  same  manner 
as  we  shall  see  the  digestion  of  fi^od  by  gastric  juice  is  promoted 
by  previous  admixture  Avith  saliva. 

Salts  of  Potassium. 

Potassium  Chloride,  KCl. — This  principle  is  found  in  the  muscles, 
blood,  saliva,  ])ile,  gastric  juice,  urine,  etc.  A  greater  part  of  it  is 
introduced  into  the  systeui  witli  the  food,  though  probably  some  is 
])roduccd  through  the  double  decomposition  of  the  potassium  phos- 
phate and  sodium  chloride  existing  in  the  blood,  sodium  phosphate 
and  jiotassium  chloride  resulting. 

KH^PO^  +  NaCl  =  NaH^PO^  +  KCl 

The  uses  of  potassium  chloride  and  sodium  chloride  are  probably 
the  same  in  the  economy.  This  })rinciple  is  discharged  from  the 
body  in  tlie  nuicus  and  the  urine. 

Potassium  ])]iosphate  is  found  in  small  (juantities  in  the  solids 
and  fiuids  of  tlic  body,  generally  existing  both  in  the  form  of  mono- 
j)otassium  phosphate  (IvH.,POJ  and  the  dipotassium  phosphate 
(K^HPO^).  The  potassium  phosphates  are  introduced  into  the 
l^ody  with  tlie  food  and  are  discharged  in  the  feces  and  urine. 
Their  function  in  the  economy  ap})ears  to  be  associated  with  the 
activity  of  protoplasm  in  general,  they  constituting  the  principal 
salts  of  the  cells  of  the  body.  The  monopotassium  phosphate  or 
the  so-called  ])rimary  phosphate  contributes  to  the  acidity  of  the 
urine,  and  is  also  the  cause  of  tlie  acidity  exhil)ited  by  muscle 
during  the  coudition  known  as  rigor  mortis. 

Potassium  Sulphate  (K.,80,)  exists  in  small  cjuautities  in  the 
blood,  etc.  It  is  introduced  into  the  body  in  the  food,  and  dis- 
charged in  the  feces  and  urine. 

Potassium  Carbonate  is  found  in  small  quantities  in  tlie  blood, 
lymph,  and  other  ])arts  of  the  body,  both  in  the  form  of  acid  car- 
bonate (KHCO.j)  and  of  nentral  carbonate  (K^CO.,).  These  salts 
are  introduced  to  a   great  extent  into  the  economy  Avith  food,  and 


SALTS.  39 

when  excreted  in  the  nrine  in  sufficient  quantity  render  it  alkaline. 
The  acid  carbonate;  appears  to  be  produced  within  the  body,  espe- 
cially in  the  blood  corpuscles  and  the  plasma,  through  the  action  of 
carbon  dioxide  and  water  upon  di})otassium  phosphate,  the  latter 
being  transformed  at  the  same  time  into  the  monopotassium  salt  as 
follows  : 

K^HPO^  +  CO^  +  H^  =  KHCO3  +  KH^PO, 

The  neutral  carbonate  may  also  be  produced  within  the  liody  through 
the  oxidation  of  an  organic  salt  of  potassium,  such  as  the  tartrate 

K^C^H^^  +  0,0  =  K^C03  +  3C0^  +  H^O 

Experiments  made  in  the  laboratory  render  it  highly  prol^able  that 
potassium  carbonate  and  sodium  chloride  react  upon  each  other  in 
the  body,  the  double  decomposition  supposed  to  take  place  giv- 
ing rise  respectively  to  sodium  carbonate  and  potassium  chloride 
(K^CO,  +  2NaCl  =  2KC1  +  Na^COg).  Inasmuch  as  both  these 
substances  are  excreted  in  the  urine,  it  is  evident  that  food  rich  in 
potassium  salts,  like  potatoes  when  eaten,  entail  a  loss  of  sodium 
chloride  to  the  economy.  Hence  the  necessity,  in  order  to  make 
good  this  loss,  of  adding  salt  to  the  food,  when  the  latter  is  largely 
of  a  vegetable  character.  On  the  other  hand,  if  the  diet  consists 
principally  of  rice,  relatively  ]ioor  in  potassium  salts,  the  use  of 
salt  can  be,  to  a  great  extent,  dispensed  with.  Salt  is  not  used,  as 
a  general  rule,  in  cases  where  the  food  consists  solely  of  fish  and 
meat,  the  blood  of  the  animals  eaten  supplying  the  sodium  salts. ^ 

Salts  of  Calcium. 

Calcium  chloride  (CaCl.,)  occurs  in  small  quantities  in  bones  and 
calcium  fluoride  (CaFl.,)  in  bone,  dentine  and  enamel.  Difference  of 
opinion  still  prevails  among  chemists  as  to  the  manner  in  which  the 
mineral  substances  of  bone  are  combined  with  each  other.  Chlo- 
rine and  fluorine  appear  to  be  present^  in  the  same  form  as  in  the 
mineral  a[)atite  (CaFl,,  SCa^P^OJ.  Calcium  sulphate  (CaSOJ  is 
also  found  in  bone  in  small  quantities.  It  is  often  introduced  into 
the  economy  through  the  use  of  spring  and  well  water  in  which  it 
is  present.  It  is  discharged  from  the  body  in  the  feces,  being  occa- 
sionally found  in  the  sediment  of  strongly  acid  urine. 

Tricalcium  Phosphate,  Ca.^P.,Oj,. — This  very  important  substance 
is  found  in  all  the  solids  and  fluids  of  the  body.  It  ^\ill  be  seen, 
however,  that  calcium  phosphate  exists  in  much  larger  proportions 
in  the  solids  than  in  the  fluids.  Only  traces  are  found  in  blood, 
saliva,  etc.,  whereas  a  thousand  parts  of  enamel  will  contain  nearly 
nine  hundred  parts  of  this  principle. 

'Bunge,  Lehrbiicli  tier  Plivsiologischen  und  Pathologisclien  Cliemie,  Dritte  Auf., 
1894,  s.  108-116. 

^Oloj  Hamniai-sten  :  A  Text  Book  of  Physiological  Chemistrv.  Translated  by 
.John  A.  Mandel,  1893,  p.  2.38. 


40  GENERAL  STRUCTURE  OF  THE  BODY, 

Quantity  of  Calcium  Phosphate/ 


Substance. 

Parts  per  1000. 

Substance.                                         Parts  per  1000. 

Blood  . 

.       0.7 

Teeth  of  infant         .         .     510.0 

Milk   . 

.       2.5 

Teeth  of  adult          .         .     610.0 

Saliva . 

.       0.6 

Teeth  of  man  at  81  years     660.0 

Urine  . 

.     25.0 

Enamel    ....     885.0 

Excrements 

.     40.0 

Rachitic  bone  .         .         .     136.0 

Bone    . 

.  400.0 

Calcium  phosphate  is  introduced  into  the  system  in  the  food  and 
is  eliminated  in  the  urine  and  feces,  being  continuously  excreted  into 
the  intestinal  canal. 

Calcium  phosphate,  although  insolul)le  in  Avater,  is  held  in  solu- 
tion in  blood,  milk,  etc.  In  the  case  of  blood  it  is  difficult  to  ex- 
plain this  unless  the  salt  is  in  combination  ^\\t\\  the  proteids  of  the 
blood  as  it  is  with  the  casein  of  milk,  and  with  the  protoplasm  of  the 
cell. 

Calcium  phosphate  is  ftjiuid  in  a  sedimentary  condition  in  the 
urine,  but  only  after  the  latter  becomes  alkaline.  Under  these  cir- 
cumstances it  is  derived  from  the  acid  phosphates,  calcium  phos- 
phate occurring  in  the  urine  as  primarv  (CaH^(PO^).,)  and  secondarv 
(CaHPO;)  phosphates. 

Calcium  phosphate  exists  in  a  solid  condition,  bones,  teeth,  carti- 
lage, etc.  Tlie  calcium  phosphate  in  a  bone  can  be  all  dissolved 
out  by  hydrochloric  acid  ;  such  a  bone  retains  its  form,  but  if  it  be 
the  fibula,  is  so  pliable  that  it  can  be  tied  in  a  knot,  a  good  illustra- 
tion of  the  importance  of  this  salt  to  the  system.  On  the  other 
hand,  after  complete  calcination  of  bone  which  destroys  its  organic 
substance,  the  ossein,  there  remains  the  so-called  bone  earth,  consist- 
ing of  calcium  and  phosphoric  acid.  The  use  of  calcium  phosphate 
in  the  economy  is  to  give  strengtli  and  solidity.  Hence  the  large 
amount  present  in  the  bones,  and  more  especially  in  the  enamel, 
the  hardest  of  all  known  organic  substances.  It  is  very  abundant 
in  the  lower  extremities,  which  support  the  weight  of  the  body. 
The  ribs  contain  less  calcium  phosphate  than  the  upper  extremities, 
hence  their  greater  elasticity. 

The  amount  of  calcium  phosphate  found  in  any  organ  or  tissue 
differs  often  according  to  age ;  thus  it  will  be  observed  that  in  the 
teeth  of  a  very  old  man,  in  a  thousand  parts  there  are  one  liundred 
and  fifty  parts  more  than  in  an  infant,  and  fifty  more  than  in  an 
adult.  The  liability  of  pregnant  women  to  meet  with  fractures, 
and  the  delay  of  union  in  these  cases,  are  due  to  their  offspring 
taking  from  the  mother  so  much  calcium  phosphate,  essential  to 
the  development  of  the  new  being. 

In  recent  years  it  has  been  sho\\m  that  the  salts  of  calcium  play 
an  important  part  in  the  phenomena  of  coagulation.  Indeed,  in 
their  absence,  as  we  shall  see,  blood  will  not  coagulate.  If  animals 
be  deprived  of  their  proper  amount  of  calcium  salts  their  bones 

^  Robin  et  Verdeil,  op.  cit.,  p.  287. 


SALTS.  41 

will  soften,  as  shown  by  the  experiments  of  Chossat/  Voit/  and 
Wecske.^  Rickets  is  generally  held  to  be  due  to  a  deficiency  in 
the  calcium  salts  of  the  food.  Recent  experiments  *  show,  however, 
that  rickets  M'ill  persist  in  children,  even  when  the  food  contains 
the  normal  quantity  of  this  salt.  The  disease  may  be  due,  there- 
fore, not  so  much  to  a  deficiency  of  calcium  phosphate  as  to  some 
want  of  assimilation. 

Neutral  Calcium  Carbonate,  CaCO.j. — This  principle  is  found  in 
the  blood,  teeth,  cartilage,  and  bones.  In  the  latter  it  is  not  as 
abundant  as  the  phosphate,  but  exists  in  the  proj^ortion  of  a  hun- 
dred parts  to  the  tliousand. 

Quantity  of  Calcium  Carbonate." 

Substance.  Parts  per  1000. 

Bone 102.0 

Teeth  of  infant 140.0 

Teeth  of  adult 100.0 

Teeth  of  man  at  eighty-one  years    ....  10.0 

As  before  mentioned,  calcium  carljonate  is  the  only  inorganic 
principle  which  exists  in  a  crystalline  form  and  uncombined  in 
the  body.  As  such,  it  is  found  in  the  otoliths  of  the  internal 
ear.  Calcium  carljonate  appears  to  exist  in  bone  in  the  form  of 
apatite  (CaFl.,3(Ca3P„0^)),  the  CO^  occupying,  however,  in  bone 
(CaC033(Ca,P,OJ)  tlie  position  of  Fl,  in  the  mineral. 

Calcium  carbonate  is  found  in  the  food,  and  is  introduced  in  this 
form  into  the  system.  It  passes  out  of  the  body  in  the  urine, 
probably  transformed  into  the  phosphate.  The  uses  of  calcium 
carbonate  in  the  economy  are  essentially  the  same  as  those  of  cal- 
cium phosphate. 

Neutral  calcium  carbonate,  although  insoluble  in  water  alone,  be- 
comes soluble  in  the  presence  of  water  and  carbon  dioxide,  being 
transformed,  however,  through  the  reaction  into  the  acid  carbonate, 
CaC03  -fH.O.  -f  CO,  =  CaH,(C03),.  In  the  latter  form  as  a  sol- 
uble acid  salt,  calcium  carbonate  occurs  in  the  blood,  lymph,  pancre- 
atic juice  and  in  small  quantities  in  the  tissues  generally.  The  cal- 
cium carbonate  of  the  saliva,  together  with  bacteria  and  organic 
matter  constitute  the  so-called  tartar  of  the  teeth. 

Salts  of  Magnesium. 

Magnesium,  wherever  present,  is  always  associated  with  calcium 
as  tertiary  magnesium  phosphate  (Mg.,(POJ3).  It  is  found  in  the 
blood,  muscle,  and  bone,  constituting  one  per  cent,  of  the  ash  of  the 
latter.     Magnesium  phosphate  is  introduced  into  the  system  with 

'  Recherches  experimentales  fsur  r  Inanation,  1843,  p.  28. 
2  Hermann,  Handbuch,  1881,  Band  vi.,  1,  s.  379. 
"Zeitschrift  fiir  Biologic,  1894,  Band  31,  s.  421. 

*Eudel,  Arcliiv  fiir  experimental  Patholoffie  und  Pliarniakologie,  1893,  Band 
33,  s.  90. 

^Roljin  et  Verdeil,  op.  eit..  p.  223. 


42  GENERAL  STRUCTURE  OF  THE  BODY. 

the  food  and,  being  excreted  by  the  walls  of  the  alimentary  canal 
and  kidneys,  passes  out  of  the  body  in  the  feces  and  urine,  occurring 
in  the  latter  as  primary  and  secondary  phosphate.  During  the 
ammoniacal  fermentation  of  the  urine  magnesium  is  precipitated  as 
ammoniiun  magnesium  phosphate  (ISIgNH^PO^). 

The  importance  of  this  salt  as  well  as  that  of  ammonium  sodium 
phosphate  and  of  ammonium  carbonate  will  be  considered  hereafter. 

Iron. 

Iron  is  found  either  in  combination  with  other  chemical  elements 
or  with  organic  substances  throughout  the  economy.  As  ferric 
phosphate  (FePO^)  it  occurs  in  the  gastric  juice,  bile.  In  the  form 
of  ferrous  sulphide  (FeS)  it  is  found  in  the  feces.  In  the  liver  and 
spleen  it  exists  as  ferratin  and  hepatin,  and  in  the  urine  also  as  an 
organic  compound.  It  enters  into  the  composition  of  haemoglobin, 
and,  as  we  shall  see,  is  one  of  its  most  important  ingredients. 
According  to  recent  obseryations  ^  it  is  only  organic  iron,  such  as 
found  in  the  yolk  of  eggs  as  hiematogen,  and  in  plants  in  the  form 
of  nucleo-albumins  containing  iron,  that  is  absorbed  by  the  system, 
inorganic  iron  being  unal)sorbable.  Ferric  chloride  is,  however,  of 
benefit  to  the  economy  when  administered  internally,  since,  being 
converted  into  ferrous  sulphide  by  the  action  of  sulphuretted  hy- 
drogen, 

Fe^Cl,  +  2H^S  =  2FeS  +  4HC1  +  CI.. 

the  organic  iron  of  the  system  amounting  to  about  4  grammes 
(61.7  grains)  may  l)c  protected  from  a  similar  transformation  with 
subsequent  elimination.  The  importance  of  iron  to  the  economy  is 
shown  by  the  fact  that  when  deficient  in  the  food  the  organic  iron 
of  the  system  is  drawn  upon  to  make  good  the  deficiency.  Thus 
for  example  ^  in  the  case  of  a  dog  in  which  the  iron  in  the  food 
amounted  to  0.9-3  grammes  (14.34  grains)  that  of  the  feces  for  the 
corresponding  period  was  as  much  as  3.59  grammes  (55.39  grains), 
the  difference,  2.66  grammes  (41.05  grains),  being  supplied  at  the 
expense  of  the  organic  iron  of  the  body. 

Silicon. — This  substance  occurs  as  silicic  acid  (H^SiO^)  in  hair 
and  the  urine.  It  is  introduced  into  the  economy  in  the  food,  being 
found  in  the  yolk  of  eggs,  and  vegetables. 

Iodine  is  found  as  thyroiodin  in  the  thyroid  gland. 

^Bunge,  Zeitsclirift  fiir  physiologische  Chemie,  1885,  Band  9,  s.  40.  Marfori, 
Archiv  fiir  exper.  Pathologie  und  Pharmakologie,  1892,  Band  29,  s.  212. 
Schmiedeberg,  Archiv  fiir  exper.  Patholdgie  und  Pharmakologie,  1894,  Band  .33, 
s.  101. 

2  Volt,  Hermann,  Tlandhnch,  Band  vl.,  Erstel  Theii,  s.  385. 


CHAPTER    II. 

PROXIMATE  PRINCIPLES  OF  ORGANIC  ORIGIN. 

As  has  been  already  stated,  in  addition  to  the  inorganic  proxi- 
mate principles  the  human  body  contains  many  of  organic  origin, 
that  is  of  principles  elaborated  by  organized  l)odies,  plants,  and 
animals.  It  is  well  known,  however,  that  many  of  these  principles 
have  been  prepared  in  the  laboratory  from  inorganic  elements  by 
chemists  without  invoking  the  aid  of  a  so-called  "  vital  force  "  and 
there  is  every  reason  to  suppose  that  in  time  they  will  all  be.  Such 
being  the  case  the  distinction  between  bodies  of  inorganic  and 
organic  origin  regarded  at  one  time  as  so  essential  is  without  j)hil- 
osophical  significance,  and  is  only  made  use  of  in  this  connection  as 
a  matter  of  convenience. 

Principles  of  Organic  Origin. 

Proximate  Principles  of  the  Second  Class. 
Nitrogen  Absent. 


Substances. 

Where  fuuiul. 

Sugar    ..... 

.       Milk. 

Starch  ..... 

Brain. 

liactic  acid    .... 

Small  intestine 

Oxalic  acid  .... 

Urine. 

luosite  ..... 

.     Muscles. 

Fat 

.     Almost  universally 

Proximate  Principles  of  the  Third  Class. 
Nitrogen  Present. 


Substauces. 

Serum  albumin 

Fibrinogen    . 

Haemoglobin 

Mucin  . 

Casein  . 

Keratin 

Sodium  taurocholate 

Cystein 

Lecithin 

Xanthin 

Indol     . 

Pepsin 


Where  found. 

Blood. 

Blood. 

Blood  corpuscles. 

Mucus. 

Milk. 

Nails. 

Bile. 

L'rine. 

Nervous  sj^stem. 

Urine. 

Feces. 

Gastric  juice. 


These  principles,  as  shown  by  the  table,  may  be  divided,  for 
convenience  of  description,  into  two  classes  :  one  in  which  nitrogen 
is  absent,  the  proximate  principles  of  the  second  class,  and  one  in 


44  PROXIMATE  PRINCIPLES  OF  ORGANIC  ORIGIN. 

which  that  element  is  present,  the  proximate  principles  of  the  third 
class.'     The  former  will  be  first  considered. 

Proximate  Principles  of  the  Second  Class,  or  non-Nitrogenous 
Principles  of  Organic  Origin. — These  principles  include  the  sugars, 
starch,  fats.  They  do  not  enter  into  the  constitution  of  the  mineral 
world  like  sodium  chloride,  calcium  phosphate,  etc.,  just  considered, 
being  ordinarily  produced,  at  least  by  plants  and  animals.  In  strik- 
ing contrast  also  with  the  principles  of  the  first  class,  those  of  the 
second  class,  with  the  exception  of  the  butter  and  sugar  of  milk, 
are  never  discharged  as  such  from  the  body  in  a  state  of  health. 
Sugar  in  the  urine,  for  example,  is  a  symptom  of  diabetes  ;  fat  in  the 
feces,  of  disease  of  the  pancreas.  The  principles  of  the  second  class, 
with  the  exception  of  starch,  are,  however,  crystallizable,  agreeing 
in  this  respect  Avith  those  of  the  first  class. 

Composition  of 

AVater H^    O 

Grape  sugar      .......  C^  H^,  O^ 

Cane  sugar C   H  ^  O^^ 

Starch ^^I'^.o  O.s 

Lactic  acid        .         .         .         .         .         .         .  C3  H^    O^ 

luosite (-\  H^„  O^' 

Steariu  (fat) C^^H^^^O^ 

It  will  be  observed  that  sugar,  starch,  lactic  acid,  and  inosite 
differ  from  fat  in  that  the  hydrogen  present  in  the  former  sub- 
stances just  suffices,  with  the  oxygen,  to  form  water,  whereas  in 
neutral  fats  the  hydrogen  is  in  excess.  It  might  naturally  be  sup- 
posed that  the  former  substances  would  form  a  natural  group  and 
the  fats  another.  Chemically  speaking,  however,  the  sugars  and 
starch  are  regarded  as  constituting  one  group,  carbohydrates ;  lactic 
acid  as  an  oxy-fatty  acid,  and  inosite  as  a  member  of  the  aromatic 
series.  Let  us  begin  our  study  of  these  principles  with  the  carbo- 
hydrates. 

A  carbohydrate  is  a  substance  which  consists  of  carbon,  hydrogen, 
and  oxygen,  the  atoms  of  carlion  varying  in  number,  the  atoms  of 
hydrogen  and  oxygen  in  the  j^roportion  to  form  water.  The  carbo- 
hydrates are  divided  into  three  distinct  groups  :  glycoses,  disaccha- 
rides,  polysaccharides,  of  which  grape  sugar,  cane  sugar,  and  starch 
are  respectively  familiar  examples.  Glycoses  include  siicii  substances 
as  glycerose,  made  up  of  the  tryoses,  glycerin  aldehyde,  and  dioxy- 
acetone,  erythrose  (C^Hj^^Oj,  as  well  as  the  monosaccliaridcs,  glucose, 

'  It  is  to  lie  undei-stood  tliat  tlie  above  division,  however  useful  for  purposes  of 
description,  is  an  artificial  one,  not  based  upon  chemical  relationship,  since  nitrog- 
enous substances  occur  in  the  body,  which  may  be  derived  from  non-nitrogenous 
ones,  and  rice  versa..  Thus,  for  exam]ile,  as  we  shall  see  hereafter,  Urea,  a  nitrog- 
enous substance,  regarded  a.s  carliamide,  is  carbon  dioxide,  in  wliicli  one  atom  of 
oxygen  is  replaced  by  the  residue  of  two  molecules  of  ammonia.  On  the  other 
liand,  bodies,  like  fats,  non-nitrogenous  substances,  may  Ijc  dci-ivcd  from  proteid 
nitrogenized  ones. 


GALACTOSE.  4o 

galactose,  and  levulose.  The  latter,  while  consisting  chemically  of 
C^Hj,Og,  differ  from  each  other  in  their  atomic  arrangement.  It 
will  te  observetl  that  in  the  glycoses  the  number  of  carlx>n  atoms 
is  the  same  as  that  of  the  oxygen  atoms.  It  may  be  appropriately 
mentionetl,  also,  in  this  connection,  that,  according  to  the  numlx-r 
of  carbon  atoms  present  in  a  glycose,  the  latter  is  called  a  triose 
(glvcerose),  tetrose,  hexose  (monosaccharides),  nonose.  Glucose  and 
galactose  are  usually  regarded  as  l^eing  the  aldoses  of  the  hexatomic 
alcohols,  sorbite  and  dulcite,  respectively  :  that  is,  as  having  the 
constitution  of  an  aldehyde  alcohol  (CHlOH)CHO).  Aldehyde  is 
alcohol  ^  dehydrogenated  and  is  produced  l:»y  the  aetii ju  of  oxygen 
upon  alcohol 

Alcohol.       Oxygen.     Aldehyde.  Water. 

C^H^O   T-   b   =  C,H,0   -f   H^O 

Galactose  is  f« jund  in  the  brain,  combined  with  proteid  in  the 
form  of  the  glucoside  -  cerebrin.  It  is  produced  in  the  economy 
through  the  hydrolytic  decomposition  of  milk  sugar,  glucose  being 
produced  at  the  same  time.  Levulose,  d-fructose.  fruit  sugar,  foimd 
in  fruits  and  honey,  is  produced  in  the  body  through  the  decom- 
position of  cane  sugar  and  is  transformed  into  glucose.  Levu- 
lose, being  the  ketose  of  mannite.  is  therefore  a  ketone  alcohol'^ 
(COCHpH). 

The  disaccharides,  cane  sugar,  milk  sugar,  and  maltose  are.  as 
their  name  implies,  dimultiple  sugars,  each  consisting  of  C..,H^Ojj, 
but  differing  in  their  atomic  arrangement.  Saccharose  cane  sugar 
is  obtained  from  the  cane  beet  root.  We  shall  see  hereafter  that 
cane  sugar  is  converted  or  inverted  into  glucose  and  levulose  by  the 
hydrochloric  acid  of  the  gastric  juice  and  intestinal  ferment.  On 
this  account  cane  sugar,  when  eaten,  becomes  indirectly  a  source 
of  glycogen. 

Dextrose,  d-ghicose.  or  grape  sugar  ( C^H^.^O^),  is  found  in  the  blood 
and  tissues  of  the  body  to  an  extent  of  about  0.5  per  cent.  It  is 
derived,  as  we  shall  see  hereafter,  from  the  digestion  of  starch, 
cane  sugar,  the  decomposition  of  proteid,  the  dehydration  of  gly- 
cogen. A  convenient  and  delicate  test  for  grape  sug-ar  is  the 
well-known  one  of  Trommer.  It  is  made  in  the  follo^^'ing 
manner  :  The  suspected  liquid  is  placed  in  a  test-tube  ;  to  this 
are  added  one  or  two  drops  of  sulphate  of  copj^er ;  then  the 
mixture    is   made  distinctly  alkaline    by  the  addition  of  a    solu- 

'  Aldehyde  1  CH3CHO1  being  alcohol  1  CH^OH  dehvdrogenated.  an  aldehyde 
alcohol  is  a  substance  containing  the  groups  CHO  and  OH.  characteristic  of  alde- 
hydes and  alcohol  respectively. 

*A  glucoside  i?  a  substance  which,  in  the  presence  of  water  and  a  ferment,  yields 
glucose,  etc.     Thus  for  example, 

Amvgdaliii.         Water.        Benzoic  aldehyde.      Hydrocyanic  acid.      Glucose. 
C.^H2;XOii-2(H,0)    =   C\HsO  '       -  '      Cks'     -^     ^CgHiA 

'A  ketone,  a^,  for  example,  acetone  (CHjCOCHj  ),  being  characterized  by  contain- 
ing the  group  CO,  a  ketone  alcohol  is  a  substance  containing  the  groups  CO  and 
OH,  characteristic  of  a  ketone  and  alcohol. 


46  PROXIMATE  PRINCIPLES  OF  ORGANIC  ORIGIN. 

tion  of  caustic  potash.  The  mixture  will  become  blue,  particu- 
larly if  sugar  is  preseut.  Now  heat  the  test-tube  till  just  before 
boiling  point,  when,  if  sugar  is  present,  a  reddish  precipitate  will 
appear  just  in  the  upper  part  of  the  tube,  and  will  gradually  be 
seen  in  the  whole  liquid.  The  reaction  is  due  to  the  cupric  oxide 
being  reduced  to  the  condition  of  a  cuprous  oxide  by  the  oxidation 
of  the  sugar.  The  solution  to  be  examined  should  be  clear.  This 
can  be  accomplished  by  boiling  the  suspected  tissue,  finely  divided, 
with  water  and  sulphate  of  soda  and  filtering.  The  organic  and 
coloring  matters  will  be  retained,  and  a  clear  extract  will  pass 
through,  the  soda  not  interfering  with  the  test.  Maltose  and  lac- 
tose respond  to  Trommer's  test.  Cane,  maple,  and  beet  sugar, 
however,  must  be  boiled  with  very  weak  sulphuric  acid  to  convert 
them  into  glucose  before  the  test  will  be  applicable.  There  are 
substances  in  the  healthy  urine  which  interfere  with  the  reaction  in 
the  reduction  of  the  copper,  though  sugar  be  added  in  considerable 
quantity.  Of  course,  this  does  not  apply  to  diabetic  urine.  Al- 
buminose,  which,  as  we  shall  see  hereafter,  is  produced  during  gas- 
tric digestion,  interferes  also  with  Trommer's  test,  as  noted  by 
Longet,  though  Dalton  j^ointed  out  first  the  fact  of  the  products 
of  stomach  digestion  having  this  curious  effect.  With  the  above 
qualifications,  Trommer's  test  is  very  reliable  and  easily  applied. 
Other  tests,  such  as  those  of  Moore,  Barreswil,  Maumerie,  Bott- 
ger,  Fehling,  the  fermentation  test,  and  that  of  torulse,  etc.,  are 
also  used. 

Lactose,  milk  sug-ar,  so-called  on  account  of  it  being  found  in 
milk,  occurs  also  in  the  amniotic  fluid  of  the  foetus,  in  the  urine  in 
the  last  days  of  pregnancy  and  first  days  of  lactation.  Milk  sugar 
is  produced  in  the  economy  in  the  mammary  glands  probably  at  the 
expense  of  glucose,  as  it  does  not  occur  in  the  blood.  According 
to  some  chemists  it  is  converted  in  the  system  into  dextrose  and 
galactose.  In  all  prol)ability,  however,  it  is  absorbed  as  such  un- 
changed. Milk  sugar,  under  the  influence  of  a  ferment,  readily  be- 
comes lactic  acid,  which  in  time  causes  the  souring  and  clotting  of 
milk,  the  change  taking  place  in  the  alimentary  canal  as  well  as  out 
of  it. 

The  remaining  disaccharide,  maltose  (Cj.,H.,„Oj,),  is  produced  in  the 
economy,  together  \vith  dextrin  and  glucose,  in  varying  amounts, 
by  the  action  of  the  saliva,  pancreatic  and  intestinal  juices  upon 
starch,  all  of  the  maltose  and  dextrin  being  finally  transformed, 
however,  into  glucose.  Sugar  is  produced  within  the  system  as  we 
have  seen  by  the  liver,  mammary  glands,  etc.  The  greater  part  of 
the  sugar  found  in  the  economy  is  introduced,  however,  cither  in 
the  form  of  fruit,  cane,  or  milk  sugar,  or  is  derived  as  we  just 
mentioned  from  starch. 


SUGAR.  -i^ 


Quantity  of  Sugar  in  100  Parts  in 

Cherries  .         .         .  .18.12  Goats'  milk  . 

Juice  of  sugar  cane  .     18.00  Cows'  milk    . 

Apricots  .         .         .  .16.48  Indian  corn-meal 

Peaches   .                   .  .11.61  Eye  flour 

Pears        .         .         .  .11.52  Barley  meal  . 

Sweat  potatoes         .  .     10.20  "Wheat  flour  . 

Beet  roots         .         .  .       8.00  Oatmeal 

Parsnips            .         .  .4.50  Beef's  liver   . 


5.80 
5.20 
3.71 
3.46 
3.04 
2.33 
2.19 
1.79 


The  exact  manner  in  which  sugar  is  elaborated  by  plants  can  not 
be  said  as  yet  to  have  been  definitely  established.  Recent  re- 
searches ^  render  it  highly  probable,  however,  that  the  first  stage  in 
the  production  of  sugar  by  plants  consists  in  the  production  of 
formic  aldehyde  through  the  reduction  of  carbonic  acid  by  the 
action  of  sunlight  upon  the  chlorophyll  of  the  leaves,  the  reaction 
being  as  folloAvs, 

Carbonic  acid.     Formic  aklehyde.     Oxygen. 

H  CO,    =     HC.HO    +     6, 

2  3  '  ,; 

Xow  it  is  well  known  that  formic  aldehyde  ^  when  produced 
synthetically  in  the  laboratory  can  be  transformed  by  appropriate 
means  first  into  paraformic  aldehyde  and  then  into  formose,  a  form 
of  sugar.^  It  is  quite  possible  therefore  that  the  formic  aldehyde 
produced  in  the  plant  passes  through  similar  stages,  becoming  ulti- 
mately perhaps  starch  or  cellulose. 

With  the  exception  of  the  i)laccs  mentioned  sugar  does  not  occur 
in  the  economy,  being  oxidized  as  rapidly  as  produced,  it  passes  out 
of  the  system  as  carbon  dioxide  and  water. 

Glucose.  Oxvgen.    Carbon  dioxide.        Water. 

CaH,,0,   -h   120    =    6(C0,)    -f    6(HP) 

Sugar,  through  its  combustion,  is  therefore  one  great  source  of 
heat.  Its  uses  in  this  respect  will  be  considered,  however,  more 
particularly  when  the  subject  of  animal  heat  is  taken  up. 

The  polysaccharides,  or  tliird  kind  of  carbohydrates,  includes 
such  substances  as  starch,  dextrin,  glycogen,  etc.,  and  consist  chem- 
ically of  some  multiple  of  C^Hj^Og.  In  the  case  of  starch,  this 
multiple  being  taken  as  3,  its  chemical  composition  is  expressed  by 
the  formula  (CgHj^O.).,. 

Although  not  crystallizable,  starch  is  far  from  being  an  amor- 
phous powder,  it  consisting,  as  found  in  the  potato,  for  example 
(Fig.   10),  of  well  marked,   laminated  granules  of  definite   form. 

^Dalton,  op.  cit.,  p.  54. 

^Eoinke,  Berichteder  deutschen  chemischen  Gesellscliaft,  1881,  Band  14,  s.   2144. 

Tormie  aldehyde  beai-s  to  methyl  alcohol  the  same  relation  that  aldehyde  beai-s 
to  alcohol,  that  is  to  say  it  is  methyl  alcohol  dehydrogenated.  It  is  usually  ob- 
tained by  the  slow  combustion  of  metliyl  alcohol  brought  about  by  an  ignited  spiral 
of  platinum  wire,  the  reaction  being  as  follows, 

Metbvl  alcohol.     Oxygen.     Formic  aldehyde.     Water. 

CH,0     +      6      =        C'lI.O "  4-    H.,0 
*  Baer,  Berichte  der  deutschen  chemischen  Gesellschaft,  1870,  Band  3,  s.  67. 


48 


PROXIMATE  PlilNCIPLES  OF  ORGANIC  ORIGIN. 


The  so-called  corpora  amylacea  found  in  the  brain,  and  formerly 
considered  as  being  of  the  nature  of  starch,  as  their  name  implies 
are  no  longer  regarded  by  chemists  ^  as  carbohydrates. 

Starch  exists  abundantly  in  corn,  wheat,  oats,  rice,  potatoes,  and 
indeed  in  almost  all  vegetable  food.  Tapioca,  arrowroot,  etc.,  so 
useful  as  articles  of  diet,  under  certain  circumstances,  are  varieties 
of  starch. 

Fig.  10. 


drains  of  potato  starch. 

Quantity  of  Starch  in  100  Parts  in 


Eice  . 

.     88.65 

Peas 

37.30 

Indian  corn 

.     67.55 

Beans 

33.00 

Barley 

.     66.43 

Flaxseed  . 

23.40 

Oats  . 

.     60.59 

Potatoes    . 

20.00 

Rye  . 

.     64.65 

Sweet  potatoes 

16.05 

Wheat 

.     57.88 

Chocolate 

11.00 

Starch  may  be  produced  from  sugar,  and  under  the  influence  of 
solar  heat  from  plants  by  a  process  of  deoxidation  from  carbonic 
acid  as  shown  by  the  following  formula  : 

Carbonic  acid.     Oxvgen.      Starch.  Water. 

eH.CO,  —  120  =  C,H,„0,  +  H^O 

The  principle  of  the  development  of  starch  through  the  deoxida- 
tion of  carbonic  acid  may  be  roughly  illustrated  in  the  following 
manner  :  A  bunch  of  fresh  mint  being  placed  within  a  cylindrical 
tube  containing  dilute  carbonic  acid  water  standing  over  the  pneu- 
matic trough  is  exjiosed  to  sunlight.  Soon  the  leaves  of  the  mint 
will  be  seen  covered  with  minute  beads  of  gas,  a  small  quantity  of 
the  latter  accumulating  at  the  top  of  the  cylindrical  tube.  By  with- 
drawing the  mint  and  passing  up  a  few  bubbles  of  nitric  oxide,  a 


1  Hoppe  Seyler,  1881,  Phj's.  Chemie,  s.  689. 


'Dalton,  op.  cit.,  \}.  57. 


STARCH.  49 

dark  brown  vapor  will  appear  at  the  top  of  the  tube,  proving  that 
the  contained  gas  was  oxygen.  Starch  is  insoluble  in  cold  water, 
but  bv  boiling  the  granules  are  liquefied,  and,  on  cooling,  remain 
fused  together  as  a  whitish,  oxaline,  homogeneous  mass.  In  this 
condition,  it  is  said  to  be  "  hydrated."  The  most  important  prop- 
erty of  starch  for  the  physiologist,  however,  is  the  readiness  with 
w^hich  it  is  converted  into  one  or  more  forms  of  sugar.  Thus,  if 
human  saliva  be  added  to  boiled  starch  and  the  mixture  be  main- 
tained at  a  temperature  of  100°  F.,  in  a  short  time  it  will  be  con- 
verted into  maltose,  dextrose,  and  some  little  glucose. 

Starch  in  its  transformation  into  maltose  passes  through  the  in- 
termediate stages  of  amylodextrin,  erythrodextrin,  achrodextrin, 
and  isomaltose,  the  latter  being  isomeric  with  maltose.  Maltose,  be- 
ing unabsorbable,  is  finally  converted  into  glucose,  and  in  this  form 
of  sugar  appears,  as  already  mentioned,  in  the  blood.  Inasmuch  as 
starch  is  finally  transformed  into  glucose,  and  as  the  latter  is  com- 
pletely oxidized,  starch,  like  sugar,  is  a  source  of  energy,  indeed  a 
most  important  one,  since  one-half  of  our  food,  as  we  shall  see,  con- 
sists of  starch.  Glycogen,  or  animal  starch  (CgHj^O.),  may  be  re- 
garded functionally  as  so  much  stored  glucose,  to  be  drawn  upon 
by  the  economy  in  time  of  need,  glycogen  being  readily  converted 
by  hydration  into  the  more  combustible  and  diffusible  glucose, 

Glycogen.  Water.         Glucose. 

C.H^A  +  HP^C^H^A 

That  such  is  the  case  is  shown  by  the  fact  of  the  entire  disap- 
pearance of  glycogen  from  the  body  in  starvation,  it  being  trans- 
formed into  glucose  to  make  good  the  deficiency  of  the  latter  in  the 
blood.  The  significance  of  glycogen  from  this  point  of  view  is 
further  shown  by  its  conversion  into  glucose  by  muscular  work. 
One-half  of  the  glycogen  of  the  body  is  probably  found  in  muscles, 
the  remaining  half  in  the  liver.  Indeed,  as  much  as  40  per  cent, 
of  the  dry  solids  of  the  latter  organ  may  consist  of  glycogen.  The 
glycogen  of  the  economy  is  derived  from  the  carbohydrates  and  the 
glucose  of  decomposed  proteid,  100  parts  of  the  latter  yielding  45.08 
parts  of  glucose.^  Glycogen,  so  far  as  it  is  affected  by  the  action  of 
diastatic  ferment,  does  not  appear  to  differ  from  vegetable  starch. 
Glycuronic  acid,  or  d-glucuronic  acid  (C^H^^jO.),  allied  chemically  to 
starch  and  dextrin,  occurs  in  the  urine  after  the  administration  of 
camphor,  turpentine,  chloral,  hydrate,  etc.,  in  a  state  of  combination 
with  the  latter.  It  may  be  obtained  by  the  reduction  of  saccharic 
acid  with  nascent  hydrogen.  Glycuronic  acid,  wdiile  resembling 
glucose  in  reducing  alkaline  copper  solution  and  in  rotating  polar- 
ized light  to  the  right,  differs  from  it  in  not  being  fermentable  with 
yeast.      Lactic  acid,  or  ethidene  lactic  acid  (CgH^.O.J,  is  a  diatomic, 

^  Weintraud  u.  Laves,  Zeitsclirift  fiir  plivsiolosjisclie  Cliemie,  1894,  Baud  19,  s. 
632. 


50  PROXIMATE  PRINCIPLES  OF  ORGANIC  ORIGIN. 

monobasic/  oxy-fatty  acid.  Lactic  acid  is  often  called  "  fermenta- 
tion lactic  acid  "  on  acconnt  of  being  developed  throngh  the  fer- 
mentation of  the  carbohydrates,  the  reaction  consisting  in  the  split- 
ting of  the  glucose  molecule, 

Glucose.  Lactic  acid. 

C  H   O  =  2C  H  O 

6  12        6  3         6        3 

A  familiar  example  of  such  fermentation  is  the  souring  of  milk, 
which  depends  upon  the  lactic  fermentation  of  milk  sugar.  Recent 
experiments  render  it  probable,  however,  that  lactic  acid  is  pro- 
duced, to  a  certain  extent,  at  least,  from  proteid  as  Avell  as  from 
carbohydrates.  When  absorbed  lactic  acid  appears  to  be  completely 
oxidized.  Lactic  acid  is  inactive  to  polarized  light,  it  consisting  of 
two  acids,  right  ethidene  lactic  acid  rotating  the  plane  of  polariza- 
tion to  the  right,  left  ethidene  lactic  acid  rotating  it  to  the  left, 
the  two  acids  neutralizing  each  other  therefore  in  this  respect. 
Owing  to  the  fact,  however,  of  the  left  ethidene  lactic  acid  being 
destroyed  by  penicillium  glaucum  when  lactic  acid,  as  such,  is  al- 
lowed to  stand  with  that  fungus,  a  means  is  afforded  of  obtaining 
the  right  ethidene  lactic  acid  alone,  or  at  least  in  sufficient  quantity 
to  rotate  the  plane  of  polarization  to  the  right.  It  is  in  the  latter 
form  that  lactic  acid,  called  also  sarco  and  para  lactic  acid,  occurs 
in  the  blood  muscle  and  elsewhere  in  the  system.  It  is  this  acid  to 
which  is  due  the  formation  of  KII.,POj,  which  causes  the  coagula- 
tion and  acidity  of  muscle  when  the  latter  passes  into  the  condition 
known  as  rigor  mortis. 

Among  the  diatomic  dibasic  acids "  that  occur  in  the  system  may 
be  mentioned  oxalic  and  succinic  acids.  Oxalic  acid  (C2ll.,0^)  is 
found  in  the  urine  and  appears  to  be  derived  from  the  oxalates  of 
the  food  rather  than  from  the  metabolism  of  the  tissues  of  the  body; 
at  least  recent  observations  ^  show  that,  upon  a  diet  of  meat  alone 
or  of  meat,  fat,  and  sugar,  no  oxalates  are  found  in  the  urine.  Oxalic 
acid,  in  the  form  of  calcium  oxalate,  gives  rise  to  one  form  of  stone 
in  the  bladder  and  to  the  urinary  sediments  arising  during  acid  and 
also  alkaline  fermentation.     Succinic  acid  (C^HgOJ,  found  in  the 

rCH^OH 

^  Lactic  acid  \  CHj         is  said  to  be  diatomic  because  it  is  derived  from  a  diatomic 
(  COOH 

r  CH.,oii 

alcohol,  propvlglvcol  \  i'Yi^         bv  the  substitution  of  one  atom  of  oxvgen  for  two 

iciLOII 
atoms  of  hydrogen,  but  monobasic,  one  atom  of  hydrogen  only  of  the  acid  being  re- 
placeable by  a  monad  element. 

2  Oxalic  acid  <  r 'oQyr    is  a  diatomic  acid  because  it  is  derived  from  a  diatomic 

alcohol,  glycol,     ^  r'H^OIT    ^'^   ^^®  substitution  of  two  atoms  of   oxygen  for  four 

atoms  of  hydrogen  in  the  latter,  and  dibasic,  two  atoms  of  the  hydrogen  of  the  acid 
being  replaceable  by  two  monadic  elements. 

''Bunge,  Lehrbuch  Der  Physiologischen  und  Pathologischen  Cliemie,  1894,  s.  340. 


FAT.  51 

spleen,  th^Toid,  and   thymns,  appears  t<3  be   derived   from   proteid 
putrefaction  and  alcoholic  fermentation. 

Inosite,  though  consisting  of  carbon,  hydrogen,  and  oxygen,  and 
the  two  latter  elements  existing  in  the  proportion  to  form  water,  is 
neither  a  carbohydrate  nor  an  oxy-fatty  acid,  l»ut  a  member  of  the 
aromatic  series,  beino- hexa-hvdroxvbenzol  (C.H.(OH).).  It  occurs 
in  the  body  in  the  brain,  miLscle,  liver,  lungs,  spleen,  suprarenal 
capsules,  testicles,  and  in  the  vegetable  kingdom  in  beans  and  un- 
ripe peas.  Xothing  is  known  as  to  its  origin.  AVhen  introduced 
into  the  system  inosite  appears  to  be  oxidized.  Phenol  oxybenzol  ^ 
(CgH.OH),  commonly  called  carbohc  acid,  though  an  antiseptic 
itself,  is  developed  normally  in  the  intestine  as  one  of  the  products 
of  the  putrefaction  of  proteid,  probably  of  tyrosin.  Phenol  as  such, 
or  in  the  form  of  the  dioxy  benzols,  pyrocatechin,  hydroquinone, 
appears  in  the  urine,  together  A\-ith  p-cresol,  p-ox^-phenyl-acetic, 
and  p-hydrocumaric  acids,  benzol  derivatives,  in  the  form  of  alka- 
line ethereal  sulphates.  Benzoic  acid  is  an  interesting  member  of 
the  aromatic  group,  since,  when  introduced  into  the  svstem,  it  com- 
bines \^'ith  glycocoll  to  form  liip})uric  acid,  the  reaction  being  as 
follows  : 

Benzoic  acid.  Glycocoll.  Hippuric  acid.  Water. 

C^HX'OOH  -  XH^CHXOOH  =  XH(C^H3C0)CHX'00H  +  H,0 

The  consideration  of  t\'rosin,  indol,  and  skatol,  will  be  deferred 
until  the  proximate  principles  of  the  third  class  are  taken  up,  as 
these  substances,  although  aromatic  in  nature,  contain  nitrogen. 

Fat. — Fat  is  an  almost  universal  constituent  of  the  body ;  it  is 
absent,  however,  in  the  bones,  teeth,  the  eyelids,  and  scrotum,  elastic 
and  mielastic  fibrous  tissue.  It  is  always  present,  even  in  extreme 
cases  of  emaciation,  in  the  orbit,  and  aroimd  the  kidneys. 

Quantity  of  Fat  ix  100  Parts  of  Tissue.' 

Sweat  ....     0.001  Liver           ....       2.4 

Saliva  .         .         .         .0.02  Muscles       .         .         .         .3.3 

Lymph  ....     0.05         Hair 4.2 

Chyle  .         .         .         .0.2  Milk 4.3 

Mucus  ....     0.3  Cortex  of  brain    .         .         .       8.0 

Blood  ....     0.4  Medulla      .         .         .         .20.0 

Cartilage  .         .         .         .1.3  Xerves         .          .         .         .22.1 

Bone  ....     1.4  Spinal  cord          .         .          .     23  6 

Crystalline  lens            .         .     2.0  Adipose  tissue     .  .         .82.7 

The  amount  of  fat  as  just  shown  varies  very  considerably  in  the 
tissues  ;  thus,  while  in  the  sweat,  lymph,  saliva,  etc.,  there  is  a  mere 
trace  of  fat,  more  than  twenty  per  cent,  is  found  in  the  nervous 
system,  and  over  eighty  in  adipose  tissue.  The  whole  amoimt  of 
fat,  according  to  Burdach,^  in  the  body  of  a  man   weighing   80 

'Benzol  (CgHg)  being  the  so-caUed  nucleus  and  OH  the  lateral  chain. 

2  Carpenter,  Phvsiology,  1881,  p.  88. 

'Traite  de  Phvsiologie,  Tome  viii.,  p.  80.     Paris,  1857. 


52  PBOXIMATE  PRIXCIPLES  OF  ORGJXIC  0 BIG IX. 

kilograms  (176  pounds)  was  4  kilograms  (8.8  pounds),  or  5.2  parts 
of  fat  to  every  100  of  body. 

Fat  exists  in  the  adipose  tissue,  for  example,  in  the  form  of  vesi- 
cles which  are  transparent  and  contain  the  oily  matters. 

Fat  consists  of  a  mixture  of  the  principle  known  to  chemists  as 
stearin,  palmitin,  and  olein.  The  first  two  are  solid  at  the  temper- 
ature of  the  body,  but  are  held  in  solution  by  the  olein.  They 
crystallize  (Fig.  11)  in  needle-like  forms,  assuming  a  beautiful  radi- 

FlG.    11. 


stearin  crystallized  from  a  warm  solution  in  olein.'  UDaltox.) 

atory  or  arborescent  appearance,  where  fluid,  fatty,  oily  substances 
under  the  microscojie  have  the  appearance  of  round  globules,  bright 
in  the  center,  and  dark  at  the  edges.  AVith  the  exception  of  the 
pho-pliorized  fat  of  nervous  tissues,  fat  does  not  exist  combined 
with  the  other  proximate  principles,  as  we  found  was  the  case 
\N-ith  the  inorganic  principles  and  the  sugars ;  there  is  no  such  mo- 
lecular union  of  fat  with  any  principle.  There  is  no  difficulty, 
therefore,  in  extracting  it  from  the  system  in  a  state  of  purity. 
Pressure  is  often  the  only  process  needed,  the  oil  Ijeing  squeezed 
out  of  the  interstices  of  the  tissues  of  the  organ  containing  it. 

Fats,  chemically  speaking,  are  glycerides  or  ethers  of  glycerin, 
that  is,  glycerin  in  which  three  atoms  of  hydrogen  are  replaceable 
by  the  residues  of  three  molecules  of  a  fatty  acid.  Thus,  for  ex- 
ample, stearin  (C^II.(C^^H,.0.,)^),  a  form  of  neutral  fat  is  glycerin, 

fOH  ' 

CjH.    ^  OH ,   in  Mhich  the  three  atoms  of  hvdrogen  in  the  three 

I  OH 
hydroxyl  groups  are  replaced  Ijy  the  residues  of  three  molecules  of 
stearic  acid  (C^^H^O.^),  thus 

C3H3   •  OC,^U^^O  =  stearin. 


FAT.  53 

In  the  case  of  olein,  C,H^(C,,H3,0,),,  and  palmitin,  C,H^(C,,H3P,),, 
the  three  atoms  of  hydrogen  in  glycerin  are  repkiced  by  the  residues 
of  three  molecules  of  oleic  acidjCj^Hg^.,,  and  palmitic  acid,  CjgH3202. 
Such  being  the  constitution,  chemically,  of  neutral  fats,  it  be- 
comes intelligible  why  stearin,  for  example,  in  the  presence  of  vapor 
of  water  heated  to  572°  F.,  takes  up  water,  and  splits  into  glycerin 
and  stearic  acid,  as  follows  : 

Tristearin.  Water.         Glvcerin.         Stearic  acid. 

The  action  of  alkali,  soda,  for  example,  upon  stearin,  is  another 
example  of  this  process,  the  stearin  splitting  up  into  glycerin  and 
stearic  acid,  the  latter  combining  with  the  sodium  to  form  sodium 
stearate  or  soap,  as  follows  : 

stearin.  Soda.  Glycerin.  Sodium  stearate. 

2(C,,H^,„0J  +  6NaOH  =  2(C3H^03)  +  GXaC^^H^^^ 

Saponification,  as  the  splitting  of  a  neutral  fat  into  glycerin  and 
fatty  acid  is  called,  whether  alkali  be  present  or  absent,  is  brought 
about  in  the  system  by  tlie  action  of  the  steapsin  of  the  pancreatic 
juice  upon  fat.  It  is  a  most  important  function,  since  the  neutral 
fat  is  emulsified  by  the  soap  so  formed,  that  is,  subdivided  into  mi- 
nute particles,  thereby  rendering  it  absorbable.  In  a  similar  man- 
ner oleic  acid,  sodium  oleate,  and  other  fatty  acids  and  soaps  are 
formed  in  the  system.  The  odor  of  the  axilla  and  feet  is  probably 
due  to  the  presence  of  fatty  acids.  It  is  an  interesting  fact  that, 
after  feeding  an  animal  with  a  fatty  acid,  the  chyle  will  be  found  to 
contain  a  considerable  amount  of  neutral  fat,  showing  that  a  syn- 
thesis the  reverse  of  saponification  takes  place,  that  is  to  say,  the 
fatty  acid,  fed  combines  with  the  glycerin  of  the  body,  three  mole- 
cules of  water  being  lost  to  form  neutral  flit.^  In  this  connection 
it  may  be  mentioned  that  there  are  other  monatomic,  monobasic," 
fatty  acids  occurring  in  the  body,  to  be  referred  to  hereafter,  such  as 
formic,  propionic,  butyric,  and  caproic  acids. 

iMunk,  Yirchow  Archiv,  1880,  Bd.  80,  _s._17. 

2  A  monatomic  acid  is  so  called  because  it  is  derived  from  a  monatomic  alcohol. 
Acetic  acid  (C'.^H^O.,),  for  example,  being  derived  from  alcohol  (C.JIgO)  among 
other  wavs  bv  oxidation,  as  follows  : 


Alcohol.          Oxygen. 

Acetic  acid.           Water. 

C^HgO  4-      0, 

=   C^HA     +     H.,0 

Acetic  acid  is  a  monobasic  acid,  one  atom  of  hydrogen  being  replaceable  by  a  monad 
element,  as  in  the  formation  of  potassium  acetate,  according  to  the  following  reac- 
tion : 

Acetic  acid.       Pota.ssic  hydrate.      Potassium  acetate.       Water. 
C2H,02     +        KOH       •=      KC^HjO.,       +  H,0 

What  has  just  been  said  of  acetic  acid  is  applicable  to  the  remaining  fatty  acids,  they 
all  having  the  constitution  chemically  of  a  hydrocarbon  group  tinited  with  COoII. 


Chocolate  nut 

.  49.00 

Salmon 

Sweet  alinouds    . 

.   24.28 

Cows'  milk 

Indian  corn 

.     8.80 

Beans 

Fowls'  eggs 

.     7.00 

Wheat 

Mackerel     . 

.     6.76 

Peas   . 

Calf's  liver 

.     5.58 

Oysters 

Beef's  flesh 

.     5.19 

Potatoes 

54  PROXIMATE  FRINCIPLES  OF  ORGANIC  ORIGIN. 

Quantity  of  Fat  in  100  Parts  of  Food.' 

.  4.85 

.  3.70 

.  2.50 

.  2.10 

.  2.10 

.  1.51 

.  0.11 

Tlie  fat  of  the  body  may  1)0  derived  possibly  to  some  extent  from 
the  fat  of  the  food.  Recent  experiments  render  it  improbable,  how- 
ever, that  such  is  the  case.  Even  were  it  so,  more  fat  is  produced  in 
the  system  than  can  be  accounted  for  l^y  the  fat  in  the  food.  The 
experiments  of  Persoz,  Boussino;ault,  Thomson,  Lawes,  Gilbert,  and 
others  ujjon  geese,  ducks,  pigs,  cows,  etc,  with  reference  to  tliis  point 
are  conclusive.  In  the  case  of  a  cow,  for  example,  under  the  observa- 
tion of  Voit,  it  was  shown  that,  of  the  2024  grammes  (72  ounces) 
of  fat  in  the  milk,  only  1658  grammes  (59  ounces)  could  have  been 
derived  from  the  fat  of  the  feed.  It  is  evident,  therefore,  that  the 
fat  obtained  in  such  cases  must  have  been  derived  from  either  the 
carbohydrate  or  proteid  material  of  the  food.  It  has  been  proved, 
however,  by  experiments  made  upon  dogs,^  for  example,  fed  upon 
sugar,  starch,  and  fat,  that  the  fat  produced  could  not  have  been 
derived  from  the  proteid,  but  from  the  carbohydrate  material  of  the 
food.  Further,  such  facts  as  the  starch  of  plants  becoming  oil,  of 
sugar  being  readily  transformed  into  alcohol  and  fatty  acids,  of  car- 
bohydrate principles  constituting  a  part  of  a  fattening  diet,  there 
can  be  no  doubt  tliat  the  fat  produced  in  the  economy  is,  under  cer- 
tain circumstances,  largely  derived  from  the  carl)ohydrates  present 
in  the  food.  On  the  other  hand,  it  is  a  matter  of  every -day  obser- 
vation that  animals  are  best  fattened  on  a  feed  consisting  of  proteid 
as  well  as  of  car))oliydrate  food  stuifs,  which  renders  it  probable 
that  fat  may  l)e  derived  from  proteid,  as  well  as  carbohydrate  })rin- 
ciples.  Indeed,  as  shown  by  Pettenkofer  and  Voit,'^  so  far  from  the 
fat  produced  in  the  body  being  proportional  to  the  carbohydrate  in- 
gested, which  ought  to  be  the  case  upon  the  supposition  that  fot  is 
derived  from  the  latter,  the  fat  deposited  is  proportional  to  the 
amount  of  proteid  destroyed.  Thus,  for  examjjle,  in  experiments 
made  upon  dogs  fed  with  starch,  although  the  amount  of  the  latter 
given  was  much  greater  in  one  animal  than  the  other,  the  amount 
of  flit  deposited  was  nevertheless  in  each  animal  about  the  same, 
showing  that  the  fat  coiikl  not  have  Ijcen  derived  from  tlie  starch, 
but  from  the  proteid  destroyed.  This  becomes  intelligible  if  w^e 
suppose  that  the  starch,  after  conversion  into  sugar  in  tlie  economy, 
is  oxidized  and  leaves  the  system  as  carbon  dioxide  and  water,  and 

'  Pavc'ii,  from  Dalton,  (>]).  cit.,  p.  (>'!. 
2Riil)iK'r,  Zeits.  fiii- Biolo^ie,  Band  22,  1880,  s.  272. 

■■'Zeits.  fiir  Biol()f,^ie,  Band  ix.,  s.  435,  1873.  Hermann,  Phvsiologie,  Sechster 
Band,  s.  252,  1881. 


FAT.  55 

that  of  the  proteid  of  the  body  decomposed,  the  non-nitrogenous 
part  is  retained  within  the  economy  as  fat,  the  nitrogenous  elimi- 
nated as  urea.  In  further  confirmation  of  this  view  it  was  also 
shown  by  Pettenkofer  and  Yoit '  that,  in  the  case  of  dogs  fattened 
upon  a  meat  diet,  the  fat  was  derived  from  the  proteid  of  the  food, 
rather  than  from  that  of  the  body  as  in  the  previous  experiments, 
but  in  the  same  manner.  Apart  from  experimental  evidence,  such 
as  that  just  mentioned,  there  are  a  nimiber  of  general  facts  which 
confirm  the  view  that  fat  may  be  derived  from  proteid  as,  for  ex- 
ample, the  fatty  degeneration  of  the  tissues,  the  conversion  of  dead 
bodies  into  adipocere,  the  development  of  fats  out  of  peptones,  the 
derivation  of  fatty  acids  and  substances  like  acetone  (CH.^COCHg) 
from  proteid,  that  in  phosphorus  poisoning  as  the  fat  increases  the 
albumin  diminishes,  etc. 

General  considerations  and  experiments  showing  then  that  the 
fat  deposited  in  the  body  may  be  derived  from  proteid,  it  may  be 
asked  of  what  use  then  are  the  carbohydrate  principles  always 
present  in  fattening  diet ;  in  what  way  do  they  contribute  toward 
the  production  of  fat  ?  Regarding  these  principles  as  a  source  of 
heat  to  the  economy,  their  role  as  a  part  of  fattening  diet  becomes 
2:>erfectly  clear,  since  in  being  burned  they  save  the  fat  otherwise 
derived  and  which  would  be  drawn  upon  for  the  same  purpose  if 
they  were  absent.  Hence,  the  fact  of  a  dog  fed  on  sugar  and  meat, 
excreting  less  urea  and  getting  fatter  than  when  fed  on  meat  alone, 
of  the  neg-roes  o-ettino-  fat  durino-  the  extraction  of  the  sugar  from 
the  cane  ;  of  dogs  fed  on  meat  and  rubol,  palm  oil,  or  stearin,  get- 
tino;  fat,  the  suw-ar  or  oil  oiven  with  the  food  in  these  instances  sav- 
ing  the  fat  otherwise  produced  from  the  proteid  from  being  biu-ned. 
The  carbohydrate  principles  evidently  then  play  in  the  production 
of  fat  this  secondary  role  of  saving  the  fat,  otherwise  produced, 
from  being  consumed. 

If  the  xiev:  of  the  origin  of  fat,  just  referred  to,  be  accepted,  it 
becomes  intelligible  why  individuals  become  fat  whatever  they  eat, 
and  that  if  the  fat  of  the  body  is  to  be  reduced,  all  Idnds  of  food 
must  be  diminished,  as  little  eaten  as  possible,  to  cut  off  the  supply, 
and  plenty  of  active  exercise  taken  to  quicken  the  circulation  aud 
respiration,  and  in  that  way  burn  off  that  already  deposited.  Fat 
is  never  discharged  from  the  body  in  health  except  in  the  butter  of 
milk,  but  is  destroyed,  burnt,  passing  away  as  carbon  dioxide  and 
water  ;  and,  therefore,  like  sugar,  being  a  source  of  heat  and  energy  : 

Fat.  Oxvgeu.    Carbonic  acid  gas.  Water. 

C„H^,„0,    +    0,„    =    57(COJ     +    5o(H,p) 

Fat  is  useful  also  as  serving  to  support  the  organs,  like  the  eye  and 
kidnev.  It  fills  up  the  spaces  between  vessels,  bones,  and  muscles, 
rounding  off  the  trmik  and  extremities  into  the  graceful  curves  of 
the  human  form. 

'Zeits.  fiirBiologie,  1869,  1870,  1871. 


56  PROXIMATE  PRINCIPLES  OF  ORGANIC  ORIGIN. 

It  prevents  the  loss  of  heat  through  its  bad  conductive  power. 
This  function  of  fat  is  well  shown  in  the  cetacea,  of  which  the 
whale,  dolphin,  and  jjorpoise  are  examples.  Such  animals,  being 
provided  with  an  immense  layer  of  fat  just  beneath  skin,  are 
enabled  thereby  to  retain  largely  their  heat. 

Cholesterin  (CjgH^^O),  although  consisting  of  carbon,  hydrogen, 
and  oxygen,  with  the  hydrogen  in  excess  and  fatty  to  the  touch, 
appears  to  have  the  constitution  chemically  of  a  monatomic  alcohol 
(C^pH^gOH).  Cholesterin  is  found  in  nervous  tissue,  blood  cor- 
puscles and  bile,  and  will  be  referred  to  again  in  connection  w^ith 
the  latter. 


CHAPTER    III. 

PROXIMATE    PRI>XIPLES  OF  THE  THIRD   CLASS. 

This  class  includes  such  substances  as  serum,  alljurain,  fibrinogen, 
casein,  hemoglobin,  mucin,  keratin,  urea,  lecithin,  pepsin,  etc. 
They  agree  mth  the  principles  of  the  second  class  in  being  of  or- 
ganic origin,  that  is  elaborated  by  organized  bodies  out  of  materials 
derived  directly  or  indirectly  from  the  mineral  and  vegetable  worlds. 

The  ^vater,  carbon  dioxide,  and  salts  found  in  the  mineral  inor- 
ganic world,  constituting  the  food  of  plants,  with  some  exceptions, 
like  the  fmigi,  are  converted  by  the  plant  through  the  agency  of  the 
sun's  light  and  heat  into  such  principles  as  starch,  sugar,  vegetable 
alVjiunin,  fibrin,  and  casein,  etc.  The  plants  in  time  serve  as  food 
for  herbivorous  animals,  which  are  eaten  by  the  carnivorous  ones, 
while,  as  we  shall  soon  see,  all  three,  plants,  herbivora,  and  car- 
nivora,  together  -svith  the  inorganic  principles,  enter  into  the  food 
of  man. 

It  will  be  seen,  therefore,  that,  so  far  as  the  organic  principles 
are  concerned  in  nature,  the  plant  is  indispensaljle  as  preparing  the 
food  for  the  animal ;  the  former  living  on  carbon  dioxide,  salts,  etc., 
which  would  be  starvation  to  the  latter. 

AVhile  the  organic  principles  are  usually  developed  in  the  order 
indicated,  it  must  be  mentioned,  however,  that  chemists  have  suc- 
ceeded in  artificially  preparing  some  of  the  principles  of  the  third 
class,  as  well  as  those  of  the  second,  from  the  direct  combination  of 
the  inorganic  elements  in  the  laboratory  by  purely  physico-chemical 
processes,  without  invoking  in  any  way  the  aid  of  a  vital  force  in 
the  case  of  either  plant  (jr  animal. 

The  proximate  principles  of  the  third  class,  with  some  exceptions 
to  be  mentioned  hereafter,  differ,  however,  from  those  of  the  first 
and  second  classes  in  not  Ix'ing  crystallizaljle. 

The  proximate  principles  of  the  third  class,  however,  are  distin- 
guished in  a  marked  degree  from  those  of  the  first  and  second  in 
containing  nitrogen.  This  element  seems  indispensable  to  the  com- 
position of  a  body  exhibiting  life.  As  is  well  known,  those  sub- 
stances which  are  xerx  changeable,  decomposing  suddenly,  like 
nitrogen  iodide,  nitrogen  chloride,  nitroglycerin,  fulminating  salts, 
gunpowder,  etc.,  owe  their  peculiar  properties  to  the  nitrogen  they 
contain. 

As  we  proceed  in  our  studies,  we  shall  see  that  the  essence  of  life 
is  in  change.  To  make  use  of  a-  homely  simile,  nitrogen  seems  to 
play  the  same  part  in  the  living  body  as  that  by  a  restless,  excitable 
spirit  in  the  living  community  ;  ever  ready  himself  to  be  affected 


58         PROXIMATE  PRINCIPLES  OF  THE  THIRD  CLASS. 

by  slight  changes  and  to  influence  in  the  same  way  those  around 
him. 

Thus  an  important  feature  of  the  nitrogenized  proximate  princi- 
ples is  the  readiness  with  which  they  undergo  putrefaction — the 
latter  being  brought  about  by  the  growth  and  multiplication  of  a 
minute  protist,  the  Bacterimn  termo  (Fig.  12),  just  as  sugar  is  de- 
composed into  alcohol  and  carbonic  dioxide  through  the  influence 
of  the  yeast  cell. 

Fig.  12. 


Cells  of  Bacterium  termo  ;  from  a  putrefying  infusion.     (Daltox.) 

The  eff^ect  of  the  bacterium  cells  in  inducing  putrefaction  in  this 
manner,  like  that  of  the  saccharomyces  or  yeast  cell  in  producing 
fermentation,  is  usually  said  to  be  due  to  catalysis.  The  word  cat- 
alysis meaning  literally  to  dissolve,  break  up,  while  frequently  made 
use  of  in  speaking  of  those  actions  in  the  economy  wliich  are  of 
this  character,  is,  however,  only  a  word,  not  an  explanation — in 
fact,  merely  a  convenient  way  of  expressing  our  ignorance  of  the 
phenomena  to  l)c  explained. 

The  susceptibility  of  these  organic  principles  to  change,  in  and 
out  of  the  body,  is  not  only  due  to  the  nitrogen  they  contain,  but 
probably  to  the  great  number  of  atoms  entering  into  their  compo- 
sition. 

It  is  more  natural  that  haemoglobin  (C,.,,.Hj,,2,.N,g^FeS30jj^,),  con- 
sisting of  2010  atoms,  should  lireak  up  into  its  constituent  parts 
on  the  slightest  change  taking  place  in  the  surrounding  conditions, 
than  sodium  chloride  or  water,  composed  of  two  or  three  atoms 
respectively.  It  is  easier  for  two  or  three  persons  to  get  along 
together  than  2010,  especially  Avhen  among  the  latter  there  are  164 
(the  nitrogenous  atoms)  most  unstable  ones. 

The  organic  principles  of  this  class  are  always  combined  with 
the  inorganic  ones,  the  union  being  most  intimate,  so  much  so  that 


CELLS.  59 

as  the  first  are  used  up  and  become  eifete,  and  are  cast  out  of  the 
body,  the  inorganic  principles  go  with  them.  Like  the  principles 
of  the  second  class,  those  of  the  third  class  are  destroyed  in  the 
system,  never  appearing  in  the  excretions  in  health  (with  the  ex- 
ception of  casein  of  milk,  mucus,  epithelium,  and  epidermis). 
Being  transformed  into  carbon  dioxide,  water,  urea,  etc.,  through  a 
process  of  splitting,  with  subsequent  oxidation,  they  are  also  a  source 
of  heat  to  the  economy  like  the  principles  of  the  second  class. 

It  is  impossible  to  offer  a  classification  of  the  nitrogenous  sub- 
stances occurring  in  the  human  body,  since  the  only  bond  which 
unites  all  of  them  is  the  nitrogen  they  contain,  whereas  the 
differences  depending  u])on  chemical  constitution,  mode  of  deriva- 
tion, etc.,  widely  separate  them.  In  endeavoring  to  give  some 
account  of  these  substances,  we  will  consider  them  successively  in 
groups,  associating  together  such  substances  as  agree  in  their  chem- 
ical constitution,  so  far  as  is  known,  in  their  general  properties, 
mode  of  derivation,  etc.  From  this  point  of  view,  inadmissible, 
perhaps,  from  a  purely  chemical  standpoint,  useful,  however,  for 
purpose  of  description,  the  proximate  principles  of  third  class,  those 
in  which  nitrogen  is  present,  may  be  divided  into  the  following 
groups:  proteins,  amides,  amines,  imides,  lactic  acid,  and  triatomic  al- 
cohol derivatives,  xanthin  bodies,  benzol  derivatives,  ferments,  etc. 

It  need  hardly  be  added,  after  what  has  been  already  said,  that 
the  above  groups  can  not  be  regarded  as  physiologically  equivalent 
or  placed  in  the  same  chemical  category,  as  some  of  the  substances 
constituting  them,  as  we  shall  sec  hereafter,  are  derived  from  the 
decomposition  of  protein  bodies,  some  by  substitution  of  residues, 
others  again  in  a  way  Avhich  is  as  yet  unknown.  AVe  will  begin 
our  study  of  the  proximate  principles  of  the  third  class  with  that  of 
the  protein  group. 

The  protein  group  of  nitrogenous  principles  constitute  the  chief 
mass  of  the  tissues,  hence  the  name  from  -pcozs'Jco  to  be  preemi- 
nent. Protein  substances,  generally  speaking,  consist  of  carbon, 
hydrogen,  nitrogen,  oxygen,  and  usually  sulphur ;  phosphorus 
iron  and  copper,  being  also  occasionally  present.  When  heated, 
})rotein  bodies  decompose,  giving  rise  to  inflammable  gases,  am- 
moniacal  compounds,  carbon  dioxide,  water,  nitrogenized  bases, 
etc.,  and  when  thoroughly  burned,  first  to  a  mass  of  carbon  and 
then  to  an  ash  consisting  principally  of  calcium  and  magnesium 
phosphates.  In  the  present  state  of  physiological  chemistry  it  is 
impossible  to  classify  the  protein  substances  satisfactorily.  The 
following  classification,  based  more  especially  upon  those  of  Ham- 
marsten^  and  Chittenden,^  will  suffice  at  least  for  convenience  of 
description. 

1  A  Text-Book  of  Plivsioloyical  Chomistrv,  bv  Olof  Ilaramarsten,  translated  bv 
John  A.  Mandel,  1893,  p.  14. 

2  Chittenden,  Digestive  Proteolysis,  Cartwrio-ht  Lectures,  Medical  Eecord,  Vol. 
45,  1894,  p.  449. 


60 


PROXIMATE  PRINCIPLES  OF  THE  THIRD  CLASS. 


Albuminous  Bodies    )  Globulins 
or 
Simple  Proteids 


(  Serum-albumin 
-^   Lacto-albumiu 
(^  Myo-albumin 
/   Serum-globulin 
\  Fibrinogen 
-    Myosin 
I  jSIyo-globulin 
V,  Cell-globulin 
'  til,  .„,:„„+       f  Acid-albumin 
Albuminates  |  Alkali-albumin 
Proteoses  and  Peptones 
Coagulated    Proteids  -|  Fibrin 


Protein  Substances 


Combined  Proteids 


Chromo-proteids' 
'  Glyco-proteids 

Nueleo-proteids .   , 
Korafin 


Albuminoids 


f  Korafi! 
J  J':iastin 


f  Hcemoglobin 

1  Myohsematin 

f  Mucins 

\  Mucoids 

f      yielding      f  Nuclei  histon 

)        nuclein      1   Cell  nuclein 

1       yielding      J   Casein 

L  parauuelein   (  Vitellin 


j  Collaji 

V  Keuro-keratin 


The  albuminous  bodies  or  simple  proteids,  while  found  more  es- 
pecially in  the  muscles,  glands,  and  blood  serum,  occur  as  well  in 
the  solids  and  fluids  of  the  body  generally,  with  the  exception  of 
the  tears,  perspiration,  and  perhaps  urine,  in  which  they  are  either 
absent  or  only  found  in  traces. 

Quantity  of  Proteids.  2 


Substance.                                        Parts 

per  1000. 

Substance. 

Parts  per  1000. 

Cerebro-spinal  fluid 

0.9 

Chyle 

.     40.9 

Aqueous  humor     . 

1.4 

Spinal  cord 

.     74.9 

Liquor  amnii 

7.0 

Brain  . 

.     86.3 

Intestinal  juice 

9.5 

Liver  . 

.   117.4 

Pericardial  fluid    . 

23.6 

Muscle 

.   161.8 

Lymph 

24.6 

Blood 

.   195.6 

Pancreatic  juice    . 

33.3 

Middle  coat  of  arterie 

s        .   273.3 

Synovia. 

39.1 

Crystalline  lens  . 

.  383.0 

Milk      .... 

39.4 

Albuminous  bodies  consist  of  carbon,  hydrogen,  nitrogen,  oxygen, 
sulphur,  and  occasionally  of  phosphorus,  iron  being  generally  a 
constituent  of  their  ash.  Their  percentage  composition  varies,  as 
follows  : 


Carbon 

Hydrogen    . 

Nitrogen 

Oxygen 

Sulphur 

Phosphorus 


54.5  per  cent. 

7.3     "       " 


50.6  - 

6.5  - 

15.0  -17.6  " 

21.50-23.50  " 

0.8  -  2.2  " 

0.42-  0.85  " 


The  molecular  weight  of  albumin  not  having  been  as  yet  deter- 
mined, its  formula  can  not  be  given.     That  of  alkali  albuminate  is 

^  In  order  to  prevent  misunderetanding  it  may  be  stated  that  the  term  ' '  proteid  ' ' 
as  suggested  by  Hoppe  Seyler  and  used  by  Hammarsten  embraces  the  substances  in- 
cluded above  as  chrorao-  and  glyco-proteids. 

2  Group  Besanez,  Lelirbucli  der  Phy.siologisclien  Clieraie,  1878,  s.  128. 


PliOTEIDS.  61 

usiiallv  accepted  as   l)eino-  approximately  C.^Hj^^Xj^SO^,  (Lieber- 
kulin). 

Although  the  constitution  chemically  of  albuminous  bodies  has 
not  yet  been  established,  judging  from  the  products  of  decomposi- 
tion', the  albumin  molecule  consists,  among  other  subtances,  of  such 
as  have  a  fotty  and  an  aromatic  nature.  The  albimiinous  bodies 
are  odorless,  tasteless,  and  usually  amorphous.  Most  of  them  are 
colloids,  that  is,  do  not  diffuse,  or  if  so,  but  slightly  through  animal 
membranes,  and  have  a  high  osmotic  equivalent.  They  rotate 
polarized  light  to  the  left.  The  presence  of  albuminous  bodies  is 
determined  by  precipitation  and  color  tests.  Thus,  for  example,  on 
heating  a  solution  of  allnunin  to  the  proper  temperature,  the  latter 
depending  upon  the  nature  of  the  albumin  present,  the  albimiin  will 
usnallv  separate  in  a  solid  form  as  crude  "  coagulated  "  albumin. 
It  should  be  mentioned  in  this  connection  that  the  reaction  of  the 
solution  containing  the  albumin  must  be  acid,  an  alkaline  albumin 
solution  not  coagulating  upon  heating,  and  a  neutral  one  but  partly 
and  incompletely.  Albuminous  bodies  are  precipitated  by  the  three 
ordinary  mineral  acids.  Thus,  for  example,  if  an  albumin  solution 
be  allowed  to  flow  gently  on  nitric  acid  in  a  reagent  glass,  as  in  the 
performance  of  Heller's  test,  a  M'hite  opaque  ring  consisting  of  pre- 
cipitated albumin  appears  where  the  two  liquids  meet.  Albumi- 
nous bodies  are  also  precipitated  by  metallic  salts,  ferroycanide  of 
potassium  in  acetic  acid  solution,  alcohol,  tannic  acid,  etc. 

Albuminous  bodies,  when  heated  to  the  boiling  point,  give,  on  the 
addition  of  nitric  acid,  a  yellow  color  known  as  the  xanthoprotein 
reaction.  A  solution  of  mercuric  nitrate  in  nitric  nitrous  acid 
known  as  Millon's  reagent,  precipitates  albumin  in  solution,  giving 
to  it  a  red  color.  Tyrosin  and  other  benzol  derivatives  give  the  same 
reaction  mth  Millon's  reagent,  contirraing  the  view  that  the  albumin 
molecule  contains  an  aromatic  group.  If  caustic  soda  or  potash 
be  added  to  an  albumin  solution,  and  then  drop  by  drop  dilute 
cupric  sulphate,  the  solution  becomes  just  reddish,  then  reddish 
violet,  and  lastly  violet  blue,  the  reaction  being  known  as  the 
Biuret  test.  In  testing  for  albumin,  as  no  one  test  is  characteristic, 
it  is  hardly  necessary  to  add  that  several  precipitate  and  color  tests 
should  be  made  use  of. 

Albumins. — These  substances  are  soluble  in  water,  coagidate  by 
boiling:  and  on  standing  with  alcohol.  Thev  are  verv  rich  in  sul- 
phur,  containing  1.6  to  2.2  per  cent.  Serum-albumin,  lacto-albu- 
min,  and  myo-albumin  are  found  respectively  as  proteid  constitu- 
ents of  blood,  ])lasma,  milk,  and  muscle.  Serum-albumin  usually 
taken  as  the  tvpe  of  the  albumins,  as  obtained  from  the  blood  of 
the  horse,  consists  chemically  of  C53.06,  HG.85,  N16.04,  SI. 80, 
022.26.'  It  is  found  in  the  lymph  exudations  generally  as  well 
as  in  the  blood. 

If  a  solution  of  serum-albumin  having  a  neutral  or  acid  reaction 
1  Hammarsten,  op.  cit.,  p.  62. 


62  PROXIMATE  PRINCIPLES  OE  THE  THIRD  CLASS. 

be  lieated  to  70°-75°  C.  it  will  coagulate,  that  is  will  be  precipi- 
tated in  an  insoluble  form.  As  it  appears,  however,  that  heating 
at  temperatures  of  73°,  77°  and  84°  C.  gives  three  distinct  coagu- 
lations, it  is  possible  that  the  substance  now  known  as  serum-albu- 
min may  really  consist  of  three  distinct  proteids.  An  important 
property  of  serum-albumin  is  tliat  it  is  not  precipitated  by  the 
addition  of  magnesimn  sulphate  (MgSO^)  to  a  liquid  containing  it. 
Advantage  is  taken  of  this  to  separate  serum-albumin  from  serum- 
globulin,  both  of  which  exist  together  in  the  blood-globulins.  These 
albuminous  bodies  are  iusolulile  in  water,  l)ut  s<»luble  in  dilute  neu- 
tral salt  solutions.  They  coagulate  by  heating.  Serum-globulin 
and  fibrinogen  are  found  in  blood  plasma  and  lymph.  Myosin,  the 
principal  proteid  constituent  of  dead  muscle,  exists  in  living  mus- 
cle apparently  in  the  form  of  a  promyosin  or  myosinogen.  Myo- 
globulin,  also  found  in  muscle,  l^ears  to  the  latter  very  much  the 
same  relation  that  serum-globulin  l^ears  to  blood  plasma.  Cell- 
globulin  is  found  in  cells. 

Serum-globulin,  often  called  para-globulin,  as  derived  from  horse's 
blood,  consists  chemically  of  C52.71,H.7.01,Xl5.85,Sl.ll,O28.24.i 
It  is  found  in  the  blood,  as  already  mentioned  in  lymph,  and  the 
exudations  generally.  Serum-globulin  in  solution  is  precipitated 
not  only  by  magnesium  sulphate,  but  also  by  sodium  chloride 
(NaCl),  incompletely,  however,  by  the  latter.  In  neutral  or  feebly 
acid  solutions,  serum-globulin  coagulates  at  a  temperature  of  75°  C 
Fibrinogen,  one  of  the  most  important  of  the  globulins  as  derived 
from  horse's  blood,  consists  chemically  of  C52.93,II.6.90,N16.66,- 
S. 1.25,0.22. 26.^  It  is  found  in  the  liquor  sanguinis  lymph  and  at 
times  also  in  the  exudations. 

Fibrinogen  differs  from  serum-globulin  in  coagulating  at  a  lower 
temperature,  5()°  to  60°  C,  and  on  being  as  completely  precipitated 
by  sodium  chloride  as  by  magnesium  sulphate.  As  we  shall  see 
hereafter,  it  is  regarded  as  giving  rise  to  the  insolul^le  proteid 
fibrin  at  the  moment  of  the  coagulation  of  the  Ijlood. 

Albuminates. — Acid  albuminate,  acid  albumin,  or  syntonin,  as  it 
is  sometimes  called,  is  produced  by  the  action  of  diluted  hydrochlo- 
ric acid  upon  proteid  as  takes  place  in  the  stomach,  in  the  digestion 
of  albuminous  food  l)y  the  gastric  juice,  tlie  latter  containing  hydro- 
chloric acid.  Alkali  albuminate  is  formed  by  the  action  of  alkali 
upon  albuminous  bodies  as  in  the  instance  of  the  alkali  of  the  in- 
testine acting  upon  proteids.  Acid  and  alkali  albuminates  are  nearly 
insoluble  in  water,  l)ut  are  soluble  in  dilute  acid  and  alkali. 

Proteoses  and  Peptones. — Proteoses  and  albumoses,  as  they  are 
also  called,  may  l)e  regarded  as  propep tones  occurring  during  the 
digestion,  of  albuminous  food  as  intermediary  products  between  al- 
bumin and  ])e]it(me  in  so  far  as  they  are  not  albuminates.  Pep- 
tones are  the   final   products  of  the  decomposition  of  albuminous 

1  Hammarsten,  op.  cit.,  loc.  cit. 
'^ Hammarsten,  op.  fit.,  loc.  cit. 


PROTEIDS.  63 

bodies,  brought  about  l)y  mean?  of  ferments,  or  }X)ssibly  in  other 
Avays.  Proteoses  are  usually  separated  from  peptones  by  satura- 
ting the  solution  containing  them  both  with  ammonium  sulphate, 
the  proteoses  being  precipitated,  the  peptones  remaining  in  solution. 
It  should  be  stated,  however,  that,  according  to  Xeumeister,  the 
deuteroproteose  occurring  in  pepsin  digestion  is  not  precipitated  by 
ammonium  sulphate.^ 

Coagulated  Proteids. — These  bodies,  of  which  fibrin  is  an  exam- 
ple, are  insoluble  in  water,  alcohol,  dikite  acids  and  alkalies,  salt 
solutions,  V)ut  soluble  in  pepsin,  hydrochloric  acid,  strong  acids  and 
alkalies,  and  alkaline  solutions  of  trypsin. 

Combined  Proteids. — This  group  of  protein  substances  is  more 
complex  than  the  albuminous  bodies  or  simple  proteids  just  consid- 
ered. They  consist,  as  their  name  implies,  of  proteid  combined 
with  non-proteid  l^odies,  such  as  coloring  matters,  carbohydrates, 
nucleic  acid. 

Chromo-proteids. — These  substances  consist  of  proteids  combined 
with  a  pigment  containing  iron,  such  as  hemoglobin,  the  coloring 
matter  of  the  red  lilood  corpuscles  and  its  derivatives,  to  be  re- 
ferred to  ag-ain,  and  histio-hiematin  or  myo-hi^matin,  found  espe- 
cially in  the  muscle  and  regarded  as  existing  in  two  forms,  myo- 
hsematin  and  oxy-myohiiematin,  corresponding  to  the  htemoglobin 
and  oxy-ha?moglobin  of  the  l:)lood. 

Glyco-proteids. — These  are  proteids  combined  with  carbohydrates 
as  in  mucins,  substances  foiuid  in  mucous  glands,  goblet  cells,  ce- 
ment substance,  epitheliiun,  connective  tissue.  Mucins  are  colloidal 
substances,  mucilaginous  and  thready  when  in  solution.  They  are 
insoluble  in  water,  soluble  in  very  weak  alkalies,  precipitated  by 
acetic  acid  and  yield,  when  treated  ^\\t\\  a  mineral  acid,  a  substance 
capable  of  reducing  a  copper  oxy -hydrate.  The  latter  property  is 
an  important  one,  since,  by  means  of  it,  mucins  are  distinguished 
from  substances  closely  resembling  them  in  their  properties.  ^lucin, 
as  derived  from  the  sub-maxillaries,  consists,  according  to  Hammars- 
ten,"  of  C.48.84,  H.6.80,  X12.;32,  S0.84,  O.31.20.  It  may  be  men- 
tioned that  while  mucin  agrees  in  composition  with  the  simple  pro- 
teids in  consisting  of  the  same  chemical  elements  it  contains  less 
nitrogen  and  usually  less  carbon.  ^luein  substances  are  usually 
divided  into  mucins  and  mucoids.  This  classification  is,  however, 
an  arbitrary  one,  as  there  are  intermediate  substances  which  make 
it  difficult  to  define  two  such  groups.  Among  the  so-called  mucoids 
may  be  mentioned  chondro-mucoid  found  in  muscle,  the  colloid 
matter  of  certain  tumors,  the  pseudo-colloid  of  ovarian  cysts  ;  the 
two  latter  Ijcing,  however,  pathological  in  nature. 

Nucleo-proteids. — These  substances  are  foimd  in  the  cells  of  both 
the  vegetable  and  animal  kingdoms.  Thev  are  characterized  more 
especially  by  yielding  through  the  action  of  pepsin,  hydrochloric 

^  Hammarsten,  op.  cit.,  p.  28. 
^Op.  cit.,  p.  32. 


64         PEOXIMATE  PRINCIPLES  OF  THE  THIRD  CLASS. 

acid,  phospliorized  substances,  which,  according  as  they  do  or  do 
not  yield  xanthin,  are  called  nucleins  or  paranucleins.  Nuclein 
occurs  as  nucleo-histon  in  the  leucocytes  of  the  blood  and  as  the 
chief  constituent  of  cell  nuclei,  parauucleiu  in  casein,  yitellin,  etc. 
The  supposed  importance  attached  to  nucleo-histon  as  a  factor  iu 
the  production  of  the  coagulation  of  the  blood  will  be  considered 
hereafter. 

Albuminoids. — The  substances  embraced  together  as  the  third 
class  of  protein  bodies  differ  so  among  thcmselyes  that  they  cannot 
be  regarded  as  a  natural  group.  The  albuminoids  agree,  howeyer, 
in  constituting  important  parts  of  the  skeleton  and  being  found 
generally  in  the  economy  in  an  insoluble  state  and  in  resisting  the 
action  of  reagents,  particularly  of  those  which  dissolye  albumins. 
The  albuminoids  are  deriyed  in  the  economy  from  the  proteids,  but 
do  not  appear  to  be  couyertible  into  the  latter. 

Keratin. — This  substance  is  the  chief  constituent  of  epidermis, 
hair,  and  nails,  and  in  the  modified  form  of  neuro-keratiu  is  found 
in  the  brain  and  the  medullary  sheath  of  nerves.  As  found  in  the 
hair  keratin  consists  of  carbon,  hydrogen,  nitrogen,  oxygen,  and 
sulphur,  being  yery  rich  in  the  latter.  Part  of  the  sulphur,  at  least, 
appears  to  be  in  a  loose  state  of  combination,  lead  combs  becoming 
black  l)v  long  usage  through  formation  of  lead  sulphide. 

Elastin. — This  albuminoid  is  found  in  the  connective  tissues  and 
in  some  cases,  as  in  the  ligamentum  nuchte,  to  such  an  extent  as  to 
constitute  a  special  tissue.  The  elastic  tissue  in  the  ligamentum 
nuchse  of  the  giraffe  and  elephant  is  much  developed.  The  liga- 
mentum nuchffi  in  the  giraffe  dissected  by  the  author  measured 
in  situ  more  than  9  feet,  6  feet  of  which,  after  removal  from  the 
body,  contracted  to  4  feet.  Elastin  differs  chemically  from  keratin 
in  containing  very  little,  if  any,  sulphur.  Elastin  is  very  insoluble 
in  boiling  water  and  in  most  reagents. 

Collagen. — This  substance  is  the  principal  constituent  of  the  con- 
nective tissues  and  as  ossein  of  the  organic  substance  of  bone.  It 
is  found  also  in  cartilage,  more  or  less  mixed  with  the  substances 
constituting  its  chemical  basis,  the  so-called  chondrigen.  Collagen 
can  be  obtained  from  bones  by  treating  the  latter  mth  hydrochloric 
acid,  which  dissolves  the  earthy  matters,  and  then  removing  the 
acid  with  water.  Collagen  consists  chemicallv,  according  to  Hof- 
mcister,'  of  C  50.75,  H  (5.47,  X  17.86,  S  +'0  24.92.  It  is  in- 
soluble in  water,  salt  solutions,  dilute  acids,  and  alkalies,  and  is 
converted  by  continuous  boiling  into  gelatine.  It  will  be  remem- 
bered that,  in  addition  to  the  protein  bodies  just  considered,  a  num- 
ber of  other  nitrogenous  principles  are  found  in  the  human  economy 
that  cannot  be  placed  in  the  above  category.  To  the  consideration 
of  these  let  us  now  turn,  premising,  however,  that,  as  most  of  them 
will  be  considered  again  more  or  less  in  detail,  a  passing  notice  will 
suffice  in  tliis  connection. 

^ Hammarsten,  op.  cit.,  p.  37. 


AMIDES.  65 

Amides.^ — Glycocoll,  or  amido-neetic  acid  ( C'H  ,XH,COOH ),  oc- 
curs iu  bile  combined  with  cliolic  acid  as  sodium  glycocholate,  and 
in  the  urine  combined  with  hippuric  acid  as  benzoic  acid,  and  with 
phenyl  acetic  acid  as  plienaceturic  acid  (Cj^Hj^XO^).  The  amides, 
leucin,  lysin,  tyrosin,  aspartic  acid,  are  normal  products  of  the  di- 
gestion of  proteids  by  the  trypsin  of  the  pancreatic  juice.  Leucin, 
chemically  speaking,  is  amido-caproic  acid  -  ( C.Hj^^XH^ )COOH) ; 
Ivsin,  diamido-caproic  acid  (C,.H,,(XH.,Y,COOH) ;  t_\TOsiu,  p-oxy- 
phenyl-amido-propionic  acid  (HOCVH^C.HgfXHJCOOH) ;  aspartic 
acid,  amido-succinic  acid  (C.,H3(XH.,)COOH).  Taurin,  or  amido- 
ethyl-sulphonic  acid  (XH.,CoH^SO..OH),  occui-s  in  the  bile  in  com- 
bination with  cholic  acid  as  sodium  taurocholate.  Urea  (COX.,HJ, 
or  carbamide,  regarded  as  a  diamide,  consists  of  the  residue  of  one 
molecule  of  carbon  dioxide  and  two  molecules  of  ammonia  in  which 
two  atoms  of  hydrogen  are  replaced  by  one  of  oxygen. 

Ammonia.  Trea. 

x„  <  H.    CO  -'  :C-TT= 
-(h;        ^^h= 

Amines.' — Auiouo;  the  amines  occurriuo;  in  the  bodv  mav 
be  mentioned  the  amines  of  the  olefines,*  cholin  and  neurin, 
derivatives  of  lecithin.     Cholin  chemically  is  trimethyl  oxy-ethyl 

(  OTT 
ammonium  hydroxide    (CH3).^=X     nrr  cjj  otj  '     Xeurin.     dif- 
fering in  its  chemical  composition  from  cholin  in  containing  one 
molecule  less  of  water,  is  trimethyl-viuyl  ammonium  hydroxide, 

r  OTT 
(CH3)3=X-    ,,p-  _  p^    and  is  a  powerful  poison.       As  a  matter 

of  general  interest  it  may  be  mentioned  in  this  connection  that  pto- 
maines, basic  substances  produced  from  proteid  by  bacterial  putre- 
faction, are  olefine  amines,  the  poisonous  ones  being  called  toxines. 
Thus,  for  example,  putresciu  occurring  in  the  urine  and  feces  in 
cystitis  is  chemically  tetra-methylene-diamin  (H.,X(CH.,)^XH,). 
Cadaverin,    found    in    cholera    feces,    is    penta-methylene-diamin 

^  An  amide  may  be  regarded  as  ammonia,  in  which  an  atom  of  hydrogen  is  re- 
placed by  a  residue.    Thus,  for  example,  acetamide  (C^HjOX  )  is  ammonia  in  which 
an  atom  of  hydrogen  is  replaced  by  the  residue  of  acetic  acid  as  follows  : 
Ammonia.  Acetamide. 

rn  fc,H30 

(h  (.h 

^  Leucin  is  regarded  by  some  chemists  as  being  rather  iso-butyl-amido-acetic  acid. 

^An  amine  or  compound  ammonia  may  be  regarded  as  ammonia  in  which  one 
or  more  atoms  of  hydrogen  are  replaced  by  one  or  more  alcoholic  radicals,  such  as 
methyl,  ethyl,  etc.     Thus 

Ammonia.        Ethvlamine.        Trietlivlamine. 

fH  (CM,  rC,H, 

N  a'  H  N  -^  H    •  X  J  CH. 

1 11  [h  [cm, 

*  defines  include  such  hydrocarbons  as  ethylene  (CoH^),  propylene  (CjHg). 


66         PROXIMATE  PRINCIPLES  OF  THE  THIRD  CLASS. 

(H.,N(CH.,).NH.,).  Leucomaines,  as  distino:nisho(l  from  pto- 
maines, are  the  products  of  protein  substance  brought  al)Out,  how- 
ever, not  by  micro-organisms,  but  by  the  metabolism  or  the  normal 
exchange  of  material  constantly  going  on  in  the  economy.  Some 
leucomaines  being  poisonous  in  small  doses,  their  accumulation  in 
the  system,  through  imperfect  excretion  or  oxidation,  is  regarded  by 
many  clinicians  as  a  source  of  disease,  of  auto-intoxication. 

Imides. — Of  the  imide  derivatives  of  the  body  may  be  mentioned, 
creatin  and  creatinin,  and  their  homolognes,  lysatin  and  lysatinin, 

(  l^TT 
derivatives  of  guanidin,  the  imide  of  nrea,^  HX  =  ^\  xfT^ '   Thus 

creatin  found  in  the  muscles,  blood,  and  urine  is  methyl  guanidin 

acetic  acid,  HXC  |  >-/ptT  \pTT  r <r)OH    C'reatinin,  readily  derived 

from  creatin,  diiferiug  from  it  only  in  containing  one  less  molecule 

of  water,  is  glycoyl  methyl  guanidin,  HNC  <  ^ir^yr  \f^ix  '    Lysatin 

(CgHjgX^O,)  and  lysatinin  (C^.H^X.^O^),  regarded  as  homolognes  of 
creatin  and  creatinin,  are  products,  like  the  latter,  of  the  decompo- 
sition of  the  proteid  of  either  the  food  or  the  body. 

Lactic  Acid  Derivatives. — Cystin  (C,.Hj,jX.,O^S.,)  is  an  interesting 
member  of  this  group,  giving  rise  occasionally  to  the  formation  of 
stone  in  the  bladder.  It  is  derived  by  oxidation  of  cystein,  the 
latter  being  a  derivative  of  lactic  acid  through  the  substitution  of 
XH2  and  SH  for  H  and  OH  in  the  former.     Thus 

Lactic  acid.  Cystein. 

H  NH 

i  I" 

CH  — C— COOH     CH3— C— COOH 

i  I 

OH  SH 

Triatomic  Alcohol  Derivatives. — Lecithin  is  regarded  as  being  a 
member  of  this  group,  as  it  is  resolved  either  naturally  or  artifi- 
cially into  cholin,  fatty  acid,  and  glycero-phosphoric  acids,  the  lat- 
ter being  glycerin  or  triatomic  alcohol,  in  which  one  hydroxyl  group 
is  replaced  by  the  residue  of  phosphoric  acid.     Thus 

Glycerin.  Glveero-phosphoric  acid. 

f  OH  "  f  PO^H, 

C3H^  \  OH  C3H^  \  OH 

[ OH  (OH 

As  the  fatty  acid  entering  into  the  constitution  of  the  lecithin 
molecule  is  not  always  the  same,  there  "will  be  different  kinds  of 
lecithin,  according  to  the  kind  of  fatty  acid  that  the  lecithin  con- 
tains— oleic,  palmetic,  stearic.  Thus,  for  example,  in  the  particular 
kind  of  lecithin,  knosvn  as  distearyllecithiu,  consisting,  according 
to  Hammarsten,-  of 

C,,H,„NPO,  =  HOCGHJ^NCf  .H,0(0H)P00G3H,(C\,H3PJ, 

^Imides  are  comijounds  of  NH.  ^Qp.  cit.,  p.  43. 


rROTAGOX.  67 

The  fatty  acid  clement  present,  as  the  name  implies,  is  stearic  acid 
(CjgHg.O.,).,,  the  cholin  and  glvcero-phosphoric  constitnents  being 
represented  by  H0(CH3),NC;Hp,  and  0(OH)POOC,H,,  respec- 
tively. Lecithin  is  found  universally  throughout  the  body,  being 
present  in  all  cells,  the  muscles,  blood,  lymph,  bile,  milk,  and  espe- 
cially in  the  tissues  of  the  nervous  system.  The  oily  drops  and 
threads,  the  so-called  myelin  forms  of  the  latter,  observed  under 
the  microscope,  arc  due  to  the  swelling  up  of  lecithin  in  water. 
Lecithin  has  a  waxy  appearance  and  is  soluble  in  alcohol  and  ether. 
Through  putrefaction  it  breaks  up  in  the  intestine  into  its  constitu- 
ents, which,  under  certain  circumstances,  appear  to  be  absorbed. 
Lecithin  in  combination  with  cerebrin  forms  protagon.  The  chem- 
ical constitution  of  cerebrin  has  not  yet  been  established  ;  it  is  a 
nitrogenous  substance,  apparently  free  from  phosphorus  and  is,  as 
already  mentioned,  a  glucoside,  yielding  that  form  of  sugar  already 
described  as  galactose. 

Protagon. — X  nitrogenizcd  phosphorized  substance  with  the  em- 
pirical formula  according  to  Gamgee  ^  of  CjgjjHgp^^N.POg.  is  the  chief 
constituent  of  the  white  substance  of  the  nervous  system,  being 
found  especially  in  the  brain. 

Xanthin  Bodies. — This  group  includes  xanthin,  guanin,  hypoxan- 
thin,  adenin,  etc. ;  substances  which  by  their  chemical  constitution 
are  closely  related  to  each  other  and  to  uric  acid.  Thus  xanthin 
(CjH^N^O.,)  differs  from  uric  acid  (C.H^N^O^)  in  containing  one 
atom  less  of  oxygen.  It  gives  rise  occasionally  to  a  form  of  stone 
in  the  bladder  of  exceeding  hardness.  Guanin  (C.H.N.O)  is  imido- 
xanthin,  that  is  xanthin  with  one  atom  more  of  hydrogen  and 
nitrogen  but  one  atom  less  of  oxygen.  Hypoxanthin,  or  sarcin 
(CgH^N^O),  is  lu'ic  acid  with  two  atoms  less  of  oxygen. 

Adenin  (C.H^X),  or  imido-sarcin,  differs  from  sarcin  in  containing 
one  atom  more  of  hydrogen  and  nitrogen  and  also  in  being  oxygen 
free.  The  xanthin  Ijodies  are  found  in  small  quantities  in  the  urine, 
and  in  the  fluids  and  tissues  of  the  body  generally,  nucleiu,  it  being 
remembered,  yielding  xanthin. 

Benzol  Derivatives. — Indol  and  skatol,  members  of  this  group,  are 
found  normally  in  the  alimentary  canal  as  products  of  the  putrefac- 
tion of  albuminous  bodies  ;  oxidized  into  iudoxyl  and  skatoxyl,  re- 
spectively, they  pass  to  the  liver  and  thence  into  the  urine,  partly  as 
the  corresponding  ethereal  sulphuric  and  partly  as  glycuronic  acids. 
Indol  is  chemically  benzo-pyrol  (C^H.N),  and  skatol,  methyl-indol 
(Cj.H.CH.^NH),  that  is,  indol  in  which  an  atom  of  hydrogen  is 
replaced  by  the  radical  methyl  CH,. 

Ferments. — The  ferments,  or  rather  the  unorganized  ferments  or 
enzymes,  so  far  as  their  composition  is  understood,  are  nitrogenous 
substances,  resembling  in  some  respects  albuminous  bodies.  These 
bodies  are  elaborated  within  the  cellsof  the  glands  producing  them, 
and  have  the  power,  even  in  very  small  quantities,  of  decomposing 
1 A  Text-Book  of  the  Physiological  Chemistry  of  the  Animal  Body,  1880,  p.  428. 


68  ENZYMES. 

or  splitting  otlier  substances  without  entering  into  combination  with 
them  or  their  products.  Among  such  enzymes  may  be  mentioned 
the  ptyalin  of  the  saliva,  the  pepsin  of  the  gastric  juice,  the  steapsin 
of  the  pancreatic  juice,  etc.,  the  uses  of  which  in  the  digestion  of 
food  will  be  considered  hereafter.  Organized  ferments,  as  distin- 
guished from  the  unorganized  or  enzymes,  are  organized  living  be- 
ings, the  putrefactive  and  fermentative  processes  that  they  give  rise 
to  being  phases  in  the  life  of  such  micro-organisms.  An  enzyme, 
or  unorganized  ferment,  differs,  therefore,  from  an  organized  one  in 
that  its  characteristic  eifect,  such  as  the  conversion  of  starch  into 
maltose  by  ptyalin,  is  effected  after  separation  from  the  cells  that 
produced  it,  whereas  the  fermentation  of  glucose  by  the  yeast  fun- 
gus Saccharomyces  cerevisiie,  resulting  in  the  formation  of  carbon 
dioxide  and  water,  is  a  stage  in  the  life  history  of  that  micro- 
orofanism. 


CHAPTER    IV. 

FOOD. 

Vital  like  all  other  kind  of  work  involves  consumption  of  ma- 
terial, expenditure  of  energy.  Portions  of  our  tissues  and  the  food 
appropriated  by  them  are  slowly  but  constantly  consumed,  with  the 
liberation  of  heat  or  energy.  The  carbon  dioxide  and  water  exhaled 
with  the  breath,  the  urea  excreted  in  the  urine  are  evidences  of  so 
much  food  and  tissue  having  been  destroyed.  Our  thoughts,  our 
words,  our  gestures  are  manifestations  of  the  transformation  of  the 
heat  or  energy  so  set  free.  This  daily,  hourly,  momentary  destruc- 
tion of  food  and  tissue  with  tlie  accompanying  liberati(in  and  trans- 
formation of  energy  demands  the  constant  renewal  of  the  materials 
of  which  the  food  and  tissues  consist.  Hence  the  necessity  of  food, 
by  which  we  mean  any  substance,  inorganic  or  organic,  solid  or 
li(piid,  that  will  nourish  the  body,  renew  the  materials  consumed  in 
j)roducing  those  forms  of  energy  called  vital. 

Under  ordinary  circumstances  the  sensations  of  hunger  and 
thirst  are  the  first  indications  that  solid  and  liquid  food  are  required 
by  the  system.  These  sensations  seem  to  be  due  to  a  certain  condi- 
tion of  the  stomach  and  mouth  induced  by  the  want  of  food  experi- 
enced by  the  general  system.  That  such  is  the  case  seems  to  be 
justified  by  facts  like  the  following.  It  is  well  known  that  the 
sensations  of  hnnjj^er  and  thirst  can  be  relieved  bv  introducino-  food 
into  the  system  through  fistular  openings  made  in  the  body  by  dis- 
ease or  wounds.  Thus  food  taken  into  the  system  through  an  open- 
ing in  the  intestine,  as  is  well  known,  will  not  only  relieve  the 
sensation  of  hunger  but  sustain  life,  and  in  the  case  of  an  opening 
iut(j  the  (esophagus,  when  water  and  spirit  were  injected  into  the 
stomach,  the  thirst  was  relieved.  It  is  also  well  known  that  bath- 
ing and  wringing  the  clothes  in  salt  water  have  been  the  means 
of  temporarily  relieving  the  thirst  of  shipwrecked  sailors. 

On  the  other  liand,  if  the  food  is  not  absorbed,  the  sensations  of 
hunger  in  the  stomach  and  of  thirst  in  the  mouth  are  only  tempo- 
rarily relieved,  even  though  solid  food  may  be  eaten  and  water  be 
drank  in  large  quantities ;  the  general  wants  of  the  system  in  such 
cases  not  being  satisfied. 

The  articles  commonly  made  use  of  as  food,  by  man,  such  as 
meat,  fish,  bread,  potatoes,  butter,  eggs,  milk,  etc.,  owe  their  nutri- 
tive value  to  the  five  so-called  food  stuffs  or  food  principles  that 
they  contain,  viz.,  water,  proteids,  fets,  carbohydrates,  salts. ^ 

'Albuminoids,  ^vliicli,  we  have  seen,  reseraljle  in  many  respects  proteids,  are  often 
regarded  as  constituting  a  sixth  food  stuHJ  gelatin  for  example  being  often  used  in 
the  making  of  soup,  etc.     Gelatin  can  not,  however,  be  said  to  constitute  a  food 


70 


FOOD. 
Composition  of  Foods. i 


Articles. 

Water. 

Proteids. 

Fats. 

Carbo- 
hydrates. 

Salts. 

Beefsteak 

Fat  pork .                

74.4 
39.0 
27.8 
78.0 
74.0 
40.0 
15.0 
8.0 
10.0 
15.0 
13.5 
13.1 
15.4 
15.0 
,  74.0 
85.0 
91.0 
6.0 
73.5 
36.8 

20.5 

9.8 

24.0 

18.1 

21.0 

8.0 

11.0 

15.6 

5.0 

12.6 

10.0 

9.0 

0.8 

22.0 

2.0 

1.6 

1.8 

0.3 

13.5 

33.5 

4.0 

2.7 

4.0 

3.5 

48.9 
36.5 
2.9 
3.8 
1.5 
2.0 
1.3 
0.8 
5.6 
6.7 
0.3 

*  2.0 

0.16 

0.25 

5.0 

91.0 

11.6 

24.3 

3.7 

26.7 

1.8 

49. 2 
70.3 
73.4 
83.2 
63.0 
64.5 
76.8 
83.3 
.53.0 
21.0 
8.4 
5.8 

"  4.8 
2.8 
5.4 

96.5 

1.6 
2.3 

Smoked  liam 

^Vliite  fish      ...            

10.1 
1.0 

Poultry 

"White  wlieaten  bread 

Wheat  flour 

1.2 
1.3 
1.7 

Biscuit 

1.7 

Eice 

0.5 

Oatmeal 

Maize 

Macaroni 

Arrow  root 

3.0 
1.4 
0.8 
0.27 

Peas  (dryl 

2.4 

Potatoes 

Carrots 

Cabbage  .    ,    

Butter 

Egg  ( 10  per  cent,  deducted  for  shell ) 

1.0 
1.0 
0.7 

2.7 
1.0 
5.4 

Milk  (S.  G.  1032) 

Cream .        

86.8 

66.0 

88.0 

3.0 

0.7 
1.8 

Skimmed  milk 

0.8 

Sugar  

0.5 

That  the  food  stuifs  shoukT  consist  of  tlic  principles  just  men- 
tioned becomes  evident  when  it  is  remembered  that  the  body  which 
the  food  nourishes  is  made  up  essentially  of  the  very  same  princi- 
ples. 

It  has  just  been  mentioned  that  the  use  of  food  is  to  repair  the 
waste  of  the  tissues,  and  through  combustion  in  the  economy  to  lib- 
erate energy.  As  the  body  consists  of  proteids,  carbohydrates,  fats, 
salts,  and  water,  all  the  food  stuffs  must  be  regarded,  in  a  broad 
sense,  as  tissue  makers.  The  proteid  or  nitrogenous  food  stuffs 
supply  the  material  for  the  production  of  proteid  or  nitrogenous 
tissue ;  carbohydrates,  in  part,  are  converted  into  fat,  salts  replace 
salts,  etc.  No  tissue  consists  of  any  one  principle,  such  as  proteid 
alone,  but  like  protoplasm  of  proteid  in  combination  with  salts, 
water,  etc.,  hence  food  must  consist  of  all  the  food  stuffs.  The  im- 
portance of  water  and  salts  in  this  respect  is  often  lost  sight  of,  es- 
pecially in  the  case  of  the  latter,  salts  being  usually  introduced  into 
the  economy,  not  as  such,  but  as  constituents  of  the  food.  Deprive, 
however,  man  or  animal  of  water  and  salts,  and  they  Mill  as  surely 
succumb  as  if  deprived  of  proteid  or  other  food  stuff'.  Further, 
Avhile  proteid  food  without  doubt  furnishes  the  materials  for  the 
building  up  of  proteid  tissue  only  a  part  of  it,  the  so-called  tissue 

stuff' in  the  same  sense  as  proteid.     It  docs  not  build  up  tissue,  nor  does  it  exist  as 
such  in  any  food,  being  prepared  by  lioiling  tlie  collagen  of  bones  and  connective 
tissues,     (ielatin  and  other  albuminoids  when  used  as  food  ))cing,  however,  oxidized 
like  carbohydrates  and  fats  are  in  this  respect  of  considerable  value. 
'Parkes,  A  Manual  of  Practical  Ilygifuc,  7th  edition,  1887,  \i.  243. 


DIET  OF  FOOD  STUFFS.  71 

proteid,  "  organ  ciweiss/'  ^  is  so  applied,  the  remaining  portion,  the 
circulating  proteid,  "  circulirendes  eiweiss,"  the  "  luxus  " '  in  the 
sense  of  proteid  being  only  plastic,  in  being  oxidized  liberates  a 
considerable  amount  of  energy.  On  the  other  hand,  while  carbo- 
hydrates in  being  completely  oxidized  in  the  body  like  fats,  must 
be  regarded  as  the  principal  sources  of  energy,  yet  inasmuch  as  they 
are  converted  into  fat  they  must  be  regarded  in  this  sense  at  least 
as  tissue  makers.  Xo  sharp  line  of  demarcation  can  then  be  drawn 
between  the  different  kind  of  food  stuffs.  They  certainly  can  not 
be  divided  as  they  were  formerly  by  Liebig  ^  into  two  classes,  plas- 
tic and  caloritacient.  All  that  can  be  stated  is  that  while  the  food 
stuffs  make  tissue,  the  water  and  salts,  however  indispensable  from 
the  latter  point  of  view,  do  not  liberate  energy,  leaving  the  body  in 
the  same  condition  as  introduced. 

It  is  well  known  that  while  earl)ohydrates  and  fiits  are  completelv 
oxidized  in  the  economy,  more  heat  is  produced  by  the  burning  of 
fat  than  of  an  equal  weight  of  starch,  1  part  of  fat  being  equal  in 
this  respect  to  2.2  or  2.4  parts  of  starch.  That  is  to  say  fat  may 
replace  in  the  diet  more  than  twice  its  weight  of  carbohydrate,  the 
ratio  being  called  the  isodynamic  equivalent.  Taking  into  consider- 
ation that  proteid  food  is  imperfectly  burned  in  the  body  and  de- 
ducting the  heat  that  would  be  liberated  by  burning  the  urea  1 
part  of  proteid  would  replace  in  the  diet  1.2  to  1.:]  parts  of  starch. 
When  compared  from  this  point  of  view  the  nitrogenous  matter 
constitutes  22  per  cent.,  the  non-nitrogenous  ones  78  per  cent,  of 
the  food,  being  therefore  in  the  pro]K>rtion  of  1  to  3.55.  From 
such  considerations  and  as  confirmed  by  experience  it  has  been 
shown  that,  apart  from  1530  grammes  (54  oz.)  of  water  drunk  as 
such,  life  can  be  best  maintained  in  a  state  of  health  on  a  diet 
consisting  of:  water,  559  grammes  (19  oz.)  derived  from  the  food; 
proteids,  130  grammes  (4.(3  oz.);  fats,  100  grammes  (3.5  oz.) ;  carbo- 
hydrates, 300  grammes  (1 0.5  oz.)  ;  salts,  20  grammes  (0.7  oz.).  The 
proportion  in  which  the  proteids,  fats,  and  carl)ohyd rates  may  re- 
place each  other  in  a  daily  diet  upon  the  principles  just  explained 
is  shown  accordino:  to  different  authorities  in  the  followinsr  table  : 

Diet  of  Food  Stuffs. 

Molesebott.  Ranke.  Voit.  At  water. 

Proteid  .  .  loO  grammes  100  grammes  118  grammes  125  grammes 
Fats         .         .      40       "  100         "  56  "  125       " 

Carbohydrates     550       "  240         "         500  "  400       " 

It  will  be  observed  that  according  to  Voit  the  nitroo-enous  are  to 
the  non-nitrogenous  food  stuffs  in  tlie  proportion  of  1  to  4.7,  in  the 

^  Voit  in  Hermann,  ITandlmcli  der  Physiologie,  Band  vi.,  s.  oUO,  ISSl. 

^Lehmann  (  Waoner  :  Handworterbnclv  1884,  ii.,  s.  18).  Frerichs  (Archiv  f. 
Anat.  und  Phys.,  1848,  s.  4(39).  Bidder  u.  Schmidt  (Die  WM-dauungsIifte,  1852,  s. 
348).  •  o        ,  , 

^Die  Organische  Chemie,  1842.  Ann.  d.  Chemie  u.  Pliar.,  xli.,  1842;  liii., 
1845;  Iviii.,  1840  ;  Ixx.,  1849  ;  Ixxix.,  1851. 


72  FOOD. 

daily  diet.  As  our  daily  food  does  not  actually  consist,  however, 
of  proteid,  carbohydrates,  etc.,  but  of  bread,  meat,  and  such  articles, 
it  becomes  as  important  to  determine  the  quantity  and  quality  of 
the  food  Avitli  wliich  the  economy  should  be  supplied  in  order  to 
maintain  a  state  of  health  as  that  of  the  food  stuffs.  Indeed,  as  a 
matter  of  fact,  the  proper  proportion  in  which  food  stuffs  should  be 
present  in  a  normal  diet  is  determined  from  the  nature  of  the  in- 
gesta,  that  is  the  food  eaten,  and  the  egesta.  As  the  various  kinds 
of  food  contain  more  or  less  the  .different  food  stuffs  it  might  natu- 
rally be  supposed  that  it  was  immaterial  whether  man  lived  upon 
animal  or  vegetable  food.  As  a  matter  of  fact,  as  we  shall  see  here- 
after, proteid  food  is  converted  l:)y  digestive  processes  into  peptone, 
whether  derived  from  beef  or  potatoes,  fats  and  salts  are  assimilated 
by  the  economy,  whether  supplied  by  the  eating  of  fish  or  rice.  As 
vegetable  foods  are  characterized  by  being  rich  in  carbohydrates  and 
relatively  poor  in  proteids  and  fats,  animal  foods  in  being  rich  in 
proteids  and  fats,  and  relatively  poor  in  carl)ohydrates,  it  follows 
that  the  economy  upon  a  diet  restricted  to  either  one  or  the  other 
kind  of  food  will  receive  either  too  much  carbon  or  too  much  nitro- 
o-en.  This  will  become  evident  from  a  consideration  of  the  amount 
of  the  carbon  and  nitrogen  sup])lied  to  the  economy  upon  an  exclu- 
sively bread  or  meat  diet  in  a  state  of  health. 

Eatio  of  Carbon  to  Nitrogen  in  Excreta. 


Carbon. 

Nitrogen. 

Respiration 

248.8  grammes. 

0  grammes. 

Perspiration    . 

2.6         " 

0         " 

Urine 

9.8         " 

15.8      " 

Fa3ces 

20.0         " 

3.0      " 

281.2  18.8 

There  are  found  in  the  excreta  281.8  grammes  of  carbon  and 
18.8  grammes  of  nitrogen,  the  carbon  being  to  the  nitrogen  in  the 
proportion  of  nearly  15  to  1. 

C  =281.2 

=  14  9 
X=   18.8  •^• 

Such  being  the  case,  it  will  be  seen  that,  upon  a  diet  restricted  to 
bread,  in  order  that  the  economy  should  receive  19  grammes  of  ni- 
trogen, 11)44  grammes  of  bread  would  have  not  only  to  be  eaten 
but  assimilated,  the  svstem  then  receivino;  30  <»:rammes  of  carbon 
to  1  of  nitrogen,  or  twice  as  much  carl)on  as  necessary. 

281.2  grammes  of  carbon  and  18.8  grammes  of  nitrogen  are 

found  in  tlie  excreta,  or  15  C  to  1  N. 

1944  gr.  of  bread  contain  583  gr.  C  and  19.4  gr.  N,  or  30  C  to  1  N. 

2981  gr.  of  meat  contain  298  gr.  C  and  89.7  gr.  N,  or  3    C  to  1  N. 

990  gr.  (2  Ib.s.)  of  bread  contain         .     C  300  gr.  and  N    9.9  gr. 

337  gr.  (I  lb.)  of  meat  contain     .       .     C    30  gr.  and  X    9.9  gr. 

1327  gr.  of  bread  and  meat  contain     .     C  330  gr.  and  N  19.8  gr. 

or  C     Ki.fJ      to     N     1. 


MIXED  DIET.  73 

On  the  otlier  hand,  if  the  food  consists  of  meat  ah)ne,  tlicn  in 
order  to  obtain  the  necessary  2S1  grammes  of  carbon  as  much  as 
2981  grammes  of  meat  would  have  to  be  eaten,  the  economy  receiv- 
ing then  three  o-rannnes  of  carbon  to  one  of  nitrogen,  the  amount 
of  carbon  being  tlien  one-fifth  of  what  it  ought  to  be,  relatively  to 
the  nitrogen,  and  the  latter  in  amount  absolutely  five  times  too  great. 
If,  however,  bread  and  meat  be  eaten  in  the  proportions  given  in 
the  table,  then  the  economy  will  receive  for  about  sixteen  grammes 
of  carbon  one  gramme  of  nitrogen,  the  ratio  differing  a  little  from 
that  of  the  excreta,  as  might  be  expected,  the  food  of  the  man  con- 
sisting, as  we  shall  see,  of  other  articles  as  well  as  of  bread  and 
meat.  In  the  latter  case  when  the  carbon  and  nitrogen  of  the  in- 
gesta  and  egesta  balance  each  otlier,  and,  indeed,  the  salts  and  water 
as  well,  the  economy  is  then  said  to  be  in  a  state  of  carbon  and 
nitrogen  equilibrium.  It  should  be  mentioned,  in  connection  with 
the  example  just  given  of  a  diet  restricted  to  meat,  that,  as  a  matter 
of  fact,  life  cannot  be  maintained  upon  such  a  diet.  As  more  than 
2.2  kilogrammes  (4.8  lbs.)  of  meat  must  be  eaten  and  digested  by  a 
man  in  24  hours  in  order  to  obtain  the  280  grammes  of  carbon,  a 
task  is  imposed  upon  the  digestive  organs  tliat  they  cannot  perform. 
A  man  soon  succumbs  upon  a  purely  meat  diet,  drawing  upon  the 
fat  of  his  own  body  to  supply  that  which  should  be  present  in  his 
food.  Even  a  carnivorous  animal,  like  a  dog,  whose  alimentary 
apparatus  is  especially  adapted  to  digest  meat,  can  only  be  kept 
alive  upon  a  purely  meat  diet,  when  fat  and  muscular  at  the  begin- 
ning of  the  experiment,  and  when  the  meat  eaten  is  equal  to 
the  -^^  or  Jg  of  the  weight  of  the  body,  a  diet  which  increases 
enormously  the  excretion  of  urea,  a  condition  far  from  physiological. 
On  the  other  hand,  if  the  food  consists  of  fat  alone,  man  or  beast 
will  live  but  a  short  time,  and  it  is  Morthy  of  mention  that  on  such 
a  diet  less  urea  is  excreted  than  in  the  starving  condition,  the  albu- 
minous tissues,  the  source  of  the  urea,  being  spared  through  the 
oxidation  of  the  fat.  If  more  fat,  however,  be  taken  than  can  be 
disposed  of  in  this  way,  as  shown  by  the  retention  of  carbon  in  the 
system,  then  fat  is  stored  up  and  the  albuminous  tissues  destroyed. 
The  effect  of  a  carbohydrate  diet  is  essentially  the  same  as  a  fatty 
one,  sugar  or  transformed  starch  being,  however,  more  readily  oxi- 
dized than  fat,  seventeen  parts  of  sugar  being  equal  to  ten  parts  of 
fat  in  this  respect ;  less  urea  is,  therefore,  excreted  upon  a  carbo- 
hydrate diet  than  upon  a  fatty  one.  A  certain  amount  of  body  fat 
appears  to  be  also  destroyed  upon  a  carbohydrate  diet. 

Of  all  foods,  milk  is  the  one  which  combines  in  itself  to  the 
greatest  extent  the  proper  substances  in  quantity  and  quality  for  the 
nutrition  of  the  body,  and  Mere  life  limited  to  its  earlv  periods,  it 
might  l)e  stated  that  milk  alone  would  suffice  for  the  maintenance 
of  life  ;  as  the  child,  however,  develops  into  the  adult  necessity  is  felt 
for  other  kinds  of  food  as  well.  All  through  life,  however,  milk 
constitutes  a  most  important  article  of  diet,  and  can  be  more  relied 
upon,  both  in  sickness  and  in  health,  than  any  other  kind  of  food. 


74  FOOD. 

While  life  can  not  be  maintained  upon  any  one  article  of  diet, 
under  certain  circumstances  the  latter  may  with  advantap^e  be  re- 
stricted larji^ely,  tliough  not  exclusively  to  some  one  kind  of  food. 
Thus,  for  example,  certain  wild  tril)es  in  South  America  subsist  al- 
most entirely  upon  beef.  The  latter  supplies  sufficient  material  for 
the  repair  of  the  tissues,  and  liberates  enough  heat  to  replace  the 
little  lost  l)y  tlie  body,  the  climate  being  warm,  and  to  supply  the 
energy  expended  in  their  daily  life.  In  the  arctic  regions,  however, 
where  the  temperature  may  fall  as  low  as  — 72°  F.  and  the  body 
loses  heat  very  rapidly,  the  food  consists  principally  of  oleaginous 
substances,  blubber,  fat,  etc.  These  substances  in  producing, 
through  combustion  in  the  economy,  a  great  quantity  of  lieat  are 
therefore  especially  suited  as  articles  of  diet.  On  the  other  hand,  in 
certain  parts  of  the  tropics,  wliere  the  temj^erature  may  be  as  high 
as  140°  r.,the  body  losing  but  little  heat,  the  staple  food,  as  might 
be  expected  from  what  has  just  been  said,  is  rice  or  dates,  which 
produce  relatively  little  heat. 

In  addition  to  what  has  already  been  said  in  reference  to  the  ex- 
creta and  nutritive  value  of  particular  kinds  of  food,  it  might  also 
be  inferred,  from  the  fact  of  the  teeth  of  man  being  of  both  the 
carnivorous  and  herbivorous  types  and  of  his  alimentary  canal  be- 
ing intermediate  in  character  between  that  of  the  carnivora  and 
herbivora,  that  the  food  should  be  of  a  mixed  kind.  The  quantity 
of  food  that  a  man  can  eat  and  live  is  very  different,  as  might  be 
supposed,  from  that  which  he  should  eat.  On  the  one  hand,  a 
young  Esquimaux  is  said  to  have  eaten  as  much  as  thirty-five 
pounds  of  food  in  twenty-four  hours ;  on  the  other  that  the  daily 
food  of  Thomas  Wood  consisted  for  eighteen  years  of  sixteen 
ounces  of  flour  made  into  a  pudding  with  water.  Leaving  out  of 
consideration  such  extreme  cases,  experience  has  shown  that  a  man 
in  full  health  and  taking  active  exercise  in  the  open  air  may  sub- 
sist for  a  considerable  time  upon  a  diet  consisting  of:  meat,  453 
grammes  (16  ounces) ;  bread,  540  grammes  (19  ounces) ;  butter  or 
fat,  100  grammes  (3.5  ounces);  water,  1530  grammes  (51  ounces). 
In  order,  however,  that  health  should  be  maintained  continuously, 
the  above  diet  should  l>e  modified  so  as  to  contain  more  bread  and 
meat,  and  also  vegetables  and  small  quantities  of  coffee,  vinegar, 
and  salt,  somewhat  as  in  the 

Daily  Ration  of  the  United  States  Soldier, 

Bread  or  flour         ......  22  ounces. 

Fresh  or  salt  beef 20         " 

Pork  or  bacon         .  .  .  .  .  .  12  " 

Potatoes  (three  times  a  week)         .  .         .  16         " 

Rice 1.6      " 

Cofifee  (or  tea  0. 24  oz. ) 1.6      " 

Sugar      ........  2.4      " 

Beans 0.64  gill. 

Vinegar  .         .         .         .         .         .         .  0.82    '• 

Salt 0.16    " 


HUXGER  AXD   THIRST.  io 

In  concluding  this  general  account  of  the  subject  of  food,  it  may 
be  stated  that  the  eifects  of  cooking  food  are  three  :  First,  to  make 
it  more  palatable  ;  second,  to  utilize  it  thoroughly  ;  third,  to  im- 
jjrove  its  digestil)ility.  Food  which  is  agreeable  to  the  taste  is 
eaten  "vvith  more  relish  ;  and,  therefore,  better  digested  than  if  un- 
palatable. If  the  food  were  not  cooked,  much  of  it  would  be  unfit 
to  eat  and  wasted,  and  even  if  it  could  be  eaten  murh  would  be  un- 
digested. 

Hunger  and  Thirst. — The  effects  of  withholding  food  entirely  or 
of  giving  it  in  too  small  quantities  are  seen  in  cases  of  starvation 
and  inanition.  As  an  illustration  of  how  life  depends  upon  waste, 
and  of  the  manner  and  relative  quantities  in  which  the  tissues  are 
destroyed  to  maintain  life,  the  records  of  death  from  want  of  food, 
solid  and  liquid,  become  of  interest  to  the  physiologist.  For  a 
starving  man  is  living  upon  himself,  and  as  nature  is  always  eco- 
nomical in  her  expenditures,  one  may  feel  siu'e  that  the  very  best 
disposition  possible  under  such  circumstances  is  made  of  the  mate- 
rial available  in  maintainino;  life.  In  the  wastiuo-  awav  that  takes 
place  in  these  cases  we  have  a  guide  as  to  the  character  of  the 
noiu-ishment  that  the  system  would  have  taken  had  food  been  sup- 
plied from  without  instead  of  from  within,  and  can  so  deduce  some 
conclusions  as  to  the  use  of  food  o-enerallv. 

Shipwrecks,  prolonged  sieges,  imjjrisonments,  forced  marches, 
etc.,  famish  the  data  by  which  some  idea  may  he  obtained  of  the 
state  of  nutrition  and  of  the  agonies  and  horrors  in  cases  of  death 
from  starvation.  Among  the  symptoms  of  starvation  mav  be  men- 
tioned, first,  severe  pain  in  the  epigastrium,  which  usually  passes 
away  in  a  day  or  so,  then  an  indescribable  feeling  of  weakness,  a 
sort  of  sinking,  in  the  same  parts  is  experienced.  The  face  be- 
comes pale  and  cadaverous,  and  there  is  a  wild  look  in  the  eye. 
General  emaciation  follows,  an  ofFensive  odor  is  noticed  about  the 
body,  which  is  covered  Avith  a  brownish  secretion.  The  voice  be- 
comes weak,  muscular  efibrt  is  almost  impossible,  the  intelligence 
can  with  difficulty  only  be  aroused.  Finally  death  takes  place, 
usually  in  eight  or  ten  days,  often  accompanied  with  mania  and 
convnlsions. 

On  post-mortem  examination  the  most  striking  fitcts  usually 
noticed  are  the  diminution  in  the  weight  of  the  body,  almost  entire 
absence  of  fat  and  blood,  and  the  loss  in  bulk  of  the  most  important 
viscera.  The  coats  of  the  intestine  are  so  thinned  as  to  be  almost 
transparent,  the  gall-bladder  is  distended  A\-ith  bile,  and  decomjiosi- 
tion  sets  in  very  rapidly. 

Death  from  inanition  or  insufficient  food,  though  more  prolonged 
than  that  from  actual  starvation,  is  essentially  the  same  process  only 
slower,  being  characterized  by  the  same  symptoms,  and  the  same 
post-mortem  changes.  ^lany  babies  and  young  children  in  large 
cities  and  even  in  the  country  die  from  inanition — actually  starved 
to  death,   undoubtedly  throngh  ignorance   in  some   cases ;  bnt  in 


76 


FOOD. 


others,  however,  the  length  of  time  in  death  from  inanition  varying 
so,  and  being  often  so  extended,  advantage  is  frequently  taken  of 
this  to  obscure  and  mask  the  true  cause  of  death  by  those  interested 
in  escaping  from  the  penalties  of  their  criminal  neglect  of  the  cliil- 
dren  placed  in  their  charge. 

As  already  observed,  one  of  tlie  most  prominent  symptoms  of 
starvation  is  the  loss  of  weight.  It  may  be  generally  stated  that 
when  this  loss  exceeds  from  twenty  to  fifty  per  cent,  of  the  weight 
of  the  body,  death  takes  ^^lace. 


In  doves,  accord- 

In cats,  accord- 

ing to  Chossat.i 

ing  to  Voit.2 

.      93.3 

97 

.      75.0 

27 

.       71.4 

67 

.       64.1 

17 

.       52.0 

54 

.      44.8 

3 

.       42.4 

18 

.      42.3 

31 

.       39.7 

.       34.2 

.       33.3 

21 

.       31.9 

26 

22.2 

18 

.       16.7 

14 

.       10.0 

1.9 

3 

Eelative  Loss  of  Tissue  in  Starvatiox  ix  100  Parts. 


Fat 

Blood 

Spleen   ...... 

Pancreas         ..... 

Liver      ...... 

Heart     ...... 

Intestines       ..... 

Muscles  .         .         .         .         , 

Muscular  coat  of  stomach 
Pharynx  and  oesophagus 

Skin" 

Kidneys  ..... 

Respiratory  apparatus   . 

Osseous  system       .... 

Ej'es      ...... 

Nervous  sj-^stem      .... 

It  will  be  observed  from  a  ghtnce  at  the  results  obtained  by 
Cho.ssat  and  Voit  that  the  ditference  in  the  relative  loss  of  the 
tissues  is  very  considerable.  Tlius  the  nervous  system  loses  only  a 
little  over  one  per  cent.,  the  muscles  over  forty  per  cent.,  while 
more  than  ninety  per  cent,  of  the  fat  disappears. 

Xow  it  has  lieen  noticed  that  in  starvation  the  temperature  falls, 
and  most  rapidly  as  deatli  approaches  ;  this  is  so  evident  that  the 
immediate  cause  of  death  is  undoubtedly  cold.  When  it  is  remem- 
bered that  one  of  the  principal  uses  of  tlie  fatty  principles  is  to  pro- 
diu.-e  heat  throu<>li  their  combustion,  the  laroe  loss  of  fat  in  such 
cases  becomes  intelligible,  the  animal  using  up  its  own  fat  as  so 
much  fuel. 

Inasnnich  as  no  food  has  been  introduced  into  tlie  Ijody  there  is 
nothing  for  the  economy  to  make  blood  out  of,  hence  the  .<mall  quan- 
tity found  in  the  body  after  death  from  starvation.  Further,  wluit 
there  is  of  it  is  of  the  most  inferior  quality,  rather  injurious  than 
otherwise ;  for  through  the  impeded  circulation  the  worn-out  and 
effete  matters  wliich  are  excreted  and  carried  out  of  the  system  so 
rapidly  in  health  accumulate  in  the  stagnating  inspissated  fluid  and 
represent  so  much  poison. 

'  Recherches  Experiinentales  sur  1' Inanition,  p.  92.     Paris,  1843. 
2 Hermann:   Physiologie,  Band  vi.,  s.  97. 


HUNGER  AND  THIRST.  ( i 

Even  tlioiigh  one  should  recover  from  the  effects  of  long  depri- 
vation of  food,  the  system  for  weeks  afterward  remains  in  a  con- 
dition peculiarly  favorable  to  the  reception  of  any  zymotic  poison. 
Hence,  from  time  immemorial,  famine  has  been  the  harbino^er,  the 
forerunner  of  epidemics,  the  plague,  etc.  Almost  invariably  after 
a  long  siege,  where  there  has  been  insufficient  food,  uidess  careful 
measures  are  taken,  disease  breaks  out  and  carries  off  many  of 
those  spared  by  the  sword.  In  the  often  quoted  words  of  Chossat, 
"  inanition  is  a  cause  of  death  which  advances  in  the  front  and  in 
silence  in  every  disease  in  which  alimentation  is  not  in  a  normal 
condition." 

Terrible  as  the  pangs  of  hunger  are,  those  of  thirst  are  worse, 
Man  and  animals  will  live  longer  without  solid  food  than  when  de- 
prived of  water,  man  dying  usually  in  a  few  days  when  no  water 
at  all  has  been  taken.  When  it  is  remembered  that  about  three- 
fifths  of  the  body  consists  of  water  this  is  readily  accounted  for. 

The  sensation  of  thirst,  though  caused  by  this  general  want  of 
the  system  for  water,  is  referred  to  the  mouth  and  throat,  M'hich  are 
first  sensibly  affected.  These  parts  become  very  dry  and  hot  and 
there  is  an  agonizing  feeling  of  constriction,  fever  sets  in,  the  blood 
is  very  much  diminished  in  quantity  and  becomes  thickened,  the 
urine  is  scanty  and  burns,  the  viscera  may  be  said  to  be  almost 
inflamed,  delirium  generally  precedes  death. 

The  importance  of  giving  water  freely,  internally  and  externally, 
in  health  and  disease  cannot  be  too  much  insisted  upon.  No  de- 
tailed argument  is  necessary  to  prove  this  point.  The  simple  fact 
that  within  four  days  even,  men  have  died  when  entirely  deprived 
of  water  speaks  for  itself. 

It  will  be  remembered  that  the  proteids,  carbohydrates,  fats  of 
the  food,  being  more  or  less  oxidized  in  the  economy,  liberate  en- 
ergy. Of  the  energy  so  set  free  the  greater  part,  as  we  shall  see 
hereafter,  disappears  as  heat,  the  remaining  part  as  muscular  or 
other  form  of  vital  energy,  the  temperature  of  the  body  remaining 
practically  constant. 

Use  of  Food. — The  use  of  food  then  is  to  repair  not  only  the 
waste  of  the  tissues,  but  also  to  supply  the  fuel  for  the  production 
of  energy.  In  the  child,  however,  the  food  not  only  supplies  these 
two  wants,  but  also  furnishes  the  materials  for  its  growth,  hence 
the  large  and  constant  amounts  of  food  demanded  by  an  active, 
healthy  child. 

Again,  the  food  of  the  female  during  gestation  must  furnish  the 
materials  out  of  which  the  child  is  developed,  as  well  as  supply  her 
own  wants.  The  food,  under  these  circumstances,  ought  to  be  most 
generous,  both  in  quantity  and  quality,  that  neither  mother  nor  child 
should  suffer. 

Striking  contrasts  are  offered,  according  to  the  particular  use 
made  of  the  food  in  one  or  more  of  the  ways  just  mentioned  by  dif- 
ferent classes  of  living  beings,  or  of  an  animal  at  different  periods 


78  FOOD. 

of  its  existence.  Thus  in  trees,  making  no  muscular  or  nervous 
effort  and,  therefore,  wasting  but  little,  all  their  food  can  be  applied 
to  increase  their  size,  hence  their  indefinite  growth.  Insects,  on 
the  contrary,  being  most  active,  are  usually  small  animals,  the 
greater  portion  of  their  food  being  used  up  in  producing  their  vari- 
ous actions,  and  little  left  for  growth.  In  the  fptal  state  of  man 
the  food  is  applied  to  growth,  in  the  adult  for  the  repair  of  the  tis- 
sue and  the  production  of  energy,  hence  a  man  cannot  grow  indefi- 
nitely, there  being  no  food  available  for  growth.  Inasmuch  as  the 
quantity  of  food  that  can  be  taken  by  an  animal  is  limited  by  the 
capacity  of  its  alimentary  canal,  it  might  be  inferred,  a  priori,  that 
if  the  greater  part  of  the  food  is  applied  to  one  particular  use,  there 
will  be  little  or  none  left  for  any  other. 

Hot-blooded  animals  re(|uire  more  food  than  cold-blooded  ones, 
their  more  active  life  demanding  a  greater  expenditure  of  energy. 
Thus  a  man  eats  usually  three  times  a  day,  a  l)oa  constrictor  once  in 
three  or  four  months.  When  hot-blooded  animals,  however,  hiber- 
nate— that  is,  sleep  for  months  at  a  time — they  pass  into  a  sort  of 
cold-blooded  state,  take  no  food,  and  exist  by  living  upon  them- 
selves. Such  animals  always  weigh  less  at  the  end  of  their  sleep 
than  at  its  beginning ;  the  loss  of  weight  being,  however,  compara- 
tively small,,  as  they  live  so  quietly  during  the  hibernating  period. 

By  bearing  in  mind  these  facts  it  becomes  intelligible  how  indi- 
viduals have  been  able  to  sustain  life  without  taking  food,  Avater 
excepted,  for  many  days  beyond  the  period  >vlien  ordinarily  death 
from  starvation  ensues.  By  taking  little  or  no  exercise,  in  passing 
most  of  the  time  in  sleep,  and  residing  in  a  tropical  climate,  or  in 
a  temperate  one  during  the  hottest  summer  months,  while  the 
experiment  lasts,  it  is  evident  that  the  system  needs  but  little 
food,  the  waste  of  the  tissues  being  reduced  to  a  minimum,  and 
there  being  but  little  need  for  heat  production,  on  account  of  the 
high  temperature  of  the  surroundings.  By  living  in  this  way,  man 
can  transform  himself  almost  into  a  cold-blooded  or  hot-blooded 
hibernating  animal.  Under  such  circumstances  he  lives  upon 
himself,  and  continually  loses  weight.  When,  as  regards  this  loss 
of  weight,  a  certain  limit  is  reached,  which  varies  according  to  the 
condition,  previous  mode  of  life,  and  peculiarities  of  the  individual, 
he  will  certainly  die  of  starvation  unless  food  be  taken,  death  from 
starvation  being  only  a  question  of  time  if  the  system  be  deprived 
of  food. 

There  are  a  number  of  substances  which,  although  they  can  not 
be  regarded  as  foods  in  the;  sense  of  being  essential  to  health,  are, 
nevertheless,  consumed  in  such  large  quantities  by  the  majority  of 
mankind  that  some  reference  at  least  should  be  made  to  them  in 
this  connection.  We  refer  to  tea,  coffee,  tobacco,  distilled  and 
fermented  liquors. 

Tea  and  Coffee. — As  the  composition  of  tea  and  coffee  are  the 
same,  they  may  be  conveniently  studied  together.     Tea  is  obtained 


ALCOHOL.  79 

from  the  leave?  of  the  Tliea  chinensis,  coffee  from  tlie  Caffea  arabica, 
the  tea  and  coffee  phiiits  respectively.  Tea  and  coffee,  while  con- 
taining food  stnffs  such  as  sugar,  gum,  tannic  acid,  fats,  salts  of 
iron,  potash,  and  soda,  owe  their  peculiar  properties  to  thei'n  or 
caffein.  The  latter  is  regarded  now  as  an  alkaloid,  being  chemi- 
cally trimethyl  xantliin  (CVH„,X^O.,  4-  H.,0)  which  has  been  re- 
cently prepared  artificially  from  xanthin.  Dimethyl  xantliin  is 
the  active  principle  of  chocolate.  The  effects  of  tea  and  coffee  upon 
the  mind  are  well  known,  wakefulness,  clearness  and  activity  of 
thought,  disposition  for  mental  or  muscular  exertion,  a  sense  of 
ease  in  respiration,  and  general  comfort.  The  exhaustion  and  nerv- 
ousness often  following  the  excessive  use  of  tea  appears  to  be  due 
to  the  loss  of  sleep  rather  than  to  any  poisonous  action  of  its  alka- 
loid. As  regards  nutrition,  tea  and  coffee  do  not  appear  so  much  to 
supply  the  economy  with  nutritive  material  as  to  promote  the  trans- 
formation of  that  already  taken,  the  exhalation  of  carbon  dioxide 
being  increased.^  As  thei'n  and  caffein  exist  in  tea  and  coffee  only 
to  the  amount  of  6  per  cent,  and  ^  per  cent.,  respectively,  a  cup  of 
tea  would  contain  only  about  1.2  grammes  (20  grains)  of  thein 
and  a  cup  of  coffee  0.05  grammes  (0.7  grain)  of  caffein,  as  the 
remarkable  effects  of  tea  and  coffee  upon  the  system  are  not  pro- 
portional, therefore,  to  the  amount  of  the  active  principle  that  they 
contain,  the  action  of  the  latter  in  the  economy  would  appear  to 
resemble  that  of  a  ferment,  the  food  and  tissue  being  transformed 
and  carljon  dioxide  set  free  as  in  the  various  fermentations  induced 
by  yeast. 

Tobacco. — As  the  employment  of  tobacco  is  most  extensive  in  all 
classes  of  society,  a  few  words  on  its  effect  upon  the  system  in  this 
connection  appear  appropriate.  The  active  principle  of  tobacco  is 
a  poisonous  alkaloid,  nicotia,  consisting  of  C\^Hj^X.,.  Experiments 
appear  to  show  that  while  the  use  of  tobacco  increases  the  elimina- 
tion of  uric  and  phosphoric  acids  the  feces  and  urine  themselves  are 
diminished,  the  exhalation  of  carbon  dioxide  being  but  little  affected. 
AMiile  the  excessive  use  of  tobacco  no  doubt  produces  a  state  of 
wakefulness,  trembling,  and  nervous  excitement,  it  cannot  be  denied 
that  when  moderately  used  it  is  often  very  beneficial,  quieting  and 
soothing  the  nervous  system  when  exhausted  by  bodilv  and  mental 
effort,  and  even  in  ordinarv  circumstances  producino-  a  o-eneral 
tranquillizing  effect. 

Tobacco  seems  also  to  promote  digestion,  stimulating  the  secre- 
tion of  the  gastric  juice  by  reflex  action,  hence  the  common  custom 
of  smoking  a  cigar  after  breakfast  or  dinner. 

Alcohol. — Before  considering  the  use  of  wines,  malt  liquors,  and 
spirits,  it  is  necessary  to  learn,  if  possible,  the  effects  of  pure  alcohol 
upon  the  human  body,  since  this  principle  is  contained  in  larire  or 
small  quantities  in  all  such  fluids^  Alcohol  chemically  consists  of 
CHgCH^OH,  and  the  first  question  to  be  investigated  is,  what  Ijc- 
1  Smith,  Philosophical  Transactions,  Vol.  149,  1859,  p.  681. 


80  FOOD. 

comes  of  it  ^vlien  taken  into  the  system  ?  According  to  some  ex- 
perimenters, very  little  alcohol  is  fonnd  in  the  excretions,  95  per 
cent,  appearing  to  be  oxidized,  burnt  up  ;  according  toothers,  how- 
ever, alcohol  is  found  in  the  ventricles  of  the  brain  unchanged,  and 
is  eliminated  by  the  lungs,  skin,  and  kidneys. 

It  appears,  therefore,  that  alcohol  may  be  consumed  in  the 
economy,  or  excreted  as  such,  or  partly  oxidized  and  partly  ex- 
creted. In  either  case,  however,  alcohol  can  be  of  no  benefit  to  the 
system,  for  if  it  is  found  as  such  untransformed  in  the  organs  or 
excreted  unchanged,  it  cannot  supply  any  want,  simply  passing 
through  the  system,  and  if  it  is  liurnt  up  it  must  interfere  with  the 
oxidation  of  other  substances,  such  as  fat,  etc.,  which  under  ordinary 
circumstances  Avould,  through  combustion,  disappear.  If  the  latter 
view  be  correct,  we  have  an  explanation  of  hard  drinkers  becoming 
often  so  fat,  the  alcohol  being  burnt  in  preference  to  their  fat,  and 
so  allowing  their  fat  to  accumulate  in  the  muscles,  in  the  liver, 
heart,  etc.,  or,  what  is  more  likely,  the  alcohol  in  some  way  inter- 
feres with  that  splitting  of  food  or  tissue  that  normally  precedes  its 
oxidation. 

Alcohol  can  never  substitute  the  natural  drink  of  man,  water. 
Many  substances  which  are  soluble  in  the  latter  are  precipitated  by 
the  former,  and,  hence,  useless  to  the  system ;  further,  it  does  not 
sujiply  any  principle  to  the  tissues. 

Alcohol,  in  diminishing  the  amount  of  urea  excreted  and  the  ac- 
tion of  the  skin,  and  in  interfering  with  natural  combustion,  per- 
verts the  whole  nutrition  of  the  body.  The  active  changes  and  the 
rapid  removal  of  the  effete  matters,  so  characteristic  of  healthy  life, 
are  retarded  by  alcohol ;  hence  the  susceptibility  of  the  dram 
drinker  to  zymotic  poisoning  and  chronic  disease.  It  is  well 
known,  also,  that  less  food  is  taken  when  alcohol  is  used,  and  so 
alimentation  is  affected.  It  is  often  urged  that  alcohol  "  keeps  the 
cold  out,"  but  as  the  cutaneous  vessels  dilate  under  the  use  of 
alcohol  through  paralysis  of  the  vaso-constrictor  nerves,  more  blood, 
and  tliercfore  more  heat,  comes  to  the  surface,  which  instead  of  be- 
ing retained  within  the  body  as  it  would  otherwise  be,  escapes,  the 
natural  effect  of  the  cold  being  to  contract  the  vessels  and  of  so 
keeping  the  heat  in  the  body.  Whether  this  be  the  true  explana- 
tion or  not,  the  fact  remains  the  same,  that  Arctic  voyagers  keep 
the  cold  out  far  better  without  the  use  of  alcohol  than  with  it. 
Finally,  in  addition  to  these  facts,  when  it  is  remembered  that 
many  persons  preserve  their  mental  and  bodily  health  perfectly 
without  ever  touching  alcohol,  it  is  difficult  to  offer  a  single  good 
physiological  reason  for  the  use  of  alcohol  at  any  time,  the  body 
being  in  health. 

It  must  not  be  forgotten,  however,  that  almost  every  people, 
savage  or  civilized,  use  alcohol  in  some  form  or  another.  Whether 
some,  as  yet  unknown,  want  is  supplied  to  the  system  by  alcohol,  or 
whether  it  is  used  merely  to  drown  sorrow  or  to  relieve  ennui,  is  an 


LIQUORS.  81 

undecided  question/  Among;  civilized  jxoplc  life  is  so  artificial 
and  man  is  so  liarassed  bodily  and  mentally  that,  unfortunately, 
perfect  health  is  far  from  Ijeing  common.  Life  at  times  becomes 
weary,  the  heart  feels  oppressed,  digestion  is  sluggish,  the  circula- 
tion impeded,  muscular  languor  is  present ;  then  alcohol  is  useful, 
for  it  is  a  nervo-muscular  stimulant.  The  action  of  the  heart  is 
accelerated,  the  l)lood  flows  more  rapidly,  the  heart  is  relieved,  and 
good  results  from  its  use.  As  a  medicine,  alcohol  is  indispensable  ; 
when  used  for  any  other  purpose,  little  or  nothing  can  ])e  said  in  its 
favor. 

Liquors,  Distilled  Liquors,  Wines,  Malt  Liquors. — Liquors  are 
prepared  by  treating  dilute  alcohol  with  sugars,  ethereal  oils,  and 
aromatics.  The  distilled  liquors  most  commonly  used  are  brandy, 
whiskey,  gin,  and  rum.  They  contain,  as  a  rule,  a  little  more  than 
50  per  cent,  of  alcohol,  and  hence,  when  abused,  their  bad  effects. 
Brandy,  the  most  valuable  of  them  as  a  medicine,  is  obtained  by 
the  distillation  of  Avine  ;  whiskey  from  rye,  wheat,  etc.;  gin  from  dif- 
ferent grains  rectified  by  juniper,  and  rum  from  molasses.  Brandy, 
whiskey,  and  gin  diminish  the  amount  of  carbon  dioxide  exhaled, 
and  so  interfere  with  vital  processes.  Bum,  however,  increases  the 
carbon  dioxide  exhaled,  and,  therefore,  is  less  hurtful  in  its  effects. 
It  has  long  been  known  that  the  rum  drinker  lives  longer  than  the 
brandy  or  gin  drinker. 

Wine,  or  the  fermented  juice  of  the  grape,  is  called  full-bodied 
or  light,  according  to  the  amount  of  alcohol  jiresent.  There  is  al- 
ways less  alcohol  in  wines  than  in  the  distilled  liquors  just  men- 
tioned ;  thus  port,  ^Madeira,  and  sherry  contain  from  15  to  20  per 
cent,  of  alcohol ;  claret,  sauterne,  hock,  about  10  to  15  per  cent. 
In  countries  where  the  light  wines  are  used  by  all  classes  of  society, 
the  horrible  effects  of  spirituous  liquors  are  almost  unknown,  the 
per  cent,  of  alcohol  being  so  small  in  light  wines. 

Wine  contains,  in  addition  to  alcohol,  sugar,  gluten,  and  a  num- 
ber of  salts,  etc.  Wine  is  nutritious  in  proportion  to  the  amount 
in  which  these  substances  are  present.  In  tlie  preparation  of  many 
wines,  like  champagne,  the  amount  of  carl>on  dioxide  is  increased ; 
hence,  their  great  use  as  diffusible  stimulants  in  those  cases  where 
the  vital  powers  demand  prompt  and  active  stimulation.  Under 
such  circumstances  there  is  no  better  medicine  than  champagne. 

Beer,  ale,  and  porter  are  made  from  malted  l^arley  with  the  addi- 
tion of  hops,  the  fluid  remaining  after  se])aration  of  nitrogenous 
matters  being  treated  with  yeast.  All  malt  licpiors  contain  alcohol ; 
about  1  to  4  per  cent,  in  the  weaker,  and  from  6  to  8  per  cent,  in 
the  stronger  kinds.  Even  as  much  as  12  per  cent,  is  found  in  the 
heavy  English  beers. 

'  Important  researches  have  been  made  recently  by  Chittenden  ( The  American 
Journal  of  the  Medical  Sciences,  April,  189() )  upon  the  effect  of  alcohol  upon  the 
various  digestive  secretions.  However  valuable,  such  investigations  will  not  throw 
any  light  upon  the  effect  of  alcohol  upon  the  system  until  supplemented  by  a  knowl- 
edge of  the  effect  of  alcohol  upon  tiie  i)rocesses  of  seci-etion,  absorption,  etc. 
6 


82  FOOD. 

Composition  of  Fren'ch  Beer.' 

Water 947.00 

Alcohol 4.50 

Dextrin,  glucose,  etc.      ......  41.40 

Nitrogeuized  substances          .         .         .         .         .  5.26 

Mineral  salts 1.84 

Bitter  principle  not  determined. 

1000.00 

A  most  noticeable  feature  in  the  composition  of  French  beer  as 
just  ji'Iven  is  the  small  amount  of  alcohol,  and  the  very  large 
quantity  of  glucose,  etc.  There  are  also  nitrogenized  substances, 
mineral  salts,  and  a  bitter  prinei])le.  Apart  from  the  alcohol  they 
contain,  malt  liquors  are  nutritious  on  account  of  these  carbohydrate 
and  nitrogenized  and  inorganic  principles.  They  are  often  of  great 
service  to  persons  who  are  run  down,  debilitated,  or  who  are  slowly 
recovering  from  some  exhausting,  low  type  of  disease,  being  taken 
then  as  a  mediciiw:'.  In  such  cases  the  small  quantity  of  alcohol  in 
the  malt  liquor  is  beneficial,  acting  as  a  stimulant,  the  hops  are  use- 
ful as  a  tonic,  and  the  remaining  jjriuciples  as  food. 

It  will  be  seen  from  what  has  been  said  of  alcohol  that  the  evil 
resulting  from  the  abuse  of  liquors  of  all  kinds  is  proportional  to 
the  amount  that  is  present  of  this  principle,  that  malt  liquors  and 
light  wines  are  less  injurious  than  brandy  and  whiskey,  and  that 
beer,  ale,  etc.,  containing  so  many  nutritious  j)riiu'iples,  closely 
approximate  to  tiic  true  idea  of  a  food. 

Condiments,  such  as  mustard,  pepper,  and  osmazome,  the  aro- 
matic matter  in  roast  meat,  while  not  contributing  to  the  repair  of 
the  tissue  or  the  liberation  of  energy,  are  important  adjuncts  to  fjod, 
stimulating  the  nervous  system  and  exciting  secretion.  Indeed 
were  it  not  for  the  flavor  imparted  to  food  by  such  substances  it  is 
doubtful  whether  it  would  be  eaten  for  any  length  of  time  by  either 
man  or  beast. 

'  Payen  :  Suhstances  Aliinentaires,  ]i.  4()"2.  In  the  origiiiid  taljle  of  Payen,  957 
is  given,  insteiul  of  947,  probably  a  typograpiiical  error. 


CHAPTER    V. 

DIGESTION. 

Ix  order  that  the  i'ood  shoukl  fullill  its  functions  in  the  economy 
it  must  be  assimilated,  and  before  that  can  be  accomplished  the 
food  must  be  first  di (jested  and  then  absorljed.  Digestion  should, 
therefore,  be  studied  first. 

Under  the  general  term  digestion  are  included  several  processes  : 
the  prehension  of  food,  its  mastication  and  insalivation,  deglutition, 
the  changes  effected  in  the  food  during  its  passage  through  the 
stomach,  the  small  and  large  intestine,  and  defecation. 

Mastication. 

The  chewing  of  food,  or  mastication,  is  effected  by  the  teeth, 
which,  in  the  adult  condition,  ifre  thirty-two  in  number,  viz.,  eight 
incisors,  four  canines,  eight  premolars,  and  twelve  molars.  A  tooth 
is  usually  described  as  having  three  parts.  That  jiortion  which  is 
seen  in  the  mouth  is  called  the  crown.  The  tapering  portion  in- 
serted in  the  socket,  or  alveolus  of  the  jaw,  is  the  root  or  fang,  and 
is  held  in  position  by  fibrous  tissue  continuous  with  the  periosteum 
of  the  jaw  and  submucous  tissue  of  the  gum.  The  intermediate 
constricted  part  of  the  tooth  between  the  crown  and  the  fang  is 
known  as  the  neck,  the  accumulation  of  fibrous  tissue  at  this  posi- 
tion being  called  the  dental  ligament. 

The  incisor  or  cutting  teeth  (Fig.  13)  four  in  each  jaw,  are  near- 
est to  the  middle  line  in  front  of  the  jaw.  They  are  inserted  in 
their  sockets  by  a  single  fang.  The  crown  of  the  tooth  is  wedge- 
shaped,  and  presents  a  wide,  sharp,  and  chisel-like  edge,  its  lingual 
or  inner  surface  is  concave  from  above  downward.  In  the  upper 
jaw  the  central  incisors  are  larger  than  the  lateral  ones,  whereas,  in 
the  lower  jaw  the  lateral  are  larger  than  the  central  ones.  The 
incisors  are  well  adapted  to  cut  and  bite  the  food. 

The  tooth  next  to  the  lateral  incisors  in  both  jaws  is  called  the 
canine  (Fig.  14),  and  corresponds  to  the  large  tearing  and  holding 
tooth  in  the  dog,  hence  its  name.  The  canine  teeth,  four  in 
number,  are  larger  than  the  incisor  teeth.  The  crown  is  conical 
and  bevelled  behind,  the  fang  is  longer  than  in  any  of  the  other 
teeth,  and  laterally  exhibits  a  slight  furrow,  as  if  indicating  a  tend- 
ency to  subdivide  into  two.  The  upper  canine  or  eye  teeth  are 
larger  and  longer  than  the  lower  ones.  The  latter  are  often  called 
the  stomach  teeth.  The  canine  teeth  assist  the  incisors  in  dividing 
the  food. 

The  premolars,  two  in  each  jaw  (Fig.  15),  succeed  the  canine. 


84 


DIGESTION. 


They  are  shorter  and  thicker  than  the  latter.     The  crown  is  cuboidal, 
convex  externally  and  internally,  and  exhibits  upon  the  triturating^ 


Fig.  13. 


Fig.  1-1. 


Canine  tixitli  of  the  uiiper  jaw.     n.  Front  view.     }k 
Lateral  view,  .sliowing  tlie  long  fang groovetlou  the.side. 

surface  two  eminences  or  cusps,  hence 
their  name  of  bicuspids.  The  fang  is 
conical     and    flattened,    and     deeply 

Incisor  teeth  of  the  upper  and  lower  gloved.      The    Upper   premolars    are 
jaws.    «.  Front  view  of  t^he  upper  and  larffcr  tliauthe  lowcr  oucs,  and  their 

lower  middle  mci.sors.   h.  rrontviewof    „~.  ,  ,t.,^. 


the  upper  and  lower  lateral  incisors. 
"         al  V  ■ 


fans::  is  more  or  less  subdivided  into 

Lateral  viewof  theupjjei-and  lower  mid-  " 

die  incisors,  showing  Ww  chisel  shape  of    twO. 
the   crown  :  a  groove   is  seen   niarkiui;-  rni  1         i       j.1  111 

slightly  the  fang  of  the  lower  tooth.        1  hc  premolar  tccth  are  succeeded  by 
(QuAiN.)  ^1^^  twelve  molar  or  grinding  teeth,  six 


16. 


in  each  jaw.  The  molar  tootli  (Fig.  16)  has  a 
cuboid  crown.  The  trituratino:  surface  in  the 
upper  molars  at  the  four  angles  is  elevated  into 
four  tubercles,  named  from  before  backwards ; 
externally  and  internally,  the  paracone,  metacone, 
protocone,  hypocone,  a  diagonal  ridge,  connecting 
usually  the  protocone  and  metacone.  In  the 
Fig.  15.  lower  molars  there  arc  five  tuber- 

j  cles  or  cusps,  three  on  the  outer 

side,  the  two  hypoconulids  and 

[)rotoconulid  from  before  back- 

\\ards,  two  on   the  inner  side, 

the  entoconulid  and  metaconu- 

lid.  Tlic  lower  molars  are  in- 
serted in  their  .sockets  by  a  pair 

of  conical  fangs,  the  upper  ones 
Firsthicuspid  tooth  of  l)y  three  fluigs,  two  external  and 
wli^TSend  view;  OUG   internal,   the   latter   is  the 

showing     the       latera  largest  aud    o-rOOVcd.  The  first  First  molar  tooth  of 

groove  of  the  fang  and            r^                      »                   .  the    upper    and    lower 

the  tendency  in  the  U|)-  mohir     tOOth that    IS,  the     0116  .laws.     Thev  are  viewed 

I)er  to  division.  (QUAiN                         ,       ■       ^         •.        .  i        •      j_i  from  the  outer    a.spect. 

andSHAKPEY.)  most  antcnorly  situated — is  the  (QuAiNaud  sharpey.) 


TEETH.  85 

largest,  the  third,  or  the  wisdom  tooth,  the  smallest.  Often,  how- 
ever, in  the  savage  races  of  mankind,  in  the  milk  teeth  of  civilized 
races,  in  the  fossil  man,  and  in  the  monkey,  the  last  molar  is  the 
largest.  It  is  by  means  of  the  molar  teeth  that  the  food  is  crushed 
and  ground  up. 

During  mastication  the  external  tubercles  of  the  lower  molars 
are  opposed  to  those  of  the  upper  ones,  and  through  the  lateral 
motion  of  the  lower  jaw  inward,  the  external  tubercles  pass  do^vn 
the  inclined  surfaces  of  the  external  ones  and  up  those  of  the  in- 
ternal tubercles  of  the  upper  teeth,  crushing  the  substances  between 
them. 

The  teeth  are  arranged  in  the  jaw  somewhat  in  the  form  of  a 
curve.  In  savage  races,  on  account  of  the  prominence  of  the 
canine  teeth,  the  curve  is  rather  of  an  oblong  form,  and  in  civilized 
races  the  curve  is  often  A^-shaped.  The  incisor  teeth  of  the  upper 
jaw  overlap  those  of  the  lower,  and  the  external  cusps  of  the  pre- 
molars and  molar  teeth  close  outside  those  of  the  lower  jaw.  It 
will  be  also  observed  that  the  central  incisors  of  the  upper  jaw  ex- 
tend over  the  central  and  half  of  the  lateral  incisors  of  the  lower 
jaw,  whilst  the  upper  lateral  incisors  come  in  contact  with  the  outer 
half  of  the  lower  laterals  and  the  anterior  half  of  the  lower  canines. 
The  canine  teeth  of  the  upper  jaw  extend  over  half  of  the  lower 
canines  and  half  of  the  lower  first  premolars.  The  first  premolar 
of  the  upper  jaw  is  opposed  to  the  half  of  the  first  premolar  and 
half  of  the  second  premolar  of  the  lower  jaw,  whilst  the  second 
upper  premolars  impinge  upon  the  posterior  half  of  the  second 
premolar  and  anterior  half  of  the  first  molar  of  the  lower  jaw. 
The  first  molar  of  the  upper  jaw  is  opposed  to  the  posterior  two- 
thirds  of  the  first  molar  and  anterior  third  of  the  second  molar  of 
the  lower  jaw.  The  second  upper  molar  impinges  upon  the  pos- 
terior third  of  the  second  and  anterior  third  of  the  last  molar  of 
the  lower  jaw.  The  last  molar  in  the  upper  jaw  is  opposed  by  that 
part  of  the  third  molar  in  the  lower  jaw  which  remains  uncovered 
by  the  second  upper  molar. 

By  this  disposition  it  will  be  seen  that  no  two  teeth  are  opposed 
to  each  other  only,  and  that,  with  the  exception  of  the  last  molar, 
each  tooth  in  the  upper  jaw  is  opposed  to  two  teeth  in  the  lower 
one.  If  a  tooth  is  lost,  or  even  two  alternate  ones,  the  remaining 
teeth  will  therefore  be  still  useful. 

If  the  teeth  of  man  be  compared  with  those  of  a  carnivorous 
animal,  like  a  lion,  or  with  those  of  a  herbivorous  one,  like  a  rhi- 
noceros, it  will  be  found  that  in  man  the  teeth  are  both  of  the 
carnivorous  and  herljivorous  kinds,  and  pretty  evenly  developed, 
whereas,  in  the  lion,  on  the  one  hand,  the  teeth  are  all  of  the 
biting,  cutting,  and  tearing  character ;  while  in  the  rhinoceros, 
on  the  other,  the  largest  teeth  are  of  the  ffrindins:  and  crushins: 
character. 

On  making  a  longitudinal  section  of  a  tooth,  of  a  molar  for  ex- 


86 


DIGESTION. 


ample  (Fig.  17),  it  will  be  observed  that  there  is  a  cavity  within 
the  crown  of  the  tooth  which  extends  into  and  throngh  the  fangs 
opening  by  a  small  apertnre  at  their  apices.  This  space  is  the  pulp 
cavity,  and  contains,  in  the  living  tooth,  the  pulp.  The  tooth  will 
be  also  seen,  from  such  a  section,  to  consist  of  three  parts,  dentine, 

or    ivory,    a    yellowish-white 
Fig.  17.  substance  bordering  the  pulp 

cavity,  enamel,  a  harder  and 
whitish  substance  capping  the 
crown,  cement,  a  translucent 
bonv-like  laver  encrusting  the 


roots. 


Fig.  18. 


Section  of  human  molar  tooth  magnifled.   (Owex.) 

The  dentine  constitutes  the  great 
bulk  of  the  tootli.  Chemically  it  con- 
sists of  about  twenty-eight  parts  of 
animal  matter  (tooth  cartilage),  and 
seventy-two  of  earthy  salts ;  among 
the  latter  arc  principally  found  cal- 
cium ph<)S}>hatc,  some  calcium  car- 
bonate, and  magnesium  pliosphate. 
When  examined  with  the  microscope 
dentine  (Fig.  1 8)  is  seen  to  consist  of 
an  amorphous  translucent  matrix,  in 
which  are  iinlx'dded  mnnerous  canals 
or  tubes,  Avhose  Avails  are  distinct 
from  the  matrix.  These  latter  are  the 
dental  or  dentinal  tubules,  and  aver- 
age in  diameter  at  their  commencement  y^Q  mm.  {-^i^-q  of  an  inch). 
The  intermediate  space  between  the  adjacent  tubules  is  about  three 
times  their  diameter.  The  dental  tubules  open  at  their  inner  ends 
or  beginnings  into  tlie  pulp  cavity,  outwardly  tlicy  pass  to  tlie  pe- 
riphery of  the  tooth.     Tlie  tubules  run  generally  in  a  parallel,  but 


Section  of  fang,  parallel  to  the  dentinal 
tiibuU's  (human  canine).  Magnified  SOO 
diameters.  1.  Cement,  with  large  bone- 
lacunic  and  indieation.s  of  lamellfc.  2. 
(iranular  layer  of  Purkinje  (interglobu- 
lar spaces).    3.  Itcutiual  tubules.     (Wal- 

DEYKK.) 


ENAMEL  OF  THE  TEETH. 


87 


Fk;.   19. 


u.  I)oiitInt'.     }i.  Odontoblastic  cells. 
c.  Filjcrs.     (Tomes.) 


somewhat  wavy  course.  As  they  pass  outward  they  become  grad- 
ually narrower,  dividing  and  subdividing,  giving  off  innumerable 
small  branches,  Avhich  anastomose  or  end  blindly.  Some  of  the 
terminal  l)ran('hes  pass  into  the  canalicula  of  the  cement,  others 
into  the  so-called  interglobular  spaces,  irregular  cell-like  cavities  in 
the  matrix.  The  Avails  of  the  dental  tubules  are  about  as  thick  as 
their  calibre.  In  the  living  tooth  the  dental  tubules  are  filled  with 
the  dental  fibers,  which  are  prolongations  fr(jm  the  odontoblastic 
cells  of  the  pulp  (Fig.  19).  Tliese  den- 
tal fibers  are  possil)ly  the  terminal  fila- 
ments of  the  nerves  supplying  the  tooth. 
The  contour  markings  observed  in  the 
teeth  are  due  to  irregularities  in  the 
matrix  or  intertubular  sul)stance. 

As  age  advances  there  is  deposited 
upon  the  inner  surface  of  the  dentine  a 
secondary  kind  of  dentine,  known  as 
osteo-dentine,  which  reseml)les  both 
dentine  and  bone.  This  appears  to  be 
due  to  a  sort  of  ossification  of  the  pulp,  the  effect  of  which  is  grad- 
ually to  obliterate  the  latter  and  the  pulp  cavity. 

Enamel. — The  crown  of  the  tooth  is  covered  with  the  enamel, 
the  hardest  of  organic  substances.  It  is,  however,  gradually  worn 
down  by  protracted  use.  The  enamel  is  thickest  upon  that  ])art  of 
the  tooth  most  used  in  trituration,  here  it  exists  in  several  layers ; 
it  is  thinnest  at  the  roots,  where  it  gradually  disappears. 

Chemically,  enamel  consists  of  about  five  parts  of  animal  matter, 
and  ninetv-five  of  earthv  constituents,  the  latter  l)eino;  mostlv  cal- 
cium  phosphate.  Microscopically,  enamel  consists  of  solid  six-sided 
prisms,  the  enamel  fibers  having  an  average 
diameter  of  ^J-q-  mm.  {-^-^-^-^  of  an  inch)  and 
a  length  of  ^^^  mm.  (  jq^q  q^  of  an  inch).  Each 
prism  rests  by  its  inner  end  upon  the  den- 
tine, the  outer  end  being  covered  with  the 
cuticle  of  the  teeth.  Usually  there  are  sev- 
eral layers  of  enamel  prisms,  the  outer  layer 
being  then  covered  with  the  cuticle.  The 
prisms,  while  arranged  in  a  j)arallel  man- 
ner, do  not  run  in  an  exactly  straight  direc- 
tion, the  course  beino-  rather  an  undulatinir 
one.  The  prisms,  when  viewed  horizontally  from  their  outer  ends, 
present  a  tessellated  appearance  (Fig.  20).  The  so-called  cuticle 
of  the  teeth,  or  membrane  of  Xasmyth,  just  referred  to  as  cover- 
ing the  outer  ends  of  the  enamel  prisms  or  fibers,  averages  about 
the  gi^  mm.  to  the  ^^Vo  ^^i"^-  (15^00  ^  the  30^00  «f  ^n  inch) 
in  thickness.  It  acts  as  a  protective  covering  to  the  enamel.  By 
some  histologists  the  cuticle  of  the  teeth  is  regarded  as  a  very  thin 
cement. 


Fig.  20. 


Section  of  enamel,  higlily 
magnified,  at  right  angles  to 
the  course  of  its  columns ; 
exhibiting  the  six-sided  char- 
acter of  the  latter.     (Leidy.) 


88  DIGESTION. 

Cement. — The  criista  petrosa,  or  cement,  covers  the  roots  of  the 
teeth,  beginning  at  the  neck  as  a  thin  layer  and  becoming  gradually 
thicker  at  the  fangs.  It  adheres  very  closely  to  the  dentine  and  to 
the  periosteal  lining  of  the  alveoli.  Cement  differs  from  bone  in 
its  lacuniTe  being  more  variable  in  their  form  and  size,  and  their 
canicula  being  larger  and  more  numerous.  In  many  animals,  like 
the  cat,  dog,  and  hog,  the  dentine,  cement,  and  enamel  are  disposed 
as  in  man.  In  the  grinding  teeth  of  the  herbivora,  however,  as  in 
those  of  the  elephant,  horse,  the  dentine,  enamel,  and  cement  alter- 
nate with  each  other  in  such  a  way  that  as  the  teeth  are  worn  an 
uneven  triturating  surface  is  always  maintained. 

Tooth  Pulp. — The  pulp  of  the  tooth  situated  in  the  pulp  cavity  is 
not  only  the  formative  organ  of  the  tooth,  l)ut  the  source  of  its 
vascular  and  nervous  supply ;  the  tooth-pulp  consisting  of  cells, 
blood  vessels,  nerves,  and  a  small  quantity  of  connective  tissue. 

The  cells  are  most  numerous  on  the  surface  of  the  pulp.  In  this 
position  they  are  known  as  odontoblasts  and  the  layers  formed  by 
them  as  the  membrana  eboris.  The  odontol)lastic  cells  exhibit 
three  kinds  of  processes  :  Those  passing  internally  into  the  pulp, 
others  which  serve  to  connect  adjacent  cells,  and  those  already  re- 
ferred to  as  being  prolonged  into  the  dentinal  tubules.  The  blood 
vessels  pass  in  and  out  by  the  openings  in  the  apex  of  the  tooth, 
forming  beneath  the  odontoblastic  layer  a  capillary  network.  The 
nerves  enter  by  the  fang  of  the  tooth  and  after  giving  off  a  few 
branches  form  a  plexus  beneath  the  odontoblastic  layer.  The  exact 
manner,  however,  in  Avhich  the  nerves  terminate  in  the  teeth  is  not 
known,  unless,  as  already  mentioned,  the  dental  fil)ers  are  of  a 
nervous  character.  The  teeth  of  the  upper  jaw  are  supplied  by 
branches  from  the  superior  maxillary  nerve,  those  of  the  lower  by 
the  inferior  maxillary. 

Xo  lymphatics,  as  yet,  have  been  found  in  the  tooth  pulp,  or  in 
other  parts  of  the  teeth.  As  age  advances,  the  pulp  of  the  tooth 
diminishes  in  size  through  its  gradual  calcification,  the  odontoblastic 
layer  atrophies,  the  connective  tissue  increases,  the  capillary  net- 
work disappears,  the  nerves  exhibit  a  fatty  degeneration,  and  the 
})ulp  ultimately  becomes  a  dried-u]>,  insensitive  mass. 

Althougii  the  pulp  may  lose  entirely  its  vitality,  yet  the  enamel 
and  dentine  may  remain  serviceable,  they  appearing  to  be  perfected 
structures.  These  are,  however,  never  reproduced  when  destroyed 
by  wear  or  decay  or  by  loss  of  the  tooth,  -with  the  rare  exception 
of  where  a  tooth  is  reproduced  for  the  third  time. 

The  way  in  which  the  teeth  are  developed  and  the  manner  in 
which  the  permanent  teeth  are  preceded  by  the  deciduous  or  milk 
.set,  will  l)e  c(»usidered  under  the  subject  of  reproduction. 

Maxillary  Bones. — Tiie  teeth  in  man  and  mammalia  are  confined 
to  the  maxillary  Ixjues,  in  which  they  are  imbedded,  the  bone  being 
moulded  so  to  speak,  around  the  roots  of  the  teeth  after  these  are 
developed  and  so  forming  the  sockets.     Between  the  jaw  and  the 


MAXILLARY  BOXES.  89 

tooth  there  is  a  space  wliich  in  tlic  living  tooth  is  filled  up  by  the 
alveodental  periosteum.  Throuoh  the  elasticity  of  this  root  mem- 
brane the  tooth  possesses  a  certain  amount  of"  motion.  Were  the 
teeth  iramova])ly  fixed  in  their  sockets  some  shock  would  be  felt 
during  mastication.  This  alveodental  periosteum,  which  passes 
imperceptibly  into  the  gum  and  periosteum,  consists  of  connective 
tissue  in  which  are  found  nerves  and  vessels.  There  is  also  no 
sharp  line  of  demarcation  between  the  gum  and  the  mucous  mem- 
brane of  the  nKjuth  on  the  one  hand  and  the  periosteum  on  the 
other. 

Of  the  maxillary  bones  the  superior,  from  being  immovably  ar- 
ticulated with  the  other  bones  of  the  head,  are  only  passive  in  mas- 
tication. The  upper  teeth,  however,  offer  fixed  surfaces,  against 
which  those  of  the  lower  jaw  are  brought  into  a})position. 

Intermaxillary  Bone. — If  the  inner  surface  of  the  superior  max- 
illary bone  be  examined  between  the  middle  line  and  alveolar  mar- 
gin, in  most  instances  a  suture  will  be  readily  recognized  running 
downward  and  outward  from  the  anterior  palatine  foramen  to  the 
outer  margin  of  the  second  incisor  tooth.  This  suture  is  interest- 
ing from  several  points  of  view,  among  others,  as  indicating  in  the 
embryo  the  distinction  existing  between  the  true  superior  maxillary 
bones  and  the  intermaxillary  bones,  the  latter  being  characterized 
by  carrying  the  incisur  teeth.  As  development  advances,  however, 
in  man  and  to  a  great  extent  also  in  monkeys,  the  superior  maxil- 
laries  coalesce  to  such  an  extent  with  the  intermaxillaries  that  the 
primitive  distinction  between  the  bones  is  almost  entirely  lost,  in 
some  instances  the  suture  itself  even  disappearing.  In  the  other 
mammalia,  however,  the  intermaxillaries  remain  quite  distinct  from 
the  superior  maxillaries  and  each  other,  and  are  readily  disarticu- 
lated. It  was  this  latter  circumstance  that  led  Goethe,^  equally 
great  as  a  poet  and  naturalist,  to  look  for  and  discover  the  inter- 
maxillary bone  in  man,  so  convinced  was  he  that  the  skull  consisted 
of  the  same  bones  in  all  the  mammalia. 

Temporo-Maxillary  Articulation. — The  inferior  maxillary  bone, 
mandible  or  lower  jaw,  consists  in  the  adult  of  a  single  piece  mov- 
ably  articulated  with  the  temporal  bone  (Fig.  21).  This  articula- 
tion is  really  a  doul)le  joint,  since  there  is  interposed  between  the 
condyle  and  the  glenoid  cavity  a  biconcave  oblong  piece  of  fibro- 
cartilage  to  the  edges  of  w'hich  is  attached  the  capsular  ligament. 
The  spaces  on  either  side  of  the  cartilage  are  lined  with  synovial 
membrane,  and  there  is  no  connection  between  the  two  cavities 
unless  the  cartilage  is  perforated.  When  the  jaw  is  simply  de- 
pressed, the  joint  acts  as  a  hinge.  Through  the  movement  of  the 
condyle  on  the  eminentia  articularis,  the  forward  and  lateral  mo- 
tions of  the  jaw  are  affected.  The  mechanism  of  the  temporo- 
maxillary  articulation  is  therefore  such  as  to  insure  great  freedom 
of  motion  to  the  lower  jaw.  The  lateral,  forward,  and  depressing 
iSamintliche  Werke,  Band  vi.,  Osteologie,  s.  65. 


90  DIGESTION. 

actions  of  the  jaw  either  succeed  each  other  or  are  variously  com- 
bined during  the  mastication  of  food. 

If  the  condyle  of  the  jaw  in  a  carnivorous  animal  be  examined, 
in  a  tiger,  for  example,  it  will  be  noticed  that  its  long  diameter  is 
transverse,  and  that  the  glenoid  cavity  is  grooved,  hollowed  out,  so 
as  to  receive  it.  This  disposition  is  carried  out  to  such  an  extent 
in  the  badger  that  the  lower  jaw  will  remain  depressed,  interlocked, 
within  the  glenoid  cavity,  even  though  all  the  ligaments  be  cut 
away.  The  motion  of  the  lower  jaw  in  many  of  the  carnivora  is  al- 
most exclusively  of  an  up  and  down  character,  there  being  little  or  no 
lateral  motion.  In  tlie  herbivora,  however,  as  in  the  sheep,  rhinoc- 
eros, etc.,  it  is  the  lateral  motion  of  the  lower  jaw  that  is  evident 
in  chewing.  In  such  animals  the  glenoid  cavity  is  rather  shallow 
and  the  condyle  oblong  or  ovate.     The  motion  of  the  jaw  in  the 

Fig.  21. 


Antci'd-posterinr  section  of  the  teiujioid-inaxillarv  articulation  of  tlie  riglit  side. 
(A.  T. .)>;,.     (QUAix!) 

rodentia  differs  from  that  observed  both  in  the  carnivora  and  her- 
bivora, being  backward  and  forward,  like  that  seen  in  the  gnawing 
action  of  a  rat.  This  motion  is  rendered  possible  in  such  animals 
through  the  long  diameter  of  the  condyle  and  the  glenoid  cavity 
having  an  antero-posterior  direction,  as  in  the  capybara. 

The  teuiporo-maxillary  articulation  coml)ines  in  man,  as  we  have 
seen,  to  a  great  extent,  in  one  joint,  the  peculiarities  just  noticed  in 
the  temporo-maxillary  articulation  of  the  carnivora,  herbivora,  and 
rodent  types  of  the  mammalia. 

The  various  movements  of  the  lower  jaw  are  effected  by  a  number 
of  different  muscles  :  to  the  consideration  of  these  let  us  now  turn. 

Muscles  of  Mastication. — Tliese  muscles  naturally  divide  them- 
selves into  two  groups,  one  of  which  elevates  the  lowxr  jaw,  moves 
it  laterally  or  in  an  antero-posterior  direction  ;  the  other  depresses 
it.     Let  us  study  the  former  group  first. 


MUSCLES  OF  MASTICATION. 


91 


Principal  Muscles  of  Mastication. 

Elevators,  etc.  Depressorts. 


Temporal. 

Masseter. 

External  )     ,  .  -, 

-r   .  1    ^  ptery<i;oul. 

Internal   j  ^       •'  - 


Digastric. 
Mylo-hyoirl. 
Genio  hyoid. 
Platysma  myoides. 


The  action  of  the  muscles  becomes  quite  apparent  when  their 
anatomy  is  understood.     The  temporal  (Fig.  22)  arising  from  the 


Fig.  22. 


The  temporal  muscle,  the  zygoma  and  masseter  having  been  removed.      (Gray.) 

temporal  fossa  and  inserted  into  the  coronoid  process  raises  the 
lower  jaw  against  the  upper.  The  action  of  the  temporal  is  aided 
by  the  contraction  of  the  masseter  and  internal  pterygoid,  the  for- 
mer muscle  (Fig.  27)  arising  from  the  zygomatic  arch  and  passing 
backward  into  the  lower  border  of  the  jaw,  the  latter  (Fig.  2-))  hav- 
ing its  origin  in  the  pterygoid  fossa  and  its  insertion  in  the  lower 
and  back  part  of  the  inner  side  of  the  jaw.     The  action  of  these 


Fig.  23. 


Fig.  24. 


View  of  the  pterygoid  muscle  from  the  outer  View  of   the    jitcrygoid    mu.scle  from   the 

side.     3:j.     1.    Exteriial  pterygoid.     2.    Internal        inner   side.     ' ,.     1.   'L.xternal   pterygoid.     2. 
pterygoid.     ((iUAlN.)  Internal  iitei'v^oid.     ((jrAlN.) 


92 


DIGESTION. 


muscles  is  well  seen  in  the  carnivora,  in  Avhlcli  tliey  are  very  large. 
The  maximum  eifect  of  the  masseter  can  also  be  well  observed  in 
the  rodentia,  the  muscle  being  enormously  developed  in  these  ani- 
mals. The  lateral  and  forward  motion  of  the  lower  jaw  is  due  to 
the  action  of  the  external  pterygoid.  This  muscle  (Fig.  24)  arises 
from  the  sphenoid,  palate,  and  superior  maxillary  bones  and  passing 
backward  and  outward  is  inserted  into  the  neck  of  the  condyle  of 
the  lower  jaw  and  into  the  inter-articular  fibro-cartilage.  If  the 
condyle  of  the  jaw  on  one  side,  the  left  for  example,  be  fixed,  it  will 
be  seen  from  the  direction  of  the  fibers  of  the  external  pterygoid 
that  if  the  muscle  of  the  opposite  side  contracts  it  will  draw  the 
lower  jaw  forward  and  laterally  in  an  inward  direction,  the  condyle 
playing  upon  the  articular  eminence,  the  car- 
FiG.  25.  tilage  being  interposed,  it  having  been  also 

drawn  forward  by  the  muscle.  This  alter- 
nate lateral  motion  of  the  lower  jaw  is  very 
evident  in  the  chewing  of  the  food,  particu- 
larly well  seen  in  the  herbivora,  in  which 
order  the  external  pterygoid  muscle  is  rela- 
tively much  developed.  If  the  external 
pterygoid,  however,  act  together,  the  lower 
jaw  is  drawn  forward  along  the  diagonal  A  D 
of  the  parallelogram,  the  two  sides  of  which, 
ABAC  (Fig.  25),  are  the  directions  taken 
by  the  jaw  when  alternately  acted  upon  by  the  external  pterygoids. 

As  regards  the  second  group  of  the 
masticatory  muscles  there  can  be  no  Fig.  26. 

doubt  as  to  the  function  of  the  mylo- 
hyoid (Fig.  26),  genio-hyoid,  and 
platysnia  myoides  muscles.  The  two 
former  muscles  passing  from  the 
hyoid  bone  to  the  mylo-hyoid  ridge 
and  genial  tubercle  of  the  lower  jaw 
respectively  will  depress  the  jaw 
when  the  hyoid  bone  is  fixed.  The 
same  effect  is  produced  by  the  pla- 
tysma,  it  being  partly  inserted  into 
the  lower  border  of  the  jaw.  The 
action  of  the  digastric  muscle  is  not 
so  sim])le  as  that  of  the  other  de- 
pressors. 

The  digastric  muscle,  as  its  name 
implies,  is  double-bellied,  consisting 
of  an  anterior  and  jiosterior  muscular 
part  with   an   intervening   tendinous 

portion.  The     tendon  often     passes  ,  i^.  The  lower  jaw  and  hyoid  bono,  from 

^  iTi  '"-'low,  with   the  invlo-hvoid  muscles  at- 

thrOUgll  the  Stylo-hyOld  muscle,  ghd-  tauhed.     B.  The  saiue  from  behind,  with 

,,  ■,         "■            ,*,                    •    1     1  "ic  mvlo-hvoid  and  genio-hyoid  muscles 

ing  tlirough  a  small  synovial   bursa,  attached.    (A.  t.)   h. 


MUSCLES  OF  MASTICATION.  93 

and  is  connected  with  the  body  and  great  cornu  of  the  os  hyoides 
by  a  broad  band  of  aponeurotic  fibers  in  the  form  of  a  loop  and 
lined  with  synovial  membrane.  The  posterior  belly  of  the  digastric 
muscle  passes  upward,  l)ack\vard,  and  outward  from  the  tendon  to 
the  digastric  groove  of  the  temporal  bone,  the  anterior  belly  up- 
ward and  forward  to  the  inner  surface  of  the  jaw,  near  the  sym- 
physis. An  interesting  fact  to  be  noticed  is  that  the  anterior  belly 
is  supplied  by  the  mylo-hyoid  branch  of  the  inferior  maxillary 
branch  of  the  fifth  nerve,  the  posterior  belly  by  the  facial,  as  we 
shall  see  when  we  come  to  study  the  nervous  system ;  this  shows 
that  the  muscle  is  essentially  a  double  one. 

Such  being  the  disposition  of  the  digastric  muscle,  it  follows  that 
if  the  jaw  be  fixed  and  the  anterior  belly  alone  contracts,  the  hyoid 
bone  will  be  elevated  anteriorly,  as  it  is  by  the  genio-hyoid  and 
mylo-hyoid  muscles  in  the  first  stage  of  deglutition.  If,  however, 
the  posterior  belly  alone  contracts,  the  hyoid  bone  will  be  raised 
upward  and  backward,  its  action  being  similar  to  that  of  the  stylo- 
hyoid muscle.  Should  both  l>ellies  contract,  then  the  hyoid  bone 
will  be  elevated  almost  perpendicularly.  On  the  other  hand,  should 
the  hyoid  bone  be  fixed  by  its  depressor  muscles,  the  loMcr  jaw  will 
be  slightly  depressed  if  the  anterior  belly  of  the  digastric  muscle 
acts  alone  ;  should  the  posterior  1)elly  act  independently,  then  the 
mastoid  process  will  be  drawn  downward,  and  with  it  the  back  of 
the  head,  thereby  elevating  the  upper  jaw  and  opening  slightly  the 
mouth.  This  action  of  the  posterior  belly  alone,  or  with  the  an- 
terior one  acting  with  it,  is  no  doul)t  aided  by  the  deep  muscles  of 
the  neck.  AYhile  it  is  possiljle  that  the  lower  jaw  can  be  depressed 
by  the  anterior  belly  of  the  digastric  acting  alone,  it  is  most  prob- 
able that  the  posterior  belly  acts  ^\  ith  the  anterior  one  in  produc- 
ing this  effect,  the  muscle  acting  in  the  reverse  direction  of  that 
just  referred  to  producing  the  movement  of  the  back  of  the  head. 
This  view  is  confirmed  by  the  fact  that  in  several  animals,  in  the 
orang,  for  example,  as  observed  by  the  author,^  the  posterior  belly 
of  the  digastric  muscle  is  alone  present  and  inserted  into  the  angle 
of  the  jaw.  That  the  mouth  is  to  a  certain  extent  opened  by  the 
elevation  of  the  upper  jaw  through  the  backward  motion  of  the  head 
due  to  the  contraction  of  the  posterior  belly  of  the  digastric  and  of 
the  muscles  of  the  neck,  may  be  shown  in  various  ways.  For  ex- 
ample, when  the  chin  is  placed  upon  a  table,  the  lower  jaw  being 
then  immovable,  or  when  the  lower  jaw  is  firmly  fixed,  as  in  certain 
surgical  operations,  it  will  be  observed  that  the  mouth  can  be 
slightly  opened,  though  the  lower  jaw  cannot  be  depressed. 

It  must  be  admitted,  however,  that  the  movement  of  the  upper 
jaw  in  this  respect  has  not  much  significance,  as  the  opening  of  the 
mouth  is  essentially  due  to  the  depression  of  the  lower  jaw. 

Resume. — The  eifect  of  mastication  is  that  the  solid  food  taken 
into  the  jnouth  is  cut  and  crushed  and  ground  up  by  the  teeth. 
III.  C.  Chapman,  Proc.  Acad,  of  Nat.  Sciences,  1880,  p.  101. 


^4  DIGESTION. 

The  little  pieces  that  ooze  out  between  the  teeth  and  the  cheeks  are 
pushed  under  the  teeth  again  by  the  muscular  action  of  the  cheeks 
and  lips,  while  the  fragments  that  escape  within  the  inner  side  of 
the  teeth  are  forced  back  by  the  tongue.  The  importance  in  man 
of  the  action  of  the  cheeks,  lips,  and  tongue  in  mastication  is  well 
seen  when  there  is  a  paralysis  of  the  facial  or  hypoglossal  nerves. 
In  such  cases  the  food  accumulates  between  the  cheeks  and  the 
teeth,  and  the  want  of  action  of  the  tongue  is  seen  both  in  the  dif- 
ficulty of  mastication  and  deglutition.  The  same  effect  can  be 
produced  by  cutting  the  corresponding  nerves  in  animals.*  The 
thorough  mastication  of  the  food  insures  its  further  digestion. 
Indeed,  a  most  fertile  source  of  dyspepsia  is  the  too  common 
oustom  of  bolting  the  food.  In  the  latter  part  of  the  last  century 
it  was  shown  by  Spallanzani "  that  different  kinds  of  meat  when 
enclosed  in  perforated  tubes  and  so  swallowed,  passed  through  his 
alimentary  canal  comparatively  undigested.  Wlien  the  meats,  how- 
ever, were  first  broken  up  and  then  placed  within  the  tubes  very 
little  undigested  matter  was  found  in  them  when  passed  by  the 
anus. 

In  gramnivorous  birds,  like  the  common  fowl,  for  example,  the 
want  of  teeth  is  supplied  by  pebbles  swallowed  with  the  food,  the 
gizzard  triturating  the  food  by  means  of  tlie  pebbles. 

Mastication  should  be  kept  up  until  the  food  is  thoroughly 
ground  up.  The  teeth  are  so  exquisitely  sensible  to  the  presence 
of  any  hard  matter  that  we  are  enabled  by  them  to  know  at  once 
whether  the  process  of  mastication  is  comjjleted.  During  mastica- 
tion not  only  is  tlie  food  thoroughly  triturated,  but  it  becomes 
gradually  incorporated  with  the  saliva.  To  the  consideration  of  the 
production  and  effects  of  this  secretion  let  us  now  turn. 

iPanizza,  Gaz.  Med.,  1835,  p.  419. 

^Fisica  Animale  et  Vegetabile.     Venezia,  1782,  Tomo  secondo,  p.  52. 


CHAPTER   VI. 


DIGESTION.—  (Contiiwed.) 


INSALIVATION  AND  DEGLUTITION. 


Fm. 


Insalivation. 

The  saliva  consi.sts  of  a  mixture  of  the  secretion  of  the  parotid, 
submaxillary,  and  sublingual  glands,  usually  known  as  the  salivary 
glands  (Fig.  27),  and  also  of  the  labial,  buccal,  lingual,  molar,  and 
pharyngeal  glands.  The  salivary  glands  are  regarded  at  present 
by  histologists  as  being 
compound  tubular  rather 
than  racemose  or  grape-like 
glands  as  was  formerly  sup- 
posed, the  secreting  power 
residing  in  the  cells  Avith 
which  the  diverticula  of  the 
ducts  are  lined.  According 
to  recent  researches '  the 
lumen  of  the  duets  appears 
to  be  prolonged  as  a  capil- 
lary network  extending  be- 
tween and  even  into  tlic 
.secreting  cells. 

Ivct  us  consider  now  the 
properties  of  the  saliva  se- 
creted by  these  different 
glands  1)€'ginning  with  the 
parotid,  which  is  secreted 
more  abundantly  than  that 
of  the  other  glands.  The  parotid  saliva  as  obtained  from  sali- 
vary fistula  or  by  introducing  a  tube  directly  into  the  duct  of 
Steno,  is  an  alkaline,  clear,  watery  fluid,  the  latter  property  en- 
abling it  to  readily  mix  with  and  soften  the  food.  The  flow  of 
the  parotid  saliva  is  most  active  during  mastication,  about  three 
times  as  much  saliva  being  secreted  on  the  ma.sticating  side  of  the 
mouth  as  on  the  ojiposite  one.  These  facts,  taken  into  consider- 
ation with  that  of  the  orifice  of  the  duct  of  Steno  being  opposite  the 
second  molar  tooth,  so  situated  that  the  saliva  at  once  comes  in 
contact  with  the  food  that  is  being  masticated,  suggest  the  view 
that  the  function  of  the  parotid  saliva  is  to  aid  ma.stication. 

The  facts  of  comparative    physiology  confirm    this  conclusion. 
Thus,  in  the  ruminantia,  which  chew  their  food  very  thoroughly, 

'  La.sertcin,  Pfluger's  Archiv,  Band  o5,  1893,  s.  417. 


The  ?<alivary  glands.     (Gray.) 


96  DIGESTION. 

the  parotid  glands  are  very  large ;  on  the  other  hand  they  are 
usually  absent  in  the  cetacca,  whales,  dolphins,  etc.,  and  but  little 
developed  in  the  otter,  seal,  hij)p()])otamus,  the  latter  not  needing 
parotid  glands,  the  water  in  which  they  live  or  pass  much  of  their 
time  sufficiently  moistening  their  food.  It  has  also  been  shown 
that  if  the  duct  of  Steno  be  divided  in  the  horse,  the  time  required 
in  chewing  a  feed  of  oats  is  three  times  as  much  as  under  ordinary 
circumstances.  The  food  is  also  swallowed  with  difficulty  under 
such  circumstances,  through  the  want  of  its  proper  admixture  with 
the  saliva.  It  is  well  known  also  that  less  saliva  is  produced  in 
the  horse  on  a  feed  of  oats  than  on  one  of  hay  or  straw,  and  that 
food  already  moistened  excites  little  if  any  flow  of  saliva. 

Reflection  upon  the  relative  development  of  the  submaxillary 
glands  in  different  kind  of  mammals  in  connection  with  their  habits 
leads  to  the  conclusion  that  the  principal  use  at  least  of  the  sub- 
maxillarv  saliva  is  that  of  lubricating  the  food,  and  of  so  promoting 
its  deglutition.  Thus,  in  the  carnivora  in  which  the  food  is  rather 
bolted  than  chewed,  the  submaxillary  glands  are  large,  the  parotids 
small.  In  the  great  ant-eater,  Myrmecophaga  jubata,  while  the 
parotid  gland  is  so  small  as  to  have  escaped  even  the  notice  of 
Cuvier,  the  sul)maxillary  gland  is  over  sixteen  inches  in  length  and 
secretes  an  extremely  viscid  tenacious  saliva  which  lubricates  the 
extensible  tongue  to  which  the  ants  adhere  and  upon  whi-ch  the 
animal  subsists.  That  the  function  of  the  submaxillary  saliva  in 
man  is  to  lulu'icate  the  food  and  so  aid  its  deglutition  is  shown  by 
its  viscidity  as  compared  M'ith  the  parotid  saliva,  its  consistence  be- 
ing such  that  it  coats  but  does  not  penetrate  the  bolus  of  food. 
Further,  the  submaxillary  is  often  mixed  with  the  sublingual  saliva 
even  before  it  passes  into  the  mouth,  the  duct  from  the  sublingual 
gland,  the  so-called  duct  of  Bartholinus,  not  unfrequently  joining 
the  duct  of  Wharton  or  terminating  with  it  by  a  common  orifice. 
The  sublingual  saliva  transmitted  to  the  mouth  mostly  by  the  ducts 
of  Kivinus  is  more  viscid  than  the  submaxillary  saliva  and  pro- 
motes deglutition,  therefore,  even  to  a  greater  extent. 

That  the  function  of  the  submaxillary  and  sublingual  saliva  is 
essentiallv  to  aid  the  swallowinsr  of  the  food  is  still  further  shown 
by  the  fact  that  the  placing  of  a  sapid  substance  upon  the  tongue 
immediately  induces  a  copious  flow  of  submaxillary  saliva  which  is 
due,  as  we  shall  see  hereafter,  to  the  reflex  stimulus  of  tlu;  chorda 
tympani  nerve. 

The  fluids  secreted  by  the  labial,  buccal,  or  molar  glands,  etc., 
have  never  been  studied  separately  in  man.  In  animals  in  which 
the  ducts  of  the  parotid,  submaxillary,  and  sublingual  glands  have 
been  ligated,  the  fluid  still  secreted  by  the  mouth  comes  from  the 
glands  just  mentioned,  and  consists  of  a  thick,  opaque,  grayish 
mucus,  containing  salivary  corpuscles,  desquamated  epithelial  cells, 
etc.  The  turbidness  of  the  mixed  saliva  is  due  to  this  secretion, 
that  from  the  salivary  glands  ])ro})er  being  transparent. 


INS  A  LIVA  TION.  9  7 

It  has  been  learned  from  the  researches  of  Heidenhain/  Lav- 
dowsky,-  Langley/^  and  others,  that  the  minute  structure  of  the  sali- 
vary glands  differs  considerably  according  as  they  are  examined  after 
a  period  of  rest  or  activity,  and  that  such  differences  are  more  marked 
in  the  so-called  mucous  glands,  like  the  submaxillary,  in  which 
the  secretion  is  viscid,  mucin-like,  than  in  the  serous  or  albumi- 
nous ones,  like  the  parotid,  in  which  the  secretion  is  limpid.  Thus, 
if,  after  a  period  of  rest,  a  section  of  a  "mucous"  gland — the  sub- 
maxillary gland  of  the  dog,  for  example — be  examined,  the  cells 
of  an  alveolus  (Fig.  28,  A)  will  be  found  to  stain  with  carmine 
more  readily  in  certain  parts  than  in  others.  The  nuclei  and  sur- 
roimding  protoplasm,  and  the  demilune  cells — apparently  young 
cells  lying  next  to  the  basement  membrane — become  deeply  tinged, 
while  the  remaining  portion  of  the  cell  remains  uncolored,  due  ap- 
parently to  its  protoplasm  in  this  situation  having  been  converted 
into  a  mucin-like  substance.  If,  however,  similar  sections  of  the 
gland  be  made  after  a  period  of  activity  induced  by  stimulation 
of  the  chorda  tympani  nerve,  it  will  be  observed  (Fig.  28,  B)  that 
but  a  small  portion,  if  indeed  any  part,   of  the  cell  has   resisted 

Fig.  28. 


Section  of  a  "  mucous"  gland.  ^-1.  In  a  state  of  rest.  B.  After  it  has  been  for  some  time  ac- 
tively secreting.  (I.  Demilune  cells,  c.  Leucocytes  lying  in  the  interalveolar  spaces.  The  darker 
shading  in  both  figures  is  intended  to  indicate  the  amount  of  staining.     (After  Lavdowsky. ) 

coloration  with  carmine,  and  that  the  cells  have  diminished  in  size. 
If  sections  of  a  "  serous"  gland — the  parotid  gland  of  a  rabbit, 
for  example — after  periods  of  rest  and  activity,  be  treated  in  the 
same  way  with  carmine,  differences  of  the  same  kind  will  be  ob- 
served. Thus,  after  rest  the  cells  of  the  parotid  (Fig.  29,  A)  will 
be  found  to  be  pale,  transparent,  with  few  granules,  staining  by 
carmine  with  difficulty,  the  nuclei  irregular  in  outline,  apparently 
as  if  shrunken.  After  a  period  of  activity,  on  the  other  hand 
(Fig.  29,  B),  from  stimulation  by  the  sympathetic  nerve,  the  cells 
will  be  seen  to  have  become  turbid,  full  of  granules,  staining  readily 

'  Hermann,  Physiologie,  Fnnftcr  Band,  s.  58.     Leipzig,  1880. 
^Archives  of  Mic.  Anat.,  1877,  xiii.,  s.  281. 
''Journal  of  Physiology,  1879,  vol.  ii.,  p.  2G0. 


98 


DIGESTION. 


with  carmine,  the  nuclei  large  and  round,  with  conspicuous  nucleoli, 
and  the  cells,  as  a  whole,  smaller.  Such  facts  lead  us  naturally  to 
conclude  that  during  a  period  of  rest  the  cells  of  the  salivary- 
glands  are  elaborating  from  the  blood  their  characteristic  secretion, 
the  elements  of  the  latter  existing  in  the  blood,  but  not  the  secre- 
tion itself,  as  such  ;  that  the  secretion,  as  formed,  is  stored  up  (the 
part  not  staining  with  carmine)  until  needed,  when  at  the  proper 
moment  it  is  forced  into  the  interior  of  the  gland  and  thence  passes 
into  the  duct,  the  normal  stimulus  to  the  secretion  being,  as  we  shall 
see  hereafter,  impressions  made  upon  the  tongue,  etc.,  and  which 
are  transmitted  by  the  appropriate  nerves  supplying  the  glands. 
The  secretion  of  the  saliva  is  not  a  phenomenon  of  mere  filtration 
due  to  pressure,  osmosis,  etc.  Apart  from  the  fact  that  the  saliva 
does  not  exist  as  such  in  the  blood  it  can  be  shown  that  it  is 
excreted  under  a  pressure  greater   than   that  exerted  l)y  the  blood 

Fig.  29. 


Section  of  a  "  serous"  glaud  :  the  parotid  of  tlio  rabbit.     .1.  At  rest.     B.  After  stimulation 
of  the  cervical  sympathetic.     (After  Ueidexhais.) 

of  the  carotid  artery  of  the  same  side.  AVere  pressure  the  only 
influence  at  work  in  the  secretion  of  the  saliva  the  latter  would 
flow  back  to  the  blood  rather  than  to  the  duct.  Furdier,  it  is  well 
known  that  during  paralysis  of  the  secretory  nerves,  as  due  to 
atropin  ])oisoning,  an  increased  flow  of  blood  to  the  submaxillary 
glaud  induced  by  stimulation  of  the  chorda  tympani  nerve  will  not 
cause  secretion.  Moreover,  the  salivary  glands  exhibit  a  kind  of 
elective  affinity  in  regard  to  the  excretion  of  substances  from  the 
blood,  salts  of  p(jtassium,  comliinations  of  iodine  and  bromine  being 
eliminated,  but  not  those  of  iron.  It  is  al.-^o  shown  that  during 
the  process  of  secretion,  chemical  action  is  going  on,  the  tem- 
perature of  the  saliva  and  venous  blood  coming  from  the  gland 
being  1.5°  C.  higher  than  that  of  the  arterial  blood  supplying 
the  gland,'  and  that  the  production  of  carbon  dioxide  is  increased. - 
Inasmuch  as  during  digestion,  it  is  the  mixed  saliva  which  modifies 
the  food,  it  will  not  be  necessary  to  dwell  especially  upon  the 
physical  or  chemical  properties  of  any  one  particular  kind  of  it.  It 
may  be  mentioned,  however,  in  this  connection  that  while  the 
parotid  saliva  is  rich  in  ptyalin  it  contains  no  mucin,  whereas  the 

iLudwig  and  Spiess  :  Sitz.  d.  AViener,  Acad.  Math.  Nat.  Classe,  1857,  xxv.,  s.  548. 
^Pliuger:  PHugor's  Arcliiv,  1868,  Band  i.,  s.  686. 


INS  ALT  VA  TION.  9  9 

submaxillary  and  su1)lingual  saliva  are  especially  rich  in  mucin 
and  are  more  alkaline  than  the  parotid  saliva.  The  saliva,  as  we 
find  it  in  the  mouth,  consisting  then  of  a  mixture  of  all  the  differ- 
ent kinds  of  saliva,  is  an  alkaline,  colorless,  turbid,  mucilaginous, 
ropy  fluid  with  a  specific  gravity  of  about  1003.  While  the  reac- 
tion of  the  saliva  is  usually  alkaline  as  just  mentioned,  it  should  be 
stated  that  it  may  be  acid  after  meals.  The  turbidity  of  the  saliva 
is  due  to  the  presence  of  the  cells  of  the  buccal  epithelium,  salivary 
corpuscles  which  are  apparently  altered  leucocytes,  and  food  resi- 
dues. The  ropy  character  of  the  saliva  is  due  to  its  mucin  which 
we  have  seen  is  chemically  a  compound  proteid.  Like  all  the 
digestive  secretions  the  saliva  consists  largely  of  water,  organic 
matter,  and  salts. 

Composition  or  Human  Saliva.' 

In  1000  parts. 

Water 994.2 

Solids 5.8 

Mucus  and  epithelium    .          .          .          .          .          .  2.2 

Soluble  organic  matter  (Ptyalin)     .         .         .         .  l.-i 

Potassium  sulphocyauide        .         .         .         .         .  0.04 

Salts 22.00 

Judging  from  the  composition  of  the  ash  the  salts  in  the  saliva 
appear  to  exist  in  the  form  of  potassium  and  sodium  chloride,  po- 
tassium sulphate,  and  potassium,  sodium,  calcium,  and  magnesium 
phosphate.  In  the  freshly  secreted  saliva  there  is  also  found  carbon 
dioxide  gas  (6o  to  07  per  cent.),  most  of  which  existed  in  combina- 
tion as  carbonates  and  traces  of  oxygen  and  nitrogen.  It  was  shown 
many  years  since  "  that  hydrated  starch  when  mixed  with  warm  saliva 
was  liquefied  and  converted  into  sugar.  Any  one  can  convince 
himself  that  such  is  the  case  by  mixing  in  a  test-tube  a 
little  boiled  starch  with  his  own  saliva  and  testino-  for  sugar.  It 
will  also  be  found  that  saliva  has  the  same  effect  upon  raw 
starch,  only  a  longer  time  is  required  to  produce  it.  The  ordinary 
acceptation  of  what  takes  place  in  the  conversion  of  starch  into 
sugar  by  the  saliva  is  that  solul)le  starch  is  first  formed  and  then 
erythro-dextrin  (as  shown  by  the  red  color  given  with  iodine) 
which  is  further  transformed  into  maltose  (C,.,H.,.,Oj^H.,0),  achro- 
dextrin,  and  a  small  quantity  of  glucose  (C^.Hj^OJ.  It  has  been 
ascertained  by  experimenting  with  the  different  substances  of  which 
the  saliva  consists  that  it  is  the  soluble  organic  matter,  the  ptyalin 
or  salivary  diastase,  to  which  this  transforming  property  is  due,  and 
that  the  different  kinds  of  saliva  will  convert  starch  into  sugar  as 
well  as  the  mixed  saliva.  The  phenomenon  appears  to  be  one  of 
hydrolysis  and  fermentation,  the  starch  in  the  presence  of  ptyalin 
taking  up  water  and  then  splitting  into  two  or  more  substances. 

^  Hammerhacher,  as  quoted  by  Ilammai-sten.  A  Text-book  of  Physiological 
Chemistry,  translated  by  Mandel,  i8i)3,  p.  17:^. 

^Leuchs,  Kastner's  Archiv  fiir  Chemie,  1831,  s.  105. 


100  DIGESTION. 

Ptyalin  has  not  been  obtained  as  yet  in  a  sufficiently  pure  state  to 
determine  its  chemical  nature.  It  is  regarded  as  an  enzyme,  an 
amylolytic  ferment  ^  acting  by  its  presence  (catalysis)  simply  on  ac- 
count of  its  specific  action  upon  starch,  one  part  of  ptyalin  trans- 
forming as  much  as  two  thousand  parts  of  starch  into  sugar.  Not- 
withstanding that  the  action  of  ptyalin  is  very  rapid  and  energetic, 
only  a  very  small  quantity  of  sugar  is  produced  in  the  mouth,  the 
starch  being  so  soon  swallowed.  As  the  starch  remains,  however, 
sufficiently  long  in  the  mouth  to  become  thoroughly  mixed  with 
the  saliva,  and  as  the  transformation  into  sugar  continues  after  the 
starch  passes  into  the  stomach,  for  some  time  at  least,  sugar  is  pro- 
duced, and  can  be  detected  in  that  organ.  It  is  well  known  that 
outside  of  the  body  the  action  of  jityalin  upon  starch  will  be  com- 
pletely arrested  by  admixture  with  a  very  weak  solution  of  hydro- 
chloric acid.  It  has  been  inferred,  therefore,  that  the  conversion 
of  starch  into  sugar  by  the  saliva  in  the  stomach  will  be  suspended 
by  the  action  of  the  hydrochloric  acid  of  the  gastric  juice.  We 
shall  see,  however,  that  the  function  of  the  gastric  juice  is  not  that 
of  neutralizing  the  action  of  the  saliva,  but  of  digesting  proteids. 
If  the  gastric  juice  secreted  only  suffices  for  the  latter  purpose, 
there  will  be  none  available  for  the  suspension  of  the  action  of  the 
ptyalin.  Hence  the  amount  of  starch  converted  into  sugar  by  the 
saliva  in  the  stomach  will  depend  upon  the  relative  amounts  of  food 
and  gastric  juice  present  and  upon  the  rapidity  with  which  the  food 
is  mixed  with  the  latter,  the  greatest  amount  of  sugar  being  pro- 
duced in  the  early  stage  of  digestion.  It  has  also  been  shown  out- 
side of  the  body  (digestion  in  vitro)  that  the  accumulation  of  the 
products  of  salivary  fermentation  will  not  only  retard  but  finally 
arrest  the  action  of  ptyalin,  but  that  with  the  removal  of  such  prod- 
ucts as  by  dialysis  the  fermentation  action  recommences.  It  is  rea- 
sonable to  suppose,  therefore,  that  as  the  digestive  products  are  as 
rapidly  absorbed  as  produced,  the  action  of  ptyalin  in  the  economy- 
is  long  continued.  The  importance  of  the  saliva  as  regards  the 
transformation  of  starch  into  sugar  must  not,  however,  be  exagger- 
ated, since  as  we  shall  see  the  intestinal  and  pancreatic  juices  are 
equally  efficient  in  this  respect.  It  is  stated  that  while  ptyalin  is 
present  in  the  parotid  saliva  of  the  child  at  birth,  it  does  not  ap- 
pear in  the  suljmaxillary  saliva  until  two  months  later.  The  signifi- 
cance of  the  ])otassium  sulphocyanide  which  is  always  found  in  the 
saliva  in  traces  is  not  apparent.  The  remaining  salts,  wliile  ren- 
dering the  saliva  alkaline,  have  not  been  sliown  as  yet  to  fulfill  any 
particular  function  in  digestion. 

The  amount  of  saliva  secreted  during  twenty-four  hours,  in  man, 
has  never  been  exactly  determined.  As  the  saliva  is  constantly  be- 
ins:  reabsorbed,  a  source  of  error  in  anv  calculation  as  to  the  amount 

1  On  the  Presence  of  the  Amylolytic  Fornicnt  and  its  Zymogen  on  the  Salivary 
Glands,  by  C.  W.  Latimer,  M.t).,  and  J.  W .  ^\'urren,  M.D.,  Journal  of  Experi- 
mental Medicine,  Vol.  J  I.,  1897,  jx  465. 


DEGLUTITION.  101 

secreted  in  a  given  time  would  be  the  risk  of  counting  the  same 
saliva,  or,  at  least,  the  elements  entering  into  its  composition  more 
than  once.  According  to  Dalton,^  31.1  grammes  (about  480  grains) 
of  saliva  can  be  obtained  from  the  mouth  in  twenty  minutes  with- 
out any  artificial  stimulus.  The  natural  stimulus  to  the  secretion 
of  the  saliva,  however,  is  the  presence  of  food  in  the  mouth  ;  indeed, 
the  sight,  or  even  the  thought  of  food,  in  some  individuals  will 
make  the  mouth  "  water."  The  amount  of  saliva  secreted  will  de- 
pend, therefore,  on  the  quantity  and  quality  of  the  food. 

It  has  been  estimated  approximately  that  about  loOO  grammes 
(3.3  lbs.)  of  saliva  are  secreted  in  the  twenty-four  hours.  In 
concluding  our  account  of  the  saliva  there  may  be  mentioned  ap- 
propriately in  this  connection  the  peculiarity  it  possesses  of  attract- 
ino-  or  entanolino;  bubbles  of  air  in  the  mass  of  food.  The  effect  of 
this  is  that  stomach  digestion  is  facilitated  through  the  easy  access 
afforded  to  the  gastric  juice  when  the  food  comes  in  contact  with 
this  secretion.  Moist,  heavy  bread  is  not  readily  acted  upon  by 
the  secretions  through  its  not  being  permeated  with  air  in  the 
manner  just  referred  to. 

While  one  of  the  uses  of  the  saliva  in  man  is  certainly  the  trans- 
formation of  starch  into  sugar,  undoubtedly  its  most  important 
function  is  that  of  aidino;  mastication  and  deo;lutition,  the  secretion 
of  the  parotid  gland  promoting  specially  the  former  function,  that 
of  the  submaxillary  and  sublingual  glands  the  latter,  as  we  have 
seen  in  speaking  of  the  secretions  separately. 

Deglutition. 

After  the  food  has  been  thoroughly  masticated  and  mixed  with 
the  saliva,  it  is  swallowed.  The  mouth  being  closed,  deglutition 
or  the  act  of  swallowing  begins  by  the  tongue,  more  especially  the 
tip,  aided  by  the  cheeks,  collecting  the  particles  of  the  food  into  a 
mass  or  bolus.  Through  the  action  of  the  hyoglossi  muscles  the 
tongue  is  then  moved  forward  and  upward,  the  tip,  middle,  and  root 
being  successively  pressed  against  the  hard  palate,  whereby  the 
bolus  is  forced  backwards  through  the  fauces  (isthmi  faucium) 
towards  the  pharynx.  As  the  bolus  of  food  passes  through  the 
fauces,  the  tongue  being  drawn  upward  and  backward  by  the  con- 
traction of  the  stylo-glossi  muscles,  and  the  anterior  pillars  of  the 
fauces  coming  together,  l)y  the  action  of  the  palato-glossi  muscles 
like  two  curtains,  the  bolus  of  food  is  thereby  prevented  from  re- 
turning to  the  mouth.  The  importance  of  the  tongue  in  degluti- 
tion may  be  appreciated  from  the  fact  that  it  is  impossible  to  per- 
form the  act  on  those  cases  in  which  the  tongue  has  been  entirely 
amputated,  is  congenitally  deficient,  or  the  hypo-glossal  nerve  is 
paralyzed.  In  amputation  of  the  tongue  there  is  usually  left  a 
portion  of  the  base  sufl&cient  to  press  against  the  palate,  making 

iDalton,  Physiology,  1882,  p.  144. 


102 


DIGESTION. 


deglutition  possible.  At  the  same  moment  tliat  the  opening^into 
the  mouth  is  cut  oiF  the  posterior  half-arches  of  the  fauces  approach 
each  other  throup-h  the  action 
of  the  palato-pharyngei  muscles, 
the  interval  between  them  being 
filled  by  the  uvula  (azyzos  uvuhe 
muscles)  and  the  soft  palate  be- 
ing rendered  tense  by  the  tensor 
palati  and  elevated  by  the  le- 
vator palati  the  opening  from 
the  pharynx  into  the  posterior 
nares  is  effectually  closed.  The 
importance  of  the  latter  condi- 
tion is  seen  in  cases  of  cleft  pal- 
ate or  paralysis  of  the  velum  in 
which  deglutition,  at  least  of 
liquids,  is  impossible,  the  latter 
when  swallowed  returning  by 
the  nose.  In  the  meantime  the 
pharynx  together  witli  the  lar- 
ynx being  elevated  by  the  con- 
traction of  the  stvlo-pharvno;ei, 
stylo-hyoid,  genio-hyoid,  mylo- 
hyoid, thyro-hyoid,  and  digastric 
muscles,  the  latter  actinp;  more 
particularly  through  its  anterior  belly,  the  pharynx  is  ^videned  and 
the  entrance  to  the  larynx  closed,  the  latter  being  pressed  up  against 


hh.  Anterior  half  arches,    cc.  Posterior 
half  arches,    ff.  Tonsils.     (Valentin.) 


Fig.  31. 


Base  of  craniinii. 


Pharyux. 


Nose. 


Salivary  glands. 

Uyoid  hone. 

Larvux. 


Thvroiil  gland. 

Ill  f  IIJ^B^ 

(njsoijhagus.  iPf  l^K  Trachea. 

Vertical  section  of  mouth  and  |iliarynx.     (Milne  Edwards.) 

the  epiglottis  and  the  glottis  itself  closed  by  the  constrictors  of  the 
larynx.  That  tlie  epiglottis  is  indisjwnsable  in  the  swallowing  of 
liquids  at  least  is  shown  by  the  fact  that  in  its  absence  "  liquids  go 


DEGLUTITIOX.  103 

down  the  wrong  way,"  that  is  pass  into  the  larynx  instead  of  into 
the  cesophagns.  Solids,  however,  can  l)e  swallowed  in  the  absence 
of  the  epiglottis,  since  the  larynx  being  drawn  up  under  the  base 
of  the  tongue  is  sufficiently  well  covered  by  the  latter  to  prevent 
food  entering  it.  If,  however,  a  small  fragment  of  food,  a  crumb, 
for  example,  be  swallowed  incautiously  in  the  absence  of  the  epi- 
glottis, it  is  very  apt  to  pass  into  the  larynx  and  give  rise  to  a  fit 
of  coughing.  At  the  moment  of  the  closing  of  the  openings  of 
the  pharynx  into  the  mouth,  nares  and  larynx,  the  mylo-hyoid 
muscles  contract  quickly  and  powerfully  and  the  bolus  of  food  is 
projected  or  shot  down  under  high  pressure  through  the  pharynx 
into  the  cesophagns,  reaching  the  cardiac  orifice  in  about  0.1  second 
where  it  is  usually  temporarily  retained.  In  some  cases,  however, 
owing  to  the  cardiac  orifice  of  the  stomach  being  relaxed,  the  bolus 
of  food  passes  directly  into  the  stomach.  The  rapid  movement 
just  described  is  followed  immediately  by  a  second  slower  one  due 
to  the  muscular  contraction  of  the  pharynx  and  cesophagns  and 
which  carries  down  any  food  that  may  have  esca])e(l  the  first  move- 
ment and  which  forces  it,  together  Avith  the  food  that  has  already 
reached  the  cardiac  orifice,  through  the  latter  into  the  stomach,  the 
time  elapsing  from  the  beginning  of  deglutition  amounting  to  about 
six  seconds.  If  the  region  of  the  stomach  be  auscultated  during 
deglutition  at  times  two  sounds  may  he  heard,  the  first  a  '^  scpiirt 
sound"  due  to  the  projection  of  the  bolus  into  the  stomach  by  the 
contraction  of  the  mylo-hyoid  muscles,  the  second  a  "  press  sound" 
due  to  the  action  of  the  pharynx  and  cesophagns  which  occurs  at 
the  end  of  swallowing  and  which  scpieezes  the  residue  of  the  food 
from  the  (esophagus  into  the  stomach.  It  will  be  observed  that 
under  such  circumstances  the  oesophagus  contracts  after  the  food 
just  swallowed  has  passed  into  the  stomach.  While  such  api)ears 
to  be  the  mechanism  of  the  deglutition  of  water  and  of  semi-fluid 
food,  it  should  be  mentioned  that  Avhere  a  large  mass  of  dry  food 
or  of  considerable  consistence  is  swallowed  the  mylo-hyoid  muscles 
do  not  appear  to  contract  with  sufficient  force  to  shoot  the  bolus 
down  to  the  cardiac  orifice,  the  muscular  action  of  the  pharvnx  and 
the  cesophagns  being  necessary  to  accomplish  this  effect.  In  that 
case  there  is  but  one  movement  of  deglutition  and  one  auscultation 
sound,  the  "  press  sound,"  and  the  cesophagns  contracts  before  the 
bolus  passes  into  the  stomach  as  in  rabbits,  for  example,  whose 
food  is  usually  dry.  The  passage  of  the  food  through  the  ])harvnx 
and  cesophagns  are  effected  by  means  of  muscular  fibers  which  are 
disposed  in  the  pharynx  as  the  constrictors  and  in  the  oesophagus 
in  two  layers,  an  external  longitudinal  and  an  internal  circular,  the 
fibers  being  striated  in  the  upper  third,  unstriated  in  the  lower 
third,  and  mixed  in  the  middle  third  of  the  tube.  This  disposition 
is  interesting  as  accounting  perhaps  for  the  cesophagns  contracting 
in  three  segments,  and  for  the  lower  third  remaining  contracted  for 
a  short  time  after  the  food  has  passed  into  the  stomach,  thereby 


104  DIGESTION. 

preventing  regurgitation.  The  time  elapsing  during  the  contrac- 
tion of  each  of  the  live  mnscuhir  segments  involved  in  deglutition 
and  therefore  of  the  total  time  between  the  beginning  of  degluti- 
tion and  the  moment  that  the  bolus  reaches  the  stomach  is  given  in 
the  following  table  : 

Time  of  Deglutition. 

Secouds. 

Contraction  of  mylo-hyoids  and  constrictors  of  pharynx  0.3 
Contraction  of  first  part  of  oesophagus  .  .  .0.9 
Contraction  of  second  part  of  oesopliagus  .  .  .18 
Contraction  of  tliird  part  of  oesophagus       .         .         .3.0 

6T0 

It  has  also  been  shown  that  if  a  second  act  of  swallowing  is  made 
within  six  seconds  of  the  first  one  the  pharyngeal  cesophageal  wave 
of  coutraction  does  not  reach  the  stomach  until  six  seconds  after 
the  second  swallow,  just  as  if  this  had  Ijeen  the  only  one,  the  second 
deglutition  not  only  stimulating  the  oesophagus  to  contract,  but  in- 
hibiting that  part  which,  though  stimulated,  has  not  yet  contracted. 
Such  is  also  the  case  if  we  make  several  swallows  successively,  as 
in  drinking  a  glass  of  water,  the  a?sophagus  not  contracting  until 
after  the  last  swallow  and  after  the  same  interval  of  time  as  would 
have  elapsed  if  deglutition  had  only  been  performed  once.  The 
theory  of  deglutition  that  we  have  just  described  is  essentially  that 
first  offered  by  Kronecker  and  Falk/  though  afterwards  much  better 
established  by  Meltzer.^  The  method  of  experimentation  made  use 
of  by  the  latter  was  to  insert  small  rubber  balloons  in  the  pharynx 
oesophagus  at  different  levels  and  to  connect  the  .same  by  tubes  with 
a  tambour  and  recording  levers,  the  latter  being  placed  together 
with  the  pen  of  a  time-marker  in  contact  with  a  kymograph.  Such 
being  the  disposition  of  the  apparatus,  with  an  act  of  swallowing 
curves  were  produced  upon  the  kymograph  (Fig.  32),  due  to  the 

Fig.  32. 


2.  Line  inarkiiiK  soeonds.  3.  Tracing  of  the  l)ag  in  tlie  (isophagiis  12  centimeters  from  the 
teeth.  ('.  Compression  of  the  bag  by  the  bolus.  1>.  ("ompressiou  by  the  residues  of  the  bohis 
carried  on  by  the  coutraction  of  the  pharynx.     E.  Contraction  of  the  cesophagus.     (Laxdois.) 

pressure  exerted  upon  the  balloons  by  the  bolus  of  food  as  it  was 
first  shot  down  by  the  action  of  the  mylo-hyoid  muscles,  and,  sec- 
ondly, by  the  action  of  the  pharynx  and  (esophagus.  In  accord- 
ance with  the  way  the  curves  were  produced,  they  always  presented 

iDuBoisEeymond's  Archiv,  1880,  1881,  1883. 

2  New  York  Medical  Journal,  1894.  Journal  of  Experimental  Medicine,  Vol. 
II.,  1897,  p.  453. 


DEGL  UTITIOX.  1 05 

two  elevations  or  one  elevation  with  two  crests,  the  first  elevation 
or  crest,  dne  to  the  rapid,  the  second  to  the  slow,  contraction  wave. 

By  such  curves  Dr.  Meltzer  determined  in  his  own  person,  (1) 
the  length  of  time  elapsing  between  the  beginning  of  deglutition 
and  the  moment  that  the  food  arrived  at  the  stomach  ;  (2)  the  in- 
terval of  time  between  the  Uvo  waves  of  contraction  when  the  bal- 
loon was  in  the  pharynx ;  (3)  the  time  during  wliich  the  food 
passed  through  the  five  contracting  segments. 

The  act  of  deglutition  is  usually  divided,  for  convenience  of 
description,  into  three  periods,  stages,  or  movements:^  (1)  The 
passage  of  the  bolus  from  the  mouth  through  the  fauces  into  the 
pharynx  ;  (2)  from  the  pharynx  into  the  oesophagus ;  (3)  from  the 
oesophagus  into  the  stomach.  If  the  description  of  the  process  just 
given  is  regarded,  however,  as  correct,  the  division  into  three  move- 
ments, the  limits  of  which  in  any  case  are  entirely  arbitrary,  loses 
much  of  its  significance  and  may  as  well  be  discarded.  While  the 
beginning  of  deglutition,  or  the  part  confined  to  the  mouth,  is  vol- 
untarv,  the  remainder  is  involuntarv  in  character,  being:  due  to  an 
impression  made  upon  the  mucous  membrane  of  the  palate,  etc., 
by  the  food,  Avhich  stimulates  the  center  in  the  medulla,  from  which 
emanate  the  impulses  that  pass  to  the  muscles  involved.  Indeed, 
without  solid  or  liquid  food  in  the  pharynx  it  is  impossible  to  per- 
form the  second  act  of  deglutition  ;  apparently,  tliis  is  done  some- 
times for  three  or  four  times  without  there  beinp;  anvthinw  to  swal- 
low,  but  there  is  really  always  present,  under  such  circumstances, 
sufficient  saliva  to  produce  the  necessary  impression. 

It  may  be  stated  in  this  connection  that  the  different  parts  of  the 
oesophagus  appear  to  contract  independently  of  each  other  ^  the 
propagation  of  the  contraction  wave  not  depending  upon  the  con- 
tinuity of  tissue  since  one  or  more  segments  of  the  cesophagus  mav 
be  removed,  and  yet  the  remaining  parts  will  contract  in  response 
to  the  stimulus  of  impulses  passing  from  the  medulla. 

It  is  hardly  necessary  to  call  attention  to  the  fact  that  solid  and 
liquid  foods  can  be  swallowed  in  all  positions.  It  is  a  common 
feat  among  jugglers  to  drink  a  bottle  of  wine  or  a  glass  of  beer 
while  standing  on  their  heads  or  hands. 

1  Majendie,  These  soutenue  a  1'  Ecole  de  Medecine  de  Pari^,  en  1808.  Precis 
Elementaire  de  Physiologie,  Tome  ii.,  p.  59. 

^A.  Mosso,  Moleschott,  Untersuchungen,  1878,  Band  xi.,  s.  327.  Kronecker  ii. 
Meltzer  ;  Du  Bois  Eeymond,  Archiv,  1881,  s.  465. 


CHAPTER    VII, 


DIGESTION.— (ro;i///,,/«^) 


GASTRIC  DIGESTION. 


The  stomach  is  a  musculo-membranous  sac  whose  walls  have 
on  an  average  a  thickness  of  a  little  more  than  two  millimeters  (a 
line).  When  distended  it  measures  laterally  about  37.5  centime- 
ters (15  inches),  and  antero-posteriorly  12.5  centimeters  (5  inches) 
with   a   capacity  usually  of  3    liters  (5    pints).     The  capacity  of 


Fig.  33. 


Call  liladilcT.  -- 


Spleen. 


-  Small  iutestiue. 
J Colon. 


—   Rectum. 


Digestive  apijaraturs  of  man.     (Milnk  I^dward.s.) 

the  stomach,  however,  is  often  less  and  sometimes  even  much 
greater,  varying  with  the  age,  sex,  and  habit  of  the  individual.  It 
is  held  in  position  in  the  upper  part  of  the  abdominal  cavity  by 
its  connection  with  the  oesophagus  and  the  folds  of  the  peritoneum. 
When  empty,  the  sides  of  the  stomach  are  usually  in  contact,  and 
the  whole  organ  presents  a  flattened  appearance.  When  distended 
by  food,  however,  the  anterior  wall  of  the  stomacli  becomes  superior, 
and  is  applied  to  the  diaphragm.     This  is  due  to  the  ends  of  the 


MOTIONS  OF  THE  STOMACH.  107 

stomach  and  lesser  curvature  being  comparatively  immovable.  As 
the  food  enters  the  stomach  from  the  oesophagus,  it  turns  to  the 
left,  and,  passing  into  the  cardiac  end,  or  greater  pouch,  thence 
proceeds  along  the  greater  curvature  to  the  pyloric  end,  returning 
by  the  lesser  curvature  to  the  cardiac  portion,  to  ])egin  the  same 
course  over  again.  Each  of  these  revolutions  occupies  from  about 
one  to  three  minutes,  and  are  slowest  at  first,  becoming  more  rapid 
as  digestion  advances.  The  food  undergoes,  therefore,  a  sort  of 
churning  action,  passing  from  one  side  of  the  stomach  to  the  other. 
Hereby  it  is  thoroughly  incorporated  with  the  gastric  juice,  gradu- 
ally broken  down,  liquefied,  and  finally  converted  into  what  is  known 
as  the  chyme.  During  the  beginning  of  digestion  the  pyloric 
orifice  is  so  firmly  closed  by  the  contraction  of  the  circular  muscular 
fiber  aided  by  the  circular  fold  of  mucous  membrane  developed 
there  that  no  food  passes  into  the  duodenum.  After  the  churning 
movement  just  described  has  continued,  however,  for  about  a  quar- 
ter of  an  hour  the  circular  muscular  fibers  of  the  pyloric  orifice 
relax.  Then  the  liquid  pultaceous  part  of  the  food  and  later  the 
more  solid  portions  and  even  hard  bodies,  such  as  coins,  stones,  are 
pushed  or  forced  into  the  duodenum  by  the  vigorous  peristaltic  con- 
tractions of  the  pyloric  jjart  of  the  stomach,  the  fundus,  or  cardiac 
portion,  taking  little  or  no  part,  acting  rather  as  a  reservoir.  In 
deed,  when  digestion  is  at  its  height,  the  cardiac  portion  of  the 
stomach  is  quite  distinctly  separated  from  the  pyloric  portion  by  a 
"  transverse "  constricting  band,  the  so-called  "  sphincter  antri 
pylorici "  situated  from  seven  to  ten  centimeters  from  the  pylorus. 
The  organ  then  presents  an  hour-glass  form,  of  which  two-fifths 
consist  of  the  cardiac  portion.  It  is  worth  mentioning  in  this  con- 
nection, that  this  hour-glass  form  of  the  stomach,  present  only  in 
man  during  digestion,  is  the  form  presented  in  the  manatee  whether 
digestion  is  going  on  or  not ;  the  author  having  found  in  the  dis- 
section of  several  individuals  the  stomach  ahvays  presenting  this 
form,  whether  it  was  full  of  food  or  empty.^ 

After  the  food  has  been  digested  and  the  stomach  has  been 
emptied  of  its  contents,  which  processes  are  effected  within  a  period 
of  from  two  to  four  hours,  all  the  motions  just  described  cease,  and 
do  not  recommence  again  until  a  fresh  supply  of  food  is  taken. 
The  churning  and  peristaltic  motions  of  the  stomach  just  described 
depend  upon  its  muscular  fibers  assisted  by  the  diaphragm.  The 
muscular  coat  of  the  stomach  which  averages  about  a  millimeter 
(2V  ^^  "^'^  inch)  in  thickness,  consists  of  three  sets  of  fibers,  the 
longitudinal,  circular,  and  oblique,  which  are  disposed  from  without 
inward,  in  the  order  just  named — that  is,  the  longitudinal  fibers  are 
external,  the  oblique  are  internal,  while  the  circular  fibers  lie  be- 
tween the  other  two. 

These  three  sets  of  fibers  are,  however,  very  unequally  developed. 
Thus,  the  longitudinal  fibers  are  best  seen  in  the  lesser  curvature  ; 
'II.  C.  Chapman,  Proc.  Acad,  of  Nat.  Sciences,  Phila.,  1876,  p.  452. 


108  DIGESTION. 

the  circular  fibers  are  rather  indistinct  to  the  left  of  the  cardiac  ori- 
fice, and  are  most  marked  at  the  pyloric,  forming  then  its  sphincter 
muscle  ;  while  the  oblique  fibers  are  limited  to  the  cardiac  portion 
of  the  stomach,  passing  over  it  from  left  to  right.  It  is  at  the  point 
where  these  oblique  fibers  cease  that  the  stomach  becomes  con- 
stricted in  digestion  into  the  two  parts  already  described. 

Through  the  contraction  of  the  longitudinal  and  circular  fibers 
the  food  is  forced  along  toward  the  pylorus,  which,  through  its 
sphincter  muscle,  resists  at  first  as  we  have  seen  the  passage  of  any 
food  into  the  small  intestines.  The  cardiac  orifice  is  guarded  by 
the  fibers  in  that  situation,  as  well  as  by  the  contraction  of  the 
lower  part  of  the  oesophagus  already  referred  to.  The  movement 
of  the  food  is  also  due,  no  doubt,  partly  to  the  pressure  exerted  by 
the  diaphragm  and  the  intestines.  The  natural  stimulus  to  these 
motions  of  the  stomach  during  digestion  is  the  presence  of  food. 
The  account  that  we  have  just  given  of  the  movements  that  the 
stomach  midergoes  during  digestion  in  man,  is  based  upon  the  ex- 
periments and  observations  made  by  Beaumont  ^  upon  St.  Martin 
supplemented  by  those  recently  made  upon  animals.^' 

Alexis  St.  Martin,  a  voyageur  in  the  service  of  the  American 
Fur  Company,  a  man  about  eighteen  years  of  age,  of  good  constitu- 
tion, robust  and  healthy,  was  accidentally  wounded  by  the  discharge 
of  a  musket  on  the  6th  of  June,  1822.  The  charge,  consisting  of 
powder  and  duck  shot,  entered  the  left  side  posteriorly  and  ob- 
liquely, blowing  off  integument  and  muscles  of  the  size  of  a  man's 
hand,  fracturing  the  sixth  and  seventh  ril)s,  lacerating  the  lower 
portion  of  the  left  lobe  of  the  lungs,  the  diaphragm,  and  perforating 
the  stomach.  Notwithstanding  the  serious  nature  of  the  wounds 
St.  Martin  recovered  at  least  so  far  as  concerned  his  general  health. 
The  perforation  through  the  walls  of  the  stomach,  hoAvever,  re- 
mained permanently  open,  having  resisted  all  treatment.  This 
perforation  (Fig.  34)  was  situated  three  inches  to  the  left  of  the 
cardiac  portion  of  the  stomach,  near  the  superior  termination  of  the 
great  curvature,  and  measured  about  two  and  a  half  inches  in  cir- 
cumference. The  opening  was  closed  under  ordinary  circumstances 
by  a  movable  valve  formed  through  a  doubling  of  the  coats  of  the 
stomach,  which  had  been  formed  during  the  progress  of  the  case, 
and  which  effectually  prevented  the  escape  of  food.  This  valve 
could  be  easily  depressed,  when  the  interior  of  the  stomach  could 
then  be  examined. 

St.  Martin,  after  the  recovery  of  his  health,  performed  all  the 
duties  of  a  common  servant — chopping  wood,  carrying  burthens, 
etc. — married  and  had  several  children  and  enjoyed  general  good 
health  up  to  eighty  years  of  age.     For  a  number  of  years,  off  and 

^  Experiments  and  Observations  on  the  Gastric  Juice,  Plattsburgh,  1833. 

^Hofmeister  and  Schiitz,  Archiv  fiir  exper.  Path.  u.  Phar.,  Band  xx.,  1886,  s.  1. 
Rossbach,  Deutsclies  Archiv  fiir  klinisclie  Medecin,  Band  xlvi.,  1890,  s.  323. 
Moritz,  Zeitschrift  fiir  Biologic,  Band  xxxii.,  1895,  s.  313. 


GASTRIC  FISTULA. 


109 


on,  St.  Martin  was  under  the  observation  of  Beaumont,  under 
strictly  physiological  conditions.  It  is  this  circumstance  which 
makes  this  case  so  important  in  the  history  of  the  physiology  of  di- 
gestion, the  cases  of  gastric  fistula  that  had  hitherto  occurred  ^  not 
having  afforded  much  opportunity  for  the  study  of  gastric  diges- 
tion. It  should  be  mentioned,  however,  that  since  the  celebrated 
case  of  St.  Martin  interesting  cases  of  gastric  fistula,  the  result  of 
wounds  or  gastrotomy,  have  been  made  use  of  for  purposes  of  phys- 
iological investigation  among  others  by  Schmidt  and  Richet,  the 
results  of  which  will  be  referred  to  presently.  Up  to  about  the 
middle  of  the  eighteenth  century  it  was  still  a  subject  of  discussion 

Fig.  34. 


Ordinary  appearance  of  the  left  breast  and  side,  tlie  aperture  filled  with  the  valve  ;  the  suliject  in 
an  erect  position.     (BEAUMONT.) 

among  physiologists  as  to  whether  the  action  of  the  stomach  in  di- 
gestion was  of  a  chemical  or  purely  mechanical  nature.  The  con- 
troversy was  finally,  however,  brought  to  a  termination  by  the  dis- 
covery of  Reaumur,-  in  1752,  that  there  existed  in  birds  a  gastric 
juice,  and  that  food  was  softened  and  partly  digested  in  the  stomach 
of  those  animals  independently  of  any  mechanical  action  of  its  walls. 
Reaumur's  experiments  consisted  in  inserting  into  the  stomach  of  a 
bird  (bustard)  a  tin  tube  containing  meat,  the  ends  of  which  were, 
however,  covered  with  a  grating,  and  permitting  the  tube  to  remain  a 
sufficient  time  in  the  stomach  for  the  gastric  juice  to  mix  with  the  food 

'  De  Fistula  Ventriculi,  Eobcrtas  Marcus,  Berolini,  1835. 
^Memoires  de  1' Academic  des  Sciences,  1752,  Tome  Ixix.,  p.  461. 


110  DIGESTION. 

and  digest  it,  the  walls  of  the  tube  resisting  any  pressure  that  might 
be  exerted  by  the  "walls  of  the  stomach.  In  substituting  for  the 
tube  containing  the  meat  small  pieces  of  sponge,  Reaumur  was  able 
to  collect,  by  pressing  the  sponges  after  they  had  been  rejected,  a 
small  quantity  of  a  liquid  which  gave  an  acid  reaction,  and  which 
was  the  first  specimen  of  a  solvent  fluid  from  the  stomach  ever  ob- 
tained. The  next  step  in  advance  was  made  in  1777  by  Edward 
Stevens,^  who  employed  a  juggler,  whose  habit  was  to  swallow 
stones,  to  swallow  instead  little  silver  balls,  which  had  previously 
been  filled  with  diiferent  kinds  of  food,  the  walls  of  which,  being 
perforated,  permitted  the  entrance  of  the  gastric  juice.  After 
twenty  to  forty  hours  these  balls  M'onld  be  passed  by  the  anus,  and 
their  contents  would  be  found  to  be  more  or  less  digested.  From 
the  result  of  those  experiments  Stevens  concluded  that  digestion 
cannot  be  accounted  for  by  heat,  trituration,  putrefaction,  or  even 
fermentation  alone,  but  l:)y  a  most  powerful  humor  which  is  secreted 
by  the  tunic  of  the  stomach,  and  is  poured  into  the  cavity  of  the  same. 

A  few  years  later  there  appeared  the  celebrated  work  of  Spal- 
lauzani,^  in  which  the  observations  of  Reaumur  and  Stevens  were 
repeated  and  confirmed,  and  extended  in  a  series  of  experiments 
made  upon  quite  a  number  and  variety  of  animals  including  sev- 
eral interesting  observations  made  by  the  author  upon  himself,  some 
of  which  have  already  been  alluded  to  in  speaking  of  the  subject  of 
mastication.  Spallanzani  began  his  experiment  upon  himself  by 
first  swallowing  little  linen  bags  in  which  the  diiferent  articles  of 
food,  animal  or  vegetable,  were  sewn  up.  These  were  usually  passed 
by  the  anus  within  a  period  varying  from  t^venty-three  to  twenty- 
four  hours,  and  were  found  either  empty  or  nearly  so,  the  contents 
beino;  more  or  less  digested,  accordino;  to  the  kind  of  food  used  and 
the  length  of  time  durino;  which  thcv  had  remained  within  tlie  bodv. 
The  necessity  of  first  masticating  the  food  before  swallowing  it  was 
then  demonstrated  ;  and,  in  conclusion,  a  little  gastric  juice  was 
olitained  by  vomiting,  and  the  effect  of  this  upon  boiled  beef  tried 
outside  the  body,  with  the  result  of  showing  that  the  beef  became 
pultaceous,  and  that  there  was  no  jjutrefiiction.  Spallanzani  dis- 
tinctly recognized  a  most  imjwrtant  fact,  that  the  process  of  diges- 
tion, beginning  in  the  stomach,  is  completed  in  the  intestines. 

In  1803  a  woman  with  a  gastric  fistula,  coming  under  the  care 
of  Dr.  Helm,^  in  Vienna,  that  physician  profited  by  the  opportunity 
to  make  some  study  of  gastric  digestion,  Init  added  little  of  value 
to  what  had  already  been  established. 

In  1824  Front  ^  endeavored  to  show,  by  analysis,  that  the  acidity 
of  tlie  gastric  juice  in  animals  was  due  to  hydrochloric  acid. 

Shortly    afterward,    between    1825    and    1827    simultaneously, 

'  De  Alimentorum  Concotione,  Thesaura'^  Medicus  Smellie,  Tomus  iii.,  p.  481. 
'^FLsica  -Vnimak'  e  Vegetahile,  Tomo  secundo,  Venezia,  1782. 
^. Jacob  Helm,   Zwei  krankengeschiten,  Vieniic,   1803.     3Iarcus,   op.    cit.,   p.  21. 
*  Philosophical  Transactions,  1824. 


GASTRIC  JUICE.  Ill 

Leuret  and  Lassaigne/  Tiedemann  and  Gmelin  ^  made  a  detailed 
and  extended  series  of  observations  npon  digestion  ;  those  of  the 
latter  being  the  most  elaborate.  The  experiments  were  made  prin- 
cipally npon  dogs,  cats,  horses,  cows,  sheep,  birds,  reptiles,  and 
fishes,  the  observations  on  man  being  exceptional.  In  some  of  the 
experiments  the  means  of  obtaining  the  gastric  juice  were  the  same 
as  those  used  l)y  Kcaumur,  etc.,  already  referred  to.  In  many  of 
them,  however,  another  plan  was  adopted.  The  animal  to  be  ex- 
perimented upon  after  fasting,  was  made  to  swallow  stones,  nails, 
etc.,  a  few  hours  afterward  the  animal  was  killed,  it  having  been 
ascertained  that  such  hard  substances  would  excite  the  stomach  to 
secrete  a  considerable  amount  of  gastric  juice — sufficient  in  quantity 
to  analyze  and  experiment  with.  Notwithstanding  the  number  of 
animals,  experiments  performed,  and  the  variety  of  the  observations, 
nothing  definitely  was  established  as  to  the  composition  and  prop- 
erties of  the  gastric  juice,  to  what  elements  it  owed  its  digestive 
powers,  or  exactly  what  effect  it  had  upon  different  kinds  of  food. 
It  will  be  seen,  therefore,  from  this  historical  digression  that  little 
was  positively  known  of  gastric  digestion,  as  it  takes  place  in  man, 
before  the  observations  and  experiments  of  Beaumont  were  made. 

Beaumont  was  the  first  to  observe  digestion  as  it  goes  on  in  the 
healthy  human  stomach,  to  describe  not  only  the  motions  of  the 
latter,  but  also  the  manner  in  which  the  gastric  juice  is  secreted,  its 
effect  upon  food,  the  changes  that  food  undergoes  in  the  stomach,  to 
collect  the  normal  gastric  juice  in  such  quantities  that  it  could  be 
analyzed  and  studied  with  reference  to  its  effect  upon  food  outside 
the  body,  to  determine  the  influence  exerted,  by  temperature,  exer- 
cise, and  the  nervous  system,  upon  digestion,  the  length  of  time  that 
food  remains  in  the  stomach,  and  numerous  other  interesting  facts. 
Further,  it  was  this  remarkable  case  of  St.  Martin  that  first  sug- 
gested to  Basso w,^  the  Russian  naturalist,  the  making  of  a  per- 
manent gastric  fistula,  afterwards  also  successively  performed  by 
Blondlot,^  and  frequently  resorted  to  at  the  present  day  as  a  con- 
venient means  of  obtaining  fresh  gastric  juice. 

Let  ns  turn  now  to  the  consideration  of  the  manner  in  which  the 
gastric  juice  is  produced,  its  composition,  effect  upon  food,  etc.,  as 
learned,  by  means  of  gastric  fistuloe,  from  the  examination  of  gastric 
juice  obtained  by  the  stomach  pump,  and  from  experiments  made 
with  artificial  gastric  juice. 

During  the  intervals  of  digestion  the  stf)mach  is  empty,  its 
mucous  membrane  being  simply  covered  with  a  very  thin,  trans- 
parent, viscid  mucus.  At  this  time  the  reaction  of  the  membrane 
is  either  faintly  alkaline  or  neutral.  With  the  introduction  of  food 
into  the  stomach,  the  membrane  at  once  changes  its  pale  appear- 
ance, becoming  red  and  turgid  from  the  increased  amount  of  blood. 

1  Eecherches  pour  Servir  a  1'  Histoire  de  la  Digestion.     Paris,  1825. 

2  Recherches  sur  la  Digestion.     Paris,  1837. 

"Bulletin  de  la  Societe  des  I^ aturalistes  de  Moscow,  1843,  Tome  xvi.,  p.  315. 
*Traite  analytique  de  la  digestion,  1843. 


112  DIGESTION. 

Small  drops  of  gastric  juice  appear  as  small  pellucid  points  on  the 
surface  of  the  membrane,  which  has  now  an  acid  reaction,  and 
gradually  a  little  stream  of  gastric  juice  begins  to  flow  upon  the 
food  in  the  stomach.  Beaumont  showed  most  conclusively  that 
food  is  the  natural  stimulus  to  the  secretion  of  the  healthy  gastric 
juice.  For  the  exciting  impression  of  food  is  diffused  over  the 
wdiole  secreting  surface,  and  the  maximum  effect  is  thereby  obtained. 
Local  stimulus,  however,  like  that  of  an  India-rubber  tube,  will  ex- 
cite a  flow,  and  this  Beaumont  used  when  a  small  quantity  of 
gastric  juice — an  ounce  and  a  half,  for  example — was  required  un- 
mixed with  mucus  or  food. 

Tlie  human  gastric  juice,  which  is  rarely  obtained  free  from  food 
residues,  mucus,  and  saliva,  is  a  clear  or  faintly  cloudy,  almost 
colorless  fluid,  having  a  sour  odor  and  taste,  strong  acid  reaction 
and  low  specific  gravity  1.001—1.010.  As  a  general  rule  it  con- 
tains also  an  admixture  of  glandular  cells  or  their  nuclei ;  mucous 
corjiuscles  and  more  or  less  changed  cylindrical  epitheliimi. 

Composition  of  Gastric  Juice. 

The  first  to  attempt  to  analyze  the  gastric  juice  was  Scopoli,  an 
Italian  chemist,  in  the  last  century.  The  gastric  juice  examined 
was  obtained  by  Spallanzani  from  a  raven,  and,  according  to  Sco- 
poli, consisted  of  an  animal  matter,  earthy  salts,  and  what  would 
now  be  called  hydrochloric  acid.  The  gastric  juice  of  St.  Martin 
was  examined  among  others  by  the  late  Professor  Dunglison,  who, 
in  a  letter  to  Beaumont,^  states  that  it  contained  free  muriatic  and 
acetic  acids,  phosphates,  and  muriates,  with  bases  of  potassium, 
sodium,  magnesium,  and  calcium,  and  an  animal  matter  soluble  in 
cold  water,  but  insoluble  in  hot. 

Among  the  more  recent  analyses  of  human  gastric  juice,  that  of 
the  woman  with  a  gastric  fistula,  made  by  Schmidt,  is  especially 
worth  of  mention. 

Composition  of  Human  Gastric  Juice  Holding  Saliva.  2 

Water 994.400 

Pepsin,  etc.        .......  3.195 

Hydrochloric  acid 0.200 

Calcium  chloride        ......  0.061 

Sodium  chloride         ......  1.464 

Potassium  chloride    ......  0.550 

Calcium        ] 

Magnesium  'phosphate     .         .         .         .         .  0.125 

Ferrum         J 

Loss 0.005 


1000.000 

iQp.  cit.,  pp.  7S,  SI. 

^Annalen  tier  Chcmie,  ]8')4,  Band  xcii.,  s.  40.  Schmidt  p:ivcs  as  the  mean  of 
the  two  analyses  tlie  numbers  994.404  for  the  water,  and  1.4()")  for  tlie  sodium  chlo- 
ride. These  are  probably  typograpliical  erroi-s,  as  the  other  numljere  are  those  given 
in  the  table. 


GASTRIC  JUICE.  113 

According  to  this  analysis,  then  liiunan  gastric  juice  consists  of 
water,  pepsin,  hydrochloric  acid,  chlorides,  and  phosphates.  It 
should  be  mentioned,  however,  that  the  organic  matter  of  the  gas- 
tric juice  consists  not  only  of  pepsin,  but  of  another  unformed 
ferment  or  enz^-me,  the  so-called  rennin.  It  would  appear  also 
from  recent  investigation  that  the  amount  of  hydrochloric  acid  as 
given  by  Schmidt  is  too  small,  due  jjrol^ably  to  the  gastric  juice 
analyzed  by  him  having  been  diluted  with  water  or  saliva.  At 
least,  Richet^  found  the  hydrochloric  acid  of  the  himian  gastric  juice 
also  obtained  from  a  fistula  amounting  as  the  average  of  eighty 
observations  to  1.7  parts  per  thousand,  the  variation  being  from 
0.5  to  3  parts  per  thousand,  an  estimate  not  differing  essentially 
from  the  later  ones  of  Szabo,^  Ewald,^  and  Boas.*  It  may  be  men- 
tioned that  the  samples  of  gastric  juice  analyzed  by  Szabo  was 
taken  from  the  stomach  of  a  man  by  means  of  a  stomach  piunp, 
M-ithout  the  addition  of  water. 

The  epithelium  of  the  stomach  consists  of  columnar  cells,  among 
which  occur  the  so-called  goblet,  or  mucus-secreting  cells.  The 
.  latter  appear  to  be  columnar  cells,  whose  protoplasm  has  been  trans- 
formed into  mucinogen,  or  mucin,  which  swells  up  the  cell  at  its 
free  end,  hence  its  name,  as  it  passes  into  the  cavity  of  the  stomach. 
With  the  escape  of  the  mucin,  the  more  or  less  empty  cell  resumes 
the  character  of  the  ordinary  columnar  cell. 

It  has  already  been  mentioned  that  the  gastric  juice  is  secreted 
by  the  mucous  membrane  of  the  stomach  ;  let  us  consider  now,  so 
far  as  is  known,  the  manner  of  its  elaboration. 

The  mucous  membrane  of  the  stomach,  in  the  living  healthy  sub- 
ject, is  of  a  velvety,  pulpy  consistence,  with  an  average  thickness  of 
about  1.2  millimeters  (V=g-  of  an  inch),  and  in  color  of  a  pale  pink 
or  reddish  appearance,  which  rapidly  changes  after  death  into  a 
brownish  hue.  The  mucous  membrane  is  loosely  attached  to  the 
submucous  coat  or  the  layer  of  areolar  tissue  which  lies  between  the 
mucous  coat  within  and  the  muscular  coat  without.  It  is  through 
the  looseness  of  this  attachment  that  the  longitudinal  folds  into  which 
the  membrane  is  usually  thrown  are  due,  and  which  are  effaced  when 
the  stomach  is  distended.  The  epithelium  presents,  more  particu- 
larly at  the  cardiac  orifice,  a  marked  contrast  as  compared  with  the 
pavement  epitheliimi  lining  the  oesophagus. 

If  the  mucous  membrane  of  the  stomach  be  gently  washed  by 
allowing  a  small  stream  of  water  to  run  over  it  slowly,  which  will 
carry  off  the  adhering  mucus,  and  then  be  examined  ^vith  a  simple 
lens,  little  polygonal  spaces  or  depressions  "will  be  noticed  in  its  sur- 
face, varying  in  size  from  ^  to  J  of  a  millimeter  (o-o"o  ^^  T'ff'o  ^^  ^^ 
inch)  in  diameter.     If  these  depressions  or  alveoli  be  ftirther  exam- 

^  Comptes  Eendus,  Tome  Ixxxiv.,  p.  450,  1877. 
^ Zeit.<chrift  fiir  Physiolo^ische  Chemie,  Band  1,  1877,  s.  140. 
"  Die  Lehre  von  Der  Verdauung,  1879,  s.  52. 

*  Deutsche  Med.   Wochenschr.,  1892,  2S^r.  49,  s.   1110.     Diagnostik  u.  Therapie 
Der  Magen  Krankheiten,  1894,  s.  20. 
8 


114 


DIGESTION. 


Fifi.  35. 


ined  with  the  microscope,  they  will  be  seen  to  consist  of  a  number 
of  small  round  apertures  of  about  ^V  ^o  y^"  ^^  ^  millimeter  (^^-g-  to 
3  Fo"  ^^  ^^^  inch)  in  diameter.  These  minute  apertures  are  the  mouth- 
like openings  of  the  gastric  follicles,  small  tubules  varying  in  length 
from  2  to  5  millimeters  [-^^  to  ^  of  an  inch),  and  which  are  im- 
bedded in  the  mucous  membrane,  the  blind  or  closed  ends  of  the 
tubules  looking  outwardly  toward  the  submucous  coat,  the  open 
ends  inwardly  toward  the  interior  of  the  stomach. 

The  gastric  tubules  differ  considerably  in  their  structure  and 
form,  according  to  the  part  of  the  stomach  examined.  Thus,  in 
the  pyloric  portion  of  the  stomach  the  tubules  are  lined,  to  a  cer- 
tain extent  at  least,  with  a  continuation  of  the  columnar  epithe- 
lium covering  the  inner  surface  of  the  stomach ;  in  the  upper  parts, 
however,  of  these  tubules  the  lining  cells  become  shorter  and  more 
cubical  in  character,  and  correspond  apparently  in  their  function 
with  the  central  ^  cells  found  in  the  tubules  found  in  the  cardiac 
part  of  the  stomach.  The  pyloric  tubules,  while  terminating  usu- 
ally in  a  branched  manner,  terminate  also  simply.  If  the  middle 
zone  of  the  stomach  be  noAV  examined,  both  simple  and  branched 
tubules  (Fig.  '>•"))  will  be  Found  resembling  those  in  the  pyloric  por- 
tion, but  while  the  upper  portion  of 
the  tubule  is  lined  with  columnar 
epithelium,  the  succeeding  part  or 
neck  is  filled  rather  than  lined  by 
large  ovoidal  or  spheroidal  granular 
cells,  the  so-called  parietal"  cells. 
Toward  the  bottom  or  fundus  of  the 
gland  these  parietal  cells  do  not  form 
a  continuous  layer,  but  are  seen  scat- 
tered here  and  there,  and  bulging  out 
so  as  to  give  the  tubule  a  varicose 
appearance,  the  remaining  portion  of 
the  tubule,  except  the  narrow  pas- 
sage-way in  the  middle,  being  occu- 
pied by  finely  granular  polyhedral 
angular  cells,  the  so-called  central 
cells,  similar,  as  just  mentioned,  to 
those  found  in  the  pyloric  tubules.^ 
In  the  cardiac  portion  of  the  stomach, 
more  particularly  around  the  cardiac 
orifice,  the  tubules  are  branched  in 

'  Principal,  chief,  adelomorphous  ( dSv^og, 
hidden)  cells. 

2  Ovoid,  border,  oxyntic  ( of w^v,  to  acidu- 
late), delomorphous  cells. 

"According  to  the  recent  observations  of 
Langendorff  and  Lasei-stein  (Pfliiger's  Archiv,  1894,  Band  Iv.,  s.  578)  the  main  tube 
of  a  gastric  tubule,  at  least  those  presenting  parietal  cells,  not  only  extends  through- 
out the  length  of  the  tubule  as  usually  described,  but  gives  off  lateral  branches, 
■which  ])ass  to  the  parietal  cells,  and  there  forms  a  network  on  which  the  cell  lies. 


Gastric  gland  from  liiuuan  stomach. 
1.  Columnar  cells.    2.  Parietal  cells. 


GASTRIC  JUICE.  115 

character,  the  upper  part  of  the  tubule  dividing  into  two  or  three 
branches,  and  there  usually  subdividing  again.  These  cardiac 
tubules,  like  simple  ones  found  in  the  middle  zone  of  the  stomach, 
contain  both  ovoid  and  central  cells.  It  will  be  observed  from 
this  brief  description  that  two  kinds  of  glands  are  found  in  the 
human  stomach,  differing  essentially  in  their  structure  :  pyloric  tu- 
bules, simple  and  branched,  situated  in  the  pyloric  part  of  the 
stomach,  containing  columnar  and  central  cells  :  cardiac  tubules, 
simple  and  branched,  situated  in  the  middle  and  cardiac  parts  of 
the  stomach,  containing  columnar  and  central  cells  also. 

While  undoubtedly  such  a  distinction  as  that  just  described  ex- 
ists between  the  gastric  glands  in  man,  the  exact  line  of  demarca- 
tion between  the  two  is  not  as  distinct  as  in  certain  animals,  the 
dog  for  example,  the  diiferent  kind  of  glands  passing  in  man  into 
each  other  through  intermediate  forms.  Judging  from  what  has 
been  learned  of  the  process  of  salivary  secretion,  analogy  would 
lead  us  to  suppose  that  the  gastric  juice  is  secreted  in  an  essentially 
similar  manner,  and  such  would  appear  to  be  the  case,  as  shown 
more  particularly  by  the  researches  of  Heidenhain.^  Thus,  if  sec- 
tions of  the  gastric  glands  of  an  animal  be  examined  before  the  tak- 
ing of  food,  the  so-called  central  cells  of  the  cardiac,  as  well  as  those 
of  the  pyloric  glands,  will  be  found  pale,  finely  granular,  and  not 
staining  readily  with  aniline  or  carmine.  With  the  beginning  of 
digestion,  however,  these  cells  become  swollen,  coarsely  granular, 
turbid,  and  stain  more  readily  with  the  above  reagents ;  as  diges- 
tion continues,  the  coarse,  granular,  and  tm'bid  condition  and  dis- 
position to  stain  increase,  while  at  the  same  time  the  cells  become 
smaller  and  shrunken.  The  only  conclusion  to  be  drawn  from  the 
changes  in  these  cells  is  that  the  readily  stainable  material,  etc., 
developed  during  digestion  constitutes  the  antecedent  stages,  the 
mother  substances,  or  zymogens  of  pepsin  and  rennin,  the  so-called 
pepsinogen  and  renninogen.  Inasmuch,  however,  as  the  parietal 
cells  of  the  cardiac  portion  of  the  stomach  do  not  exhibit  during  di- 
gestion the  histological  changes  observed  in  the  central  cells  of  the 
cardiac  and  pyloric  glands,  only  swelling  up  and  projecting  some- 
what externally  from  the  wall  of  the  gland,  and  from  the  fact  of 
parietal  cells  being  present  in  the  glands  of  the  stomach  of  the  frog 
coincidentally  with  the  presence  of  acid,  the  pepsin-forming  cells 
being  confined  almost  entirely  to  the  lower  part  of  the  oesophagus  in 
that  animal,  it  appears  reasonable  to  attribute  to  the  parietal  cells 
the  production  of  the  hydrochloric  acid  of  the  gastric  juice.  If 
such  be  the  case,  however,  it  is  somewhat  difficult  to  understand 
why,  after  injecting  ferrocyanide  of  potassium  and  ferric  lactate  into 
the  blood  of  an  animal,  as  in  the  experiment  of  Bernard,"  the  pro- 
duction of  Prussian  blue  should  be  limited  to  the  surface  of  the 
stomach,  since  if  the  ovoid  cells  of  the  glands  actually  produce  the 

'  Hermann,  Handbuch,  Funfter  Band,  1S80,  s.  141. 
^Liquides  de  1' Organisme,  Tome  ii.,  p.  375.     Paris,  1859. 


116  DIGESTION. 

acid  the  presence  of  which  is  necessary  for  the  formation  of  the 
salt,  the  Prussian  blue  should  be  visible  in  the  cells  of  the  fundus 
or  their  vicinity,  as  well  as  upon  the  surface  or  mouth  of  the  gland, 
unless  the  acid  is  expelled  from  the  gland  as  rapidly  as  produced, 
which  is  not  improbable.  If  the  above  view  be  accepted  as  correct 
then  the  gastric  juice  is  secreted  by  only  the  cardiac  tubules,  those 
containing  parietal  cells  producing  acid  and  central  cells  elaborat- 
ing the  zymogens,  the  cells  of  the  pyloric  tubules  elaborating  only 
the  latter,  and  the  columnar  epithelial  cells,  mucus. ^  As  a  confirm- 
ation of  this  view  it  may  be  mentioned  that  an  infusion  of  the  mu- 
cous membrane  of  the  pyloric  portion  of  the  stomach  does  not  pos- 
sess digestive  properties  unless  acidulated.  It  will  be  recalled  also 
in  this  connection,  that  in  speaking  of  the  motions  of  the  stomach,  at- 
tention was  called  to  the  fact  of  the  cardiac  portion  of  tlie  stomach 
acting  as  a  reservoir  for  the  food,  the  pyloric  portion  as  the  expul- 
sive part.  The  significance  of  this  distinction  becomes  more  ap- 
parent now  that  it  has  been  shown  that  digestion  is  limited  to  the 
cardiac  part  of  the  stomach.  The  nature  and  chemical  constitu- 
tion of  pepsin,  although  it  was  discovered  many  years  since,^  is  still 
imperfectly  understood,  it  not  having  been  obtained  as  yet  in  a  suf- 
ficiently pure  state  to  admit  of  analysis.  It  is  regarded  as  being 
an  unformed  ferment,  an  enzyme  on  account  of  its  characteristic  ef- 
fect upon  proteid  matter.  Like  other  ferments  a  small  amount  of 
pepsin  will  convert  a  large  amount  of  proteid  into  peptone,  the 
action  of  the  pepsin  being  retarded  like  ptyalin  by  any  great  excess 
of  the  products  of  digestion.  One  of  the  most  striking  peculiarities 
of  pepsin  is  that  it  only  acts  on  acid  media  and  upon  albuminous 
bodies,  the  latter  swelling  up,  becoming  transparent,  and  then  dis- 
solving under  its  influence.  Hence  the  gastric  juice  to  be  effica- 
cious contains,  as  we  have  seen,  both  pepsin  and  hydrochloric  acid. 
It  should  be  mentioned  that  while  hydrochloric  acid  can  be  re- 
placed by  certain  acids  such  as  lactic,  nitric,  or  jDhosphoric  acids, 
the  latter  are  not  so  effective. 

Like  other  enzymes  the  action  of  pepsin  is  influenced  by  tempera- 
ture, the  most  favorable  being  about  o8°C.  (100°F,),  while  a  pro- 
longed exposure  to  one  of  80 °C.  (176°F.)  will  destroy  the  enzyme. 
A  solution  of  pepsin  may  be  obtained  relatively  pm*e  by  treat- 
ing the  mucous  membrane  of  the  stomach  with  dilute  phosphoric 
acid  and  then  adding  lime  water.  The  resulting  precipitate  which 
carries  down  the  pepsin  being  then  dissolved  with  dilute  hydro- 
chloric acid  and  the  salts  removed  by  dialysis,  the  non-diffusible 
pepsin  remains  in  the  dialyzer.  Rcnnin,  derived  from  zymogen 
rennin  l)y  tlie  action  of  an  acid  and  Avhose  chemical  construction  is 
still  unknown,  is  regarded  as  being  an  enzyme  on  account  of  the 

^According  to  more  recent  investigations  the  changes  undergone  by  the  cells 
during  digestion  are  somewhat  different  from  those  described  in  the  text.  The  re- 
sults, lu)wever,  can  be  reconciled  to  a  great  extent  if  the  diHerent  conditions  under 
which  tlic  cells  were  examined  be  taken  into  consideration.  J.  N.  Langlev,  Journal 
of  Physiology,  1880,  Vol.  II.,  p.  261. 

2  Schwann,  Miiller's  Archiv,  1836,  s.  66. 


GASTRIC  JUICE.  117 

property  it  possesses  of  coagulating  or  curdling  milk.  Some  dif- 
ference of  opinion  still  prevails  as  to  the  nature  of  the  process  of 
curdling.  Recent  researches  render  it  probable,  however,  that  the 
casein  of  milk^  is  split  by  rennin  into  two  bodies,  one  of  which, 
paracasein  (cheese),  in  combining  with  calcium  salts  is  precipitated 
as  the  insoluble  curd,  while  the  other,  the  "  whey  proteid,"  remains 
in  solution.  There  appears  to  be  no  doubt  that  the  curdling  of 
milk  docs  not  take  place  in  the  absence  of  calcium  salts.  There  is 
still  some  diiference  of  opinion,  however,  whether  the  latter  act  by 
combining  witli  the  paracasein  to  form  an  insoluble  compound,  the 
curd,  or  whether  they  influence,  in  some  way,  the  separating  out  of 
the  paracasein.  Although  the  chemical  nature  of  rennin  is  as  little 
understood  as  that  of  pepsin,  that  it  is  an  enzyme  is  still  further 
shown  by  the  fact  that  one  part  will  precipitate  800,000  parts  of 
casein.^  It  might  be  supposed  that  the  curdling  of  milk  in  the 
stomach  was  due  to  the  acid  of  the  gastric  juice,  since  casein  is 
precipitated  by  lactic  acid,  developed  from  lactose  by  bacteria,  as 
in  the  souring  of  milk.  Apart,  however,  from  the  fact  of  the 
casein  not  being  split  into  curd  and  whey  by  the  acid  but  is  simply 
precipitatic  as  such,  curdling  will  take  place  even  after  the  gastric 
juice  has  been  rendered  neutral,  but  will  not  take  place  if  the  latter 
is  boiled,  the  elevated  temperature  destroying  the  enzyme.  The 
advantage  of  the  curdling  of  milk  in  the  stomach  is  not  apparent, 
unless  it  be  supposed  that  its  digestion  is  promoted  when  in  that 
condition.  That  such  is  the  case  is  rendered  probable,  however, 
from  the  fact  that  the  curd  is  readily  digested  by  the  gastric  juice, 
being  converted  into  peptone  like  other  proteids.  A  comparatively 
pure  solution  of  rennin  may  be  obtained  according  to  Hammarsten^ 
in  the  following  way  :  An  infusion  of  the  mucous  membrane  of  the 
stomach  being  acidulated  with  hydrochloric  acid,  is  just  neutralized 
and  then  shaken  with  magnesium  carbonate  until  the  pepsin  is  pre- 
cipitated. The  filtrate  l)eing  precipitated  with  basic  lead  acetate  is 
decomposed  with  very  dilute  sulphuric  acid,  and  the  acid  liquid  fil- 
tered and  treated  with  a  solution  of  stearin  soap.  The  rennin  is 
precipitated  by  the  fiitty  acids  set  free,  and  when  the  last  are  placed 
in  water,  and  removed  by  shaking  with  ether,  the  rennin  remains 
in  the  watery  solution. 

Hydrochloric  Acid  of  the  Gastric  Juice.  . 

The  hydrochloric  acid  produced  by  the  parietal  cells  of  the  car- 
diac tubules  appears  to  be  derived  from  the  decomposition  of  the 

1  Casein  is  sometimes  called  caseinogen,  in  which  case  paracasein  is  named  casein. 
The  term  caseinogen,  if  we  wish  to  be  consistent  in  onr  nomenclature,  should  be  re- 
served, liowever,  for  a  mother  substance  of  casein  which  may  yet  be  shown  to  exist 
in  the  cells  of  the  mammary  glands,  as  pepsinogen,  the  mother  substance  of  pepsin, 
exists  in  the  gastric  glands. 

^  Landois,  A  Text-book  of  Human  Physiolt)gy.  Translated  by  Stirling,  1891,  p.  306. 

''Hammareten,  op.  cit. ,  p.  184.  J.  W.  Warren,  M.D.,  On  the  Presence  of  a  Milk- 
curdling  Ferment  (Pexin)  in  the  Gastric  Mucous  Membrane  of  Vertebrates,  Journ. 
of  Exp.  Med.,  Vol.  2,  1897,  p.  475. 


118  DIGESTION. 

sodium  chlorides  of  the  blood  supplied  by  the  food  through  the 
action  of  the  primary  acid  sodium  phosphate/  the  reaction  being 
as  follows  : 

XaCl  +  XaH^PO^  =  HCl  +  Na^HPO, 

In  confirmation  of  the  above  view,  it  may  be  mentioned  that  dur- 
ing gastric  digestion  in  the  dog,  while  the  excretion  of  chlorides 
diminishes,  the  alkalinity  of  the  urine  increases,  the  sodium  car- 
bonate (XaHCOg)  to  which  the  latter  is  due,  being  the  final  form 
assmned  bv  the  sodium  liberated  in  the  decomposition  of  the  chlo- 
rides.' On  the  supposition  that  the  secondary  sodium  phosphate 
(Na.,HPO^)  formed  according  to  the  above  reaction  remains  in  the 
blood  and  meets  there  carbon  dioxide  and  water  it  becomes  intelli- 
gible how  through  mutual  reaction,  the  sodium  carbonate  of  the 
urine  may  be  formed.     Thus 

Na^HPO,  +  CO^  +  H^O  =  NaH^PO,  +  NaHC03 

As  a  further  proof  that  the  hydrochloric  acid  of  the  gastric  juice 
is  derived  in  the  manner  just  mentioned,  it  may  be  stated  that,  ac- 
cording to  recent  experiments,^  if  a  dog  be  given  with  his  food 
sodium  bromide  instead  of  sodium  chloride,  more  than  fifty  per 
cent,  of  the  hydrochloric  acid  of  the  gastric  juice  will  be  replaced 
by  hydrobromic  acid.  In  this  connection  it  should  be  stated,  how- 
ever, that  when  sodium  iodine  is  given  instead  of  sodium  chloride 
the  gastric  juice  contains  but  little  hydroiodic  acid.  The  greater  part 
of  the  hydrochloric  acid  present  in  the  gastric  juice  is  regarded  as 
existing  in  a  free  state.  From  the  fact,  however,  that  pepsin  will 
convert  proteid  into  acid  albumin  like  hydrochloric  acid,  though 
more  slowly,  as  well  as  for  other  reasons,  it  is  inferred  that  part  of 
the  hydrochloric  acid  at  least  exists  in  combination  with  pepsin  as 
a  "paired  acid,"  pepsin-hydrochloric  acid.  The  existence  of  an 
acid  in  the  free  state  as  in  the  case  of  the  hydi'ochloric  acid  of  the 
gastric  juice,  though  a  rare  occurrence  in  the  animal  economy,  is 
not  the  only  one  known.  Many  years  since  it  was  observed  by 
Troschel  *  on  a  visit  to  Messina  that  the  salivary  glands  of  the 
Dolium  galia,  a  gastropodous  mollusk,  excreted  a  fluid  containing 
free  mineral  acids  shown  afterwards  by  Boldeker  to  be  hydrochloric 
and  sulphuric  acids. 

Action  of  Gastric  Juice  Upon  Food. 

Let  us  turn  now  to  the  consideration  of  the  action  of  the  gastric 
juice  upon  the  dififerent  articles  of  food  as  learned  either  from  exper- 
iments made  with  the  normal  secretion  obtained  from  gastric  fistulae, 
with  artificial  gastric  juice,  and  from  an  examination  of  the  contents 
of  the  stomach.     It  may  be  mentioned  in  this  connection  that  an 

iMaly,  Hermann,  Handbuch,  1881,  Band  v.,  Zweiter  Theil,  s.  67. 
2E.  O.  Schoumow-Sumanowski,  Archiv  fiir  exper.  Path.   u.  Pliar.,  1894,  Band 
33,  s.  336. 

^Neucki  u.  Sohoumow,  Idem,  Band  34,  1894,  s.  313. 
*Poggendorff's  Annalen,  Band  93,  s.  614,  1854. 


ACTION  OF  GASTRIC  JUICE  UPON  FOOD.  119 

artificial  gastric  juice  can  be  readily  prepared  by  adding  a  glycerine 
extract  of  the  mucous  membrane  of  the  stomach  to  a  large  bulk  of 
0.3  per  cent,  hydrochloric  acid.  When  the  gastric  juice  so  prepared 
is  used  for  showing  the  digestion  of  proteids  and  certain  albuminoids, 
to  which  we  shall  see  its  action  is  limited,  the  temperature  should  be 
maintained  at  about  37 °C.  (100°F.),  and  the  mixture  stirred  from 
time  to  time.  When  meat  is  subjected  to  the  action  of  gastric  jnice, 
whether  obtained  from  a  fistula  in  the  stomach  or  artificially  pre- 
pared, it  gradually  becomes  softer,  changes  in  color,  and  breaks 
down  into  a  grumous,  pultaceous  mass.  Under  the  microscope  the 
muscular  fibers,  though  broken  up  into  small  pieces  and  retaining 
but  little  tenacity,  are  readily  recognized  through  their  character- 
istic strite.  The  intermuscular  connective  tissue,  the  sarcolemma, 
disappears,  however,  being  completely  dissolved  out.  ^leat  is, 
therefore,  not  actually  dissolved  in  the  stomach,  but  is  rather  dis- 
integrated and  converted  into  a  pultaceous  liquid,  A\hich  readily 
passes  into  the  small  intestine. 

In  a  similiar  manner  white  of  q^^,  fibrin,  the  casein  of  milk, 
gelatin,  glutin,  etc.,  are  broken  down,  lic|uefied,  and  converted  into  a 
grayish  soup-like  liquid.  The  gastric  juice,  however,  not  only  acts 
physically  upon  the  albuminous,  proteid  foods,  softening,  disintegrat- 
ing, and  liquefying  them,  but  chemically  also,  transforming  them 
into  peptones,^  albumin,  becoming  alljumin  peptone,  gelatin,  gelatin 
peptone,  etc.  The  transformation  of  proteid  into  peptone  by  the 
action  of  the  gastric  juice  according  to  the  generally  accepted  -  view 
is  essentially  as  follows  :  The  proteid  is  first  converted  by  the  hy- 
drochloric acid  into  acid  albumin  or  syntonin,  the  latter  then,  under 
the  influence  of  the  pepsin,  takes  up  water,  and  splits  into  two  sub- 
stances, viz.,  hemialbumose  and  antialbiunose  which  passing  through 
intermediate  stages  finally  become  hemipeptone  and  antipeptone,  a 
mixture  of  the  two  latter  being  called  amphopeptone.  Peptones 
have  hitherto  been  separated  from  their  antecedents,  the  so-called 
albumoses  or  proteoses  ^  by  saturating  a  mixtiu-e  containing  them 
both,  with  ammonium  sulphide,  it  being  supposed  that  all  of  the  pro- 
teids present  would  be  precipitated  except  the  peptones.  As  there 
is  good  reason  however  for  supposing  that  certain  of  these  inter- 
mediate products  of  proteolytic  digestion  (deuteroalbumose)  are  not 
precipitated,  some  doubt  *  still  exists  as  to  whether  peptones  have 
ever  been  obtained  pure.  Further,  the  only  way  by  which  the 
hemipeptone  can  be  separated  from  the  antipeptone  in  the  ampho- 
peptone mixture  or  the  final  product  of  peptic  digestion  depends 

'  Lehmann,  Lehrbuch  der  Physiologische  Chemie,  1853,  Band  ii. ,  s.  46. 

^  Kiihne,  \'erhand  Nat.  Hist.  Med.  Vereins,  X.  F.,  Band  i.,  Heidelberg,  1876. 
Neumeister,  Lehrbuch  der  physiologischen  Chemie,  1897,  s.  2ol.  Chittenden, 
Cartwright  Lectures,  Medical  Eecord,   New  York,  1891,  pp.   485,  516,  545. 

^The  term  proteose  is  sometimes  used  as  synonymous  with  albumose,  sometimes 
in  a  more  general  sense  as  including  albumoses.  From  the  latter  point  of  view 
albumose  derived  from  albumin,  caseose  from  casein,  etc.,  would  be  regarded  as 
proteoses. 

*Hammarsten,  op.  cit.,  p.  28. 


120  DIGESTION, 

upon  the  fact,  as  we  shall  sec  hereafter,  that  while  antipeptone  re- 
sists all  further  digestion,  heniipeptone  is  decomposed  through  the 
action  of  the  trypsin  of  the  pancreatic  juice  into  the  amido  acids 
leucin  and  tyrosin.  It  is  obvious  however  that  while  this  method 
suffices  for  the  obtaining  of  antipeptone  it  necessarily  involves  the 
destruction  of  the  heniipeptone. 

Indeed  the  existence  of  the  latter  peptone  is  rather  an  inference 
from  the  fact  that  through  the  action  of  trypsin  upon  amphopeptone 
two  bodies  appear,  leucin  and  tyrosin,  of  which  hemijicptone  is  sup- 
posed to  be  the  antecedent/  A  convenient  method  of  showing  the 
conversion  of  proteid  into  peptone  by  gastric  juice  and  at  the  same 
time  the  necessity  of  the  latter  containing  both  pepsin  and  dilute 
hydrochloric  acid  is  as  follows  :  Prepare  three  cubes  of  equal  size 
of  coagulated  white  of  egg,  put  one  cube  into  a  test-tube  containing 
gastric  juice,  another  into  a  second  tube  in  which  the  gastric  juice 
has  been  boiled  that  is  in  a  weak  solution  of  hydrochloric  acid 
(0.2  per  cent),  the  pepsin  having  been  destroyed,  a  third  in  a  tube 
in  which  the  gastric  juice  has  been  neutralized  that  is  in  a  solution 
of  pe]>sin  (0.8  per  cent.).  After  a  few  hours  if  the  temperature  be 
maintained  at  about  that  of  the  body  and  the  mixture  stirred  from 
time  to  time  it  will  be  found  that,  while  the  albumin  in  the  gastric 
juice  has  been  reduced  to  a  grumous  condition  converted  into  am- 
phopeptone, that  in  the  boiled  gastric  juice  or  the  weak  solution  of 
hydrochloric  acid  has  only  been  transformed  into  syutonin,  and  that 
in  the  neutralized  solution  or  the  solution  of  pepsin  but  little  if  at 
all  modified,  some  syutonin  being  formed  if  the  action  be  prolonged. 
Peptones  from  whatever  proteids  they  may  be  derived,  whether  al- 
bumin, fibrin,  casein,  etc.,  and,  however  derived,  while  differing 
somewhat  from  each  other  in  their  ultimate  composition,  are  gener- 
ally characterized  by  the  following  properties  :  They  are  completely 
soluble  in  water  and  diffuse  readily  through  animal  membranes,  the 
latter  pro])erty  rendering  them  suscejitible  of  absorption  which  the 
proteids  from  which  they  are  derived  are  not.  They  are  precipi- 
tated from  neutral  or  feebly  acid  solutions  by  mercuric  chloride, 
tannic  acid,  bile  acids,  and  phospho-molybdic  acid,  but  are  not  pre- 
cipitated by  boiling,  by  nitric  or  acetic  acids,  or  potassium  ferro- 
cyanide.  They  give  a  red  color  with  Millon's  reagent  (mercuric 
nitrate  in  nitric  acid),  a  yellow  color  with  nitric  acid,  the  xantho- 
proteic reaction ;  a  rosy  red  color  with  Fehling  solution,  the 
biuret  reaction.  Tliey  rotate  the  plane  of  polarized  light  to  the 
left.  It  has  already  been  mentioned  incidentally  that  the  gastric 
juice  acts  only  upon  proteids  and  albuminoids.     Thus,  for  example, 

'  It  mast  be  admitted  that  considerable  difference  of  opinion  still  prevails  as  to 
exactly  the  manner  in  which  proteid  is  converted  into  peptone.  Indeed,  according 
to  a  recent  autliority,  we  know  notliini^  certain  at  the  present  time  concerninu:  the 
essence  of  pei)tonization.  We  know  not  whether  peptones  are  splitting  i)roducts  of 
albumin — still  less  whetlier  the  splitting  products  so  arising  resemble  or  ditlcr  from 
each  other — or  whether  the  peptones  arise  through  a  change  in  the  j)osition  of  the 
atoms  without  modification  of  the  size  of  tiie  molecule  or  througli  a  taking  up  of 
water.     Bunge,  op.  cit.,  s.  180. 


ACTION  OF  GASTRIC  JUICE  UPON  FOOD.  121 

while  the  gastric  juice  dissolves  the  albuminous  wall  of  the  fat  ves- 
icle, thus  setting  the  fat  free,  it  has  no  effect  upon  the  fat  itself. 
Gastric  juice  does  not  act  upon  carbohydrates.  Any  starch,  for  ex- 
ample, that  may  be  converted  into  maltose  or  dextrose  in  the 
stomach  is  due  to  the  saliva  swallowed  or  possibly  to  gastric  mucus. 

It  was  shown  many  years  since  ^  and  also  more  recently  ^  that 
cane  sugar  is  converted  in  the  stomach  into  glucose.  This  eifect 
appears  to  be  due,  however,  not  so  much  to  the  gastric  juice  proper 
as  to  its  hydrochloric  acid,  since  a  0.2  per  cent,  solution  of  the  latter 
converts  cane  sugar  into  glucose  and  levulose  outside  of  the  body. 
It  is  possible  also  that  the  cane  sugar  converted  into  dextrose  in  the 
stomach  may  l^e  due  to  a  soluble  enzyme.  As  the  conversion  of 
cane  sugar  into  glucose  takes  place  very  slowly  in  the  stomach  it  is 
not  usually  thought  that  any  great  amount  of  glucose  is  produced 
in  this  part  of  the  alimentary  canal.  The  action  of  the  gastric 
juice  in  this  respect  may  be,  however,  more  important,  at  least  in 
man,  than  is  generally  supposed,  since,  as  we  shall  see  hereafter, 
there  is  still  some  doubt  as  to  exactly  how  cane  sugar  is  converted 
into  glucose  in  the  small  intestine.  Submaxillary  mucin  and  elas- 
tin  are  dissolved  by  the  gastric  juice,  the  latter  but  slowly,  however. 
Neither  keratin,  or  nuclein  are  dissolved  by  the  gastric  juice, 
hence  the  cell  nucleus  is  insoluble  in  the  latter.  While  the 
membrane  of  the  vegetable  cell  is  not  dissolved  by  the  gastric 
juice,  that  of  the  animal  cell  is,  but  less  readily,  in  proportion  as  it 
approximates  in  composition  to  keratin.  Oxyheemoglobin,  or  the 
coloring  matter  of  the  l)lood,  is  decomposed  by  the  gastric  juice 
into  hiematin  and  acid  alljuminate.  Hence  the  blood  is  changed  in 
the  stomach  into  a  dark  brown  mass.  According  to  the  observa- 
tions of  Beaumont,  bones  were  dissolved,  to  a  certain  extent  at 
least,  by  the  gastric  juice,  while  water,  alcohol,  and  other  fluids^ 
appeared  to  be  absorbed  in  the  stomach  as  such  or  to  pass  unaflPected 
into  the  intestine. 

It  is  well  known  mider  certain  circumstances  that  the  coats  of 
the  stomach  itself  are  unaffected  by  the  action  of  the  gastric  juice 
during  life,  ])ut  are  digested  after  death.  It  is  said  that  when  one 
of  the  old  alchemists  announced  that  he  possessed  a  universal  sol- 
vent, the  question  was  at  once  asked  in  what  did  he  keep  it.  Natur- 
ally enough  it  was  asked  in  the  last  century  of  those  who  held  that 
the  gastric  juice  would  dissolve  organic  substances,  why  it  did  not 
act  upon  the  stomach  itself.  We  have  seen,  however,  that  the 
gastric  juice  does  not  digest  all  kinds  of  organic  food,  ])ut  that  its 
action  is  limited  rather  to  particular  kinds  of  it,  it  having  no 
action  upon  fat,  starch,  epidermis,  etc.  The  answer  would  then 
appear  to  be,  that  the  stomach  is  lined  with  some  substance  that 
the  gastric  juice  does  not  act  upon.      According  to  this  idea  Ber- 

^  Bouchardat  et  Sandras,  Supplement  a  TAnnuaire  de  therapeutique,  pour  1846, 
p.  83. 

2  Leube,  Virchow's  Archiv,  1882,  Band  88,  s.  222.  "Qp.  dt,  p.  97. 


122  DIGESTION. 

narcl  ^  held  that  the  lining  epithelium  of  the  stomach  protected  it 
from  the  gastric  juice,  assuming  that  the  epithelium  was  as  con- 
stantly renewed  as  destroyed.  A  confirmation  of  the  view  that  the 
epithelium  lining  of  the  stomach  gives  it  its  immunity  from  diges- 
tion during  life,  is  shown  by  the  fact  tliat  worms,  like  the  thread- 
worm, ascaris,  etc.,  whose  body  wall  is  covered  with  epithelium,  are 
able  to  live  in  the  stomach,  bathed  at  times  in  gastric  juice.  After 
the  death  of  the  worm,  however,  from  any  cause,  the  mouth  or  anus 
being  opened,  then  the  gastric  juice  is  able  to  penetrate  within  its 
body  and  will  then  act  upon  the  viscera  until  often  nothing  will  be 
left  of  the  worm  except  its  outer  body  wall,  which  will  float  about  in 
the  stomach,  unaifected  by  the  gastric  juice.  In  the  same  way,  if 
the  epithelium  of  the  stomach  be  loosened  from  the  parts  beneath, 
it  will  be  found  undigested  in  the  gastric  juice  ;  as  a  matter  of  fact, 
it  is  not  digested  whether  living  or  dead  any  more  than  the  skin  of 
the  ascaris  is  digested.  There  is  no  reason  for  assuming,  then,  that 
during  life  it  is  rapidly  regenerated  because  it  is  constantly  being 
destroyed.  After  death  the  epithelium  loosening  itself  from  the 
coats  of  the  stomach,  the  latter  Avill  no  doubt  be  attacked  by  the 
gastric  juice,  the  epithelium  itself  remaining  unaffected.  It  must 
be  admitted  that  this  explanation  is  not  entirely  satisfactory,  being 
open  to  objections  like  all  other  explanations  that  have  been 
offered.  It  presents,  however,  this  advantage,  that  it  does  not  in- 
voke the  aid  of  a  vital  spirit,^  nor  of  catalysis,^  nor  does  it  attribute 
to  the  alkalinity  of  the  blood  a  preserving  power  in  the  stomach 
that  it  does  not  possess  in  the  intestine,^  Ijut  depends  simply  upon 
the  fact  as  to  whether  or  not  epithelium  alive  or  dead  is  digested  by 
the  gastric  juice. 

One  of  the  most  interesting  facts  connected  with  gastric  digestion 
is  the  entire  absence  of  putrefaction.  It  was  long  since  observed  ^ 
that  meat  does  not  putrefy,  at  least  for  a  long  time  if  kept  in  gastric 
juice,  while  the  normal  secretion  itself  remains  perfectly  free  from 
putrefaction  even  months  after  withdrawal  from  the  stomach.  This 
effect  of  the  gastric  juice  is  undoubtedly  due  to  its  hydrochloric  acid, 
which  exerts  an  anti-fermentative  action.  If,  however,  the  gastric 
juice  is  neutralized,  then  a  fermentation  is  set  up  in  the  stomach 
whereby  lactic  and  other  organic  acids  are  generated.  The  hydro- 
chloric acid,  like  weak  mineral  acids,  acts  also  as  an  antiseptic,  at 
least  to  some  extent.  Thus  the  cholera  bacillus,  varieties  of  strep- 
tococcus infecting  Avounds,  the  staphylococcus  pyogenes  aureus  are 
killed  by  the  gastric  juice.  Since  the  hydrochloric  acid  prevents 
fermentation  with  the  generation  of  gases,  the  nitrogen  (72.5  per 
cent.),  carbon  dioxide  (20.7  per  cent.),  and  hydrogen  (0.7  percent.) 
that  are  found  (Planer)  in  the  stomach  "^  are   either  derived  from 

iPhysiologie  Exjierimentale,  1S56,  Tome  II.,  p.  404. 

2  Hunter,  Pliil.  Transactions,  Londfin,  1772,  p.  447. 

3Dalt(.n,  Pliysi()lo<ry,  2d  edit.,  18(il,  p.  132. 

*Pavy,  Pliil.  Transactions,  London,  18G.3,  p.  169. 

■'^Spailanzani,  op.  cit.,  pp.  107-308.  ^Landois,  op.  cit.,  p.  308. 


AMOUNT  OF  GASTRIC  JUICE. 


123 


the  air  and  saliva  shallowed,  or,  being  generated  in  the  intestine, 
pass  backward  into  the  stomach.  As  the  oxygen  that  passes  into 
the  stomach  is  absorbed  by  the  blood  little  or  none  is  found  there, 
it  being  replaced  by  carbon  dioxide  in  the  proportion  of  one  volume 
of  the  former  to  two  of  the  latter. 

It  is  impossible  to  state  exactly  the  amount  of  gastric  juice  se- 
creted by  a  man  during  the  twenty-four  hours.  Approximately  it 
may  be  said  to  amount  to  about  seven  kilogrammes  (15.4  pounds) 
daily.  This  estimate  is  based  upon  the  amount  of  gastric  juice  ab- 
solutely collected  from  animals  whose  weight  was  compared  with 
that  of  an  adult  man,  and  by  the  amount  of  gastric  juice  necessary 
to  digest  a  known  quantity  of  meat,  one  gramme  of  meat  requiring 
13.5  grammes  of  gastric  juice.  It  must  be  remembered,  however, 
that  the  amount  of  gastric  juice  secreted  varies  with  the  kind  of 
food,  and  even  with  the  same  food  under  diiferent  circumstances. 
Further,  as  the  gastric  juice  is  reabsorbed  with  the  food,  there  is 
some  risk  of  counting  the  same  gastric  juice,  or  at  least  the  elements 
of  the  same  over  again.  Moreover,  it  has  been  shown  that  the 
amount  of  gastric  juice  secreted  will  vary  considerably  according  to 
the  chemical  nature  of  the  contents  of  the  stomach.  Thus,  while 
water  and  peptones,  particularly  the  latter,  promote  in  a  marked 
degree  the  secretion  of  the  gastric  juice,  acids,  alkalies,  and  neutral 
salts  have  in  this  respect  but  little  effect.^ 


Digestion  of  Food  in  Stomach. 


Kiud  of  food. 

Pig's  feet,  tripe 

Salmon,  trout  . 

Barley  soup 

Milk 

Potatoes,  roasted  ;  beans 

Roast  turkey    . 

Soft  boiled  eggs 

Beefsteak,  broiled    . 

Pork,  raw 

Hard  boiled  eggs 

Mutton  soup     . 

Oyster  soup 

Potatoes,  boiled  . 

Beef  and  vegetable  soup 

Duck,  roasted  . 

Veal,  broiled    . 

Veal,  fried 

Pork,  boiled     . 

Cabbage,  boiled 

Pork,  roasted  . 


boiled 


Time. 

1  hour. 
1     " 

1  hour  30  min. 

2  hours. 
2     " 

2  hours  30  min. 
2       "      30     " 

2  "      30     " 

3  hours. 
3      " 

3  hours  30  min. 
3      "      30     " 
3      "      30     " 

3  "      30     " 

4  hours. 
4      " 

4      " 

4  hours  30  min. 

5  hours  15  min. 


It  will  be  observed  from  the  observations  of  Beaumont,  that  cer- 
tain articles  of  food  are  digested  in  the  stomach  much  more  rapidly 

^Khigine,  Archives  des  Sciences  Biologique,  St.  Petei-sburg,  1895,  Tome  III.,  p. 


461. 


■Beaumont,  op.  cit.,  p.  269. 


]  24  DIGESTION.  i 

than  others.  Thus,  pig's  feet,  tripe,  are  digested  in  one  hour,  milk 
and  roast  potatoes  in  two,  soft  boiled  eggs  in  three  hours,  hard 
boiled  in  three  and  a  half,  roast  duck  in  four,  Avhile  roast  pork  re- 
quires for  its  digestion  more  than  five  hours.  It  is  highly  probable, 
however,  that  when  the  food  is  liquid  in  character,  water,  for  ex- 
ample, it  remains  in  the  stomach  but  a  short  time,  not  longer,  per- 
haps, judging  from  experiments  upon  dogs,  than  from  twenty  to 
thirty  minutes.  It  must  not  be  supposed,  however,  that  because 
certain  articles  of  food  are  slowly  digested,  that  necessarily  they  will 
give  rise  to  uneasiness  or  inconvenience  in  the  stomach,  but  there 
are  times  when  the  administration  of  food,  with  reference  to  its 
rapid  digestion,  becomes  of  vital  importance.  Thus,  in  certain 
critical  periods  of  disease,  when  a  life  hangs  upon  a  thread,  when 
every  moment  that  life  can  be  prolonged  is  invaluable,  the  judicious 
administration  of  food  that  can  be  easily  and  quickly  digested  and 
absorbed  may  be  the  only  means  of  saving  the  patient.  It  must  be 
borne  in  mind  that  the  natural  stimulus  of  the  gastric  juice  is  the 
presence  of  food,  and  that  for  the  time  being  there  is  a  limit  to  the 
amount  of  this  secretion,  like  all  others.  Hence,  whenever  there 
have  been  great  prostration  of  strength  and  loss  of  tone,  the  stomach, 
enfeebled  like  the  rest  of  the  body,  can  digest  but  little  ;  food  under 
such  circumstances  should  be  given  cautiously,  both  in  quantity  and 
quality. 

From  a  great  nimiber  of  experiments  performed  upon  St.  Martin, 
Beaiunont'  concluded  that  the  natural  temperature  of  the  human 
stomach  was  100°  F.  (37.7 °C.),  and  that  the  injection  of  food 
into  the  stomach  did  not  elevate  the  temperature.  The  importance 
of  heat  in  digestion  will  be  seen  Avhen  this  function  is  contrasted  in 
the  hot-  and  cold-blooded  animals  ;  in  the  latter,  where  the  heat  of 
the  body  is  about  that  of  the  surrounding  air  during  winter  diges- 
tion stops  altogether,  or  goes  on  very  slowly ;  while  in  the  former, 
the  temperature  being  independent  of  external  conditions,  at  least 
within  narrow  limits,  digestion  goes  on  independent  of  change  in 
the  season. 

In  reference  to  the  influence  of  exercise  upon  digestion,  Beau- 
mont observed  that  moderate  exercise  conduces  considerably  to 
healthy  and  rapid  digestion  ;  severe  and  fatiguing  exercise,  on  the 
contrary,  retards  it.  This  is  readily  understood  when  it  is  remem- 
bered that  exercise  elevates  the  temperature  and  accelerates  the  cir- 
culation. On  the  other  hand,  if  too  much  blood  is  diverted  from 
the  stomach  to  the  brain  or  extremities  by  much  mental  or  physical 
exercise  indigestion  ensues.  No  rules,  however,  can  be  laid  down 
absolutely  in  this  respect.  In  some  individuals  there  is  an  uncon- 
trollable desire  to  sleep  after  eating,  the  good  effects  of  which  are 
so  evident  that  it  is  absurd  to  resist  the  feeling,  whereas,  in  other 
cases,  gentle  exercise  is  equally  imperatively  demanded. 

It  is  a  matter  of  common  observation  that  animals,  as  a  general 
1  Op.  cit.,  pp.  273,  276. 


-;    -^  -  EFFECT  OF  EXERCISE,  ETC.  125 

r- 

rule,  take  little  or  no  exercise  after  eating.  That  digestion  is  re- 
tarded, and  even  entirely  stopped,  by  too  much  exercise,  the  author 
has  had  ample  opportunities  of  observing  from  post-mortem  exami- 
nation made  both  on  human  beings  and  animals  who  had  eaten  food 
a  short  time  before  death,  and  who  were  kno^ni  to  have  taken  a 
considerable  amount  of,  and  often  violent,  exercise  during  that 
period.  Other  physiologists  seem  to  have  had  the  same  experience. 
Thus,  in  the  last  century,  as  related  by  Saunders,^  Dr.  Harwood,  of 
Cambridge,  procured  two  dogs,  equally  well  fed ;  one  of  these  he 
kept  quiet,  the  other  he  compelled  to  take  constant  exercise  imme- 
diately after  eating.  A  few  hours  after  feeding,  both  dogs  were 
killed.  The  food  was  found  entirely  digested  in  the  stomach  of 
the  dog  that  had  been  kept  quiet,  while  in  that  of  the  one  that  had 
been  compelled  to  take  the  exercise,  the  food  Mas  undigested. 

Every  one  knows  from  experience,  how  digestion  is  influenced  by 
the  nervous  system — a  bad  piece  of  news,  a  sudden  shock,  stopping 
digestion  entirely,  perhaps  for  hours.  Beaumont  observ^ed  that 
whenever  the  nervous  system  was  disturbed  or  depressed  by  anger 
or  fear,  by  undue  excitement,  from  stimulating  liquors,  from  over- 
loading the  stomach,  etc.,  the  mucous  membrane  became  pale  and 
moist  or  red  and  dry,  and  the  secretions  vitiated,  diminished,  or  al- 
together suppressed.  ^ . 

It  will  be  observed  from  what  has  been  said  of  the  action  of  the 
gastric  juice  upon  food  that  gastric  digestion  must  be  of  a  prepara- 
tory character  fitting  the  food  for  further  digestion.  Isot  only  the 
carbohydrates  and  fats  pass  through  the  stomach  practically  un- 
changed, but  even  a  part  of  the  proteid,  the  hemipeptone  moiety 
does  not  undergo  complete  digestion  until  it  reaches  the  small  in- 
testine. It  is  for  this  reason  that  it  is  possible  to  remove  the 
stomach  almost  entirely  from  an  animal,  a  dog,  for  example,  with- 
out apparently  its  health  being  materially  aifected  f  at  least  a  dog 
has  lived  for  years  after  its  stomach  was  removed  and  in  good 
health.^  It  should  not  be  inferred,  however,  from  such  an  experi- 
ment that  the  stomach  is  a  useless  organ,  but  rather  one  which  in 
converting  the  food  into  chyme,  so  modifies  it  as  to  make  it  more 
fit  for  further  digestion  in  the  small  intestine. 

'  A  Treatise  on  Structure,  Economv,  and  Diseases  of  the  Liver,  London,  1803,  p. 
201. 

^F.  F.  Kaiser,  Beitriige  zur  Operativen  Chirurgie,  Czerny,  1878,  s.  141. 
"M.  Ogata,  Du  Bois  Keymond's  Archiv,  1883,  s.  89. 


CHAPTER  VIII. 

DIGESTION.—  {Continued.) 

INTESTINAL  DIGESTION.    INTESTINAL  JUICE.    PANCREATIC 
JUICE.   LIVER.   GLYCOGEN.   BILE.   FECES.    DEFECATION. 

We  have  seen  tliat  shortly  after  food  is  taken  into  the  stomach  it 
passes  in  small  quantities  through  the  pyloric  orifice  into  the  small 
intestine,  or  the  part  of  the  alimentary  canal  intervening  between 
the  stomach  and  the  ilio-cffical  valve.  The  small  intestine  is  a 
cylindrical  tube  and  in  situ  measures  on  an  average  from  5  to  6 
meters  (15  to  18  feet),  but  when  separated  from  the  mesentery  or 
the  peritoneum,  which  holds  it  in  position  in  the  abdominal  cavity, 
it  will  be  found  to  be  a  little  longer — 6.2  meters  (about  20  feet).  It 
has  a  diameter  of  about  3  centimeters  (1.2  inches). 

The  small  intestine  is  composed,  in  addition  to  its  external  or 
peritoneal  coat,  of  two  others  :  of  a  mucous  membrane,  including  an 
epithelial  and  submucous  or  fibrous  coat,  and  of  a  muscular  coat 
lying  exteriorly  between  the  peritoneum  and  the  mucous  membrane. 
The  muscular  coat  consists  of  unstriped  muscular  fiber,  arranged  in 
two  layers,  longitudinally  or  parallel  with  the  long  axis  of  the  in- 
testine, and  circularly  or  at  right  angles  with  the  axis  ;  the  circular 
fibers  being  better  developed  than  the  longitudinal  ones. 

Peristaltic  Movement  of  Intestine. 

It  is  the  slow  and  p-radual  contraction  and  relaxation  of  these 
muscular  fibers  that  gives  rise  to  the  so-called  peristaltic  or  vermic- 
ular movement  by  which  the  food  is  propelled  along  the  intestine. 
The  peristaltic  motion  of  the  intestine  is  well  seen  in  an  animal 
when  opened  in  pure  digestion.  What  is  jiositivcly  known,  how- 
ever, of  the  intestinal  movements  in  man  is  derived  from  patholog- 
ical cases  where  the  abdominal  walls  were  so  thin  that  the  motion 
could,  to  a  certain  extent,  be  seen  and  felt,  or  from  cases  of  intestinal 
fistulse  to  be  presently  referred  to  again. 

Like  the  movements  of  the  stomach,  the  natural  stimulus  to  the 
vermicular  motion  of  the  intestine  is  the  presence  of  food,  during 
the  intervals  of  digestion  the  intestine  being  at  rest. 

The  peristaltic  movement,  as  learned  either  from  observations  upon 
animals  or  man,  is  usually  propagated  from  the  stomach  towards  the 
csecum,  the  wave  during  digestion  passing  over  a  distance  of  one 
centimeter  (|-  inch)  mthin  a  period  of  from  20  to  50  seconds.^ 

The  movement  is  easily  retarded  or  even  brought  to  a  standstill 

1  Cash,  Proc.  of  the  Eoyal  Society,  London,  1887,  vol.  41,  p.  212.  Fubini, 
Landois,  op.  cit.,  p.  283. 


MOVEMENTS  OF  SMALL  LNTESTINE.  127 

by  a  slight  resistance,  the  contractions  of  the  muscular  fibers  not 
being  powerful.  It  is  an  interesting  fact  that  if  a  small  piece  of 
intestine  is  resected  and  then  placed  witliin  the  abdominal  cavity, 
but  with  its  natural  lower  end  sutured  to  the  upper  portion  of  the 
intestine  food  will  pass  from  below  upwards,  accumulating  in  the 
upper  portion  of  the  intestine  and  causing  dilatation.'  Experiments 
of  this  kind  appear  to  indicate  that  the  propagation  of  the  peri- 
staltic motion  in  the  normal  direction  depends  upon  some  peculiar 
disposition  of  the  muscular  fibers.  Xevertheless  under  certain  cir- 
cumstances anti-peristalsis  may  occur,  that  is,  the  normal  movement 
is  reversed,  passing  from  the  csecum  to  the  stomach." 

In  addition  to  the  peristaltic  movement  of  the  small  intestine, 
the  loops  of  the  latter  often  exhibit  a  rhythmical  to  and  fro  move- 
ment, the  so-called  pendular  movement.  As  at  such  times  the 
blood  is  expelled  from  the  submucous  venous  flexus  by  the  contrac- 
tion of  the  circular  muscular  fibers  it  is  possible  as  suggested  by 
Mall  ^  that  this  movement  promotes  the  circulation  of  the  blood  in 
the  intestine,  and  aids  in  maintaining  the  pressure  of  the  blood  in 
the  portal  vein. 

Valvulae  Conniventes  and  Villi. 

Before  turning  to  the  consideration  of  the  intestinal  secretions, 
attention  should  be  called  to  a  peculiar  disposition  of  the  mucous 
membrane  of  the  intestine,  which,  to  a  certain  extent,  retards  the 
passage  of  the  food  and  exposes  it  longer  to  the  digestive  fluids 
and  to  a  greater  absorbing  surface.  We  refer  to  the  \dlli  and  the 
valvulae  conniventes.  On  opening  the  small  intestine  and  gently 
washing  it,  one  will  observe  that  instead  of  it  being  smooth,  it 
presents  a  velvety  appearance.  This  is  due  to  the  mucous  mem- 
brane (Fig.    36)   being  raised  up   into  millions  of  little  cones  or 

Fig.  36. 


Portions  of  the  mucous  membrane  from  the  ileum,  moderately  magnified,  exhibiting  the  villi 
on  its  free  surface,  and  between  them  the  orifices  of  the  tubular  glands.  1.  Portion  of  an  agmin- 
ated  gland.    2.  A  solitary  gland.    3.  Fibrous  tissue.     (Leidy.) 

cylinders,  the  villi,  which  project  inwardly  into  the  cavity  of  the 
intestine.  As  these  little  structures  are  intimately  connected  with 
the  subject  of  absorption,  our  account  of  their  anatomy  will  be  de- 

1  Mall,  Johns  Hopkins  Hospital  Eeports,  Vol.  1,  1896,  p.  93. 
^Griitzner,  Deutsche  Med.  Wochenschrift,  1894,  s.  897. 
"Op.  cit.,  p.  37. 


128 


DIGESTION. 


ferred  until  the  next  chapter,  merely  mentioning  them  here  as 
offering  a  certain  amount  of  resistance  to  the  passage  of  food,  just 
as  any  roughened  surface  offers  resistance  as  compared  with  a 
smooth  one  to  a  substance  passing  over  it. 

While  the  villi  are  found  all  through  the  small  intestine,  the 
valvuloe  conniventes,  which  have  the  same  function  in  this  respect, 
are  restricted  to  a  certain  portion  of  it,  being  absent  in  the  upper 
half  of  the  duodenum  and  in  the  lower  third  of  the  ileum.  The 
valvulse  conniventes  (Fig.  ^37)  are  duplicaturcs  of  the  mucous  mem- 
brane extending  transversely  across  the  intestine  at  right  angles  to 


Fig.  37. 


Portion  of  small  intestine  laid  open  to  sliow  valvulte  conniventes.     (Brinton.) 

its  long  axis,  and  occupying  usually  one-third  or  a  half  of  the  cir- 
cumference, and  sometimes  extending  all  around  the  tube.  The 
folds  are  widest  in  the  middle,  measuring  often  12|  millimeters 
(about  ^  inch).  On  either  side  of  the  middle  line  they  thin  away 
until  they  are  lost  in  that  part  of  the  mucous  membrane  attached 
to  the  muscular  coat.  Inasmuch  as  there  can  be  counted  usually 
over  800  of  these  folds,  it  can  be  readily  understood  how  the  extent 
of  the  mucous  membrane  is  increased  by  them.  Naturally  the  food 
will  take  a  longer  time  to  pass  over  and  between  these  barriers,  so 
to  speak,  than  over  a  plane  surface,  and  this  is  of  advantage  in 
digestion  and  absorption,  as  the  food  will  be  more  thoroughly  in- 
corporated with  the  secretions  and  have  a  better  chance  of  being 
absorbed. 

It  is  often  stated  that  the  valvule  conniventes  are  only  found  in 
the  intestine  of  man.  This  is  incorrect,  as  they  are  present  not 
only  in  the  gorilla,  chimpanzee,  and  orang,^  but  also  in  the  ox, 
llama,  camel,  elephant,  and  ornithorynchus.  They  are  remarkably 
well  developed  in  the  sharks,  giving  rise  in  those  animals  to  the 
so-called  spiral  valve.  Merely  mentioning  that  the  solitary  glands 
and  patches  of  Peyer,  also  found  in  the  small  intestine,  will  be  de- 
scribed when  the  subject  of  the  blood  is  considered,  let  us  pass  on 
now  to  the  study  of  the  intestinal  and  pancreatic  juices  and  the  bile 
and  of  the  role  that  these  secretions  play  in  digestion. 

As  the  food  passes  into  the  small  intestine  it  becomes  incorporated 
with  the  bile,  the  pancreatic  and  intestinal  juices.     The  first  two 

^H.  C.  Chapman,  Proc.  Acad.  Nat.  Sciences,  1880,  p.  166. 


INTESTINAL  JUICE. 


129 


secretions  pass  into  the  duodenum  from  the  liver  and  the  pancreas 
respectively ;  the  last,  however,  is  secreted  by  glands  found  all 
through  the  intestinal  tract.  While  the  changes  that  the  food  un- 
dergoes in  the  small  intestine  are  due  to  the  simultaneous  effects  of 
these  secretions,  it  is  better,  however,  to  study  the  effects  of  each 
separately  whenever  possible,  in  order  to  ascertain  their  relative 
importance  in  digestion?  AVe  willl)egiu,  then,  with  the  intestinal 
juice. 

Intestinal  Juice. 

The  intestinal  juice,  or  succus  entericus,  consists,  in  the  upper  part 
of  the  intestine,  of  a  mixture  of  the  secretions  of  Bruuner's  and 
Lieberkiihn's  gland,  but  in  the  lower  part,  of  the  secretion  of 
Lieberkiihn  glands  alone.  The  glands  of  Brunner  are  confined  to 
the  duodenum,  those  of  Lieberkiihn  occur  throughout  the  small 
intestine. 

Glands  of  Brunner. 

The  succus  entericus,  as  it  is  also  called,  is  secreted  by  two  kinds 
of  glands,  the  glands  of  Brunner  or  Brunn  and  the  follicles  of 
Lieberkiihn.  The  former  are  confined  to  the  duodenum ;  the 
latter,  however,  are  found  not  only  in  the  small  intestine  but  in  the 
large  intestine  also.  The  duodenal  or  glands  of  Brunner  (Fig.  38) 
are    branched    tubular    glands  ; 

they  average  about  a  millimeter  Fir;.  38. 

(2T  ^^  ^^^  inch)  in  diameter  and 
to  the  naked  eye  appear  like  little 
round  bodies  in  the  submucous 
tissue.  The  excretory  duct,  which 
transmits  the  secretion  from  the 
grape-like  masses  of  which  the 
gland  consists,  pierces  the  mucous 
membrane  and  opens  into  the 
cavity  of  the  intestinal  canal. 

According  to  Hirst  and  Hei- 

T       I     •      1     ,1  11  J?    T)  ?       bular  glands,  4.   5.  Orifice  of  a  duodenal  gland,  6. 

denhain,'    the    cells    Ot    Brunner  S    v.  XwS  vesicles  of  tlie  latter,  more  higlfly  mag- 

D-lnnd«5  pvbibit  P=;c;pntiqllv  fhp  "ifie<l.  exhibiting  the  epithelial  cells  lining 
gianUS    exniUli;    eSSentiauy    tne     their  internal  surface.     (Leidy.) 

same  changes   during  periods  of 

rest  and  activity  as  those  of  the  j^yloric  tubules  of  the  stomach, 
being  large  and  clear  during  the  period  intervening  between  meals 
and  small  and  cloudy  during  digestion,  the  secretion  being  elabo- 
rated during  the  former  period  and  poured  out  during  the  latter. 

The  reaction  of  the  secretion  is  alkaline.  According  to  Grutzner," 
it  will  digest  fibrin  in  an  acid  solution,  and  Budge  ^  and  Krolow 
state  that  a  watery  extract  will  convert  starch  into  sugar.  Beyond 
these  facts  nothing  is  known  positively  of  the  properties  of  the 
secretion  of  Brunner's  glands. 

'  Hermann,  Physiologie,  Fiinfter  Band,  s.  163. 
^Pfliiger's  Archiv,  Band  xii.,  s.  288. 
'^  Hoppe-Seyler,  Phys.  Chemie,  s.  270. 


A  vertical  section  of  the  duodenum  highly 

magnified.    1.  A  fold-like  villus.    2.  Epithelium 

f  the  mucous  membrane.     3.  Orifices  of  the  tu- 


130  DIGESTION. 


Glands  of  Lieberkiihii. 


By  far,  however,  the  greatest  quantity  of  the  intestinal  juice  is 
secreted  by  the  follicles  of  Lieberkiihn,  otherwise  known  as  the 
simple  tubular  glands  of  the  intestine.  These  glands  resemble 
somewhat  the  pyloric  tubules  of  the  stomach,  consisting  of  a  base- 
ment membrane  lined  with  a  single  layer  of  columnar  cells,  among 
which  numerous  goblet  or  mucin-producing  cells  occur.  The 
tubules  having  a  diameter  of  about  J^  of  a  millimeter  {-^^-^  inch) 
extend  through  the  mucous  membrane,  their  blind  ends  looking 
towards  the  muscular  coat,  their  mouths  into  the  cavity  of  the  in- 
testine. The  secretion  of  these  tubules  will  therefore  pass  into  ,the 
interior  of  the  intestine.  The  tubules  are  as  closely  packed  together 
as  possible  and  are  only  absent  in  that  part  of  the  duodenum  where 
the  glands  of  Brunner  are  found,  and  in  the  remaining  part  of  the 
small  intestine,  the  Peyer's  patches  and  solitary  glands,  and  even 
here  they  are  not  entirely  absent. 

From  the  immense  number  of  these  tubules  one  would  infer  that 
a  very  considerable  quantity  of  intestinal  juice  is  secreted.  The 
exact  amount  daily  poured  into  the  intestine  has  never  been  accu- 
rately determined  ;  it  does  not  appear  to  be,  however,  as  much  as 
we  would  have  anticipated. 

Methods  of  Obtaining  Intestinal  Juice. 

Various  experimental  processes  have  been  resorted  to  from  time 
to  time  M'ith  the  object  of  obtaining  intestinal  juice  and  of  deter- 
mining its  composition  and  properties.  Among  the  earlier  methods 
may  be  mentioned  that  of  withdrawing  in  a  living  animal  a  loop  of 
intestines,  ligating  it  in  two  places,  replacing  it  for  a  while  in  the 
abdominal  cavity,  and  then  opening  it,  the  fluid  secreted  in  the 
meantime  being  assumed  to  be  intestinal  juice.'  Another  method 
consisted  in  cutting  off  the  bile  and  pancreatic  juices  by  ligating 
the  bile  and  pancreatic  ducts,  the  changes  undergone  by  the  food 
being  attributed  under  such  circumstances  to  the  intestinal  juice.^ 
More  recently  another  method  of  procedure  has  been  adopted. 
This  consists  in  completely  excising  a  loop  of  intestine  without  in- 
juring its  nerves  or  blood  vessels,  suturing  the  cut  ends  of  the  ali- 
mentary canal,  ligating  one  end  of  the  excised  loop  and  attaching 
the  other  to  the  abdominal  wall  so  as  to  make  a  permanent  fistula.^ 
A  later  modification  of  the  above  method  is  to  attach  both  ends  of 
the  excised  loop  to  the  abdominal  wall,  the  intestinal  fistula  then 
presenting  an  entrance  and  an  exit  orifice.^  The  secretion  ^  obtained 
from  a  dog,  for  example,  by  this  method  is  of  a  yellow  color,  alka- 
line in  reaction,  and  consists  of  water,  albuminous  principles,  and 

iFrericlis,  Wajjner  Physiologie,  1846,  Band  III.,  s.  581. 
^Bidder  &  Sclimidt,  Die  Verdauungssilfte,  1852,  s.  271. 
"Thiry,  Sitzherichte  d.  Wiener  vVkiid.,  1864,  p.  77. 
*Moleschott,  Untersuch.  ziir  Naturlehre,  Bandxiii.,  1888,  s.  40. 
sEohmann,  Pfluger's  Arcliiv,  1887,  Band  41,  s.  411. 


INTESTINAL  JUICES  IN  MAN.  131 

salts.  Amons:  the  latter  may  be  mentioned  sodium  carbonate,  to 
which  the  alkalinity  of  the  secretion  is  due,  and  which,  perhaps, 
aids  also  in  the  emulsification  of  the  fats.  The  intestinal  juice  ap- 
pears to  act  more  particularly  upon  the  carbohydrates,  it  containing 
enzymes,  which  convert  starch  into  maltose,  and  the  latter  into  glu- 
cose, and  inverts  cane  sugar  into  levulose  and  glucose.  It  has 
little  or  no  effect,  however,  upon  proteids  or  fats.  Although  the 
method  (Thiry-Vella)  of  obtaining  intestinal  juice  from  an  animal, 
just  described,  is  less  objectionable  than  those  formerly  made  use  of, 
it  is  questionable,  at  least,  whether  the  secretion  so  obtained  was 
normal.  Even  admitting,  however,  that  it  was  so,  it  does  not  fol- 
low that  its  properties  would  be  necessarily  the  same  as  those  of 
human  intestinal  juice. 

Intestinal  Juice  in  Man. — Indeed,  what  is  positively  known  of 
the  properties  of  the  secretion  in  man  has  been  learned  rather  from 
observations  made  upon  intestinal  fistulae  occurring  in  human  be- 
ings as  the  result  of  wounds  or  operations,  such  as  those  described 
by  Busch  and  Demant,  than  from  experiments  performed  upon 
animals.  The  case  of  Busch, ^  just  referred  to  was  that  of  a  woman 
thirty-one  years  of  age,  in  the  sixth  month  of  her  fourth  pregnancy, 
being  tossed  by  a  bull,  was  wounded  in  the  abdomen.  The  wound 
was  situated  between  the  lunbilicus  and  pubes,  and  consisted  of  two 
contiguous  openings  communicating  with  the  intestinal  canal.  It 
is  probable  that  these  two  openings  were  in  the  upper  third  of  the 
small  intestine. 

Notwithstanding  her  ravenous  appetite  the  patient  became  very 
much  emaciated  in  consequence  of  her  food  passing  out  of  the  upper 
of  the  two  openings  just  referred  to.  It  occurred  to  Bosch,  how- 
ever, that  the  life  of  the  woman  might  be  saved  by  introducing 
cooked  food  into  the  lower  opening,  or  that  communicating  with 
the  lower  portion  of  the  intestine.  This  plan  of  treatment  proved 
successful.  The  nutrition  of  the  patient  rapidly  improved.  The 
opening,  however,  not  uniting,  the  woman  was  made  the  subject  of 
the  observations  contained  in  the  paper  just  referred  to. 

It  will  be  observed  that  fi'om  the  peculiar  conditions  of  the  case, 
food  introduced  by  the  mouth,  unless  absorbed  by  the  stomach, 
would  pass  on  into  the  upper  portion  of  the  intestine,  and  so  out  of 
the  body  by  the  upper  of  the  two  openings,  having  been  modified 
in  its  course  by  the  saliva,  gastric,  intestinal,  and  pancreatic  juices, 
and  the  bile ;  whereas,  food  introduced  into  the  lower  of  the  two 
openings  would  be  modified  by  the  intestinal  juice  only,  as  it  passed 
along  the  small  intestine,  and  if  not  digested  or  absorbed  would 
pass  out  by  the  anus  unchanged.  The  conditions  of  the  experiment 
were,  therefore,  perfectly  physiological. 

The  intestinal  juice  was  secreted  in  response  to  the  natural  stimu- 
lus of  the  food,  while  its  eifect  upon  the  different  kinds  of  food 
could  be  studied,  either  mixed  or  unmixed  with  the  gastric,  pancre- 
^  Yirchow's  Archiv,  1858,  Band  xiv.,  s.  140. 


132  DIGESTION. 

atic  juices,  etc.  Necessarily,  the  quantity  of  iutestinal  juice  ob- 
tained at  any  one  time,  by  the  introduction  of  sponges,  etc.,  was 
not  sufficient  to  admit  of  detailed  analysis ;  the  reaction  was  de- 
termined, however,  to  be  alkaline.  The  general  results  of  Busch's 
observations  and  experiments  upon  the  intestinal  juice  may  be 
summed  up  as  follows  : 

Starch,  both  raw  and  hydrated,  was  invariably  converted  by  it 
into  maltose ;  cane  sugar,  however,  was  not  changed  into  maltose, 
appearing  in  the  feces  as  cane  sugar.  The  intestinal  juice  digested 
more  or  less  cooked  meat  and  coagulated  albumin,  but  had  little  or 
no  effect  upon  fat ;  the  latter  when  introduced  into  the  lower  open- 
ing of  the  intestine  is  always  found  in  the  feces  as  fat  unchanged. 

In  the  case  of  intestinal  fistula  lately  observed  by  Demant,^  starch 
was  converted  into  maltose  or  glucose,  but  proteid  substances  did 
not  appear  to  be  transformed  into  peptone.  No  effect  was  observed 
upon  neutral  fats,  though  oily  matters  containing  free  acid  were 
emulsified.  The  results  of  the  observations  of  Demant  confirm  in 
the  main  those  of  Busch.  It  must  be  remembered,  however,  that 
the  fistula  in  the  former  case  was  situated  much  lower  than  in  the 
latter,  and  that  the  experiments  upon  the  different  kinds  of  foods 
were  performed  outside  of  the  body  after  the  intestinal  juice  had 
been  drawn  from  the  fistula.  The  observations  of  Busch  were, 
therefore,  made  under  more  strictly  physiological  conditions  than 
those  of  Demant,  and  deserve  greater  confidence. 

It  will  be  observed  that  while  starch  was  converted  into  glucose, 
that  fat  was  but  little  modified  by  the  intestinal  juice  of  either  man 
or  dog ;  that  while  proteid  was  digested  at  least  in  the  woman,  cane 
sugar  was  unaffected,  whereas,  proteid  was  undigested  in  the  dog,  but 
cane  sugar  was  inverted  into  levulose  and  glucose.  The  fact  that 
the  cane  sugar  passed  through  the  intestine  of  the  woman  with  the 
fistula  miaffected  by  the  intestinal  juice  is  important  since  cane 
sugar  like  maltose  is  unabsorbable.  As  such,  either  the  amount  of 
cane  sugar  converted  into  glucose  in  the  stomach  must  be  greater 
than  is  usually  supposed,  or  the  cane  sugar  must  be  transformed 
into  glucose  by  some  enzyme  as  it  passes  through  the  walls  of  the 
intestine,  otherwise  it  will  not  be  absorbed  by  the  blood.  That 
the  latter  is  the  case  is  rendered  probable  from  the  fact  that  cane 
sugar  is  converted  into  glucose  by  artificial  intestinal  juice.  Basing 
our  view  more  especially  upon  the  case  of  intestinal  fistula  observed 
by  Busch,  it  will  be  seen,  that  the  action  of  the  intestinal  juice  in 
digestion  is  of  a  supplementary  character,  reinforcing  the  effects  of 
the  saliva  upon  starch,  and  of  the  gastric  juice  upon  the  albumi- 
noids, but  having  no  effect,  however,  upon  cane  sugar  or  fat. 

It  should  be  mentioned   in  this  connection,  that,  according  to 

some  chemists,   intestinal   juice    possesses   no  digestive   properties 

whatever,  not  acting  at  all  upon  carbohydrates  or  proteid s  and  but 

to  a  limited  extent  upon  fats.     By  such  intestinal  juice  is  regarded 

^  Virchow,  Archiv,  1879,  Band  Ixxv.,  s.  419. 


PANCREATIC  JUICE. 


133 


as  being  useful  in  neutralizing  through  its  sodium  carbonate  the 
acid  contents  of  tlie  intestine  derived  from  the  stomach,  and  in  pro- 
moting; the  emulsitication  of  the  fats/ 

Pancreatic  Juice. 

The  pancreas,  in  its  general  structure,  resembles  so  closely  the 
parotid  and  sul^maxillary  glands  that  it  was  known  to  the  older  an- 
atomists as  the  abdominal  salivary  gland  (Fig.  o9).     It  is  situated 

Fig.  .39. 


View  of  the  pancreas  and  surrounding  organs.  J.  /.  The  under  surface  of  the  liver,  g. 
Gall-bladder.  /.  The  common  bile-duct.  s.  The  stomach,  d.  Duodenum,  h.  Head  of  the  pan- 
creas, t.  Tail,  and  i,  body  of  that  gland.  Pancreatic  duct  (e)  and  its  branches,  r.  The  spleen. 
V.  The  hilus.     c,  c.  The  crura  of  the  diaxjhragm.     (Quais.) 


in  the  upper  and  posterior  part  of  the  abdominal  cavity,  behind  the 
stomach  and  between  the  duodenum  and  the  .-spleen.  It  is  about  18 
centimeters  (7.2  inches)  long,  4  centimeters  (1.6  inches)  broad,  and 
1.5  centimeters  (0.6  inch)  thick,  and  usually  weighs  about  75 
grammes  (2.6  ounces).  The  pancreas  in  its  minute  structure  is  a 
compound  tubular  gland,  the  lumen  of  each  secreting  tubule  being 
continuous,  as  in  the  case  of  the  salivary  glands,  with  a  system  of 
capillaries  lying  between  the  secretory  cells.  In  addition  to  the 
latter  there  occur  also  smaller  cells  ill-defined  in  shape,  the  so- 
called  bodies  of  Langerhaus,  which  appear  to  be  the  early  stages  of 
the  secreting  cells.  The  duct  of  the  pancreas  (duct  of  Wirsung) 
running  along  the  whole  length  of  the  gland  opens  into  the  duode- 
num along  with  the  common  bile  duct,  8  to  ITJ  centimeters  (3  to  4 
inches)  below  the  pylorus.  Not  infrequently  there  is  also  a  supple- 
mentary pancreatic  duct  (duct  of  Santorini)  opening  into  the  duo- 
denmn  a  little  below  the  main  duct. 

^Bunge,  op.  cit.,  s.  186. 


134  DIGESTION. 

Methods  of  Obtaining  Pancreatic  Juice. 

The  first  physiologist,  so  far  as  known  to  the  author,  who  at- 
tempted to  obtain  the  natural  pancreatic  juice  from  a  living  animal, 
was  Regnerus  de  Graaf/  who,  in  1662,  opened  the  intestine  of  a 
dog  and  introduced  a  dlick's  quill  into  the  orifice  of  the  pancreatic 
duct.  The  fluid  obtained  by  de  Graaf  was  not  however  pancreatic 
juice,  being  acid  in  reaction,  whereas  the  normal  pancreatic  juice  is 
alkaline. 

Although  experiments  w^ere  performed  during  the  last  century 
and  the  beginning  of  the  present  one  little  or  nothing  was  learned 
of  the  functions  of  the  pancreas  till  the  epoch-making  discoveries  of 
Bernard  ^  in  1846. 

Bernard's  method  of  obtaining  the  pancreatic  juice  consisted  in 
opening  the  abdomen  of  a  living  dog  and  inserting  a  canula  into  the 
principal  pancreatic  duct.  Bernard  showed  that  during  the  inter- 
vals of  digestion  no  pancreatic  juice  is  secreted,  and  that  the  organ 
is  of  a  pale  color.  The  animal  experimented  upon  should,  there- 
fore, be  fed  moderately  an  hour  or  so  before  the  operation.  The 
pancreas  then  becomes  rose  colored,  full  of  blood,  and  secretes  a 
viscid,  alkaline  juice,  which  flows  into  the  duodenimi,  even  before 
the  digested  food  gets  there  from  the  stomach. 

Further,  Bernard  determined  in  a  general  way  the  composition 
of  the  pancreatic  juice  in  the  dog  and  demonstrated  its  action  upon 
starch,  fat,  and  proteids.  Bernard  did  not  succeed,  however,  in 
establishing  a  permanent  pancreatic  fistula.  Since  then,  however, 
this  has  been  accomplished  among  others  by  Bernstein  ^  and  Heiden- 
hain.*  The  method  adopted  by  the  latter  of  making  a  permanent 
pancreatic  fistula  consists  in  completely  excising  in  an  animal,  a 
dog  for  example,  that  part  of  the  duodenum,  into  which  the  main 
duct  opens,  and  sewing  it  to  the  abdominal  wall,  the  continuity  of 
the  intestine  being  restored  by  suturing  its  cut  ends.  By  establish- 
ing such  a  fistula  it  can  be  shown  that  the  flow  of  the  pancreatic 
secretion  begins  as  soon  as  food  enters  the  stomach,  the  latter  stinui- 
lating  the  gland  to  secrete,  as  we  shall  see  hereafter,  reflexly.  The 
flow  of  the  secretion  usually  attains  a  maximum  during  the  first 
three  hours  after  the  taking  of  food.  It  then  diminishes  to  the  fifth 
or  seventh  hour,  when  it  increases  again,  a  second  smaller  maximum 
being  reached  about  the  eleventh  hour.  From  that  time  on  the 
floW'  diminishes  until  about  the  seventeenth  hour  when  it  ceases 
altogether.^  The  amount  of  pancreatic  juice  secreted  in  twenty- 
four  hours  has  never  been  satisfactorily  determined.  It  may  be 
mentioned,  however,  that  a  permanent  fistula  yields  far  more  pan- 
creatic juice  than  a  temporary  one.     The  composition  and  specific 

•  Opera  Omnia,  1678,  p.  292.     Memoire  sur  le  Pancreas. 
^Pbvsiologie  Experimentale,  Tome  ii.,  p.  180,  Paris,  1856. 
^Berichted.  Sachs,  Ges.  d.  Wiss.  Math.-phys.  CI.,  1869,  s.  96. 

*  Hermann,  Ilandbuch,  Fiinfter  Band,  i.  Theil,  1883,  s.  178. 
^Heidenliain,  op.  cit.,  s.  183. 


FORMA  TIOX  OF  PA XCBEA  TIC  JUICE.  135 

gravity  of  the  pancreatic  juice  varies  like  the  amount  according  as 
it  is  obtained  from  a  temporary  or  permanent  fistula  as  shown  by  the 

Composition  of  Pancreatic  Juice  of  a  Dog  from  a  Temporary 
AND  Permanent  Fistula. 

Permanent  Fistula.  = 

979.0 
20.0 


Collected  on  first  opening 
the  duct.^ 

Water 

.       900.8 

Solids 

.       99.2 

c  ..,      f  Organic  Matter   ....     90.4  12.4 

feoiicis    |j^oi.ganic     "        .         .         .         .8.8  7.6 

The  ash  from  1000  parts  of  juice  yielded — 

Soda 0.58  3.32 

Sodic  chloride 7.35  2.50 

Potassic  chloride         .         .         .         .0.02  0.93 

Phosphates  of  alkaline  earths  and  iron    0.53  0.08 

Sodic  phosphate  .....  0.01 

Lime  and  magnesia    .         .         .         .0.32  0.01 

The  pancreatic  secretion  from  a  temporar}^  fistula  is  a  clear,  color- 
less, somewhat  sirupy  fluid  ^vith  a  strong  alkaline  reaction,  due  to 
the  presence  of  sodium  carbonate,  and  a  specific  gravity  of  1030. 
The  juice  is  rich  in  albumin,  the  latter  coagulating  like  white  of 
egg  when  heated  and  contains,  in  addition,  three  enzymes,  a  pro- 
teolytic one,  trypsin,  a  diastatic  one,  amylopsin,  and  a  fat-splitting 
one,  steapsin,  and  possil)ly  a  fourth  milk-curdling  one.  The  min- 
eral constituents  consist  of  alkalines,  chlorides  and  carbonates,  phos- 
phoric acid,  lime,  magnesia,  and  iron.  The  pancreatic  secretion 
from  a  permanent  fistula  is  a  copious  watery  fluid,  having  a  specific 
gravity  of  1011,  and  containing  less  albumin  and  enzymes  than 
that  from  a  temporary  one.  The  composition  of  human  pancreatic 
juice  is  as  yet  but  imperfectly  known,  the  opportunity  of  collecting 
it  being  very  rare.  It  may  be  mentioned,  however,  that  accord- 
ing to  Herter^  the  juice  obtained  in  a  case  of  stoppage  of  the  duct 
was  a  clear,  odorless,  alkaline  fluid,  and  contained  the  three  enzymes. 
The  pancreatic  juice  obtained  from  a  young  woman  with  pancreatic 
fistula  following  extirpation  of  a  tumor  of  the  pancreas  consisted, 
according  to  Zawadsky,*  in  100  parts,  of  water  86.4,  organic  sub- 
stances 13.2.  Of  the  latter,  9.2  parts  were  proteids,  0.3  salts. 
The  juice  transformed  protcid  into  peptone,  starch  into  maltose,  and 
emulsified  fats. 

Formation  of  Pancreatic  Juice. 

It  has  been  learned  from  the  researches  of  Heidenhaiii '^  more 
particularly,  that  each  cell  of  the  pancreas  of  a  dog,  for  example, 

'  Bidder  tt  Schmidt,  Die  Verdaumigssiifte,  1852,  s.  245. 

^('.  Schmidt,  Ann.  d.  Chemie,  xcii.,  1854,  s.  84. 

^McKendrick,  Phvsiologv,  Vol.  2,  1889,  p.  125.      Mandel,  op.  cit.,  p.  202. 

M'entralbhitt  fiir  Pliysiologie,  Band  v.,  1891,  s.  179. 

^Heidenhain,  op.  cit.,  s.  188. 


136 


DIGESTION. 


after  a  period  of  about  thirty  hours'  fasting  consists  of  two  zones, 
an  outer  zone,  which  is  either  homogeneous  or  delicately  striated 
and  readily  staining  with  carmine,  and  a  large  inner  zone  finely 
granulated  and  staining  with  difficulty  ;  the  nucleus,  situated  partly 
in  the  outer  zone  and  partly  in  the  inner  one,  being  irregular  in  form. 
If  the  cell  be  examined,  however,  during  a  period  of  activity — six 
hours,  for  example,  after  food  has  been  taken — the  out(!r  zone  of  the 
cell  will  be  found  to  be  the  longest,  the  inner  zone  in  some  instances 
having  disappeared  altogether,  and  the  whole  cell  M'ill  be  seen  to 
have  become  smaller  and  staining  readily  throughout  almost  its 
whole  extent,  througli  the  small  size  of  the  inner  zone,  the  nucleus 
being-  now  reo-ular  in  outline. 

The  natural  inference  to  be  drawn  from  these  observations  is,  that 
during  secretion  the  inner  zone  furnishes  either  the  secretion  or  the 
materials  of  the  same,  and  consequently  diminishes  in  extent  in 
proportion  to  the  activity  of  the  process,  while  the  outer  zone  en- 
larges through  assimilation  of  materials  brought  to  the  cell  by  the 
blood,  and  that  the  materials  of  the  inner  zone  are  elaborated  at  the 
expense  of  that  of  the  outer  one.  That  such  is  actually  the  case 
appears  to  have  been  shown  by  the  observations  of  Kuhne  and  Lea,^ 
made  upon  the  pancreas  of  the  living  rabbit,  in  which  the  changes 
just  described  were  observed  as  they  took  place  (Fig.  40,  A,  B). 


Fig.  40. 


A  portion  of  the  iiaiicrcas  of  the  rabbit,  .1  at  rest,  B  iu  a  state  of  activity,  a.  The  inner 
granular  zone,  which  in  J  is  hirger,  and  more  closely  studded  with  granules,  than  in  B,  in  whicli 
the  grannies  are  fewer  and  coarser,  b.  The  outer  transparent  zone,  small  in  A,  larger  in  B,  and 
in  the  latter  marked  with  faint  stria?,  c.  The  lumen,  very  obvious  in  B,  but  indistinct  iu  A.  d. 
An  indentation  at  the  junction  of  two  cells,  seen  in  B,  but  not  occurring  in  ,1.  (Kuhne  and 
Sheridan  Lk.v.) 

The  fact  that  a  glycerin  extract  made  out  of  a  pancreas  taken 
out  of  the  body  while  still  warm  has  no  digestive  effect,  whereas 
the  same  glycerin  extract  made  out  of  a  pancreas  kept  for  twenty- 
four  hours  will  digest  fibrin,  shows  that  the  pancreas  contains  at  the 
moment  that  it  is  taken  out  of  the  body  but  little  trypsin,  but  that 
it  does  contain  a  sul)stance,  the  so-called  trypsinogen,  readily  con- 
verted into  trypsin.  If  such  be  the  case  it  would  a])pear  then  that 
the  trypsin,  the  active  proteolytic  enzyme  or  ferment  of  the  pan- 

1  Verhandl.  Nat.  Hist.  Med.  Verein,  N.  F.,  Band  1,  Heidelberg,  1877. 


ACTION  OF  TBYPSTX.  137 

creatic  jiiice,  is  developed  out  of  the  zymogen,  trypsinogen,  stored 
up  in  the  inner  zone  of  the  cell,  and  that  the  latter  is  elaborated 
out  of  the  materials  of  the  outer  zone.  As  to  whether  the  other 
enzymes,  the  amylopsin  and  steapsin,  are  produced  in  the  same  way 
has  not  yet  been  positively  established.  In  all  probability,  however, 
they  are  derived  from  mother  suV^stances  or  zymogens,  which,  if 
ever  isolated,  might  be  appropriately  named  amylopsinogen  and 
steapsinogeu.  The  pressure  under  which  the  pancreatic  juice  is 
stated  ^  to  be  secreted  is  al^out  1 7  millimeters  of  mercury. 

It  has  already  been  incidentally  mentioned  that  pancreatic  juice 
acts  upon  proteids,  carbohydrates,  and  fats.  This  is  due  to  the 
secretion  containing,  as  we  have  just  seen,  three  enzymes,  trypsin, 
amylopsin,  and  steapsin,  to  the  consideration  of  which  let  us  now 
turn. 

Action  of  Trypsin. — The  chemical  cciu.-titution  of  trypsin  i.-;  un- 
known, it  never  having  been  isolated  in  a  sufficiently  pure  state  to 
admit  of  analysis.  It  is  regarded  as  being  an  enzyme  on  account 
of  its  characteristic  action  upon  proteid.  Extracts  containing  tryp- 
sin can  be  prepared  in  various  ways.  The  ordinary  method  is  to 
mince  the  gland  and  to  cover  for  some  time  with  glycerin.  The 
gland  should  be  kept  for  a  few  hours  before  using,  in  order  to  en- 
sure the  conversion  of  trypsinogen  into  trypsin.  By  adding  a  0.3 
per  cent,  solution  of  sodiiun  carbonate  to  a  pancreatic  extract  an 
artificial  pancreatic  juice  is  obtained  which  suffices  very  well  for  the 
demonstration  of  the  action  of  pancreatic  juice  upon  proteids.  As 
pancreatic  juice  decomposes  very  rapidly,  diffiiring  in  this  respect 
from  gastric  juice,  it  is  advisable  to  add  to  the  artificial  pancreatic 
juice  a  little  thymol  or  chloroform.  The  action  of  trypsin  is  re- 
tarded by  cold  and  accelerated  by  heat,  40°  C.  (104°  F.),  but  is 
stopped  at  high  temperatures,  the  enzyme  being  then  entirely  de- 
stroyed. Like  other  enzymes  the  action  of  trypsin  is  retarded  by 
an  accumulation  of  digestive  products.  Trypsin,  like  pepsin,  con- 
verts proteid  into  peptone.  Any  proteid  that  passes  through  the 
stomach  undigested  into  the  intestine  ^vill,  therefore,  be  converted 
there  into  peptone.  The  mode  of  action  of  trypsin  differs,  how- 
ever, in  many  respects  from  that  of  pepsin.  Trypsin  acts  best  in 
alkaline  media,  though,  to  some  extent,  also  in  neutral  and  faintly 
acid  ones.  Proteids  do  not  swell  up  under  the  action  of  trypsin 
before  they  are  changed  into  peptone,  but  are  eroded  or  eaten  away. 
Tryptic  differs  still  further  from  peptic  digestion  in  that  the  proteid 
splits  at  once  into  deutero  albumoses  without  passing  through 
primary  albtunoses  stages.^  The  most  remarkable  difference,  how- 
ever, between  the  action  of  pepsin  and  trA-psin  is  that,  while  the 
action  of  pepsin  is  limited  to  the  conversion  of  proteid  into  anti- 
aud  hemipeptone,  that  of  trypsin  carries  the  process  a  step  fiirther, 
hemipeptone  being  converted  by  the  latter  into  leucin  or  amido- 

1  A.  Henry  &  P.  Wollheim,  Pfliiger's  Archiv,  Band  xiv.,  s.  457. 
^  Xeumeister,  Lehrbuch  der  physiologischen  Chemie,  1897,  s.  246. 


138  DIGESTION. 

caproic  acid,  tyrosin  or  oxyphenyl-amido  propionic  acid,  aspartic 
acid  or  amido-succinic  acid,  tryptophan,  a  body  of  nnknown  nature, 
lysatinin,  etc. 

The  significance  of  the  conversion  of  hemipeptone  by  the  ac- 
tion of  trypsin  into  leucin,  tyrosin,  etc.,  is  far  from  apparent.  If 
proteid  be  regarded  as  repairing  the  waste  of  the  tissue  its  use- 
fulness m  this  respect  woukl  be  lessened  by  part  of  it  being  con- 
verted into  leucin,  tyrosin,  etc.,  and  on  the  supposition  that  it 
is  a  source  of  heat,  less  would  be  liberated  by  the  oxidation  of 
leucin,  tvrosin,  etc.,  than  by  the  oxidation  of  proteid,  the  former 
bodies  being  of  simpler  chemical  constitution.  On  the  other  hand, 
if  leucin,  tyrosin,  on  account  of  being  amido  acid,  are  considered 
in  any  way  as  antecedents  of  urea  then  that  part  of  the  proteid 
from  which  they  are  derived,  usually  regarded  as  so  valuable,  would 
appear  to  be  only  so  much  waste  material.  Trypsin  converts  al- 
buminoids as  well  as  proteids  into  peptones.  Thus,  gelatin,  which 
frequently  is  transformed  only  into  galactose  by  pepsin,  is  finally 
converted  into  gelatin-peptone  by  trypsin.  The  action  of  trypsin 
on  other  bodies  is  not  well  established.  It  appears,  however,  to 
dissolve  elastic  tissue,  membrane  of  fat  cells,  cartilage,  liver,  etc.,  ex- 
cept the  nuclei.     Trypsin  does  not  act  upon  carbohydrates  or  fats. 

Action  of  Amylopsin. — The  action  of  the  diastatic  ferment  of  the 
pancreatic  juice,  amylopsin,  appears  to  be  identical  with  that  of  the 
ptyalin  of  the  saliva.  Amylopsin  acts,  however,  more  energetically 
than  ptyalin,  converting  raw  starch  at  the  temperature  of  the  body 
almost  at  once  into  maltose  and  with  but  little  dextrose  or  glucose. 
When  it  is  borne  in  mind  that  starch  constitutes  about  one-half 
of  our  daily  food  and  that  its  conversion  into  maltose  by  ptyalin  and 
intestinal  juice  is  somewhat  limited,  the  amylolytic  function  of  the 
pancreatic  juice  will  be  seen  to  be  a  most  important  one.  The 
chemical  nature  of  amylopsin  is  not  known.  It  is  regarded  as 
being  an  enzyme  not  only  on  account  of  its  characteristic  action 
upon  starch,  but  from  being  affected  by  heat,  etc.,  in  the  same 
manner  as  the  other  members  of  that  class.  Amylopsin  does  not 
appear  to  exert  any  inverting  eifect  upon  cane  sugar. 

Action  of  Steapsin. — Little  is  known  of  the  nature  of  steapsin, 
the  third  enzyme  of  the  pancreatic  juice.  It  has  never  been  iso- 
lated in  a  pure  state,  and  is  readily  destroyed.  It  is  regarded  as 
being  an  enzyme  on  account  more  especially  of  its  action  upon  fat, 
the  latter,  as  we  have  seen,^  under  its  influence  taking  up  water  and 
splitting  into  glycerin  and  the  fatty  acid  of  the  particular  fat  used. 

Tristearin.  Water.  Stearic  acid.  Glvccrin. 

CsTHi.oOe     -h     3(H,0)     =     3(C,8ll3eO,)     +     C,ll,0, 

This  is  a  most  important  function,  since  the  fatty  acid  so  set  free  in 
combining  with  the  alkali  of  the  pancreatic  and  intestinal  juices 
and  of  the  bile  forms  soap,  which  will  emulsify  the  fat,  and  thereby 

1  P.  53. 


A CTION  OF  STEAPSIN.  139 

render  it  susceptible  of  absorption.  It  should  be  mentioned  in 
this  connection,  in  order  to  avoid  misapprehension  tliat  in  the  emul- 
sification  of  a  given  quantity  of  fat  eaten,  that  only  a  fractional 
part  (5  per  cent.)  is  split  into  glycerin  and  fatty  acid,  the  small 
quantity  of  soap  formed  from  the  latter  sufficing  to  emulsify  the 
rest  of  the  fat,  which  remains  neutral,  and  is  absorbed  as  such. 
It  may  be  mentioned  in  this  connection  that  a  fat  is  said  to  be 
emulsified  when  it  is  subdivided  into  verv  minute  globules,  which 
do  not  run  together  and  wliich  remain  uniformly  distributed 
throughout  the  medium  in  which  they  are  present.  That  the 
emulsification  of  a  neutral  fat  is  due  to  the  action  of  the  soap  formed 
through  the  splitting  and  subsequent  saponification  of  a  part  of  it 
can  be  shown  in  numerous  ways.  Among  others  tlie  addition  of  a 
0.3  per  cent,  solution  of  sodium  carbonate  to  a  slightly  rancid  oil, 
that  is  an  oil  containing  a  little  free  acid  will  produce  at  once  a  fine 
emulsion,  due  to  the  soap  formed  through  the  fatty  acid  combining 
witli  the  alkali,  whereas  the  addition  of  alkali  to  a  perfectly  pure 
oil  will  form  no  emulsion.  It  is  difficult  to  say  just  why  soap  sub- 
divides fat  to  the  extent  that  obtains  in  a  fine  emulsion.  If  the 
minute  globules,  once  formed,  become,  however,  surrounded  by  a 
film  of  soap,  as  is  supposed,  that  would  account  at  least  for  them 
not  coalescing.  The  emulsification  of  fat  in  the  intestine  through 
the  action  of  steapsin  and  soap  is  well  seen  in  a  rabbit  fed  with  oil. 
As  the  pancreatic  duct  opens  in  this  animal  into  the  intestine  30 
centimeters  (12  inches)  below  the  opening  of  the  bile  duet,  a  favor- 
able opportunity  is  presented  of  observing  the  effect  of  pancreatic 
juice  upon  fat  unmixed  with  bile.  In  a  rabbit  so  fed  emulsified  fat 
is  only  found  to  any  extent  in  that  part  of  the  intestine  and  lym- 
phatics below  the  opening  of  the  pancreatic  duct. 

This  observation  not  only  suggested  to  Bernard  the  idea  that  the 
pancreatic  juice  emulsified  the  fat — that  is,  reduced  it  to  a  fine  state 
of  subdivision,  and  so  rendered  it  absorbable — but  was  also  the 
starting-point  of  his  researches  upon  the  functions  of  the  pancreas 
generally.  It  has  also  been  often  shown  that  pancreatic  juice  as 
obtained  from  a  fistula  or  artificially  prepared  when  shaken  A\-ith 
oil  will  produce  at  once  a  fine  and  permanent  emulsion.  "While 
there  is  no  doubt  that  fat  is  emulsified  in  the  economy  by  the  pan- 
creatic juice  in  the  manner  just  described,  it  is  nevertheless  well 
known  that  fat  is  more  readily  split  into  fiitty  acid  and  glycerin, 
with  subsequent  emulsification  liy  a  mixture  of  pancreatic  juice  and 
bile,  than  by  the  former  alone.  The  bile,  though  not  containing  a 
fat-splitting  enzyme,  appears  to  aid  in  some  way  the  action  of  the 
steapsin  of  the  pancreatic  juice,  and  jiromotes  emulsification  through 
its  alkaline  salts,  being  better  fitted  to  combine  with  the  fatty  acid 
set  free  by  the  steapsin  to  form  soap  than  the  alkaline  salts  of  the 
pancreatic  juice  itself.  The  further  influence  of  the  bile  in  pro- 
moting the  emulsification  and  absorption  of  fats  will  be  referred  to 
again.     In  addition  to  the  three  enzymes  just  described,  the  pan- 


140  DIGESTION. 

creatic  juice  is  said  ^  to  contain,  at  least  in  animals  like  the  pig  and 
certain  herbivora,  a  fourth  enzyme  as  yet  unnamed,  which  causes 
the  coagulation  of  neutral  or  alkaline  milk. 

Internal  Secretion  of  Pancreas. 

Kecent  experiments  ^  have  shown  that  extirpation  of  the  pancreas 
in  animals  is  followed  by  the  appearance  of  sugar  in  the  urine,  even 
when  no  carbohydrate  food  is  eaten.  It  is  also  well  known  that 
in  certain  cases,  at  least,  diabetes  mellitus  in  man  is  associated  with 
disease  of  the  pancreas.  The  glycosuria  so  produced  is  not  due, 
however,  as  might  be  supposed,  to  suppression  of  the  pancreatic 
juice  since  the  ducts  of  the  latter  can  be  ligated  or  occluded  with- 
out any  sugar  appearing  in  the  urine.  It  has  been  inferred,  there- 
fore, that  the  pancreas  produces  an  internal  as  well  as  an  external 
secretion  which  contains  possibly  an  enzyme,  which,  passing  into 
the  lymph  and  blood,  promotes  the  combustion  of  sugar  or  prevents 
in  some  way  its  production  by  the  liver  or  other  organs. 

Functions  of  the  Liver. 

The  liver  may  be  regarded  as  a  compound  tubular  gland,  the 
hepatic  cells  being  disposed  in  each  lobule,  in  columns  radiating 
from  the  central  vein,  each  cell  being  in  contact  on  one  side  with  a 
blood  capillary  and  on  the  other  with  a  bile  duct.  Indeed,  the 
latter  begin  as  interspaces  between  two  adjoining  hepatic  cells,  and 
as  the  biliary  capillaries  so  formed  become  in  time  the  interlobular 
biliary  ducts,  so  the  hepatic  cells  pass  more  or  less  abruptly  into 
those  lining  the  latter. 

The  Bile. 

The  bile  is  elaborated  by  the  hepatic  cells  out  of  the  materials 
supplied  by  the  blood  of  the  portal  vein  and  hepatic  artery.  The 
bile  is  not,  however,  a  mere  filtrate,  as  its  important  constituents 
do  not  exist  as  such  in  the  blood,  but  are  produced  by  oxidation, 
etc.,  within  the  hepatic  cells  themselves.  The  pressure  under  which 
the  bile  is  secreted  is  said  to  be  equal  to  15  mm.  (-|  of  an  inch)  of 
mercury  greater  than  that  exerted  by  the  blood  of  the  portal  vein. 
The  bile  appears  to  be  secreted  continuously  within  the  hepatic 
cells,  and,  passing  into  the  intercellular  spaces  or  beginnings  of  the 
bile  ducts,  is  transformed  by  the  biliary  ducts  proper  and  the 
hepatic  duct  into  the  gall-bladder,  where  it  is  temporarily  stored 
until  it  passes  into  the  intestine.  It  appears,  however,  in  cases  of 
human  beings  with  a  biliary  fistula  that  the  bile,  though  secreted 
continuously  in  the  hepatic  cells,  is  ejected  in  spurts  by  the  large 
bile  ducts  through  the  contractions  of  their  muscular  fibers.  The 
relaxation  of  the  orifice  of  the  ductus  choledecus  and  the  flow  of 

'  Ilammarsten,  op.  cit.,  p.  210. 

^Mehring  u.  Minkowski,  Archiv  fiir  exper.  Path.  u.  Phar.,  Band  xxvi.,  1890, 
s.  371.     Minkowski,  Ebenda,  Band  xxxi.,  1893,  s.  85. 


THE  BILE.  141 

the  bile  into  the  duodenum  is  intimately  associated  with  the  state 
of  digestion,  the  flow  beino;  greatly  accelerated,  from  3  to  5  hours 
and  from  13  to  15  hours  after  the  taking  of  food.  The  amount  of 
bile  secreted  is  usually  said  to  be  influenced  by  the  kind  of  food 
eaten,  more  being  secreted  upon  a  flesh-fat  diet  than  upon  a  purely 
fat  or  vegetable  one.  Recent  researches  appear  to  show,  however, 
that  the  flow  of  bile  is  not  materially  affected  by  the  diet.^  Draughts 
of  water  increase  the  flow,  but  diminish  relatively  the  solids  of  the 
bile.  The  quantity  of  bile  secreted  by  man  in  a  given  period  can 
only  be  approximately  determined.  Judging  from  that  obtained 
from  a  fistula,  as  much  as  1344:  grammes  (48  oz.)  may  be  secreted 
in  24  hours. ^ 

The  bile  as  obtained  in  cases  of  biliary  fistulae  is  clear,  greenish, 
brownish-yellow,  neutral  in  reaction,  and  of  a  specific  gravity  of 
1.002.  When  mixed,  however,  with  the  secretion  of  the  gall- 
bladder and  bile  ducts  which  appear  to  owe  their  properties  to  the 
presence  of  a  nucleo-albumin,  rather  than  to  mucin,^  the  bile  is 
more  or  less  ropy  in  consistence,  with  an  alkaline  or  neutral  reac- 
tion. It  has  a  faint  odor,  a  bitter  taste  and  a  specific  gravity  of 
about  1.020,  and  bright  golden-red  in  color,  as  is  the  case  also  in 
the  bile  of  the  omnivora  and  carnivora,  that  of  the  herbivora  being, 
on  the  contrary,  of  a  golden  or  bright  green,  the  diflFerence  being 
due,  as  we  shall  see,  to  the  relative  amount  in  which  the  bile  pig- 
ments, bilirubin  and  biliverdin,  are  present.  It  is  oxidation  of  the 
latter  which  gives  rise  to  the  changes  in  color  which  the  bile  ex- 
hibits after  exposure. 

The  bile  when  shaken  up  with  air  or  water  foams  up  into  a 
frothy  mixture.  This  property  is  due  to  the  presence  of  the  biliary 
salts.  The  bile  is  also  dichroic — that  is,  it  presents  two  different 
colors  according  to  its  mass,  when  examined  with  transmitted  light ; 
thus,  while  a  layer  of  ox  bile  two  or  three  centimeters  thick  is 
green,  that  of  five  or  six  centimeters  appears  red.  The  bile  is  also 
fluorescent ;  thus,  if  green  bile  be  vieAved  by  the  violet  or  blue  rays 
of  the  spectrum,  it  becomes  faintly  luminous,  with  a  yellow,  green- 
ish tint. 

The  bile,  chemically,  is  a  highly  complex  fluid,  consisting  of 
water,  biliary  salts,  mucus,  pigment,  cholesterin,  fats,  and  inorganic 
salts,  the  water  and  solids  being  in  100  parts  in  the  proportion  of 
about  86  to  14. 

Of  the  different  principles  which  constitute  the  bile  most  of  them 
pre-exist  as  such  in  the  blood,  the  biliary  acids  and  the  biliary  pig- 
ment are  not  found,  however,  in  the  latter,  but  are  elaborated  by 
the  liver  cells  out  of  the  principles  brought  to  them  by  the  blood. 

The  biliary  salts  do  not  consist,  as  one  would  suppose  from  their 
name,  of  simply  inorganic  salts,  such  as  are  ordinarily  found  in  the 

1  Eobson,  Proc.  Eoyal  Society,  \'ol.  47,  1890,  p.  507. 
^Copeman,  Journal  of  Physiology,  Vol.  x.,  1889,  p.  231. 
^  Hammarsten,  op.  cit. ,  p.  145. 


142 


DIGESTION. 


Composition  of  ' 

THE  Bile. 

' 

Frerichs. 

Gorup  Besanez 

Man,            Man, 

Man, 

Man, 

Woman, 

Boy, 

iet.  18.          cet.  22. 

ffit.  49. 

£et.  68. 

St.  28. 

set.  12. 

Water          .         .         .     86.00       85.92 

82.27 

90.87 

89.81 

82.81 

Solids          .         .         .     14.00       14.08 

17.73 

9.13 

10.19 
5.65 

17.19 

Biliary  acids  witli  alkali     7.22         9.14 

10.79 

7.37 

.... 

14.80 

Fat     ....       0.32         0.92 

4.73 

3.09 

Cholesterin          .         .0.16         0.26 

Mucus  and  pigment    .       2.66         2.98 

2.21 

1.76 

1.45 

2.39 

Inorganic  salts    .         .       0.65         0.77 

1.08 

0.63 

secretions,  but  of  soda,  united  with  glycocholic  and  taurocholic 
acids,  the  organic  nitrogenized  acids  so  characteristic  of  the  bile,  and 
upon  which,  to  a  great  extent,  the  properties  of  the  latter  depend. 
Tlie  biliary  salts,  the  sodium  taurocholate  (C.,,.H^^NSO-Na)  and 
the  sodium  glycocholate  (C^jH^^NOi-Na),  may  be  obtained  from  the 
bile  by  appropriate  means  in  the  form  of  crystals. 

Fig.  41. 


Sodium  glycocholate  from  ox  bile,  after  two  days'  crystallization.  At  the  lower  part  of  the 
figure  the  cry.stal.s  are  melting  into  drops,  from  the  evaporation  of  the  ether  and  absorption  of 
moisture.     (Daltox.) 

It  is  an  interesting  fact  that  the  biliary  salts,  like  glucose,  lac- 
tose, and  glycogen,  exert  a  right-handed  rotation  on  polarized  light, 
all  other  substances  in  the  animal  body,  so  far  as  is  known,  having 
the  opposite  effect  when  examined  by  polarized  light. 

The  biliary  acids  themselves  may  be  separated  from  their  respec- 
tive salts  by  means  of  dilute  sulphuric  acid  or  lead  acetate  and  sul- 
phydric  acid.  The  relation  existing,  chemically,  between  these  two 
acids,  is  shown  in  the  formula : 

Taurocholic  acid.  Glycocholic  acid. 

C.eH,.NSO,   -   Hp-S   =   C^.H^.NO, 

'Gorup  Besanez,  Lehrbuch  der  Pliysiologischen  Cheraie,  1878,  s.  519.  It  should 
be  mentioned  in  this  connection  that  the  later  analyses  of  Trifanowski,  SocoloffJ  and 
Hoppe-Seyler  difler  quantitatively  somewhat  from  those  given  in  the  text. 


THE  BILE.  143 

by  which  it  is  seen  that,  in  dedncting  water  and  sulphur,  tauro- 
cholic  becomes  glycocholic  acid.  As  a  general  rule,  both  the  bil- 
iary acids  are  present  in  human  bile,  though  the  proportion  in 
which  they  exist  may  vary  considerably. 

It  has  already  been  mentioned  that  the  bile  acids  do  not  exist  in 
the  blood,  but  are  elaborated  in  the  liyer.  This  has  been  shown 
by  experiments  performed  upon  animals.  Thus,  for  example,  after 
ligation  of  the  choledechus  duct,  the  bile  acids  pass  into  the  lymph, 
and  thence  by  the  thoracic  duct  into  the  blood,  whereas,  if  both 
ducts  are  ligated,  no  acids  pass  into  the  blood,  which  would  not  be 
the  case  if  they  were  produced  by  any  other  organs  than  the  liyer. 
It  has  also  been  stated  that  in  animals  in  which  the  liyer  has  been 
extirpated,  the  bile  acids  do  not  accumulate  in  the  blood  or  else- 
w^here,  a  further  proof  that  they  are  elaborated  by  the  liyer. 

Taurocholic  and  glycocholic  acids  when  boiled  with  acids  or  alka- 
lies take  up  water  and  split  into  cholalic  acid  and  tauriu  and  cho- 
lalic  acid  and  glycin  respectiyely,  as  shown  by  the  following  re- 
actions : 

Taurocliolic  acid.  Water.  Cbolalic  acid.  Taiirin. 

Glycocholic  acid.         Water.        Cholalic  acid.  Glycin. 

AYhile  cholalic  acid  is  a  noD-nitrogenous  acid  and  derived,  therefore, 
possibly  from  sugar  or  fat,  it  is  associated  in  both  the  above  cases 
with  nitrogenous  bodies  derived  from  proteid,  taurin  or  amido-ethyl 
sulphonic  acid,  and  glycin  or  amido-acetic  acid.  The  reactions  just 
given  are  especially  interesting  as  it  has  been  shown  that  the  biliary 
acids  split  in  a  similar  manner  in  the  intestine  into  taurin,  glycin, 
and  cholalic  acid.  While  the  further  fate  of  these  substances  is 
perhaps  not  perfectly  understood,  it  appears  probable  that  they  are 
partly  reabsorbed  by  the  blood  and  partly  voided,  the  dyslysin 
(C^^Hg^jOg)  occurring  in  the  feces,  being  dehydrated  cholalic  acid.^ 
The  presence  of  bile  acids  is  usually  shown  by  the  well-known  Pet- 
tenkofer's  test.  This  test  depends  upon  the  fact  that  when  sul- 
phuric acid  is  added  to  cane  sugar,  a  substance,  fiirfurol,  is  formed 
which  is  acted  upon  by  the  biliary  acids  in  such  a  manner  that  the 
liquid  assumes  a  beautiful  cherry-red  or  red-violet  color.  Petten- 
kofer's  test  is  usually  performed  in  the  following  manner  :  One 
part  of  cane  sugar  being  dissolved  in  four  parts  of  water,  one  drop 
of  the  solution  is  added  to  every  cubic  centimeter  of  the  solution 
to  be  examined.  To  this  mixture  a  few  drops  of  sulphuric  acid 
are  slowly  added,  the  temperature  of  the  mixture  not  being  allowed 
to  rise  above  70°  C.  (158°  F.).     If  bile  acids  be  present  in  pro- 

'To  avoid  misuiidei-standins,  it  may  be  mentioned  that  there  are  different  kinds 
of  cholalic  acid,  one  variety  kno\^^l  as  choleic  acid,  occurrinsj  in  ox  bile,  another, 
fellic  acid,  in  human  bile.  etc.  Indeed,  recent  to  the  recent  observations  of  Lassar 
Cohn,  Zeitschr.  fiir  Phys.  Chemie,  Band  19,  1894,  s.  570,  it  appeai-s  that  both  these 
acids  are  found  in  human  bile  and  even  in  greater  quantity  than  cholalic  acid  proper. 


144  DIGESTION. 

portions  of  1  to  500  in  a  solution  treated  this  way,  a  cherry-red  color 
first  appears,  M'hich  rapidly  changes  to  violet,  and  then  to  a  deep  red 
purple.  Inasmuch,  however,  as  there  are  other  substances,  such  as 
albuminous  matters,  amylic  alcohol,  olein,  morphine,  codeine,  etc., 
which  present  this  same  play  of  colors  when  treated  with  cane 
sugar  and  sulphuric  acid,  it  is  necessary  to  point  out  the  precau- 
tions which  must  be  taken  in  applying  Pettenkofer's  test  for  bile, 
in  order  to  exclude  these  sources  of  error.  With  the  exception  of 
the  morphine,  which  is  unlikely  to  occur  in  an  extract  of  the  ani- 
mal fluid,  especially  in  the  proportions  just  referred  to,  this  can  be 
accomplished  if  the  suspected  liquid  be  first  evaporated  to  dryness, 
the  dry  residue  extracted  with  absolute  alcohol  and  decolorized,  if 
necessary,  with  animal  charcoal,  then  precipitated  with  ether,  and 
the  precipitate  dissolved  in  water.  Spectrum  analysis  of  Petten- 
kofer's test  can  also  be  used  in  distinguishing  bile  from  the  sub- 
stances just  referred  to,  and  which  give  the  same  reactions. 

Pettenkofer's  test,  when  carefully  applied,  is  an  extremely  deli- 
cate one,  since  a  solution  of  sodiima  glycocholate  in  the  proportion 
of  1  to  2000,  and  sodium  taurocholate  of  1  to  3000  of  water  re- 
spectively, can  be  recognized  by  it. 

Bile  Pigments. 

The  color  of  the  bile,  as  we  have  already  mentioned,  depends 
upon  the  proportion  in  which  the  bile  pigments,  bilirubin  and  bili- 
verdin,  are  present.  Bilirubin  (CjgH^gNgOg),  the  red  or  orange-red 
coloring  matter  of  the  bile,  can  be  obtained  from  gall  stones  by 
extraction,  is  crystallizable,  readily  soluble  in  alkaline  liquids  and 
chloroform,  less  so  in  alcohol  and  ether,  but  entirely  insoluble  in 
pure  water.  If  to  a  solution  of  bilirubin,  spread  out  on  the  surface 
of  a  porcelain  plate,  for  example,  a  drop  of  nitrous  nitric  acid  be 
added,  a  characteristic  play  of  colors — green,  blue,  violet,  red,  and, 
finally,  yellow — will  be  observed  at  the  circumference  of  the  drop 
of  acid  as  it  diffuses  itself  through  the  solution,  and  which  is  due 
to  the  successive  oxidation  of  the  bilirubin.  This  reaction  is  an 
exceedingly  delicate  one,  the  play  of  colors  being  evident  in  solu- 
tions of  bilirubin  containing  only  1  part  in  80,000,  and  is,  there- 
fore, utilized  as  Gmelin's  test  in  determining  the  presence  of  the 
bile  pigments.  Bilirubin,  though  found  as  hsematoidin  in  blood 
extravasations  and  apoplectic  clots  in  different  parts  of  the  body, 
appears  to  be  normally  elaborated  by  the  hepatic  cells  out  of  the 
hsematin  or  the  coloring  matter  of  disintegrated  red  blood  corpus- 
cles, the  process  being  apparently  one  of  hydration  with  subsequent 
splitting  off  of  iron. 

Hicmatin.  Watt'r.  Iri)ii.  Hilirubiii. 

C3.H3>\0,Fe  +   2HP  -  Fe  =  ^0.,il,s^S>, 

As  a  confirmation  of  the  view  that  a  genetic  relation  cjxists  be- 
tween bilirubin  and  luematin  it  may  be  mentioned  that  in  Amphioxus 


CHOLESTERIX. 


145 


and  the  invertebrata  in  "which  red  blood  corpuscles  do  not  occur  in 
the  blood,  bile  pigments  are  not  found  in  the  bile,  and  that  the  intra- 
venous injection  of  haemoglobin  or  of  substances,  like  water,  which 
disintegrate  the  red  blood  corpuscles,  increase  the  bile  pigments. 
Of  the  iron  that  separates  from  the  hsematin  in  the  formation  of 
bilirubin  the  greater  part  appears  to  be  used  again  in  the  reforma- 
tion of  htematin,  the  remaining  part  being  secreted  in  the  bile. 
Bilirubin,  through  oxidation,  as  in  the  first  stage  of  Gmelin's  test, 
loses  its  red  color  and  becomes  green,  being  transformed  into  bile 
verdin  (C3.,H3j.X^Oj.),  the  green-colored  pigment  of  the  bile. 

Biliverdin  crystallizes  somewhat  imperfectly  from  an  evaporated 
solution  in  glacial  acetic  acid,  is  insoluble  in  water,  ether,  and 
chloroform,  but  is  readily  soluble  in  alkaline  solutions  and  alcohol. 
It  frequently  constitutes  an  ingredient  of  human  gall  stones.  Its 
presence  can  not  only  be  determined  by  Gmelin's  test,  but  by  means 
of  spectrum  analysis. 

Both  bilirubin  aud  biliverdin  pass  as  the  coloring  matters  of  the 
bile  into  the  alimentary  canal  from  which  they  are  partly  absorbed 
and  partly  transformed  by  putrefactive  processes  into  hydrobilirubin 
(C32H^^,N^O.),  constantly  found  as  one  of  the  coloring  matters  of  the 
feces,  and  is  probably  identical  with  the  urobilin,  the  urinary 
pigment. 

Fig.  42. 


Cholesterin,  from  an  encysted  tumor.    (Dalton.) 


Cholesterin. — Cholesterin  (C^-H^^O),  so-called  on  account  of  its 
having  been  first  obtained  as  a  solid  deposit  from  the  bile,  is  a  con- 
stant ingredient  of  that  fluid  occurring  in  the  proportion  of  from 
one  to  three  per  cent.  Cholesterin  is  usually  regarded  as  being  a 
monatomic  alcohol,  its  chemical  constitution  being  expressed  by 
the  formula  CgH^^OH.  It  is  a  crystallizable  body  appearing  as 
thin,  colorless,  transparent,  rhomboidal  plates,  usually  with  an  ob- 
10 


146  DIGESTION. 

long  piece  cut  out  of  the  corner  (Fig.  42)  when  deposited  from  its 
ethereal  or  alcoholic  solution.  Cholesterin  is  held  in  solution  in  the 
bile  by  the  bile  acids,  being  insoluble  in  water  and  dilute  saline 
fluids. 

Cholesterin  is  found  in  the  blood,  spleen,  nervous  system,  etc. 
It  differs,  therefore,  from  the  bile  acids  and  pigments,  in  that  it  is 
not  elaborated  by  the  liver,  but  is  simply  separated  from  the  blood 
by  the  latter,  whence  it  passes  as  a  constituent  of  the  bile  into  the 
alimentary  canal,  and  is  excreted  in  the  feces  apparently  unchanged. 
The  bile  contains,  in  addition  to  the  bile  acids,  pigments,  and  cho- 
lesterin, small  quantities  of  neutral  fats,  soaps,  lecithin,  and  urea. 
Among  the  inorganic  constituents  of  the  bile  may  be  mentioned 
sodium  chloride,  calcium  and  magnesium  phosphate,  and  iron. 
The  gases  of  the  bile  consist  principally  of  carbon  dioxide  with  a 
small  quantity  of  nitrogen  and  traces  of  oxygen. 

Functions  of  the  Bile. — It  was  long  since  inferred  by  Haller  ^ 
from  the  fact  of  the  bile  passing  into  the  vipper  rather  than  the 
lower  part  of  the  intestine  that  it  plays  some  important  part  in 
digestion.  That  such  is  the  case  is  shown  by  the  fact  that  in  cases 
of  biliary  fistula,  far  less  fat  is  absorbed  by  the  lymphatics  of  the 
small  intestine  than  in  the  normal  condition,  the  bile  aiding  the 
pancreatic  juice  in  splitting  and  emulsifying  the  fats  and  promot- 
ing their  subsequent  absorption.  Indeed,  according  to  some  ob- 
servers, emulsification  of  the  fats  does  not  take  place  in  the  absence 
of  the  bile."  This  important  function  of  the  bile  appears  to  be  due 
to  its  bile  acids,  although  the  exact  manner  in  which  they  act  in 
this  respect  is  not,  as  yet,  clearly  understood.  Bile  appears  to  have 
also  a  slight  diastatic  action.  On  the  other  hand,  the  bile  must  be 
regarded  as  an  excretion  as  well  as  a  secretion,  since  part,  at  least, 
of  the  bile  acids  and  pigments,  the  cholesterin  and  lecithin,  are  ex- 
creted in  the  feces.^  As  bile  promotes  the  onward  movement  of  the 
contents  of  the  alimentary  canal,  it  is  usually  regarded  as  being  a 
natural  purgative.  It  is  well  known  that  in  cases  of  biliary  fistula 
or  occlusion  of  the  bile  ducts  that  when  fat  or  meat  is  eaten  the  feces 
become  very  offensive,  and  from  this  reason  it  has  been  inferred 
that  the  bile  is  an  antiseptic.  While  bile  undoubtedly  retards  in 
some  way  putrefaction,  its  action  in  this  respect  does  not  appear  to 
be  directly  antiseptic,  as  bile  itself  outside  of  the  body  putrefies 
rapidly.  In  conclusion,  it  may  be  mentioned  that  peptic  digestion 
is  brought  to  a  standstill  in  the  intestine  through  the  acid  chyme 
of  the  stomach  being  neutralized  or  made  alkaline  through  ad- 
mixture with  the  pancreatic  juice  and  the  bile,  the  pepsin  being 
carried  down  with  the  precipitate  formed  by  the  mixture  of  chyme 
and  bile  and  which  consists  partly  of  proteids  and  partly  of  bile 
acids. 

'  Elementa  Physiologie,  Tomus  sextus,  p.  615. 
2Da.stre,  Comptes  Rendus,  Soc.  Biol.,  1887,  p.  782. 
3  See  p.  22. 


GLYCOGEN.  147 

Origin  and  Function  of  Glycogen. 

The  liver,  as  might  be  inferred  from  its  size,  possesses  other  func- 
tions than  that  of  merely  elaborating  bile,  one  of  the  most  impor- 
tant of  which  is  the  production  of  glycogen.  Glycogen  {C^^f}^^ 
is  isomeric  with  starch  and  dextrin.  It  differs,  however,  physically 
from  the  latter  in  that  its  solution  is  opalescent,  while  that  of  dex- 
trin is  clear,  and  that  the  addition  of  iodine  gives  to  the  solution 
of  glycogen  a  deep  brownish-red  color,  but  to  that  of  dextrin  a 
rosy  red,  and  to  starch  the  characteristic  blue.  The  presence  of 
glycogen  in  the  cells  of  the  liver  is  usually  shown  by  the  iodine 
reaction  just  referred  to,  the  organ  having  been  removed  about 
twelve  hours  after  a  meal  and  hardened  in  alcohol.  Glycogen  is 
soluble  in  both  hot  and  cold  water,  but  insoluble  in  ether  and  alco- 
hol, and  is  one  of  the  few  substances  in  the  animal  body  that  de\a- 
ate  the  plane  of  polarization  to  the  right.  Glycogen  in  solution, 
like  other  starchy  bodies,  is  readily  converted  into  glucose  when 
boiled,  for  example,  with  a  dilute  mineral  acid,  or  brought  in  con- 
tact at  the  temperature  of  the  body  with  saliva,  pancreatic  or  intes- 
tinal juice,  or  serum.  Glycogen  becomes  glucose  also,  if  simply 
allowed  to  remain  in  the  liver  after  death,  or  if  brought  in  contact 
with  its  tissue  after  removal  from  the  body,  the  phenomenon  being 
essentially  one  of  hydration,  as  shown  by  the  formula 

filvcogen.  Water.  Glucose. 

C;H,„0,  +   H,0  =  C,H,,0, 

Glycogen  can  be  readily  obtained  in  the  following  manner  :  Im- 
mediately after  death,  the  liver  of  a  well-fed  animal  is  taken  out  of 
the  body  and  cut  up  into  small  pieces,  and  coagulated  with  boiling 
w^ater.  A  concentrated  decoction  is  then  made  of  the  liver  tissue 
thoroughly  ground  up,  and  decolorized  with  animal  charcoal. 
Strong  alcohol  being  now  added,  the  glycogen  will  be  precipitated 
as  a  white  powder ;  but  this  is  impure,  being  mixed  with  a  small 
quantity  of  glucose,  biliary  salts,  and  albuminous  matter.  The  lat- 
ter can  be  removed,  however,  by  washing  with  alcohol,  and  boiling 
■v^dth  potassium  hydrate.  The  residue  being  filtered  and  dissolved 
in  water,  and  any  albuminous  principles  still  present  being  removed 
with  acetic  acid,  the  glycogen  is  reprecipitated  with  alcohol,  and 
then  dried,  when  it  can  be  kept  for  a  long  time,  it  retaining  its 
properties  indefinitely.  The  quantity  of  glycogen  in  the  liver  may 
amount  in  man  to  as  much  as  ten  per  cent. — that  is  to  say,  assum- 
ing that  the  liver  in  man  weighs  about  1400  grammes  (50  ounces), 
the  glycogen  present  would  be  240  grammes  (5  ounces),  the  amount 
depending,  however,  upon  the  length  of  time  elapsing  since  the  tak- 
ing of  food,  and  the  character  of  the  latter,  increasing  with  diges- 
tion and  diminishing  with  fasting,  and  disappearing  altogether  if 
no  food  be  taken  for  four  or  five  days,  being  more  abundant  on  a 
vegetable  than  on  an  animal  diet,  and  particularly  abundant  if  the 
food  consists  largely  of  carbohydrate  matter.     When  the  chemical 


148  DIGESTION. 

composition  of  glucose  and  glycogen  is  compared,  and  when  it  is 
remembered  that  all  of  the  starch  and  sugar  of  the  food  are  trans- 
formed into  glucose  during  digestion,  the  above  becomes  intelligible, 
on  the  supposition  that  the  glucose  carried  by  the  portal  vein  to  the 
liver  during  absorption  is  converted  by  and  stored  up  in  the  liver 
cells  as  glycogen,  the  transformation  of  the  glucose  into  glycogen 
being  one  of  dehydration,  as  shown  by  the  formula  : 

Glucose.  Water.  Glycogen. 

C.H^P^  —  H^  =  C,H^„0, 

The  fact  of  glycogen  being  developed  on  an  animal  diet  as  well 
as  on  a  vegetable  one,  though  in  less  amoimt,  so  far  from  being  an 
objection  to  the  origin  of  glycogen,  as  just  offered,  is  a  confirmation 
of  it,  since  it  is  readily  conceivable  how  nitrogenized  matter  like 
glycin  may,  for  example,  split  uj)  in  the  economy  into  glucose  and 
urea,  as  shown  by  the  formula  : 

Glycin.  Urea.  Glucose. 

the  glucose  becoming  then  glycogen,  as  when  derived  from  vege- 
table matter,  and  the  urea  being  eliminated  by  the  kidneys. 
That  such  a  transformation  of  nitrogenized  matter  actually  takes 
place  in  the  system,  at  least  under  certain  conditions,  appears 
from  the  fact  that  in  certain  cases  of  diabetes,^  when  the  food 
contained  no  carbohydrate  matter,  the  glucose  increased  pari 
passu  with  the  urea.  The  above,  to  a  certain  extent  theoretical, 
considerations  are  confirmed  by  experimental  ones.  Thus  it  has 
been  shown  by  Bernard,^  Pavy,'^  Doch,^  Tscherinow,^  and  others 
that  the  amount  of  glycogen  in  the  liver  is  notably  increased  within 
a  few  hours  after  the  taking  of  starchy  or  saccharine  articles  of 
food,  and  that  while  glycogen  is  developed  on  an  animal  diet,  the 
amount  produced  is  far  less  than  on  a  vegetable  one.  Glycerin  in- 
creases the  amount  of  glycogen  but  it  appears  to  do  so  only  indi- 
rectly by  interfering  in  some  way  with  its  reconversion  into  glucose 
by  the  liver  cells.  Fat  does  not  influence  the  production  of  glycogen. 
There  appears  to  be  no  doubt,  therefore,  that  the  carbohydrate 
and  nitrogenized  principles  in  part  of  the  food  being  transformed 
into  glucose  are  conveyed  in  the  blood  of  the  portal  vein  to  the 
liver,  and  that  the  glucose  so  derived  is,  probably  by  dehydration, 
converted  into  glycogen,  and,  for  the  time  being,  at  least,  is  stored 
up  as  such  in  the  liver  cells.  That  the  glycogen  remains,  however, 
only  temporarily  in  the  liver,  appears  from  the  fact,  as  shown  first 
by  Bernard,*'  that  in  a  fasting  animal,  or  in  one  that  has  been  fed 

1  Singer,  Med.  Chir.  Trans.,  xliii.,  p.  327. 

2  Physiologie  Experimentule,  p.  159.     Paris,  185.5. 

^  Nature  and  Treatment  of  Diabetes.     London,  18G2. 
*Pflugei-'s  Archiv,  1872,  Band  v.,  s.  571. 
^Virchow's  Archiv,  1869,  Band  xlvii.,  s.  102. 
«0p.  cit.,  p.  204. 


GLYCOGEN.  149 

on  an  exclusively  meat  diet,  that  the  liver  and  the  blood  of  the 
hepatic  vein  contain  glucose,  though  there  is  not  the  slightest  trace 
of  it  in  that  of  the  portal  vein,  the  glycogen  stored  up  in  the  liver 
during  the  intervals  of  digestion  being  gradually  converted  into 
glucose,  and  conveyed  away  by  tlie  hepatic  veins  into  the  general 
circulation. 

That  the  transformation  of  glycogen  into  glucose  is  merely  a 
question  of  time,  is  shown  by  the  fact  that  a  decoction  made  out  of 
a  liver  taken  out  of  the  body  of  a  fasting  animal  is  clear,  whereas 
if  it  is  made  out  of  one  taken  from  an  animal  fed  within  a  few 
hours,  it  is  decidedly  opalescent  through  the  glycogen  it  contains 
not  as  yet  having  been  transformed  into  glucose. 

It  is  denied  by  some  experimenters  that  the  liver  actually  con- 
tains glucose  during  life.  Inasmuch,  however,  as  glucose  can  be 
demonstrated  in  the  liver  within  twenty  seconds  after  the  death  of 
the  animal  from  which  it  has  been  taken,  it  can  hardly  be  doubted 
that  such  is  the  case.  AYhile  there  may  be  a  difference  of  opinion 
as  to  whether  the  liver  contains  glucose  during  life,  there  is  no 
difference  of  opinion  as  to  its  containing  glucose  after  death.  In- 
deed, if  all  the  blood  be  washed  out  of  the  liver  by  forcing  water 
through  the  portal  vein,  the  liquid,  as  it  escapes  by  the  hepatic 
vein,  will  be  found  to  contain  glucose,  and  this  even  upward 
of  half  an  hour  after  repeated  injections.  And  then,  when  the 
presence  of  glucose  can  no  longer  be  demonstrated,  if  the  liver  be 
put  aside  in  a  warm  place  for  a  few  hours,  glucose  can  again  be 
obtained,  it  beino^  a  long"  time  before  its  o-lveoo-en,  the  source  of  the 
glucose,  is  exhausted. 

The  conversion  of  glucose  into  glycogen,  and  the  storage  of  the 
latter  in  the  liver  is  of  advantage  to  the  economy,  since  the  sugar 
produced  during  digestion  would  otherwise  accumulate  to  such  an 
amount  in  the  blood  that  it  would  be  excreted  by  the  kidneys  and 
therefore  wasted.  On  the  other  hand,  as  the  sugar  of  the  blood  is 
diminished  in  amount  the  loss  is  made  good  by  the  reconversion  of 
the  glycogen  into  glucose  and  the  passage  of  the  latter  into  the 
blood.  The  principal  use  of  glycogen  appears,  therefore,  to  depend 
upon  the  readiness  with  which  it  is  developed  out  of  glucose  and 
reconverted  into  the  same,  the  sugar  of  the  blood  being  thereby 
maintained  in  normal  amount.  Glycogen  occurs  not  only  in  the 
liver  but  in  the  muscles,  placenta,  brain,  and  other  parts  of  the  body 
as  well.  The  glycogen  of  muscle  is  usually  regarded  as  so  much 
stored  up  carbohydrate  material,  which  can  be  readily  converted  into 
glucose  and  in  being  oxidized  will  liberate  energy.  As  a  confirma- 
tion of  this  view  it  may  be  mentioned  that  the  glycogen  of  both 
muscles  and  liver  is  rapidly  used  up  by  muscular  exercise  imless 
food  is  supplied. 

In  conclusion,  it  may  be  pointed  out  that  the  transformation  of 
glucose  into  glycogen,  and  of  glycogen  into  glucose  in  the  animal, 
finds  an  analogy  in   the  vegetable,  since,  as  is  well   kuo%A'n,  the 


150  DIGESTION. 

starch  in  the  leaves  of  a  plant  having  been  converted  into  sngar, 
passes  down  to  the  roots,  where  not  infrequently  it  is  reconverted 
into  starch. 

Production  of  Urea  by  the  Liver. 

One  of  the  most  important  functions  of  the  liver,  to  a  consider- 
able extent  at  least,  is  the  production  of  urea.  Urea  (CH^N^O)  is 
usually  regarded  as  being  a  carbamide  or  an  amide  of  carbon  diox- 

NH 
ide,  CO<^TT-?  that  is,  CO.,,  in  which  an  atom  of  oxygen  is  re- 
placed by  the  residues  of  two  molecules  of  ammonia.  Such  being 
its  chemical  constitution,  its  production  by  the  liver  can  be  readily 
accounted  for  on  the  supposition  that  the  leucin,  tyrosin,  and  other 
amides  developed  in  the  digestion  of  proteid  food  stuiFs  are  trans- 
formed into  ammonium  carbamate,  which  being  carried  to  the  liver 
is  there  dehydrated,  and  becomes  urea. 

Ammonium  carbamate.  Water.  Urea. 

While  there  may  be  some  doubt  as  to  whether  urea  is  produced 
in  exactly  this  way  in  the  liver,  recent  experiments  prove  conclu- 
sively that  urea  is  produced  in  the  liver  in  some  such  way.  Thus, 
for  example,  according  to  Schroder,^  when  blood  obtained  from  a 
well-fed  dog  was  passed  through  the  blood  vessels  of  the  liver  of 
another  recently  killed  dog  a  noticeable  increase  in  the  amount  of 
urea  was  observed,  whereas  when  the  blood  used  was  obtained  from 
a  fasting  animal  there  was  no  increase  of  urea.  It  was  shown  also 
by  the  same  experimenter  that  the  addition  of  ammonium  carbonate 
to  the  blood  circulating  through  the  liver  increased  the  amount  of 
urea.  This  result  can  be  explained  by  supposing  that  the  ammo- 
nium carbonate  becomes  ammonium  carbamate  and  then  urea,  or 
urea  directly  by  dehydration,  as  follows  : 

Ammonium  carbonate.  Water.  Urea. 

(NHJX'O,     —     2Hp     =     CON^H^ 

On  the  other  hand  it  has  been  shown  ^  in  cases  of  animals  in 
wdiich  the  blood  of  the  portal  vein  has  been  made  to  pass  directly 
into  the  vena  cava  without  going  through  the  liver  at  all  that  car- 
bamates appear  in  the  blood  and  that  the  amount  of  urea  diminishes 
notably,  carbamates  not  being  converted  into  urea  in  the  absence  of 
the  liver.  Among  its  other  functions  the  liver  performs  the  im- 
portant one  of  removing  and  retaining  heterogeneous  bodies  from 
the  blood,  or  of  rendering  such  as  arc  of  a  poisonous  nature  innox- 
ious.    Thus,  for  example,  while  salts  of  copper  are  retained  by  the 

^  Archiv  fiir  exper.  Path.  u.  Pliar.,  1882,  Band  xv.,  s.  364  ;  1885,  Band  xix.,  s. 
373. 

^Hahn,  Pawlow,  Massen,  and  Nencki,  Archiv  fiir  exper.  Path.  u.  Pliar.,  1893, 
Band  xxxii.,  s.  161. 


THE  LARGE  INTESTINE.  151 

liver,  alkaloids  such  as  phenol  and  cresol,  poisonous  aromatic  sub- 
stances derived  from  the  putrefaction  of  proteid  food  in  the  intes- 
tine, are  converted  into  the  harmless  ethereal  or  congugate  sulphates 
and  which,  passing  into  the  general  circulation,  are  excreted  by  the 
kidneys.  By  a  similar  synthesis,  indol  and  skatol,  also  putrefactive 
products,  after  being  converted  by  oxidation  into  indoxyl  and 
skatoxyl  are  transformed  by  the  liver  into  the  corresponding 
ethereal  sulphuric  acids,  indoxyl-sulphuric  acid  (indican)  and 
skatoxyl  sulphuric  acid,  and  ])ass  in  that  form  into  the  urine. 

Putrefactive  Processes  in  the  Intestines  Caused  by  Micro-organisms. 

It  is  well  known  that  various  kinds  of  micro-organisms  are  in- 
troduced into  the  alimentary  canal  with  the  food  and  drink  which 
cause  fermentation  and  putrefaction  with  the  evolution  of  hydrogen, 
carbon  dioxide,  marsh  gas,^  sulphuretted  hydrogen.  Thus,  for  ex- 
ample, bacilli  occur  which,  acting  upon  the  carbohydrates,  produce 
acetic,  lactic,  butyric  acids,  etc.,  or  upon  proteids  breaking  them  up 
into  leuciu,  tyrosin,  cresol,  phenol  and  its  derivatives  indol,  skatol, 
fatty  acids,  etc.  Organized  ferments,  fungi,  are  present,  which  ap- 
pear to  transform  starch  into  glucose,  cane  sugar  into  glucose  and 
levulose,  and  split  fat  into  fatty  acid  and  glycerin.  It  has  already 
been  mentioned  that  many  micro-organisms  are  destroyed  by  the 
acid  of  the  gastric  juice,  and  it  might  be  suj^posed,  therefore,  as  the 
reaction  of  the  intestinal  secretions  is  alkaline,  that  the  small  intes- 
tine would  present  conditions  favorable  for  fermentation  and  putre- 
fliction.  Recent  observations^  made  upon  cases  of  fistula  of  the  ileum 
in  human  beings  show,  however,  that  upon  a  mixed  diet  while  acetic 
and  other  acids  are  produced  by  the  bactericidal  fermentation  of 
the  carbohydrates,  the  products  of  the  putrefaction  of  proteid  are 
not  developed,  putrefaction  being  prevented  from  the  presence  of 
these  acids.  In  the  large  intestine  the  alkali  secreted  being  usually 
more  than  sufficient  to  neutralize  the  acid  derived  from  the  fermen- 
tation of  the  carl)ohydrates,  the  reaction  of  its  contents  is  alkaline, 
and  such  proteid  as  has  escaped  digestion  and  absorption  undergoes, 
therefore,  putrefaction. 

The  Large  Intestine. 

This  portion  of  the  alimentary  canal  is  so  called  on  account  of  its 
relatively  large  size.  It  measiu-es  usually  in  length  from  1.2  to 
1.5   meters  (5  to  6  feet),  and  in  diameter  from  .3.7  to  7.5  centi- 

'  Marsh  ga.s,  light  carburetted  hydrogen  or  methane  (CH4),  the  only  hydrocarbon 
found  in  the  body,  appears  to  be  developed  in  the  intestine  from  cellulose,  according 
to  the  following  reaction 

Cellulose.  Water.  Methane.   Carbon  dioxide. 

QH.oOj    -I-    H/J    ==.    .3CH,    +     .SCO^ 

"Macfadyen,  Xencki  u.  Sieber,  Archiv  fiir  exper.  Patli.  u.  Phar.,  1891,  Band 
28,  s.  311.  M.  Jakowski,  Archives  Des  Sciences  Biologiques,  St.  Petei-sburg,  1892, 
Tome  I.,  p.  539. 


152  DIGESTION. 

meters  (1.5  to  3  inches).  The  general  direction  of  the  large  intestine 
beginning  with  the  csecnm,  is  from  the  right  iliac  fossa  upward, 
then  transversely  across  to  the  left  side  of  the  body ;  thence  down- 
ward into  the  left  iliac  fossa,  finally  terminating  as  the  rectum. 
The  small  intestine  is  thus  surrounded  by  the  large  intestine,  the 
latter  being  disposed  in  the  form  of  a  horseshoe. 

The  large  intestine,  like  the  small,  consists  essentially  of  two 
coats,  a  mucous,  including  the  submucous,  and  a  muscular.     In  ad- 
dition, the  large  intestine  is,  to  a  great  ex- 
FiG.  43.  tent,  covered  with  peritoneum,  which  serves 

to  maintain  it  in  position,  and  to  connect  it 
with  certain  of  the  abdominal  and  pelvic 
viscera.  While  the  villi  and  valvuhe  con- 
nivcntes  are  absent  in  the  large  intestine, 
throughout  the  whole  extent  of  its  mucous 
membrane  there  are  found  tubular  and  sol- 
section  of  the  mucms  mem-  itary  glauds  which  do  not  differ  essentially 
}irVxhibithfg"the'orifi!'es"o?  i"  their  minutc  structure  from  those  of  the 
l^^lSiSg'magnm^""  Small  intestine.  _  The  tubular  glands  (Fig. 
43)  of  the  large  intestine  are,  however,  more 
numerous,  longer,  and  more  closely  set  together  than  those  of  the 
latter,  and  often  are  subdivided  at  their  caecal  extremities. 

The  mucous  membrane  of  the  large  intestine  is  paler,  thicker,  and 
more  closely  adherent  to  the  underlying  parts  than  that  of  the  small 
intestine.  The  muscular  coat  of  the  large  intestine  differs  consider- 
ably in  certain  points  from  that  of  the  small  intestine.  Thus,  in 
the  colon  more  particularly,  the  longitudinal  fibers  are  gathered  to- 
gether in  three  Avell-marked  bands,  one  of  which  is  anterior,  while 
the  other  two  are  latero-posteriorly  situated.  The  large  intestine  is 
divided  by  anatomists  into  three  portions,  the  cajcum,  colon,  and 
rectum,  these  differing  in  their  size,  shape,  and  the  character  of 
their  mucous  and  muscular  coats. 

The  most  important  part,  physiologically,  of  the  caecum  or  caput 
coli,  the  widest  portion  of  the  large  intestine,  is  the  ileo-csecal  valve, 
by  means  of  which  the  contents  of  the  ileum,  after  they  have  passed 
into  the  large  intestine,  are  prevented  from  returning  into  the  small 
intestine.  The  small  intestine  opens  into  the  large  intestine  by  a 
slit-like  aperture  (Fig.  44,  a  e)  which  lies  nearly  transverse  to  the 
direction  of  the  latter.  This  aperture  is  bounded  above  and  below 
by  two  semilunar  folds  or  valves  which  project  inward  toward  the 
cseciun  and  colon.  At  each  end  of  the  aperture  the  two  valves  or 
folds  run  into  each  other  and  are  then  prolonged  at  each  side  as  a 
ridge  or  fr£enum,  which  gradually  fades  aAvay.  That  portion  of  the 
valve  which  looks  toward  the  ileum  is  covered  with  villi,  and  in 
other  respects  resembles  the  mucous  membrane  of  the  small  intes- 
tine, while  that  upon  the  opposite  side  of  the  valve  is  destitute  of 
villi,  and  its  mucous  membrane  is  like  that  of  the  large  intestine. 
Each  segment  of  the  valve  is  covered  with  mucous  membrane,  and 


THE  LARGE  INTESTINE. 


153 


Fig.  44. 


consists  of  submucous  tissue  aud   muscular  fibers,   derived  fi'om 
the  circular  muscular  fibers  of  both  the  ileum  and  large  intestine. 

The  lono^itudinal  muscular  fibers 
of  the  ileum,  however,  run  con- 
tinuously into  those  of  the  large 
intestine,  taking  no  part  in  the 
formation  of  the  valve,  but  are 
stretched  across  it.  The  effect  of 
distention  of  the  caecum  by  its  con- 
tents is  that  the  frsena  being  put 
on  the  stretch,  the  edges  of  the 
valves  are  brought  in  apposition, 
closing  the  ileo-c»cal  aperture  so 
completely  that  all  reflux  from  the 
large  intestine  into  the  ileum  is 
prevented,  but  at  the  same  time  no 
hindrance  is  oifered  to  the  passage 
of  the  contents  of  the  ileum  into 
the  laro-e  intestine.  An  interest- 
ing  feature  about  the  csecum  is  its 
vermiform  appendix  (Fig.  44,  p), 
a  worm-like  tube,  beginning  at  its 
lower  end  and  terminating  in  a 
blind  extremity,  attaining  usually 
about  a  length  of  from  7.5  to  15 
centimeters  (3  to  6  inches),  and  ha\'ing  a  diameter  aljout  the  size 
of  a  cpiill. 

The  vermiform  appendix,  so  far  as  is  known,  has  no  use  in  man, 
but  is  a  very  interesting  structure  as  representing  in  man,  in  a  ru- 

FiG.  45. 


View  of  the  Ueo-colic  valve  from  the  large 
intestine.  The  figure  shows  the  lowest  part 
of  the  ileum,  ;,  joining  the  caecum,  c,  and  the 
ascending  colon,  o,  which  have  been  opened 
anteriorly,  so  as  to  display  the  ileo-colic 
valve  ;  a,  the  lower,  and  e,  the  upper  segment 
of  the  valve,    p.  Vermiform  appendix. 


Caecum  of  capybara.     (From  nature.) 


dimentary  condition,  tliat  which  is  well   developed  and   performs 
important  functions   in   many  animals.      Thus  in  the  horse,  tapir, 


154  DIGESTION. 

elephant,  rabbit,  and  beaver,  the  Cfficiun  is  very  large  ;  in  the  capy- 
bara  (Hydrochserus),  a  species  of  rodent,  the  caecnm  (Fig.  45,  V) 
measnred  65  centimeters  (26  inches)  in  length,  -svhile  in  a  koala 
(Phascolarctos),  a  small  marsupial,  also  examined  by  the  author,  it 
attained  a  length  of  125  centimeters  (50  inches).  Xow,  by  com- 
paring the  cfecum  in  the  capybara  with  the  vermiform  appendix 
in  man,  it  will  be  found  that  the  latter  corresponds  to  the  blind 
part  of  the  cseciun,  V,  in  the  capybara,  while  the  csecum,  or  caput 
coli,  in  man  is  homologous  with  that  part  of  the  caecum  in  the  capy- 
bara communicating  with  the  large  in- 
Fio.  46.  testine,  I.     In  other  words,  the  csecum 

in  the  animals  just  mentioned  is  equal 
in  man  to  the  vermiform  appendix  and 
csecum.  Further,  it  will  be  observed 
that  the  crecum  of  the  capybara  (Fig.  45) 
is  much  longer  than  the  stomach  of  that 
animal  (Fig.  46),  the  latter  measuring 
only  25  centimeters  (10  inches),  while 
it  is  needless  to  state  that  just  the  re- 
verse relation  obtains  as  regards  the 
same  parts  in  man.     The  significance  of 

stomach  of. ai.ybai  a.     arom  nature.)    this     COUtrast    is     evidcut     CUOUgh    whcn 

the  digestion  of  food  in  man  and  the 
capybara  is  considered.  In  the  first  instance,  as  we  have  seen, 
the  action  of  the  stomach  is  very  important ;  in  the  latter  instance 
it  is  but  relatively  so,  the  imperfect  digestion  of  food  in  the  stomach 
of  the  capybara  being  completed  in  its  caecum. 

In  the  same  manner  the  cseciun  in  the  tapir,  horse,  and  elephant, 
etc.,  supplements  the  imperfect  digestive  action  of  the  stomach  in 
these  animals.  On  the  other  hand,  in  the  giraife,  in  which  there 
are  four  well-developed  stomachs,  the  caecum  is  relatively  small. 
In  a  word,  there  is  an  inverse  ratio,  both  anatomically  and  physio- 
logically, between  the  stomach  and  the  caecum  ;  when  the  one  is 
large  and  active,  the  other  is  small  and  inactive,  and  vice  versa. 
The  conclusion  must  not,  however,  be  drawn  that  the  caecum  in 
these  animals  secretes  a  gastric,  or  any  other  digestive  juice.  The 
caecum  rather  appears  to  be  a  receptacle  where  the  fluids  absorbed 
by  the  food  in  its  rapid  pas.sage  through  the  alimentary  canal  have 
time  to  produce  their  digestive  effects. 

The  acid  reaction  often  noticed  in  the  caeciun  of  animals,  and 
sometimes  in  man,  is  not  due  to  acid  secretion,  but,  as  we  have  seen, 
to  a  kind  of  lactic  or  butyric  acid  fermentation  set  up  in  the  food, 
the  normal  reaction  of  the  secretion  of  the  caecum  being  alkaline. 
That  the  vermiform  appendix  in  man  is  a  rudimentary  organ  is  con- 
firmed by  the  fact  that  it  is  relatively  longer  in  the  embryo  than  the 
adult.  It  is  worthy  of  note  that  the  vermiform  appendix  is  found 
as  in  man  in  all  four  anthropoid  apes,  the  gorilla,  chimpanzee, 
orang,  and  gil)bon  ;  and  more  remarkable  still  that  it  is  present  in 
a  marsupial,  the  wombat  (Phascolomys). 


CONTENTS  OF  LARGE  INTESTINE.  155 

In  addition  to  what  has  already  been  said  of  the  colon,  an  im- 
portant feature  is  its  sigmoid  flexure,  so  called  from  the  S-like  curve 
the  colon  makes  just  before  passing  into  the  rectum.  This  curva- 
ture, as  we  shall  see,  is  the  position  where  the  feces  are  temporarily 
retained. 

The  large  intestine  terminates  in  the  rectum,  which,  while 
straight  in  animals  in  which  it  was  originally  described,  is  far 
from  being  such  in  man.  In  fact,  the  rectum  in  man  first  passes 
obliquely  downward  from  left  to  right,  from  opposite  the  left  sacro- 
iliac articulation  to  the  middle  line  of  the  sacrum.  It  then  curves 
forward  back  of  the  prostate  in  the  male,  and  the  vagina  in  the 
female,  and  finally  passes  backward  and  downward,  terminating  in 
the  anus.  The  anus  is  a  dilatable  orifice,  lined  with  mucous  mem- 
brane and  covered  with  skin,  the  skin  and  mucous  membrane  be- 
coming continuous  with  each  other.  The  margin  of  the  anus  and 
low^er  part  of  the  rectum  are  embraced  by  the  external  and  internal 
sphincter  muscles,  the  levators  ani  and  coccygei.  These  muscles 
serve  to  support  the  bowel,  and  to  close  its  anal  orifice.  The  in- 
ternal sphincter  muscle  consists  of  the  circular  fibers  only  greatly 
developed.  It  is  situated  2.5  centimeters  (1  inch)  above  the  anus, 
extending  over  12  millimeters  (about  ^  inch)  of  the  intestine,  and 
is  about  4  millimeters  (2  lines)  thick. 

The  rectum,  20  centimeters  (about  8  inches)  in  length,  is  not 
sacculated  like  the  rest  of  the  large  intestine,  the  longitudinal  mus- 
cular fibers  being  scattered  over  its  surface.  While  the  upper  part 
of  the  rectum  is  narrow,  at  the  lower  part  it  is  dilated  into  a  kind 
of  reservoir  just  above  the  anus.  The  mucous  membrane  of  the 
rectum  is  more  vascular,  thicker,  and  redder  than  that  of  the  colon, 
and  moves  more  freely  over  the  muscular  coat.  It  is  thrown  into 
numerous  folds,  most  of  which  are,  however,  effaced  when  the  rectum 
is  distended. 

The  Contents  of  the  Large  Intestine. — While  there  is  no  reason 
to  suppose  that  anything  like  true  digestion  takes  place  in  the  large 
intestine  of  man,  various  important  changes  are  effected  there  by 
which  the  undigested  residue  of  the  food  is  transformed  into  the 
feces,  the  most  marked  changes  being  in  the  consistence,  color, 
and  odor,  and  which  are  gradually  developed  as  it  passes  from  the 
caecum  through  the  colon  into  the  rectum.  As  the  undigested  food 
passes  through  the  large  intestine  its  liquid  portions  are  being  con- 
stantly absorbed,  the  feces,  therefore,  have  a  much  firmer  consistence 
than  the  contents  of  the  ileum.  The  large  intestine  is,  therefore, 
physiologically  important,  as  presenting  an  extensive  absorbing, 
if  not  a  digestive  surface.  The  absorbing  power  of  the  rectum  is 
well  known.  Indeed,  life  can  be  sustained  for  months  by  giving 
nutritious  enemata. 

The  color  of  the  feces  is  of  a  dariv  yellowish-brown,  and  appears 
to  be  due  to  the  presence  of  stercobilin,  the  latter  being  either  iden- 
tical with  or  a  derivative  of  hydrobilirubin.     It  is  well  known  that 


156  DIGESTION. 

wlieu  the  bile  is  deficient  or  absent,  the  stools  become  lighter  or 
clay -colored.     The  color  of  the  feces  varies  also  according  to  the  diet. 

While  the  cause  of  the  odor  of  the  feces  cannot  be  said  to  be  ex- 
actly understood,  there  can  be  no  doubt  that  it  is  due  to  a  great  ex- 
tent to  the  skatol  and  indol  which  have  escaped  absorption,  to  the 
decomposition  of  the  bile,  and  to  the  secretion  of  the  glands  of  the 
colon  and  rectum. 

The  reaction  of  the  feces  is  variable,  sometimes  acid,  often  alka- 
line or  neutral,  depending  chiefly  upon  the  kind  of  food  eaten. 

The  entire  quantity  of  feces  passed  in  twenty-four  hours  upon  a 
mixed  diet  amounts  usually  to  from  1 20-150  grammes  (4-5  ounces), 
but  on  a  vegetable  diet  to  as  much  as  383  grammes  (11  ounces), 
which  is,  as  might  be  expected,  the  vegetable  diet  containing  so 
much  indigestible  matter.  When  the  contents  of  the  large  intes- 
tine are  examined  microscopically,  there  will  be  found  a  number  of 
undigested  substances  derived  from  the  vegetable  and  animal  foods. 
Among  other  matters,  the  spiral  vessels  of  vegetables,  the  cortex  of 
grains,  hard  vegetable  seeds,  structures  generally  consisting  largely 
of  cellulose,  muscular  tissue  in  various  stages  of  disintegration, 
tendinous  and  elastic  structure,  the  organic  constituents  of  bone. 

The  feces  chemically  may  be  said  to  consist  of  seventy-five  parts 
of  water  to  twenty-five  of  solid  residue.  In  the  latter  there  have 
been  found  among  other  substances  the  ammonium-magnesium  phos- 
phate, the  magnesium  phosphate,  salts  of  sodium,  potassium,  cal- 
cium, iron,  fatty  acids,  excretin.  The  feces  contain  also  mucous 
pigment  and  different  kinds  of  micro-organisms,  the  latter  being 
often  present  in  vast  numbers. 

The  large  intestine  contains  in  addition  to  the  feces  more  or  less 
gas,  consisting  at  one  time  or  another  of  hydrogen,  carburetted  and 
sulphuretted  hydrogen,  carbon  dioxide,  and  nitrogen, which  are  not 
infrequently  also  eliminated  by  the  rectum.  These  gases  are  devel- 
oped, as  already  mentioned,  during  the  putrefaction  of  proteid  food, 
most  of  the  nitrogen,  however,  being  derived  from  the  air  swallowed 
with  food. 

Defecation. 

In  health  the  feces  are  usually  discharged  once  in  twenty-four 
hours.  This  rule,  however,  is  far  from  being  invariable,  being 
modified  by  individual  peculiarities. 

Indeed,  there  are  well  authenticated  cases  of  the  act  of  defecation 
not  having  been  performed  during  a  period  of  eight  years,  and  even 
longer,  the  unabsorbed  food  apparently  having  been  either  rejected  by 
the  mouth,  or  eliminated  by  the  skin  or  kidneys.  On  the  other  hand, 
there  seems  to  be  no  reason  to  doubt  that  there  have  been  also  cases 
in  which  the  bowels  were  evacuated  as  often  as  twelve  times  daily, 
and  that  for  thirty  years,  and  yet  without  the  health  being  affected.^ 

1  Dunglison,  Human  Physiology,  8th  ed.,  Vol.  i.,  p.  191.  Pliiladelphia,  1856. 
('hapman,  Lectures  on  the  Diseases  of  Thoracic  and  Abdominal  \'iscera,  p.  294. 
Philadelphia,  1844. 


RESUME  OF  DIGESTION.  157 

The  feces  are  gradually  passed  through  the  contraction  of  the 
muscular  fibers  of  the  large  intestine  into  the  sigmoid  flexure  of  the 
colon,  where  they  accumulate,  and  are  retained  for  some  time.  It 
is  probably  the  descent  of  the  feces  from  the  sigmoid  flexure  of  the 
colon  that  is  the  immediate  cause  of  the  desire  to  defecate,  the  action 
being  to  a  certain  extent,  as  we  shall  see,  under  the  control  of  the 
will.  It  is  often  thought  that  the  feces  accumulate  in  the  rectima ; 
the  lower  part  of  the  rectum,  however,  in  health  is  almost  always 
empty,  though  in  old  persons,  or  in  those  of  a  constipated  habits, 
the  feces  are  often  found  there. 

In  the  act  of  defecation,  the  feces  first  pass  from  the  sigmoid 
flexure  of  the  colon  into  the  upper  constricted  part  of  the  rectum, 
then  into  the  lower  portion,  the  sphincter  muscle  at  first  resisting, 
then  giving  away,  through  the  inhibition  of  the  nervous  centers 
controlling  the  sphincter  ani,  and  the  fecal  mass  leaves  the  body. 
The  action  is  assisted  by  the  levator  ani,  which  favors  the  relaxa- 
tion of  the  external  sphincter,  and  by  the  compression  of  the 
viscera  through  the  action  of  the  diaphragm  and  the  abdominal 
muscles.  AMien  the  glottis  is  closed  a  point  of  support  is  further 
given  to  the  latter  muscles. 

Resume  of  Dig^estion. 

In  concluding  the  subject  of  digestion,  it  does  not  appear  to  be 
superfluous  to  give  a  brief  resume  of  the  different  processes  of 
which  we  have  given  a  somewhat  detailed  account. 

The  food,  after  having  been  taken  into  the  mouth,  is  masticated, 
and  through  the  action  of  the  tongue  and  checks  having  been  col- 

c?  o  ci 

lectcd  into  a  bolus,  is  then  swallowed.  The  saliva  poured  into  the 
mouth  acts  mechanically,  aiding  mastication  and  deglutition  ;  and 
chemically,  in  converting  some  of  the  starch  into  maltose,  etc. 

The  proteid  substances  of  the  food  are  converted  into  peptones, 
and  cane  sugar  to  some  extent  into  glucose,  by  the  gastric  juice, 
which  has  also  the  effect  of  dissolving  the  walls  of  the  fat  vesicles, 
the  fat  itself  thus  set  free,  however,  being  unaffected  by  this  secre- 
tion. That  part  of  the  starch  which  has  escaped  conversion  by  the 
saliva  either  in  the  mouth  or  stomach,  passes  together  with  the  cane 
sugar  unchanged  into  the  small  intestine. 

The  intestinal  juice  supplements  the  action  of  the  saliva  upon 
starch,  of  the  gastric  juice  upon  proteids  and  cane  sugar.  The 
pancreatic  juice  converts  starch  into  maltose,  proteid  into  peptone, 
and  splits  the  fat  into  fatty  acid  and  glycerin,  so  rendering  it  sus- 
ceptible of  emulsion.  The  bile  assists  in  the  emulsifying  of  fats, 
and  promotes  their  absorption  ;  it  further  retards  putrefaction,  and 
in  stimulating  the  peristaltic  acid  of  the  intestine  acts  as.  a  natural 
purgative. 

The  conversion  of  starch  into  maltose,  of  albumin  into  peptone, 
etc.,  appears  to  consist  in  a  hydration  of  these  substances,  brought 
about  by  the  presence  of  ptyalin,  pepsin,  etc.,  entering  into  the 


158  DIGESTION. 

composition  of  the  saliva,  gastric  juice,  etc.,  respectively.  These 
enzymes  or  ferments  to  which  the  action  of  the  alimentary  secre- 
tions is  due,  are  elaborated  out  of  the  blood,  and  stored  up  during 
the  intervals  of  digestion  by  the  cells  of  which  the  glands  consist. 
The  ptyalin,  pepsin,  trypsin,  etc.,  poured  out  at  the  moment  of 
secretion,  differ  somewhat  from  the  principles  actually  present  in 
the  gland  during  the  intervals  of  digestion,  being  developed  out  of 
the  latter  at  the  moment  of  secretion.  That  the  phenomenon  of 
secretion  is  not  one  of  mere  filtration,  is  shown  by  the  pressure 
exerted  by  the  secretion,  and  that  chemical  action  is  going  on  is 
made  evident  through  the  heat  and  carbon  dioxide  developed. 

The  contents  of  the  large  intestine  consist  essentially  of  the  un- 
digested part  of  the  food,  decomposed  bile,  and  of  such  digested 
principles  as  have  not  been  absorbed.  As  these  pass  through  the 
large  intestine  they  gradually  assume  the  consistence,  color,  odor, 
etc.,  of  the  feces.  The  latter  accumulating  in  the  sigmoid  flexure 
of  the  colon,  pass  into  the  rectum  and  thence  out  of  the  body,  their 
expulsion  constituting  the  act  of  defecation. 


CHAPTER   IX. 

ABSORPTION. 

While  the  digested  food  in  the  alimentaiy  canal  may  be  said  to 
be  inside  of  the  body,  using  the  word  in  its  ordinary  acceptation, 
physiologically  it  is  still  outside  of  it,  for  if  the  food  simply  re- 
mained in  the  alimentary  canal  it  would  be  of  no  use  for  nutritive 
purposes.  Indeed,  unless  the  digested  food  gets  into  the  blood,  and 
is  so  carried  to  all  parts  of  the  organism,  and  repairs  the  waste  of 
its  tissues,  and  supplies  the  material  for  the  liberation  of  energy,  it 
might  as  well  not  be  taken  into  the  system  at  all.  The  process  by 
which  the  digested  food  passes  from  the  interior  of  the  alimentary 
canal  into  the  blood,  is  known  as  absoq^tion. 

It  is  not  to  be  understood,  however,  that  absoi^ption  is  by  any 
means  limited  to  the  alimentary  canal,  or  that  the  substances  of 
which  food  consists  are  the  only  ones  that  can  be  absorbed.  We 
shall  soon  see  that  oxygen  is  absorbed  by  the  blood  as  it  circulates 
through  the  lungs,  that  the  skin  will  take  up  various  substances, 
and  that  effusions  found  under  certain  circumstances  in  the  cavities 
of  the  pleura,  pericardium,  peritoneum,  etc.,  can  be  absorbed  by 
these  serous  surfaces.  Inasmuch,  however,  as  we  have  just  seen 
how  the  food  is  digested,  our  study  of  absorption  will  begin  with 
the  consideration  of  the  process  as  it  goes  on  in  the  alimentary 
canal. 

That  the  ancients  were  well  aware  that  the  human  body  absorbs, 
is  evident  from  their  writings.  Thus  Hippocrates,'  for  example, 
speaks  of  "  the  veins  of  the  stomach  and  intestine  attracting  the 
clearest  and  most  fluid  parts  of  the  solid  and  liquid  food." 

While  the  ancients  were  correct  in  considering:  the  veins  as  a 
means  of  absorption,  it  must  not  be  inferred,  however,  that  the 
course  of  the  circulation  was  understood  by  them,  it  not  being 
learned  until  modern  times  that  the  venous  blood  from  the  capil- 
laries of  the  stomach  and  intestine  is  conveyed  by  the  gastric  and 
mesenteric  veins  to  the  portal  vein  and  thence  to  the  liver  and  from 
the  latter  by  the  hepatic  vein  and  inferior  vena  cava  to  the  heart. 
Nothing,  however,  appears  to  have  been  known  in  ancient  times 
of  the  lymphatic  system.  It  is  well  known  that  in  the  MTitings  of 
Galen  there  are  preserved  vague  illusions,  like  those  of  Erasistra- 
tus,"  "  to  arteries  in  the  mesentery,"  "  full  of  milk,"  and  of  Hiero- 
philus  ^  to  "  particular  veins  ending  in  certain  glands,"  but  the  con- 
text shows  that  these  old  anatomists  regarded  the  vessels  alluded 

1  Opera  Omnia,  p.  119.     Ludg.  Batav.,  1665. 

^Galenus,  Opera  Omnia,  Tomus  i.,  Cap.  5,  p.  61.     Yenetiis,  1556. 

3 Ibid.,  Cap.  19,  p.  141. 


160  ABSORPTION. 

to,  which  were,  no  doubt,  lymphatics,  as  niitrieut,  and  not  as  ab- 
sorbent in  their  function. 

While  it  is  true  that  the  upper  part  of  the  thoracic  duct  in  the 
horse  was  described  by  the  Roman  anatomist  Eustachius '  in  1563, 
the  history  of  the  lymphatic  system  really  begins  with  Gasparis 
Aselli's  discovery,  in  1622,  in  the  dissecting  amphitheatre  at  Pavia, 
of  the  lacteals  of  the  small  intestine  in  the  dog.  Aselli  tells  us 
in  his  work  -  on  the  lacteals  that,  on  opening  a  dog  to  show  some 
friends  the  recurrent  laryngeal  nerves,  he  was  surprised  to  find  in 
the  mesentery,  in  addition  to  the  arteries  and  veins,  delicate,  white 
lines,  which,  at  first,  he  thought  were  nerves.  On  pricking  one  of 
them,  ho^s'ever,  and  seeing  a  whitish,  milk-like  fluid  escape,  he  ex- 
claimed, like  Archimedes  of  old,  "  Eureka  ! "  for  he  felt  he  had 
made  a  great  discovery. 

Aselli  further  extended  his  observations  to  other  animals,  and 
found  the  lacteals  in  cats,  lambs,  pigs,  cows,  and  the  horse.  It  was 
not,  however,  until  1628,  two  years  after  Aselli's  death,  that  the  lac- 
teals were  demonstrated  in  man.  For  this  observation  science  is 
indebted  to  Peiresc,  Senator  from  Aix,  who,  wishing  to  know 
whether  Aselli's  discovery  could  be  extended  to  man,  permitted  the 
body  of  a  criminal  who  had  been  executed  to  be  opened,  when  the 
lacteals  w^ere  found  (Fig.  47),  the  anatomist  interested  in  the  post- 
mortem examination  having  attended  to  the  feeding  of  the  criminal 
before  execution. 

Aselli  supposed  that  the  lacteals  which  he  had  discovered  in  the 
mesentery  carried  the  chyle  to  the  liver.  This  error  was  corrected 
by  Pecquet,'^  a  Frenchman,  who  showed,  in  1649,  that  in  the  dog, 
and  afterward  in  the  horse,  ox,  pig,  etc.,  the  mesenteric  lymphatics, 
or  lacteals,  terminated  in  a  reservoir,  the  receptaculum  chyli,  now 
often  called  in  honor  of  its  discoverer  the  reservoir  of  Pecquet ;  and 
further,  that  this  receptaculum  was  the  beginning  of  the  thoracic 
duct.  The  functional  significance  of  the  forgotten  discovery  of 
Eustachius  became  then  for  the  first  time  apparent,  for  it  was 
shown  that  the  lymphatics  of  the  small  intestine  and  thoracic  duct 
oifered  a  route  by  which  the  digested  food  could  be  carried  from  the 
alimentary  canal  to  the  blood  in  the  subclavian  vein,  and  thence  to 
the  heart.  Two  years  after  the  important  discovery  of  the  recep- 
taculum chyli — that  is,  in  1651 — lymphatics  were  demonstrated  in 
the  liver  and  other  parts  of  the  body  by  Rudbeck  *  and  Bartho- 
linus,'^  and  their  course  and  connection  with  each  other  and  the 
mesenteric  lymphatics  made  out. 

iQpuse.  An:it.,  Aiitig  13,  p.  280.     Lud.t?.  Batav.,  1707. 

2  De  Laetibus  Sine  Lacteis  Venis,  Cap.  ix.     ^Mediolani,  MDCXXVII. 

''.Joannis  Pecquet!,  Diepsei  Experimenta  Nova  Anatomica,  Cap.  v.  and  vi., 
Amst.,  IGfil. 

*  Olai  Kudbeck,  Nova  Exercitatio  Anatomica  exhibens  ductos  hepaticos  aquosos 
vasa  glandularum  serosa.  Clericus  &  Mangetus,  Bibliotheca  Anatomica,  Tomus  ii., 
p.  029.     Genevfe,  1099. 

5  Thorns  Bartholinic,  Anatomia  de  Lacteis  Thoracis  et  vases  Lymphaticis. 
Hagic  Com,  1000. 


LACTEALS,    THORACIC  DUCTS,  ETC. 


161 


Fk;.   A1 


The  lymphatic  system  iu  general  consists  of  vessels  which,  be- 
ginning as  capillary  spaces  in  the  skin,  mncous  membrane,  glands, 
etc.,  within  the  tissues,  converge  toward  each  other  and  gradually 
uniting  with  larger  and  larger  trunks  finally  terminate  in  the  sub- 
clavian veins  as  the  right  and  left  thoracic  dncts.  The  lymjih 
from  the  right  side  of  the  head  and  that  from  the  upper  extremity 
passes  into  the  blood  of  the  right  subclavian  vein,  while  that  from 
the  rest  of  the  body,  including 
the  lymph  and  chyle  from  the 
small  intestine,  is  conveyed  into 
the  blood  of  the  left  subclavian 
vein  by  the  left  thoracic  duct 
(Fig.  47). 

The  lymphatics,  in  their  gen- 
eral structure,  resemljle  very 
closely  the  veins,  consisting, 
like  these  vessels,  of  three 
coats,  an  external  one,  com- 
posed essentially  of  white  fi- 
brous tissue  ;  a  middle  muscu- 
lar elastic  coat,  the  elastic 
muscular  fibers  being  arranged 
circularly,  and  an  internal  epi- 
thelial layer  constituting  the 
internal  coat.  The  lymphatics 
also  contain  valves,  consisting 
usually  of  two  semilimar  folds. 

Here  and  there,  along  the 
course  of  the  lymphatics,  solid 
bodies  may  be  seen  varying  in 
size  between  a  hemp  seed  and 
an  almond,  which  apparently 
surround  the  vessels,  and 
through  which  the  contents 
must  pass  in  their  way  to  the 
thoracic  ducts.  These  bodies 
are  the  lymphatic  glands,  and 
are  more  evident  in  certain  parts  of  the  body  than  iu  others,  being 
well  developed,  for  example,  in  the  cervical,  axillary,  and  inguinal 
regions.  The  minute  structure  and  uses  of  these  glands  will  be 
described  when  the  elaboration  of  the  blood  is  considered.  The 
lymphatics  not  only  connect  the  interstices  of  the  tissues  ^^itll  the 
blood,  beginning  m  the  one  and  ending  in  the  other,  but  they  also 
communicate  with  the  serous  cavities.  Indeed,  the  serous  cavities, 
like  the  peritoneum,  pleura,  etc.,  can  be  regarded  morphologically 
as  dilated  lymphatic  sacs  lying  ^  between  the  viscera,  these  inter- 


■a. 

Laeteals,  thoracic  duct,   etc.    a.    Intestine,    h. 
Vena  cava  inferior,     c.c.  Kight  and  left  subclavian 
veins,    d.  Point  of  opening  of  thoracic  duct  into 
(Daltox.  ) 


left  subclavian. 


'  The  Lymphatic  Svstem,  p.  222. 
York,  1872. 

11 


Eecklinghausen,  Strieker's  Histology.     New 


162  ABSORPTION. 

organic  spaces  representiug  on  a  large  scale  the  minute  inter-lacunar 
spaces,  which  "sve  have  just  seen  often  constitute  the  beginning  of  a 
lymphatic. 

Lymphatics  are  found  very  generally  throughout  the  system. 
According  to  Sappey/  however,  they  have  never  been  demonstrated 
in  teeth,  hair,  nails,  etc.  Possibly,  though,  future  researches  may 
show  that  lymphatics  exist  even  in  such  situations. 

It  is  only  within  recent  years  that  the  fluid  contained  in  the 
lymphatics,  or  lymph,  has  been  satisfactorily  studied.  The  lymph 
obtained  by  experiments  made  upon  animals  in  the  beginning  of 
this  century  was  in  too  small  quantities  to  admit  of  thorough 
analysis,  while  the  human  lymph  examined  was  probably  abnormal. 
It  was  only  as  recently  as  1853  that  Colin  ^  succeeded  in  making  a 
fistula  in  the  thoracic  duct  of  the  horse,  and  showed  by  this  method 
of  investigation  that  large  quantities  of  normal  lymph  could  be  ob- 
tained in  a  short  space  of  time. 

Lymph  is  a  transparent,  yellowish,  alkaline  liquid  ;  the  opaline 
appearance  that  it  sometimes  exhibits  is  due  to  small  particles  of 
fat,  while  the  rosy  tint  that  is  often  observed  in  it  is  caused  by  the 
red  corpuscles  that  have  passed  into  it  from  the  blood.  When  exam- 
ined under  the  microscope,  lymph  is  seen  to  consist  of  a  liquor,  and 
small  bodies  floating  in  it,  the  lymph  corpuscles  or  globules.  These 
measure  on  an  average  about  -^i^  of  a  mm.  (2-5Vo'  ^^  ^"  inch) ; 
they  are  homogeneous  or  granular  in  appearance,  and  are  indistin- 
guishable, as  we  shall  see,  from  the  white  corpuscles  of  the  blood. 
When  we  come  to  study  the  red  blood  corpuscles  in  man  and  ani- 
mals, one  of  the  most  striking  facts  to  be  noted  wdll  be  the  great 
difference  in  their  size.  As  regards  the  lymph  or  white  corpuscles, 
however,  it  has  been  shown  that  their  average  diameter  bears  no 
relation  to  that  of  the  red  corpuscle,  being  as  large,  for  example,  in 
the  musk  deer,  where  the  red  corpuscle  is  small,  as  in  man  where  it 
is  large.  Further,  the  white  corpuscle  in  birds  is  usually  smaller 
than  that  of  mammals,  whereas  the  red  corpuscle  of  birds  is  larger 
than  that  of  the  mammal,  while  in  the  frog  both  the  white  corpuscle 
and  the  red  are  larger  than  those  of  the  mammal. 

Like  the  blood,  the  lymph  coagulates  when  drawn  from  the  liv- 
ing body.  This  is  due  in  both  cases  to  the  fibrin  which  these  fluids 
contain.  The  lymph  clot,  however,  is  less  solid  than  that  of  the 
blood,  and  little  or  no  serum  exudes  from  it.  The  clot  consists  not 
only  of  fibrin,  but  of  the  lymph  corpuscles  that  the  lymph  carries. 

Chemically  the  liquors  of  the  lymph  differs,  as  we  shall  see,  from 
the  liquor  of  the  V)lood  (piantitativisly,  rather  than  qualitatively, 
both  these  fluids  consisting  essentially  of  water,  proteid,  fibrin,  and 
salts.  Usually  the  lymph  contains  as  much  fibrin  as  the  blood, 
but  less  proteid.  There  is  more  water  in  the  lymph  than  in  the 
blood,  but  the  amount  of  salts  in  both  liquids  is  about  the  same. 

1  Anatomic,  tome  deuxieme,  p.  791. 
2Phys.  Comp.,  1856,  Tome  ii.,  p.  100. 


COMPOSITION  OF  THE  LYMPH.  163 

From  the  fact  of  these  two  liquids,  the  liquors  of  the  lymph  and 
blood,  being  alike  in  their  chemical  composition,  it  has  been  inferred 
that  the  lymph  is  nothing  but  that  part  of  the  blood  which  has  es- 
caped, leaked  out,  so  to  speak,  from  the  vascular  system  into  the 
surrounding  tissues,  and  which  is  afterward  soaked  up  by  the  Ijin- 
phatics. 

Composition  of  the  Lymph.' 

Water 95.0 

Solids 5.0 

Fibrin 0.1 

Proteids 4,1 

Fat,  etc. Traces 

Extractives 0.3 

Salts 0.5 

While  the  question  has  not  yet  been  definitely  settled,  it  may  be 
mentioned  as  appropriately  here  as  elsewhere,  that  according  to  the 
researches  of  Heidenhain^  the  formation  of  lymph  cannot  be  at- 
tributed to  the  simple  filtration  and  diffusion  of  the  blood  plasma, 
some  kind  of  secretory  action  being  exerted  by  the  endothelial  cells 
of  the  walls  of  the  capillaries  as  well.  The  gases  of  the  lymph 
consist  principally  of  carbon  dioxide  with  some  nitrogen  and  traces 
of  oxygen. 

It  has  already  been  mentioned  that  the  red  corpuscles  often 
found  in  the  lymph  are  really  red  blood  corpuscles  that  have 
escaped  from  the  capillaries.  While  it  is  possible  that  some  of  the 
lymph  corpuscles  may  also  be  only  white  blood  corpuscles  that  have 
passed  from  the  blood  with  the  red  ones  into  the  lymph,  the  lymph 
corpuscles  in  general  appear  to  originate  in  an  entirely  different 
manner,  there  being  good  reasons  for  supposing  that  they  are  pro- 
duced in  the  lymphatic  glands,  spleen,  etc.  The  consideration  of 
the  origin  of  the  lymph,  or  white  corpuscles,  and  their  relation  to 
the  red  ones  and  the  glands  just  mentioned,  wc  will,  however,  defer 
until  the  blood  is  studied,  and  pass  on  to  the  consideration  of  the 
quantity  of  the  lymph,  and  the  causes  of  its  flow  through  the 
system. 

Naturally,  from  the  conditions  of  the  case,  the  amount  of  lymph 
produced  can  be  estimated  only  approximately.  It  may  be  men- 
tioned, however,  that  nearly  six  kilos  (13  pounds)  of  lymph  were 
collected  in  twenty-four  hours  from  a  lymphatic  fistula  in  the  arm 
of  a  woman  by  Gubler  and  Quevenne,^  Various  causes  have  been 
assigned  for  the  flow  of  lymph.  Of  these,  some  are  more  impor- 
tant than  others.  One  of  the  principal  causes  of  the  flow  of  the 
lymph  is  undoubtedly  the  vis  a  tergo  resulting  from  the  constant 
passing  of  the  serum  of  the  blood  into  the  lymphatic  system,  and 
as  the  lymph,  on  account  of  the  valves  (Fig,  48)  in  the  vessels, 
must  flow  always  from  the  periphery  or  the  radicles  of  the  system , 

iLandois,  op.  cit,  p.  393.  zpfuggr'g  Archiv,  Band  xlix.,  1891,  s.  209. 

"Landois,  op.  cit.,  p.  394. 


164 


ABSORPTION. 


Fi<;.  48. 


toward  the  great  trunks  and  blood  vessels,  each  successive  addition 
of  serum  to  the  lymphatic  system  will  act  as  a  force  propelling  for- 
ward the  lymph  already  there. 

From  the  fact  that  the  lymphatics  contain  unstriped  muscular 
fiber,  it  is  probable  that  these  vessels  at  times  contract  upon  their 
contents.  This  action,  however,  would  appear  to  be  slight,  inas- 
much as  the  rhythmical  contractions  of  the  lymphatics  in  mam- 
mals are  rarely  observed.  It  should  be  mentioned  in  this  connec- 
tion, however,  that  frogs,  toads,  lizards,  etc.,  the 
lymphatics  of  which  are  unprovided  with  valves, 
possess  the  so-called  lymphatic  hearts.  The  latter 
are  dilated  portions  of  the  lymphatics,  exhibiting 
contractility,  and  which  pulsate  regularly. 

The  influence  of  muscular  contractions  upon  the 
flow  of  the  lymph  must  not  be  forgotten,  for  pres- 
sure upon  the  lymphatics  from  this  source  will  have 
the  same  eflect  as  we  shall  see  it  has  in  accelerating 
the  flow  of  blood  in  the  veins. 

From  the  disposition  of  the  terminal  portion  of 
the  lymphatic  system  in  the  thoracic  cavity,  it  might 
naturally  be  inferred  that  during  inspiration,  inas- 
much as  all  the  parts  are  dilated,  that  the  flow  of 
lymph  into  the  thoracic  ducts  would  be  increased, 
and  that,  during  expiration,  as  all  of  the  parts  are 
contracted,  the  lymph  will  then  flow  onward  into 
the  left  subclavian  vein,  regurgitation  being  impos- 
sible through  the  presence  of  valves.  Experiment 
has  shown  that  such  is  in  fact  the  case.  With  each 
inspiration  the  thoracic  ducts  become  dilated  through 
the  increased  flow  of  lymph ;  at  that  moment  the 
lymph  flows  freely  from  the  right  thoracic  duct  into 
the  right  subclavian  vein.  With  each  expiration 
the  lymph  is  expelled  Avith  increased  force  from  the 
left  thoracic  duct  into  the  left  subclavian  vein,  and  when  a  fistula 
is  made  in  that  situation  the  lymph  issues  as  an  intermittent  jet. 
Of  the  difierent  causes  just  given  for  the  flow  of  the  lymph,  it 
would  appear  that  the  vis  a  terr/o  and  the  respiratory  movements  are 
the  most  important,  the  contractility  of  the  vessels  and  the  pressure 
of  surrounding  parts  being  of  secondary  importance. 

Up  to  this  moment,  in  speaking  of  the  lymphatic  system,  we 
have  only  alluded  incidentally  to  the  lymphatics  of  the  small  intes- 
tine, or  the  lacteals.  As  these  vessels  have  a  special  interest  for  us 
in  connection  with  the  absorption  of  the  digested  food,  let  us  study 
them  no\v  a  little  more  in  detail. 

The  lacteals,  or  lymphatics  of  the  small  intestine,  begin  in  the 
villi,  wliich  structures  we  only  alluded  to  in  speaking  of  the  ali- 
mentary canal,  reserving  for  tlie  present  moment  their  more  detailed 
consideration.     The  villi  (Fig.  49)  are  small  processes  of  the  mucous 


Valves  of  the  lym- 
phatics.   (Sappey.) 


STRUCTURE  OF  THE  VILLI. 


165 


membrane  of  the  small  intestine,  measuring  on  an  average  about  the 
Y^^  of  a  mm.  ( Jg  of  an  inch)  in  length,  and  al^out  the  ^-'-j  of  a  mm. 
{■^^  of  an  inch)  in  breadth.  They  are  usually  conical,  and 
flattened  in  form,  though  sometimes  cylindrical,  or  terminating  in 
an  enlarged  or  clubbed-like  extremity.  The  villi  are  largest  and 
most  numerous  in  the  duodenum  and  the  so-called  jejunmn.  They 
are  closely  set  upon  the  inner  surface  of  the  intestine  over  the  val- 
vule conuiventes,  as  well  as  between  the  same,  and  give  rise  to  the 
characteristic  velvety  appearance  of  the  mucous  membrane  in  this 
situation. 

It  has  been  estimated  that  in  the  upper  part  of  the  small  intestine 
there  arc  fifty  to  ninety  villi  to  the  square  line,  their  total  number 
amounting  to  about  four  millions.  The  Villi  can  be  well  seen  by 
examining  a  piece  of  intestine  under  water  mth  a  simple  lens,  the 
mucus  having  been  first  removed  by  gentle  washing.  When  studied 
with  the  microscope  the  villus  is  seen  to  consist  of  a  prolongation  of 
the  epithelial  layer  of  the  mucous  membrane  of  the  intestine,  enclos- 
ing a  network  of  blood  vessels,  the  beginning  of  the  lymphatics,  or 
the  lacteals,  and  some  plain  muscular  fibers.  These  structures  are 
held  together  and  supported  l)y  lymphoid  or  retiform  tissue,  which, 


Fig.  49. 


Fig.  50. 


Villus  of  man  with  lacteal  and  blood 
vessels  injected.     (Teichmanx.) 


Villus  of  man  showing  lacteal  surrounded 
by  epithelial  cells.     (Fkey.) 


at  the  surface,  is  condensed  into  a  basement  meml^rane,  upon  which 
the  epithelial  cells  rest.     (Fig.  50.) 

Up  to  this  time  it  is  doubtful  if  nerv^es  have  been  demonstrated 


166 


ABSORPTION. 


in  the  villi.  It  is  very  pi'obablc,  however,  that  they  are  present. 
Each  villus  usually  receives  one  arterial  twig,  which,  after  penetrat- 
ing it,  breaks  up  into  capillaries  situated  just  beneath  the  basement 
membrane.  The  blood  is  returned  usually  by  one  vein.  The  lym- 
phatic, or  the  lacteal,  begins  in  the  center  of  the  villus,  usually  as  a 
single  vessel  (Fig.  49),  with  a  closed  and  somewhat  expanded  ex- 
tremity. Its  caliber  is  considerably  larger  than  that  of  the  capillary 
blood  vessels  surrounding  it. 

The  lacteal  wdthin  the  villus,  like  the  lymphatics  elsewdiere,  is 
surrounded  by  a  delicate  layer  of  flattened  cpitheloid  cells  (Fig.  50). 
These  are  connected  with  the  cells  of  the  basement  membrane 
through  those  of  the  lymphoid  or  connective  tissue  lying  between 
(Fig.  51). 

The  columnar  epithelial  cells  which  cover  the  villi,  and  also  the 
surface  of  the  mucous  membrane,  and  which  are  prolonged  into  the 
tubular  glands,  present  a  granular  appearance 
with  an  oval  nucleus.  They  terminate  to- 
ward the  basement  membrane  in  a  tapering 
manner,  and  measure  about  the  4^o^th  of  a 
mm.  (-fo^Q  o"  of  an  inch)  in  length.  Their  free 
end  (Fig.  51),  or  the  surface  looking  toward 
the  interior  of  the  intestine,  consists  of  a 
layer  of  a  highly  refractive  substance,  with 
vertical  strise  running  through  it.  These 
strite  have  been  regarded  as  being  either 
minute  canals,  or  as  solid  rods.  Some  of 
these  columnar  cells  usually  contain  inucus, 
and  swell  up  upon  the  addition  of  water  into 
the  so-called  goblet  cells  which  are  regarded 
by  some  anatomists  as  the  true  beginning  of 
the  absorbent  system. 

The  lymphatic  or  central  lacteal  connected 
with  the  columnar  cells  by  the  lymph  chan- 
nels in  the  stroma  after  emerging  from  the  villus  passes  into  the 
lymphatics  of  the  intestine.  These  are  usually  described  as  consist- 
ing of  two  sets,  the  deep  and  superficial.  The  latter  pass  into 
the  mesentery  to  the  lymphatic  glands.  The  lymphatics  coming 
from  the  latter,  as  we  have  seen,  converge  toward  the  reccptacu- 
lum  chyli. 

During  the  intervals  of  digestion  the  lymphatics  of  the  small  in- 
testine, or  tiie  lacteals,  contain  lymph,  undistinguishable  from  that 
of  the  lymphatics  of  the  rest  of  the  body.  Daring  digestion  and 
absorption,  however,  and  more  especially  when  fatty  articles  have 
constituted  part  of  the  food,  the  epithelial  cells  of  the  villi,  and  the 
lymphatics  of  the  small  intestine,  are  then  filled  Avith  the  chyle. 
The  chyle  is  a  coagulable,  alkaline,  opaque,  whitish,  milky-like 
fluid,  hence  the  name  of  the  lacteals  given  to  the  lymphatics  of  the 
small  intestine,  in  which  it  is  found. 


Diagrammatic  representation 
of  the  origin  of  the  lacteals  in 
a  villus.  e.  Central  lacteal. 
d.  Lymph  channels,  c.  Colum- 
nar epithelial  cells,  the  attach- 
ed extremities  of  which  are 
directly  continuous  with  the 
lymph  channels. 


COMPOSITION  OF  THE  CHYLE.  167 

Composition  of  the  Chyle.' 

Water 90.5 

Solids 9.5 

Fibrin 0.1 

Proteids 7.0 

Fat,  etc 1.0 

Extractives    ]  ■,  a 

Salts  J 

The  chyle,  however,  is  only  the  lymph  with  the  ])iT)(lucts  of  di- 
gestion added  to  it,  and  as  the  lacteals  absorl)  princi])ally  the  fat, 
the  essential  difference  between  the  chyle  and  the  lymph  is  that  the 
former  contains  a  great  quantity  of  fat,  the  latter  usually  only  a 
trace.  In  reference  to  any  analysis  of  the  chyle,  it  must  not  l)e  for- 
gotten that  its  composition  \\\\\  differ  according  to  whether  the  por- 
tion examined  has  been  taken  from  the  lacteals  or  the  thoracic  duct. 
Indeed,  chyle  drawn  from  the  thoracic  duct  is  not  pure  chyle,  but 
chyle  mixed  with  the  lymph  which  has  been  brought  from  the  ex- 
tremities to  the  receptaculum  chyli,  and  thence  passed  into  the 
thoracic  duct. 

The  chyle  of  the  thoracic  duct  will  contain,  therefore,  less  fat  and 
other  solid  constituents,  than  that  of  the  lacteals.  Further,  the 
amount  of  flit  in  the  chyle  will  be  variable,  depending  upon  the 
diet  of  the  man  or  animal  examined.  Thus,  the  chyle  of  a  car- 
nivorous animal  will  contain  more  fat  than  that  of  a  herbivorous 
one,  the  food  of  the  former  being  richer  in  fat  than  that  of  the  latter. 
At  one  time  it  was  supposed  that  the  lacteals  absorbed  exclusively 
the  fatty  substances,  liut  it  is  now  known  that  they  also  take  up, 
at  least  in  small  quantities,  albuminoid  and  saccharine  substances, 
salts  and  water. 

Of  the  amount  of  the  chyle  poured  into  the  thoracic  duct,  it  is 
impossible  to  give  even  an  approximate  estimate. 

When  examined  microscopically,  the  milky  appearance  of  the 
chyle  is  seen  to  be  due  to  an  immense  number  of  very  minute  fatty 
granules,  which  constitute  the  so-called  molecular  base  of  the  chyle, 
and  which  measure  on  an  average  the  ^^^  of  a  mm.  (^2^70"  ^^  ^^ 
inch)  in  diameter.  These  granules  appear  to  be  coated  with 
albumin,  which  probably  prevents  their  running  together  and 
coalescing.  The  so-called  chyle  corpuscles  found  in  greater  or 
less  number  in  the  chyle,  do  not  differ  from  those  of  the  lymph  or 
blood,  and  will  be  considered  again  when  the  latter  fluid  is  studied. 

What  lias  Ijcen  already  stated  in  reference  to  the  supposed  causes 
of  the  flow  of  the  lymph  will  apply  equally  well  to  that  of  the 
chyle  ;  but  there  is  one  condition,  in  addition  to  those  already  mem- 
tioned,  which  appears  to  influence  favorably  the  flow  of  the  chyle, 
and  so  deserves  a  passing  notice.  It  will  be  remembered  that,  in 
speaking  of  the  structure  of  the  villi,  allusion  was  made  to  the  plain 
muscular  fiber  that  they  contain.'  These  muscular  fibers  are  dis- 
persed longitudinally  around  the  lacteal,  and  their  contraction  will 
'  Landols,  op.  cit.,  p.  392. 


168  ABSORPTION. 

obviously  retract  the  villus.  The  eiFect  of  the  action  of  these  mus- 
cular fibers  will  then  be  to  force  the  contents  of  the  lacteal  out  of  the 
villus  into  the  superficial  lymphatics.  These  muscular  fibers  have 
probably,  then,  some  importance  in  aiding  the  flow  of  the  chyle 
toward  the  thoracic  duet. 

It  will  be  remembered  that,  up  to  the  time  that  the  lymphatics 
were  discovered,  absorption  was  considered  to  be  effected  by  the 
veins  only.  After  the  discovery  of  the  lymphatics,  however,  phys- 
iologists fell  into  the  opposite  error  of  attributing  absorption  solely 
to  the  lymphatics,  denying  that  the  veins  took  any  share  in  this  pro- 
cess. Indeed,  it  was  not  until  the  present  century  that  it  was  ex- 
perimentally demonstrated  that  the  veins  as  well  as  the  lymphatics 
absorb.  Apart,  however,  from  any  experimental  evidence,  the  facts 
of  comparative  anatomy  alone  should  have  shoAvn  that  of  the  two 
sets  of  vessels,  so  far  as  the  absorption  of  the  digested  food  is  con- 
cerned, the  veins  play  a  more  important  part  than  the  lymphatics. 

Thus  it  is  well  known  that  in  the  amphioxus,  the  lowest  of  the 
vertebrata,  and  in  all  the  invertebrata,  the  lymphatic  system  is  ab- 
sent. In  these  animals,  therefore,  absorption  is  carried  on  solely  by 
veins.  Further,  while  the  lymphatic  system  is  present  in  fishes, 
batrachia,  reptiles,  and  birds,  it  is  only  in  the  mammalia  that  it 
acquires  the  functional  importance  that  we  have  ascribed  to  it. 

Indeed,  according  to  Bernard,^  the  name  lacteal  cannot  be  prop- 
erly applied  to  the  lymphatics  of  the  small  intestine  in  the  oviparous 
vertebrates,  since  these  lymphatics  contain  always,  even  during  di- 
gestion, with  few  exceptions,  a  clear,  transparent  lymph  instead  of 
chyle,  an  opaque,  whitish  fluid,  the  fat  in  these  animals  being  taken 
up,  not  by  the  so-called  lacteals,  Ijut  by  the  portal  vein,  the  greater 
part  of  it  being  thence  carried  to  the  renal  veins  (Jacobsen's  system), 
and  so  to  the  vena  cava. 

Inasmuch  as  absorption  is  carried  on  by  the  veins  in  the  lower 
animals,  we  would  naturally  infer  that  these  vessels  must  be  of  great 
importance  in  this  respect  in  man  and  the  mammalia.  Magendie  ^ 
appears  to  have  ])een  the  first  to  show  conclusively  by  experiment 
that  absorption  takes  place  by  the  blood  vessels. 

Of  his  many  remarkable  and  accurate  experiments,  the  following 
may  be  mentioned  :  In  one  experiment  the  abdomen  of  a  dog  that 
had  been  well  fed  some  hours  previously  was  opened,  and  a  loop  of 
the  intestine  drawn  out.  Ligatures  were  placed  around  this  loop  at 
a  distance  of  about  37.5  centimeters  (15  inches)  apart.  The  lym- 
phatics arising  from  this  portion  of  the  intestine  being  all  ligated 
in  two  places,  were  divided  between  the  ligatures.  Of  the  five 
mesenteric  arteries  and  veins  passing  into  the  general  vascular  sys- 
tem, four  were  divided  and  ligated  so  that  the  loop  of  the  intestine 
remained  in  connection  with  the  rest  of  the  system  by  only  a  single 
vein  and  artery,  even  the  cellular  coat  of  which  was  dissected  off", 

'  Physiologie  Experimentale,  Tome  ii.,  p.  312. 
2  Journal  de  Physiologie,  p.  18.     Paris,  1821. 


VENOUS  ABSORPTION.  169 

so  as  to  remove  all  doubt  of  there  being  a  trace  of  a  lymphatic 
left.  Some  upas  was  then  introduced  into  the  loop  of  the  intestine 
prepared  in  tlie  above  manner,  which  was  then  replaced  in  the  ab- 
domen, and  in  a  few  minutes  the  characteristic  symptoms  of  poison- 
ing appeared,  showing  that  the  upas  had  been  absorbed  Ijy  the  vein. 

In  another  experiment,  where  the  poison  was  introduced  into  the 
foot,  the  only  connection  between  the  limb  and  the  rest  of  the  body 
was  through  two  quills,  introduced  into  the  divided  femoral  blood 
vessels,  the  rest  of  the  parts  having  been  dissected  oif.  In  this 
case,  also,  the  only  possil^le  means  by  which  the  poison  could  pass 
into  the  general  system  and  make  its  effects  evident  was  through 
the  circulating  blood. 

The  experiments  of  ]Magendie  were  soon  afterward  confirmed  by 
Tiedmann  and  Gmelin,'  Segalas,"  and  by  the  committee  appointed 
by  the  Academy  of  Medicine  of  Philadelphia  to  investigate  the 
subject."^ 

A  convenient  method  of  demonstrating  venous  absorption  is  to 
open  the  abdomen  of  a  frog,  withdraw  a  loop  of  the  intestine,  and 
ligate  it  in  two  places,  cut  away  all  the  mesentery,  leaving  only  a 
single  artery  and  vein,  and  introduce  a  solution  of  ferrocyanide  of 
potassium  into  the  intestine  by  an  opening  made  in  the  latter,  re- 
place the  loop  within  the  abdomen,  and,  after  a  few  minutes,  open 
one  of  the  veins  of  the  foot.  On  testing  the  blood  for  the  ferrocy- 
anide of  potassimn  by  adding  tincture  of  the  chloride  of  iron,  the 
presence  of  the  salt  introduced  into  the  intestine  will  become  at  once 
evident,  through  the  formation  of  Prussian  blue,  the  latter  being 
best  demonstrated  by  adding  the  perchloride  of  iron  to  the  serum, 
the  blood  having  been  allowed  to  stand,  or  to  a  clear  extract  of  the 
blood,  made  by  boiling  the  latter  with  a  little  sodium  sulphate  and 
filtering. 

It  is  obvious  that  the  only  means  by  which  the  salt  of  potassium 
could  pass  under  such  circumstances  from  the  intestine  into  the 
general  circulation,  and  thence  into  the  blood  of  the  extremities, 
was  by  means  of  the  vein  left  in  the  mesentery. 

As  we  have  seen  that  by  far  the  greatest  part  of  the  food  is  di- 
gested in  the  small  intestine,  it  might  be  naturally  inferred  that  the 
water,  salts,  peptones,  sugars,  and  fat  are  absorbed  by  the  veins  and 
lymphatics  of  the  small  intestine  rather  than  by  those  of  the  stom- 
ach. That  such  is  the  case  appears  to  have  been  shown,  at  least  in 
animals.  Thus,  for  example,  in  a  dog,  in  whom  a  fistula  of  the 
duodenum  had  been  established,  of  the  water  drunk  fully  99  per 
cent,  passed  within  twenty  minutes  out  of  the  fistula.* 

'  Kecherclies  sur  la  route  qui  prennent  divei-ses  substances  pour  passer  d'  Estomac 
et  du  Canal  intestinal  dans  le  Sang.     Paris,  1821. 

^Journal  de  Physiologie,  Tome  ii.,  p.  117.     Paris,  1822. 

^Philadelphia  Journal  of  the  Med.  and  Phys.  Sciences,  1821,  Vol.  iii.,  p.  273  ; 
1822,  Vol.  v.,  p.  327. 

*3.  Von  Mering,  Therapeutische  Monatshefte,  Berlin,  1893,  s.  201.  J.  S.  Ed- 
kins,  Journal  of  Phvsiologv,  1892,  Vol.  xiii.,  p.  445.  Brandl,  Zeits.  fiir  Biologie, 
1892,  Band  29,  s.  277. 


170  ABSORPTION. 

Salts  do  not  appear  to  be  absorbed  by  the  stomach  unless  intro- 
duced into  the  latter  in  a  more  concentrated  state  (o  per  cent.)  than 
when  taken  as  food.  Sugars  and  peptones  appear,  however,  to  be 
absorbed  by  the  stomach  to  some  extent,  especially  if  the  solutions 
are  concentrated  (5  per  cent.).  The  absorption  of  salts,  sugars,  and 
peptones  by  the  stomach  is  much  increased  if  given  with  alcohol 
and  condiments,  such  as  pepper  and  mustard.  Alcohol  itself  is 
readily  absorbed  by  the  stomach. 

As  fat  to  be  absorbed  must  first  be  emulsified  and  as  that  change 
is  only  effected  in  the  small  intestine,  it  is  evident  that  fat  must 
pass  through  the  stomach  without  being  absorbed.  Apart  from  the 
fact  that  food  is  rendered  fit  for  absorption  largely  by  digestion  in 
the  small  intestine,  it  should  be  mentioned  that  ample  time  is  af- 
forded for  its  absorption  by  this  part  of  the  alimentary  canal,  since 
from  nine  to  twenty-three  hours  elapse  before  the  food  eaten  passes 
out  of  the  small  into  the  large  intestine,  its  passage  being  retarded 
by  the  presence  of  the  villi  and  valvule  conniventes.  Experiments 
made  upon  animals,^  and  observations  upon  human  beings,^  con- 
firm the  view  based  upon  the  above  considerations,  that  water,  salts, 
peptones,  sugar,  and  fat  are  principally  absorbed  by  the  small  in- 
testine. In  considering  the  water  and  salts  absorbed  by  the  veins 
of  the  small  intestine,  it  must  be  borne  in  mind,  however,  that  as 
part  of  the  water,  etc.,  absorbed  is  replaced  by  that  excreted  by 
the  intestine,  the  contents  of  the  latter  are,  therefore,  more  or  less 
liquid  like  the  chyme.  As  a  proof  of  the  amount  of  proteid  ab- 
sorbed, it  may  be  mentioned  that  in  a  case  of  fistula  of  the  end  of 
the  ileum  in  a  human  being,  about  eighty-five  per  cent,  of  tlie  pro- 
teid eaten  was  absorbed  before  the  latter  reached  the  large  intestine. 
It  should  be  mentioned,  in  this  connection,  that  while  peptones  and 
albumoses  are  without  doubt  absorbed  by  the  veins  of  the  stomach 
and  small  intestine,  they  are  not  found  as  such  in  the  blood.  The 
only  conclusion  to  be  drawn  from  this  fact  is  that  peptones,  etc.,  are 
converted  into  serum  or  blood  albumin  as  they  pass  through  the 
epithelial  cells  into  the  blood.  If  such  be  the  case  then  peptones, 
etc.,  must,  in  becoming  blood  albumin,  undergo  in  the  epithelium 
dehydration  and  polymerization,  the  reverse  of  the  processes  by 
which  they  were  produced  from  proteid,  viz.,  liydration  and  split- 
ting. The  various  carbohydrates  appear  to  be  absorbed  by  the 
veins  of  the  small  intestine  in  the  form  of  glucose,  or  glucose  and 
levulose.  Thus,  starch  is  converte<l  into  maltose  and  then  into  glu- 
cose, cane  sugar  into  glucose  and  levulose,  lactose  into  glucose  and 
galactose ;  lactose  appears,  however,  under  certain  circumstances  to 
be  absorbed  as  such  unchanged.  While  the  water,  salts,  sugar,  and 
peptones  are  usually  absorbed  by  the  veins,  tlie  ennilsified  fat  is 
taken  up  by  the  lymphatics  of  the  small  intestine  or  the  lacteals. 

1  Macfjidyen,  Nciicki,  ii.  Sicber,  Archiv  fiir  expcr.  Patli.  u.  Pliar.,  Band  28, 
1891,  s.  311. 

'^  KiUiinanii,  Pfliifi^er's  Arcliiv,  1877,  Band  11,  s.  411. 


OSMOSIS. 


]71 


Fig.  52. 


Recalling  what  has  just  been  said  of  the  structure  of  a  villus,  it 
mil  be  seen  that  the  lymph  channels  in  the  stroma  afford  a  pathway 
by  which  the  fat  taken  up  l)y  the  cells  will  be  carried  into  the  cen- 
tral lacteal.  There  appears  to  be  no  douljt  that  the  Avater,  salts,  pep- 
tones, sugar,  that  escape  absorption  in  the  small  iutestine  are  taken 
up  by  the  veins  of  the  large  intestine,  ample  time  being  afforded 
since  the  time  required  for  the  passage  of  the  food  residue  through 
this  portion  of  the  alimentary  canal  amounts  to  about  twelve  hours. 
We  have  seen  that  the  principal  function  of  the  lymphatics  of 
the  small  intestine  is  to  absorb  fat,  nevertheless  they  can  and  do  take 
up  peptones,  glucose,  and  water ;  on  the  other  hand,  the  mesenteric 
veins,  in  addition  to  aI)Sorbing  these  latter  substances,  may  take  up 
also,  at  times,  considerable  quantities  of  fat.  Briefly,  then,  the  func- 
tions of  the  lymphatic  and  venous  absorbents  are  essentially  the 
same ;  as  a  rule,  however,  the  fats  pass  into  the  blood  by  the  one 
route,  the  remaining  alimentary  substances  by  the  other. 

Osmosis. 

^Ye  have  seen  that  during  absorption  the  digested  food  passes 
from  the  interior  of  the  alimentary  canal  into  the  veins  aud  lym- 
phatics. The  investigation  of  the  aiuses  of 
the  phenomena  of  absorption  resolves  itself, 
therefore,  into  the  determination  of  the  con- 
ditions on  which  depend  the  passage  of  pep- 
tone, glucose,  etc.,  aud  emulsified  fat  through 
the  epitheliiun  of  the  alimentary  canal  and  the 
wall  of  the  capillary  or  lymphatic  into  the 
blood  or  lymph. 

In  physical  science  the  diffusion  of  liquids 
into  each  other  when  separated  by  a  mem- 
brane is  known  as  osmosis.  Let  us  consider, 
briefly,  what  is  understood  by  the  term  os- 
mosis, and  see  to  what  extent  the  facts  of  ab- 
sorption that  we  have  described  can  be  ex- 
plained by  this  principle. 

A  convenient  method  of  illustrating  the 
phenomena  of  osmosis  is  to  close  one  end  of  a 
bulbous  glass  tube  (Fig.  52)  B  with  a  mem- 
brane-like parchment  C,  and  having  placed 
within  the  tube  a  solution  of  some  salt,  potas- 
sium bichromate,  for  example,  to  immerse  the 
tube  or  the  osmometer,  as  it  is  called,  in  a  vase 
of  distilled  water  A.  In  a  few  moments  tlir 
potassium  salt  will  pass  through  the  mem- 
brane into  the  water  of  the  vase  (exosmosis) 
imparting  to  the  latter  a  yellowish  hue,  and 
the  water  of  the  vase,  through  the  membrane,  into  the  salt  solu- 
tion in  the  tube  (endosmosis),  the  level  of  the  solution  in  the  tube 


tJraham's  osmometer. 


172  ABSORPTION. 

rising,  that  in  the  vase  falling.  After  a  certain  length  of  time 
has  elapsed,  varying  with  the  substances  used,  strength  of  solu- 
tion, and  other  conditions,  the  passage  of  the  salt  into  the  water 
in  the  one  direction  and  of  the  water  into  the  salt  solution  in  the 
other  ceases.  It  will  then  be  found  that  the  proportion  of  the 
salt  in  the  water  of  the  vase  and  in  the  water  of  the  tube  is  the 
same,  but  that  the  volume  of  Avater  in  the  tube  has  been  greatly 
increased.  The  ratio  of  the  weight  of  the  water  of  the  vase 
passing  into  the  solution  of  the  tube  to  that  of  the  salt  passing 
into  the  water  of  the  vase  is  called  the  "endosmotic  equivalent," 

Water 
and  is  usuallv  expressed  thus  -^  ,      •     It  should  be  mentioned, 
^  Salt  ' 

however,  that  this  ratio  is  not  a  constant  one,  varying  with  the 
strength  of  the  solutions  used.  A  more  delicate  way  of  illustrat- 
ing osmosis  is  to  replace  the  jar  of  the  last  experiment  with  an 
egg  prepared  in  the  following  way  :  At  one  end  of  the  ^gg  the 
shell  is  removed  in  such  a  way  as  to  leave  the  lining  membrane  of 
the  egg  intact ;  at  the  other  end,  shell  and  membrane  are  both  per- 
forated sufficiently  to  permit  the  passing  of  a  glass  tube  into  the 
egg  ;  which  is  held  securely  to  the  egg  by  sealing  wax.  The  egg 
is  then  passed  in  a  wine  glass  of  water,  and  the  level  of  the  water 
noted.  Shortly  afterward  the  yellow  of  the  egg  will  be  seen  rising 
in  the  tube,  and  the  level  of  the  water  falling  in  the  wine  glass. 
The  water  of  the  glass  gradually  passes  through  the  membrane  of 
the  egg,  distending  it,  and  forcing  the  contents  of  the  egg  upward. 
On  the  other  hand,  the  salts  of  the  egg — the  chlorides,  phosphates, 
sulphates — will  be  found  to  have  diffused  away  from  the  rest  of  the 
egg  into  the  AA'ater  of  the  glass,  as  can  be  readily  shown  by  appro- 
priate tests.  Thus,  if  a  few  drops  of  silver  nitrate  be  added  to 
the  water,  at  once  silver  chloride  will  be  formed  and  precipitated, 
showing  that  the  sodium  chloride  has  passed  into  the  water. 

An  important  flict  to  be  noted,  the  physiological  significance  of 
which  will  l)e  a})preciated  shortly,  is  tliat  little  or  no  albumin  is 
found  in  the  water,  scarcely  a  trace  of  it,  if  any,  passing  through 
the  egg  membrane,  particularly  if  the  water  be  distilled.  In  this 
experiment  also,  as  well  as  in  the  preceding  one,  the  substances  on 
either  side  of  the  membrane  (in  the  case  of  the  egg,  most  of  them 
at  least)  diffused  into  each  other.  This,  as  we  shall  see  in  a  mo- 
ment, depends  not  only  on  the  membrane  lacing  capable  of  imbib- 
ing both  liquids,  but  also  that  the  latter  were  miscible  with  each 
other.  If  a  membranous  septum,  however,  be  used,  which  will 
imbibe  only  one  of  the  liquids,  that  one  alone  will  traverse  the 
septum,  will  increase  the  volume  of  the  other  liquid  if  it  is  miscible 
with  it,  but  there  will  be  no  exchange  of  liquids. 

The  name  of  Dutrochet^  is  invariably  associated  with  any  dis- 
cussion of  the  phenomena  of  osmosis.     The  history  of  the  subject 

'  Memoire  pour  servir  a  la  Histoire  Anatomique  et  Physiologiquesdes  Animaux. 
Paris,  1837,  Tome  1. 


OSMOSIS.  173 

teaches  us,  however,  that  the  discovery  of  this  important  physical 
principle,  like  that  of  all  others,  was  not  a  sudden,  but  a  gradual 
one.  ]\Iany  of  the  phenomena  had  been  observed,  and  numerous 
experiments  bearing  upon  the  subject  had  been  performed  and  re- 
corded before  the  time  of  the  distinguished  French  physiologist. 
The  merit  of  Dutrochet  consisted  in  not  only  devising  and  perform- 
ing ncM'  experiments,  but  of  generalizing  the  facts  of  osmosis,  and 
applying  them  to  the  explanation  of  absorption  in  living  beings. 

This  able  investigator  described  thoroughly  the  passage  of  lic[uids 
throuoli  animal  membranes  :  he  showed  the  influence  of  different 
liquids  used,  measured  the  force  of  the  currents,  constructed  the 
osmometer,  and  called  particular  attention  to  the  currents,  nam- 
ing them  endosmotic  and  exosmotic,  according  as  they  passed  into 
the  tube  from  the  surrounding  liquid,  or  in  the  reverse  direction, 
and  applied  the  facts  to  the  explanation  of  physiological  phenomena. 
Since  then  the  suliject  of  osmosis  has  been  most  thoroughly  investi- 
gated by  Graliam.^  This  physicist  chscards  the  terms  endosmosis 
and  exosmosis,  considering  that  there  is  but  one  current,  the  inward 
one,  and  designating  it  by  the  term  osmotic,  and  the  whole  phe- 
nomena as  osmosis. 

According  to  Graham,  the  molecules  of  the  salt  in  the  outward 
current  travel  by  diffusion  through  the  porous  membrane.  "  It  is 
not  the  whole  saline  liquid  which  moves  outward,  but  merely  the 
molecules  of  salt,  their  water  of  solution  being  passed,  the  inward 
cun-ent  of  water,  on  the  other  hand,  appearing  to  be  a  true,  sensible 
stream,"  According  to  this  view,  the  only  true  current  in  the  os- 
mometer (Fig.  52)  is  that  of  the  water  from  the  jar  (A)  through 
the  membrane  (C)  into  the  bulbous  tube  (B)  containing  a  solution  of 
potassium  bichromate,  the  apparent  outward  movement  from  the 
jar  (B)  into  the  water  in  A,  being  due  to  the  diliusion  of  the  mole- 
cules of  the  salt.  So  far,  however,  as  the  physiologist  is  concerned, 
the  important  fact  in  this  experiment  is,  that  there  is  an  exchange 
going  on,  the  water  passing  one  way,  the  salt  the  other. 

Havino-  oiven  several  illustrations  of  osmosis,  let  us  consider  now 
the  causes  of  the  same.  The  phenomenon  of  osmosis  depends  es- 
sentially upon  two  conditions  :  first,  that  the  membranous  septum 
is  capable  of  imbibing  the  liquids  which  it  separates  ;  second,  that 
the  liquids  are  miscible.  It  will  be  remembered  that  in  speaking 
of  the  organic  proximate  principles,  allusion  was  made,  among  their 
other  properties,  to  that  of  their  taking  or  giving  up  of  water.  The 
swelling  up  of  a  tendon  or  muscle  when  immersed  in  water  is  a 
common  example  of  the  imbibition  by  organic  tissues  of  liquids. 
Every  organic  tissue  and,  indeed,  all  substances,  however  solid  they 
may  appear,  are  more  or  less  porous,  at  least  in  the  sense  that  the 
particles  of  which  a  body  consist  are  separated  to  a  greater  or  less 
extent  from  each  other.  It  is  due  to  the  presence  of  the  inter- 
spaces, between  the  particles  of  M'hich  a  tissue  consists,  that  imbibi- 
1  Osmotic  Force,  Phil.  Ti-ans.,  1854,  p.  178. 


1 74  ABSORPTION. 

tion  is  possible,  that  the  tissue  is  capable  of  taking  up  a  liquid, 
retaining  it  for  some  time,  and  finally  giving  it  up  again. 

The  passage  of  a  liquid  into  the  interspaces  or  interstices  of  a 
tissue  is,  however,  an  example  of  capillarity,  the  particles  of  which 
the  tissue  consists  bearing  to  the  liquid  passing  through  the  spaces 
between  them  the  same  relation  that  the  walls  of  a  capillary  tube 
bear  to  the  liquid  moving  within  them.  The  ascent  of  the  oil  in 
the  wick  of  a  lamp  is  a  familiar  example  of  capillary  action. 

In  order  that  an  osmosis  should  take  place,  it  is  evident  that 
the  membranous  septum  must  be  not  only  capable  of  imbibing  the 
liquids  through  capillary  action,  but,  further,  that  the  liquids  sepa- 
rated by  the  septum  must  be  miscible,  otherwise,  though  the  liquids 
might  get  into  the  septum,  they  would  not  diffuse  into  one  another, 
and  there  would  be  no  current.  This  brings  us,  therefore,  to  the 
consideration  of  the  second  condition  of  osmosis,  the  diffusion  of 
liquids. 

It  is  a  familiar  fact  that,  if  a  drop  of  water  rolling  over  a  sur- 
face, upon  which  it  can  preserve  its  globular  form,  comes  in  contact 
with  a  drop  of  mercury,  or  of  oil,  the  drops  do  not  run  into  each 
other  or  fuse,  the  particles  of  the  drop  of  water  having  a  greater 
affinity  for  each  other  than  for  the  particles  of  the  drop  of  mercury 
or  of  oil,  and  t'/ce  versa.  On  the  other  hand,  if  the  drop  of  water 
meets  with  a  drop  of  alcohol,  the  two  do  run  into  each  other,  losing 
their  identity,  the  particles  of  the  water  having  a  greater  affinity 
for  those  of  the  alcohol  than  they  have  for  each  other.  A  simple 
illustration  of  the  diffusion  of  liquids  is  to  place  in  a  small  vial  a 
solution  of  copper  sulphate  and  immerse  the  vial  containing  the 
solution  in  a  vase  of  water.  Soon  the  surrounding  water  will  as- 
sume a  blue  color  through  the  diffusion  into  water  of  the  copper. 

The  dissolving  of  a  substance  in  a  menstruum  is  an  illustration  of 
the  same  principle,  the  molecules  of  the  dissolving  liquid  having  a 
greater  affinity  for  the  particles  of  the  substance  to  be  dissolved 
than  these  have  for  each  other.  The  solution  of  a  substance,  how- 
ever, depends  not  only  upon  the  affinities,  chemical  or  physical,  ex- 
isting between  the  particles  of  the  substance  and  those  of  its  men- 
struum, but  also  upon  the  fact  that  when  the  cohesive  force  holding 
together  these  particles  ceases  to  act  the  particles  become  separated, 
repel  each  other,  they  acting  then  like  the  particles  of  a  gas.  The 
diffusion  of  liquids  depends,  therefore,  upon  the  affinities  existing 
between  the  particles  of  which  tlie  liquids  consist  and  a  repelling 
force  of  the  same. 

Many  interesting  and  important  facts  in  reference  to  the  diffusion 
of  liquids  have  been  established,  more  particularly  by  the  researches 
of  Graham.  It  is  not  essential,  however,  that  we  should  dwell  upon 
these,  merely  indicating  that  the  diffusibility  of  licpiids  differs  very 
much,  according  to  their  density,  composition,  the  character  of  the 
septum,  temperature,  etc. 

On  account,  however,  of  its  important  application  to  physiology 


CRYSTALLOIDS  AND  COLLOIDS.  175 

it  is  necessary,  before  leaving  the  subject  of  diffusion,  to  call  atten- 
tion to  the  distinction  made  by  Graham  bet^veen  what  this  physicist 
calls  crystalloids  and  colloids,  and  Mhich  can  be  well  illustrated  by 
the  following  simple  experiment :  If  a  piece  of  potassium  bichro- 
mate, or  a  little  of  the  same  substance  in  powder,  be  placed  in  the 
center  of  a  mass  of  boiled  starch,  in  a  few  hours  the  whole  of  the 
starch  will  be  seen  colored,  the  potash  having  diffused  tlirough  it. 
On  the  other  hand,  if  a  piece  of  caramel  be  similarly  placed  on  a 
mass  of  boiled  starch,  it  will  remain  where  placed,  not  diffusing  at 
all.  Substances  which  diffuse  readily,  like  the  salts  of  potassium, 
are  termed  crystalloids,  while  those  that  do  not  do  so  are  called 
colloids.  Thus,  in  the  experiment  with  the  egg,  the  sodiiun  chlo- 
ride, being  a  crystalloid,  diffuses  through  the  e^g  membrane,  while 
the  albumin,  being  a  colloid,  remains  within  the  egg.  The  method 
of  dialysis  of  Graham,  so  useful  as  an  instriunent  of  analysis,  is 
based  upon  this  distinction  of  crystalloids  :  thus,  if  a  fluid,  consist- 
ing of  a  mixture  of  organic  matter  and  arsenic,  be  placed  in  an 
osmometer,  in  the  course  of  twenty-four  hours,  perhaps,  three- 
fourths  of  the  arsenic  will  diffuse  through  the  membrane  into  the 
surrounding  water,  the  organic  matters  remaining  within  the  jar. 
The  application  of  the  facts  of  capillarity  and  diffusion  in  the  ex- 
planation of  osmosis,  as  illustrated  by  the  above  experiments,  is  so 
evident,  that  it  may  appear  superfluous  to  dwell  further  upon  the 
subject.  AYe  will,  therefore,  merely  call  attention  to  the  most  im- 
portant conditions. 

In  all  the  experiments  which  have  just  been  described  it  is  per- 
fectly clear  that  the  first  condition  of  osmosis  is  that  the  liquid  shall 
wet  the  membrane,  or,  in  other  words,  that  the  membrane  is  capable 
of  imbibition.  This,  we  have  seen,  is  due  to  capillary  force.  The 
second  condition  is,  that  the  liquids  having  been  imbibed  by  the 
membrane  are  miscible,  or  will  diffuse,  otherwise  they  would  get  no 
further  than  the  interstices  of  the  membrane,  and  there  would  be 
no  currents.  The  modifications  of  the  phenomena,  according  to 
whether  the  septum  is  solid,  liquid,  or  semi-solid,  as  to  whether  the 
current  is  endosmotic  or  exosmotic,  of  the  relative  force  of  the  two, 
etc.,  can  be  shown  to  depend  upon  these  two  conditions. 

Having  gone  over  this  preliminary  ground,  let  us  now  see 
whether  the  established  facts  of  capillarity  and  diffusion,  and  the 
theory  of  osmosis  deduced  from  them,  can  be  applied  to  the  ex- 
planation of  absorption,  as  it  takes  place  in  the  living  body. 

During  absorption  from  the  alimentary  canal  we  have  seen  the 
digested  food  in  a  liquid  or  semi-liquid  state  passes  through  the 
epithelium,  and  the  wall  of  a  capillary  or  lymphatic  into  the  blood 
or  lymph.  The  epithelium  and  capillary  wall  in  the  living  body 
are  comparable,  therefore,  to  the  septum  of  the  osmometer,  the 
liquids  in  the  intestinal  canal  and  the  blood  and  lymph  correspond- 
ing to  the  fluids  separated  by  the  septum  in  that  instrument. 

The  action  of  a  hydragogue  cathartic,  such  as  magnesium  sul- 


176  ABSORPTION. 

phate,  is  also  an  illustration  of  osmosis,  since  the  salt  passes  from 
the  interior  of  the  alimentary  canal  through  the  epithelial  layer  of 
the  intestine  and  wall  of  the  capillary  into  the  blood,  and  the 
watery  part  of  the  blood,  together  with  some  albumin  (the  latter 
eftect  being  due,  probably,  to  the  presence  of  the  saline),  passes 
into  the  interior  of  the  alimentary  canal.  The  osmosis  can  be  ex-^ 
perimentally  imitated  by  placing  the  solution  of  the  magnesium 
sulphate  within  the  jar  of  the  osmometer  and  the  serum  of  the 
blood  within  the  bulbous  tube,  the  serum  passing  through  the  mem- 
brane into  the  magnesium  sulphate,  and  the  latter  passing  into  the 
serum  and  increasing  its  volume. 

Supposing  that  the  jar  represents  the  alimentary  canal,  and  the 
bulbous  tube  the  blood  vessel,  the  osmosis  going  on  in  the  experi- 
ment is  essentially  the  same  as  that  in  the  living  body  after  the  ad- 
ministration of  a  hydragogue  cathartic. 

The  essential  diiference  between  the  osmosis  that  takes  place 
during  absorption  and  after  the  administration  of  a  saline  and  in 
an  osmometer  is  that  the  conditions  which  favor  osmosis  are  real- 
ized in  a  way  and  to  an  extent  in  the  living  body  that  cannot  be 
imitated  for  a  moment,  even  in  the  most  delicate  experiments. 
Thus,  it  has  been  found  that  the  activity  of  osmotic  currents  is  in 
proportion  to  the  extent  and  thinness  of  the  membrane.  When  we 
come  to  study  the  capillary  system  we  shall  see  that  the  extent  of 
absorl)ing  surface  exposed  by  it  is  enormous,  and  that  the  walls  of 
the  capillaries  are  extremely  delicate,  measuring,  on  an  average, 
perhaps  from  the  jo^oo  ^^  *^^  iio  °^  ^  millimeter  (2  5^-00"  ^^  ^^^^ 
-j^i-g-g-  of  an  inch)  in  diameter. 

"One  can  readily  imagine  how  favorable  such  a  thin  septum  would 
be  in  the  production  of  osmosis.  It  can  be  shown,  also,  as  might 
have  been  supposed,  that  an  osmotic  current  is  favored  by  having 
little  or  no  pressure  to  overcome,  such  a  current  ceasing  and  begin- 
ning again,  according  as  dense  substances,  like  mercury,  are  added 
to  or  taken  away  from  the  fluid  within  the  tube  of  the  osmometer. 
Now  in  the  living  body  the  pressure  of  the  blood,  even  in  the  larg- 
est arteries,  seldom  exceeds  150  millimeters  (6  inches)  of  mercury, 
and  this  pressure  is  very  much  reduced  as  the  blood  flows  into  the 
capillary  and  venous  system,  so  that  a  current  flowing  from  the 
intestine  toward  the  blood  meets  with  no  very  great  resistance. 

An  important,  though  not  indispensable,  condition  favoring  the 
osmotic  current  is  the  density  of  the  solution  in  the  bulbous  tube 
of  the  osmometer,  the  flow  being  usually  greater  according  to  the 
density  of  the  solution.  Hence  the  activity  of  absorption  after  the 
administration  of  hydragogue  cathartics,  such  drugs  diminishing 
the  watery  constituents  of  the  blood,  and  so  increasing  its  density, 
while,  at  the  same  time,  they  diminish  pressure.  Again,  osmotic  cur- 
rents are  more  active  if  the  liquids  are  kept  in  movement.  Thus, 
when  osmosis  has  ceased,  it  can  often  be  made  to  commence  again 
by  simply  stirring  the  liquids.     It  is  evident  from  this  how  great 


CONDITIONS  FAVORING  OSMOSIS. 


177 


and  favorable  are  the  influences  exerted  by  the  circulation  of  the 
blood  and  lymph  in  promoting  osmosis  and  absorption. 

The  importance  of  the  moyement  of  the  liquids,  or  of  one  of 
them,  in  favoring  osmosis  is  shown  by  the  simple  apparatus  repre- 
sented in  Fig.   53.     A  jar  (B),  furnished  with  two  stopcocks,  is 


Fig.  53. 


"r,.:.r""7 


filled  with  a  colored  fluid,  litmus  water,  for  example.  To  both 
stopcocks  are  fitted  equal  portions  of  intestine  (D  and  C ),  which 
are  immersed  in  the  vases  of  water  E  and  A.  Into  the  piece  of 
intestine  C  is  fitted  a  siphon  (G)  of  smaller  diameter  than  that  of 
the  intestine,  a  siphon  (F)  of  as  large  diameter  as  that  of  the  intes- 
tine being  inserted  into  the  piece  of  intestine  D.  Both  siphons  (F 
and  G)  pass  into  the  vases  H  and  I.  The  stopcocks  of  the  reser- 
voir (B)  being  opened,  the  colored  fluid  will  flow  into  the  two  pieces 
of  intestine,  but  inasmuch  as  the  small  size  of  the  siphon  G  will 
offer  an  obstacle  to  the  flow  of  the  colored  liquid  through  it  into  the 
vase  I,  the  piece  of  the  intestine  C  will  become  distended,  and  there 
will  be  an  exosmosis  from  it  of  the  colored  fluid  into  the  water  of 
the  vase  A.  On  the  other  hand,  the  colored  fluid  passing  readily 
through  the  siphon  F,  on  account  of  its  large  size,  the  piece  of  in- 
testine D  will  become  flaccid,  and  there  will  be  a  rapid  flow  of  the 
water  of  the  vase  E,  through  the  intestine  D,  into  the  colored  fluid 
flo\ving  through  it,  or  an  endosmosis. 

Too  much  importance  must  not  be  attached,  however,  to  osmosis 
as  accounting  for  the  phenomena  of  absorption,  as,  under  certain 
circumstances,  substances  are  absorbed  not  in  accordance  with,  but 
independently  of  this  physical  principle.  Thus,  for  example,  in  a 
solution  containing  equal  quantities  of  glucose  and  sodium  sulphate, 
after  a  given  time  the  sugar  will  be  completely  absorbed,  whereas 
the  sodium  sulphate,  although  far  more  diffusible,  will  still  remain 
in  considerable  amounts  in  the  intestine.  Again,  certain  coloring 
matters  are  not  absorbed,  the  cells  appearing  to  exert  some  discrimi- 

12 


178  ABSOBPTION. 

nating  power  between  different  substances.  The  absorption  of  the 
emulsified  fats  is  also  difficult  to  explain  by  osmosis.  Many  other 
illustrations  might  be  offered  to  show  that  while  absorption  appears 
to  be  due  to  osmosis  in  some  instances,  in  others  it  can  not  be  ac- 
counted for  by  that  principle  alone.  Indeed  to  such  an  extent 
is  this  the  case  that,  according  to  many  physiologists,  absorption 
is  due  not  to  osmosis,  but  to  some  specific  action  of  the  protoplasm 
of  the  living  cell  as  yet  not  understood. 


CHAPTER   X. 

THE  BLOOD. 

Feom  time  immemorial  the  blood  has  been  recognized  as  the 
most  important  fluid  in  the  human  body,  as  well  as  in  that  of  ani- 
mals— indeed,  as  indispensable  to  life.  Daily  observation  continu- 
ally shows  that  its  loss  prostrates  the  body  and  enfeebles  its  powers, 
and,  with  excessive  hemorrhage,  that  life  itself  ebbs  away. 

This  is  readily  understood  when  it  is  known  that  the  blood  in 
circulating  through  the  economy  carries  to  the  tissues,  and  the  cells 
composing  them,  material  for  their  growth,  renewal,  and  repair,  and 
removes  from  them  that  which  has  become  effete  and  worn  out  and 
equalizes  more  or  less  the  temperature  throughout  the  body.  The 
blood  is  an  alkaline  fluid,  due  to  the  alkaline  salts,  especially  so- 
dium carbonate,  dissolved  in  the  plasma.  The  degree  of  alkalinity, 
estimated  as  Xa,C03,  corresponds  in  hiunan  blood  to  0.35  per  cent, 
of  this  salt.  The  specific  gravity  of  the  blood  when  defibrinated 
amounts  upon  the  average  to  from  1.055  to  1.063.  Recent  re- 
searches ^  have  shown,  however,  that  the  specific  gravity  varies  in 
individuals,  with  age  and  sex,  with  eating  and  exercise,  the  hour  of 
the  day,  etc. 

The  opacity  of  the  blood  is  due  to  the  fact  that  it  is  not  a  homo- 
geneous liquid,  being  composed,  as  we  shall  see  presently,  of  two 
elements — corpuscles  and  liquor  sanguinis,  or  plasma  ;  these,  dif- 
fering in  their  refractive  power,  offer  an  obstacle  to  the  transmission 
of  light,  which  is  lost  in  its  passage  from  the  air  through  the  liquor 
and  corpuscles.  The  blood  has  a  saltish  taste,  and  a  faint  but  dis- 
tinct odor.  This  becomes  more  apparent  when  a  few  drops  of  sul- 
phuric acid  are  added  to  the  specimen  examined.  It  may  be  men- 
tioned, in  this  connection,  that  the  importance  of  the  odor  of  the 
blood,  as  made  use  of  in  criminal  cases,  and  often  insisted  upon  by 
medico-legal  writers,  has  been  grossly  exaggerated. 

The  temperature  of  the  blood  in  man,  as  we  shall  see  hereafter, 
is  on  the  average  37. °2  C.  (98. °9  F.),  but  it  is  very  probable  that, 
in  certain  parts  of  the  body,  it  is  several  degrees  liigher.  Bernard 
found  that  in  dogs  and  sheep  the  temperature  in  the  aorta  ranged 
from  37°  C.  to  40°  C.  (99°  F.  to  105°  F.),  and  reached  even  42°  C. 
(107°  F.)  in  the  hepatic  vein.  According  to  the  same  authority, 
the  blood  is  hotter  in  the  right  than  in  the  left  side  of  the  heart ; 
the  temperature  is  higher  in  the  arteries  than  in  the  veins,  with  the 
exception,  however,  of  the  blood  in  the  portal  vein,  which  is  Avarmer 
than  that  in  the  aorta  independently  of  digestion."     The  sudden  rise 

^L.  E.  Jones,  Journal  of  Physiology,  Vol.  viii.,  1887,  p.  1  ;  Vol.  xii.,  1891,  p.  229. 
^Sur  les  Liquides  des  1' Organisrae,  Tome  i.,  3d,  -1th,  5th  lecons. 


180  THE  BLOOD. 

of  temperature  often  observed  in  man  just  before  death,  due,  per- 
haps, to  the  loss  of  vascular  tonicity,  would  seem  to  show  that  the 
temperature  of  the  blood  in  the  deeper  vessels  in  man  is  as  high  as 
that  observed  by  Bernard  in  the  animal  just  mentioned. 

One  of  the  most  striking  features  of  the  blood  is  its  color,  red 
or  scarlet  in  the  arteries,  blue  or  black  in  the  veins.  As  first  dem- 
onstrated by  Lower,^  this  difference  is  due  to  the  venous  blood 
absorbing  air  as  it  passes  through  the  lungs.  When  we  come  to 
study  the  circulation  and  respiration,  we  shall  see  that,  as  the  red 
blood  passes  through  the  capillaries  it  loses  oxygen  and  gains  car- 
bon dioxide,  becoming  blue,  while  it  turns  again  into  red  blood  in 
the  lungs  with  the  fresh  absorption  of  oxygen.  The  blood  of  the 
pulmonary  artery,  however,  is  blue,  while  that  of  the  pulmonaiy 
vein  is  red.  The  blood  in  the  veins  coming  from  glands,  during 
secretion,  as  shown  by  Bernard,"  is  also  red,  and  this  is  the  case 
also  in  the  veins  when  the  sympathetic  is  cut.  The  explanation  in 
these  cases  seems  to  be  that  the  increased  supply  of  arterial  blood 
to  the  parts  carries  an  excess  of  oxygen  to  the  veins  sufficient  to 
maintain  the  red  color  of  the  blood  flowing  into  them. 

The  brightness  in  color  of  the  blood  depends,  to  a  certain  extent, 
upon  the  form  of  the  corpuscles ;  it  is  bright  when  they  are  flat- 
tened and  hollowed,  containing  oxygen,  and  dark  when  they  are 
distended  and  round,  containing  carbon  dioxide,  the  reflection  of 
the  light  depending  on  the  form  of  the  corpuscles. 

Numerous  experiments  have  been  made  from  time  to  time  to 
determine,  if  possible,  the  quantity  of  blood  in  the  human  body. 
Among  others  may  be  mentioned  the  often  quoted  ones  of  Weber 
and  Lehmann.'^  These  experiments  were  made  upon  two  crim- 
inals who  were  first  weighed  and  then  decapitated.  The  blood 
remaining  in  the  vessels  after  decapitation  was  calculated  l)y  inject- 
ing water  into  the  vessels  of  the  head  and  trunk  until  that  which 
passed  out  by  the  veins  exhibited  only  a  pale  yellowish  color.  This 
was  evaporated,  and  the  dry  residue  was  assumed  to  represent  a 
certain  quantity  of  blood,  the  ratio  of  blood  to  its  residue  having 
been  previously  ascertained.  The  amount  of  blood  lost  by  decapi- 
tation was  a  little  over  twelve  pounds,  and  that  estimated  by  the 
above  method  as  remaining  in  the  vessels  as  a  little  over  four 
pounds,  making  for  the  whole  body  16.59  pounds. 

Amount  of  Blood  in  the  Body. 

12  lbs.  of  blood  lost  in  execution. 

4  lbs.  of  blood  collected  by  washing. 
16  lbs.  of  blood  in  criminal  weighing  128  lbs.,  or 

1   lb.  of  blood  to  8  of  body  weight. 

^  Tractatus  de  Corde  item  de  Motu  etc. ,  Colore  Sanguinis,  etc.,  p.  180.  Anistelo- 
dami,  16G9. 

2  Op.  cit.,  i)p.  268,  299. 

^Lehrbuch  der  Phys.  Cheraie,  1852,  Tome  ii.,  s.  234. 


AMOUXT  OF  BLOOD. 


181 


The  Aveight  of  one  of  the  criminals  Avas  132.7  pounds;  this 
would  give  a  ratio  of  about  one  pound  of  blood  to  every  eight  of 
body,  a  somewhat  higher  ratio  than  that  obtained  by  experiments 
upon  dogs,  the  blood  amounting  usually  in  that  animal  to  one- 
thirteenth  of  the  body  weight. 

It  must  be  remembered,  however,  that  this  is  only  an  approxi- 
mation, for  the  amount  of  blood  left  in  the  body  after  decapitation 
cannot  be  accurately  determined  by  the  method  just  mentioned. 
Further,  the  amount  of  l)lood  in  the  body  is  notably  increased  dur- 
ino-  dio;estion.  Bernard  ^  has  shown  that  an  animal  like  the  rabbit, 
for  example,  during  digestion  can  lose  twice  as  much  blood  as  when 
fasting.  Burdaeh  -  refers  to  a  case  reported  by  AVrisberg  of  a 
woman  losing  over  twenty-one  pounds  of  blood  after  decapitation. 
Facts  like  these  show  the  importance  of  taking  into  consideration 
the  state  of  the  system  in  determining  the  quantity  of  blood.  In  a 
general  way  this  may  be  stated  in  an  adult  healthy  man  to  amount 
to  sixteen  or  twenty  pounds  and  is  distributed,  according  to  Ranke,^ 
in  round  numbers  as  follows  : 


J  vascular  system. 
i  liver. 


}  skeletal  muscles. 
\  remaining  organs. 


When  the  blood  is  examined  under  the  microscope,  for  example, 
circulating  in  the  web  of  a  living  frog's  foot,  it  will  be  seen  to  con- 
sist, as  already  mentioned,  of 
two  distinct  portions,  a  trans- 
parent colorless  liquid,  the 
liquor  sanguinis  or  plasma, 
and  of  minute  bodies  or  cor- 
puscles, the  blood  globules  or 
blood  cells.  The  corpuscles 
which  float  in  the  liquid  part 
of  the  blood  are  of  three  kinds, 
the  red,  the  white  or  leucocy- 
tes, and  the  blood  plates.  The 
red  corpuscles,  discovered  by 
Leuwenhoek*  in  1673,  are 
far  more  numerous  than  the 
leucocytes  or  blood  plates  and 
give  to  the  blood  its  red  color, 
they  being  carriers  of  oxygen. 
The  yellow  tint  exhibited  by 
blood  plasma  free  of  corpus- 
cles when  viewed  in  quantity 
appears  to  be  due  to  the  pres- 
ence of  a  pigment  the  nature 
of  which   is  not  understood. 


Human  blood  as  seen  on  the  warm  stage.  5ragni- 
fied  about  1200  diameters,  c,  c.  Crenate  red  corpus- 
cles, p.  A  finely  granular,  ff.  A  coarsely  granular 
pale  corpuscle.  '  Both  exhibit  two  or  three  vacuoles. 
In  j7  a  nucleus  also  is  visible.     (Qcaix.) 


^Op.  cit.,  Tome  i. ,  p.  419. 

^Traite  de  Physiologie,  traduit  par  .Jourdain,  Tome  vi.,  p.  116.     Paris,  1837. 

^  Physiologie,  1S71,  s.  373.  *Philos.  Transactions,  p.  23.    London,  1674. 


182 


THE  BLOOD. 


Let  us  study  the  corpuscles,  first  reserving  for  the  present  the  con- 
sideration of  the  plasma  or  the  liquor  of  the  blood. 

When  blood  is  examined  under  the  microscope  the  corpuscles  will 
be  observed  in  diiferent  positions,  some  on  their  edges  or  sides, 
others  lying  flat  (Fig.  54).  It  can  be  seen  that  they  are  circular, 
flattened  disks,  about  four  times  as  broad  as  thick  and  biconcave 
in  form.  From  this  latter  circumstance  they  are  thinnest  in  the 
center.  Therefore,  when  a  corpuscle  is  viewed  under  the  micro- 
scope from  the  flat  side,  if  the  edges  are  in  focus  the  center  will 
appear  dark,  simulating  a  nucleus  (Fig.  55) ;  whereas,  when  the 
center  is  in  focus  and  is  light  the  edges  will  appear  dark  (Fig.  56). 
In  reality,  however,  there  is  neither  a  nucleus  nor  a  membranous 
cell-wall,  the  red  corpuscle  being  a  homogeneous  structureless  mass 
of  living  matter,  soft,  transparent,  elastic,  and  of  a  pale  amber  color. 
The  red  color  of  the  blood  is  due  to  the  immense  number  of  the 
corpuscles.  Vierordt '  estimates  that  a  cubic  millimeter  in  the 
male  contains  5,000,000,  in  the  female  4,500,000. 


Fig.  55. 


Fig.  56. 


Eed  globules  of  the  blood,  seeu  a  little  beyond 
the  focus  of  the  microscope.     (Dal,ton.) 


The  same,  seen  a  little  within  the  focus. 
(Dalton.) 


The  method  we  make  use  of  in  counting  the  blood  corpuscles 
is  essentially  that  of  Malassez  and  Potain "  and  Gowers.^  It 
consists  in  sucking  up  into  a  graduated  tube  (Fig.  57,  A)  one 
cubic  millimeter  of  blood  and  then  a  five  per  cent,  solution  of 
sodium  chloride  from  a  jar  into  the  tube  until  the  blood  and  the 
solution  are  drawn  into  and  fill  the  dilated  portion  (Fig.  57,  B)  of 
the  tube.  This  dilated  portion  having  a  capacity  of  100  milli- 
meters, the  blood  will  then  be  diluted  100  times.  One  millimeter 
of  this  mixture  will,  therefore,  contain  the  y-^-^-  i)art  of  a  millimeter 

'  Physiolof^ie,  s.  9.     Tubingen,  1871. 
^Arcliiv  de  Physiologie,  p.  32.     Paris,  lS7fi. 
''Lancet,  1877,  p.  797. 


RED  CORPUSCLES. 


183 


of  blood  and  the  yl  q-  of  a  millimeter  of  the  mixture,  y-l-g-  of  ^wo  ^^ 
the  y-o^-oQ-  of  a  millimeter  of  blood.  This  mixture  of  blood  and 
salt  solution  is  then  forced  out  on  an  object  glass  (Fig.  58,  C), 
which  under  the  microscope  is  seen  to  be  divided  into  ten  squares, 
each  of  which  when  covered  by  the  compressorium  (Fig.  58,  D) 


Fig.  57. 


Fig.  58. 


■mill '  m  iiiiiiiiiHffl;i!iiiiiiiiiiiiiii!iiiiiiiiiiiiiiiiiiiiiiiiiiii 


Graduated  moist  chamlser  with  compressorium. 


has  a  capacity  of  the  -jIq-  of  a  millimeter.  Each 
square  will  then  contain  the  y^^  of  a  millimeter 
of  the  mixture,  and  consequently  will  contain  the 
j-l-g-  of  yi-Q  or  the  yo^o  o"  ^^  ^  millimeter  of  blood. 
Further,  as  each  square  is  subdivided  into  twenty 
smaller  squares,  the  object  is  to  facilitate  the  count- 
ing of  the  corpuscles.  Suppose  now,  for  example, 
that  twenty-five  corpuscles  could  be  counted  on 
each  of  the  small  squares,  then  the  large  square 
would  contain  500  corpuscles ;  but  as  the  large 
square  contains  only  the  y-Q^Q-Q^  of  a  millimeter  of 
blood,  it  follows  that  one  cubic  millimeter  will 
contain  500  x  10,000,  or  5,000,000  corpuscles. 

The  division  of  the  object  glass  into  ten  squares 

is  to  enable  one  to  make  ten  independent  observa- 

L     tious,  so  as  to  obtain  an  average  result.     A  cubic 

?    inch  of  blood,  holding  over  70,000,000,000  red 

blood  corpuscles,  will  contain,  therefore,  according 

to  Huxley,^  more  than  eighty  times  the  number  of 

Mixer.  pCOplc  UpOU  tllC  globc. 

The  number  of  red  corpuscles  varies,  however, 
not  only  with  the  sex  as  just  mentioned,  but  according  to  other 
conditions.  Thus,  for  example,  the  number  of  red  corpuscles  is 
greater  in  the  adult  than  in  youth,  or  in  old  age,  in  the  sanguineous 
than  in  the  lymphatic  temperament,  in  plethoric  than  in  auwmic 
persons  or  in  those  who  have  lost  blood  or  who  have  been  deprived 


^  Elementary  Physiology.     London,  3d  ed.,  p.  78. 


184 


THE  BLOOD. 


of  food.  Accordingly  to  Bakewell/  race  exerts  an  influence,  the 
number  of  corpuscles  differing  in  the  blood  of  the  Mohammedan, 
Hindoo,  and  Negro.  Recent  investigations  appear  to  show  that 
altitude  influences  in  a  marked  degree  the  number  of  red  corpuscles. 
Thus,  according  to  Vianet  ^  a  residence  in  the  mountains  at  a  height 
of  4,932  meters  (about  16,000  feet)  during  two  weeks  will  increase 
the  number  of  red  corpuscles  from  5,000,000  to  more  than  7,000,- 
000  per  cubic  millimeter,  8,000,000  even  being  produced  after  a 
sojourn  of  three  weeks. 

Fig.  59. 


Strieker's  warm  stage. 

The  specific  gravity  of  the  corpuscles  is  a  little  higher  than  that 
of  the  liijuor  sanguinis,  being  about  1.085.  We  shall  see  hereafter 
that  it  is  for  this  reason  that  if  blood  be  allowed  to  flow  into  a  vessel, 
coagulation  being  retarded  or  prevented,  tliat  the  corpuscles  will 
tend  to  settle  at  the  bottom,  the  plasma  being  left  as  a  clear  super- 
natant layer. 

On  observing  the  corpuscles  in  blood  removed  from  the  body,  it 
will  be  noticed  that  soon  a  number  of  them  run  together,  forming  a 
chain-like  rouleaux  of  coin  (Fig.  54).  This  is  due,  according  to 
Robin,'^  to  an  exudation  from  the  corpuscles  themselves  which 
causes  them  to  adhere  to  each  other.  Shortly  after  the  blood  is 
drawn  the  corpuscles  will  exhibit  also  small  prominences  on  their 

•  Med.  Times  and  Gazette,  Lond.,  Nov.,  1872,  p.  514. 

2  La  Seniaiiie  Medicale,  1890,  p.  464. 

^Journal  de  la  I'liyyiologie,  Toitie  i.,  p.  295.     Paris,  1858. 


RED  CORPUSCLES.  185 

surfaces,  giving  them  a  raspberry-like  appearance,  and  as  they  be- 
come dry  they  shrivel  up  and  their  edges  become  crenated  (Fig.  54). 
The  shape  of  the  corpuscles,  however,  can  be  restored  even  after 
the  lapse  of  months  and  years  by  treating  them  with  a  fluid  of  the 
density  of  serum  (1.028).  This  fact  is  important,  from  a  medico- 
legal point  of  view,  in  reference  to  determining  whether  a  stain 
upon  clothing  or  floors,  etc.,  is  blood. 

The  corpuscles  swell  up  and  dissolve  when  pure  water  is  added 
to  them,  and  acetic  acid  and  other  acids  have  the  same  effect. 

Under  the  influence  of  alkalies  the  corpuscles  instantly  swell  up, 
appear  to  burst,  and  then  entirely  disappear.  The  effect  of  heat  is 
to  produce  in  them  bud-like  processes.  In  studying  the  effects  of 
such  reagents  as  those  just  mentioned,  as  well  as  others,  the  appa- 
ratus represented  in  Fig.  59,  which  is  to  be  placed  on  the  stage  of 
the  microscope,  will  be  found  useful.  It  consists  of  a  brass  box 
opening  laterally  by  two  tubes,  with  a  solid  rod-like  projection  in 
the  middle,  and  perforated  in  the  center.  The  central  aperture  can 
be  converted  into  a  chamber  by  cementing  to  its  lower  opening  a 
cover  glass.  Surrounding  this  central  chamber  is  coiled  the  bulb 
of  a  thermometer,  whose  registering  sarface  is  attached  externally 
to  the  side  of  the  box. 

By  connecting  one  of  the  lateral  apertures  opposite  the  projecting 
rod  of  the  box  with  the  reservoir  of  hot  water  and  the  other  with  a 
waste  pipe  a  constant  flow  of  hot  water  through  the  brass  box  is  in- 
sm-ed,  and  the  temperature  of  the  central  chamber  regulated  as  de- 
sired by  the  thermometer. 

By  screA\-iug  on  to  the  rod-like  projection  of  the  brass  box  a  rod 
of  the  same  metal  and  heating  its  free  end  by  a  spirit  lamp,  the 
temperature  can  also  be  elevated  as  required. 

If  it  is  desired  to  study  the  action  of  water  upon  the  blood  cor- 
puscles, for  example,  the  apparatus  is  used  in  the  following  way : 
A  drop  of  water  is  placed  on  the  floor  of  the  chamber,  and  a  drop 
of  blood,  usually  diluted  with  salt  solution,  upon  a  cover-glass  ;  the 
latter  is  then  placed  inverted  over  the  chamber,  the  edges  of  which 
have  been  previously  oiled  or  surrounded  with  a  ring  of  putty,  so 
as  to  make  the  chamber  air-tight.  By  allowing  the  hot  water  to 
flow  through  the  brass  box,  or  heatino;  the  end  of  the  rod  bv  the 
spirit  lamp,  the  drop  of  water  on  the  floor  of  the  chamber  is  made 
to  evaporate,  and,  condensing  on  the  under  surface  of  the  cover- 
glass,  gradually  affects  the  blood  corpuscle  it  meets  there. 

The  effects  of  heat  simply  upon  the  blood  corpuscles  can  be 
studied  by  placing  the  blood  to  be  examined  upon  a  cover-glass, 
and  dropping  this  upon  another  glass  of  the  same  size,  the  edges  of 
which  have  been  previously  smeared  wdth  oil,  and  then  placing  the 
two  glasses  with  the  blood  and  oil  so  enclosed  over  the  opening  of 
the  chamber.  Further,  by  means  of  the  tubes  which  open  into  the 
chamber,  a  current  of  gas  can  be  made  to  pass  through  the  latter, 
and  its  effects  studied  upon  the  blood  placed  upon  a  cover-glass  and 


186 


THE  BLOOD. 


inverted  over  the  chamber,  in  the  manner  just  described  in  studying 
the  effect  of  water. 

The  effect  of  electricity  upon  the  corpuscle  is  to  convert  it  tem- 
porarily into  rosette-,  mulberry-,  and  finally  horsechestnut-shaped 
forms.  To  demonstrate  this  effect,  we  usually  make  use  of  the 
electrical  microscopic  stage,  placing  the  drop  of  blood  upon  the  slide 
in  such  a  position  that  when  covered  it  spreads  out  between  the  two 
poles  of  tinfoil,  which  are  about  six  millimeters  apart  and  connected 
either  with  a  Leyden  jar  having  a  surface  of  500  square  centime- 
ters, or  by  a  Du  Bois  Reymond  inductorium  fed  by  a  single  Bunsen 
cell,  according  to  the  kind  of  electricity  to  be  used. 

According  to  the  high  authority  of  Gulliver,^  the  average  diam- 
eter of  the  red  blood  corpuscle  is  the  3^2Vo"  ^^  ^^^  inch,  with  an  av- 
erage thickness  of  about  the  y^^i'oo'  ^^  ^^  inch.  The  diameter, 
however,  varies  as  much  as  from  the  -^-^-q-q  to  the  g-gVo"  ^^  ^^  inch.^ 
The  importance  of  remembering  these  variations  will  be  seen  pres- 
ently. 

Blood  Corpuscles.^ 
Mammals. 

Animal. 

Manatee .         .         . 

Elephant  ..... 

Ant-eater         ..... 

Sloth 

Whale 

Camel      ...... 

Man 

Orang      ...... 

Chimpanzee     ..... 

Dog 

Opossum  ..... 

Rabbit 

Black  Rat         ..... 

Mouse      ...... 

Brown  Rat       ..... 

Gray  S<]uirre]  .... 

Ox 

Cat 

Sheep       ...... 

Goat         ...... 

Pigmy  Mu.sk  Deer  .... 

'In  Works  of  ^Villiam  Ilewson,  Sydcnlmm  edition,  p.  237.     London,  184(). 

2 In  many  phy.-^ioloj^ncal  treatises  the  diameter  of  the  red  blood  corpuscle  in  man 
is  given  as  7.7^^  To  the  author  at  least,  the  statement  that  the  red  blood  corpuscle 
measures  0.0077  mm.  (;fi'„,)  <><'  im  incii)  is  preferable,  as  bein<T  more  intelligible  to 
the  ordinary,  as  well  as  to  the  scientific,  understanding,  involving  but  one  mental 
operation.  To  state  sucli  measurement  as  being  7.7// involves  tliree  distinct  men- 
tal operations  as  follows:  1st.  /' =0.001  of  a  millimeter;  2d.  7.7// =  7.7  X  0.001 
mm. ;  3d.  7.7  X  0.001  mm.  '--.-.  0.0077  mm.  That  the  above  calculation  is  necessarv, 
any  one  will  realize  who  endeavors  to  picture  to  himself  the  diameter  of  the  red 
blood  corpuscle  simi)ly  in  terms  of  7.7  /'. 

3  Drawn  up  principally  from  table  of  Gulliver,  op.  cit.,  p.  2:57. 


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3  9Tr 

1 

40-00" 

1 

4T6T 

1 

44¥T 

1 

"53"0¥ 

1 

6  36  6 

1 

1232  5 

FED  CORPUSCLES.  187 


Birds. 
Animal.  Diameter. 

Ostrich Trr9  ^^  ^"^  inch. 

0^1 •     ttW     "         " 

Swan 

Pigeon     . 

Tiirtle      . 

Viper 

Lizard 


1806 

1 


Reptiles. 


12  74 

_i_  _ 

1  o  5  5 


Amphibia. 
Aphiuma  ......       „^  „ 

^  36  3 

Proteu; 

Siren 

Menopoma 


400 

Siren ^ 


H.shes. 


Pike ToVo     ••         " 

Perch _!__-" 

Lamprey  ......      „  V,        "         " 

While  there  is  not  always  a  pro}X)rtional  relation  between  the 
size  of  the  blood  corpnscle  and  that  of  the  animal — that  of  the  ox, 
for  example,  being  .-mailer  than  that  of  man  or  the  doo- — Milne 
Edwards  ^  has  shown,  by  a  comparison  of  the  size  of  the  blood  cor- 
puscle in  the  five  classes  of  vertebrates,  that  there  does  exist  a  most 
remarkable  connection  between  the  size  of  the  corpuscle  and  the 
degree  of  nervo-muscular  power  of  the  animal ;  the  coqiuscles  be- 
ing small  in  the  most  highly  developed  and  active  vertebrates,  and 
large  in  those  least  so.  It  will  be  seen  also,  more  particularly,  that 
the  size  of  the  corpuscle  is  most  intimately  related  to  the  acti^•it^' 
of  the  respiration,  the  corpuscle  being  smallest  in  those  animals 
whose  respiration  is  the  most  active,  and  largest  in  those  in  which 
this  function  is  slow.  This  might  be  expected,  as  a  large  number 
of  small  corpuscles  offer  a  larger  absorbing  surface  to  the  oxygen, 
the  respiratory  element,  than  a  small  number  of  large  ones.  As 
we  proceed  we  shall  see  that  muscular  is  largely  dependent  upon 
respiratory  activity.  Hence,  if  the  above  view  be  correct,  we 
should  expect  to  find  the  blood  corpuscles  smallest  in  the  active 
vertebrates  and  laroest  in  the  sliio^o-ish  ones. 

On  comparing  the  size  of  the  blood  corpuscles  in  the  mammalia 
A\*itli  those  of  the  reptilia  or  batrachia,  we  find  such  to  be  the  case. 
Of  course,  if  this  comparison  be  carried  out  to  extreme  detaU, 
there  will  be  found  exceptions  to  the  rule,  for  no  doubt  other  con- 
ditions beside  those  of  respiration  influence  the  size  of  the  coi'pus- 
cles,  possibly  the  character  of  the  food,  etc. ;  but  that  the  connec- 
tion just  referred  to  is  something  more  than  mere  coincidence  seems 
to  be  Hilly  justified  by  ^Milne  Edwards's  elaborate  survey  of  the 
facts. 

1  Physiologic,  Tome  i. ,  p.  57, 


188  THE  BLOOD. 

It  will  be  seen  that  there  are  a  few  mammals  in  which  the  blood 
corpuscles  are  larger  than  those  of  man,  and  that  the  blood  corpus- 
cle of  the  pigmy  deer  (Tragulus)  is  the  smallest  known,  while  those 
of  a  batrachian,  the  amphiuma,  are  the  largest. 

The  exact  size  of  the  red  blood  corpuscle  in  man  is  not  only  of 
interest  physiologically,  but  also  from  a  medico-legal  point  of  view.^ 
Attention  has  already  been  called  to  the  fact  that  there  is  a  consid- 
erable variation  in  the  size  of  the  human  corpuscles,  and  hence  it 
is  often  impossible  to  say  positively  whether  a  given  corpuscle  came 
from  a  human  being's  blood  or  that  of  an  ape,  dog,  rabbit,  rat, 
mouse,  or  ox,  for  the  average  diameter  of  the  corpuscles  in  these 
animals  is  within  the  limits  of  the  variations  that  have  been  men- 
tioned as  occurring  in  man. 

When  a  large  quantity  of  human  blood  is  examined,  probably 
ninety-five  corpuscles  out  of  every  hundred  will  exhibit  the  same 
diameter,  but  in  a  medico-legal  investigation  the  amount  of  blood 
put  at  the  disposal  of  the  expert  is  often  exceedingly  small — an  old 
blood  stain,  a  single  drop,  perhaps,  and  possibly  the  variable  cor- 
puscles contained  in  this  very  drop.  Now,  as  the  size  of  the  cor- 
puscle in  the  dog  or  the  ox  varies  as  well  as  that  of  man,  if  the 
size  of  the  corpuscle  in  the  suspected  fluid  is  only  taken  into  con- 
sideration, the  blood  of  a  dog  might  be  determined  to  be  that  of 
a  man,  and  vice  versa.  In  fact,  it  is  impossible  to  say  beyond  the 
shadow  of  a  doubt  that  a  given  drop  of  liquid  is  human  blood  and 
not  that  of  the  animals  referred  to  above,  for  the  small  size  of  the 
variable  human  corpuscle  might  lead  the  examiner  to  think  the 
human  blood  had  come  from  a  dog  or  a  mouse,  while  from  the  vari- 
able large  corpuscles  in  the  blood  of  these  animals  there  might  be 
a  suspicion  that  their  blood  was  human. 

With  the  exception  of  the  camel  and  llama,  in  which  the  red 
blood  corpuscles  are  oval,  the  form  of  these  bodies  in  the  mammalia 
thus  far  examined  is  circular,  which  adds  to  the  difficulty  of  dis- 
tinguishing the  blood  of  the  domestic  mammals  from  that  of  man. 
On  looking  at  Fig.  60,  it  will  be  seen  that  the  red  blood  corpuscles 
in  birds,  reptiles,  batrachia,  and  fishes  differ  from  those  of  man  and 
the  mammalia  generally  in  being  oval  in  form  and  in  exhibiting  a 
well-marked  nucleus,  and  in  being  much  larger. 

The  only  partial  exceptions  to  the  above  statement  are  offered  by 
the  oval  corpuscles  of  the  dromedary  and  llama ;  but,  as  will  be 
seen  from  Fig.  GO,  they  are  not  nucleated.  At  the  other  end  of 
the  vertebrate  series  we  find  a  further  exception,  in  the  nearly  cir- 
cular corpuscles  of  the  lamprey,  but  these  are  nucleated.  There 
can  be  no  difficulty,  therefore,  in  distinguishing  the  blood  corpuscles 
of  the  birds,  reptiles,  etc.,  from  those  of  mammals.  The  oval 
form,  and  the  presence  of  a  nucleus,  especially,  are  sufficient  to  de- 
cide positively  that   the  blood   containing  such  corpuscles  is   not 

'  For  the  method  of  measuring  tlie  blood  cor[mscles,  the  reader  is  referred  to  the 
Author's  Manual  of  Medical  .Jurisprudence,  2d  edition,  1896,  p.  66. 


RED  CORPUSCLES. 


189 


mammalian.     Such   knowledore  has  been  of  advantao;e   more   than 
once  in  assisting  in  the  detection  of  murder. 

The  most  important  use  of  the  red  blood  corpuscles  is  undoubt- 
edly as  carriers  of  oxygen.  Blood  vriW  absorb  ten  to  thirteen 
times  as  much  oxygen  as  water,  this  function  depending  entirely,  as 
yve  shall  see  presently,  upon  the  haemoglobin  of  Avhich  the  corpus- 
cles largely  consist.  In  concluding  our  account  of  the  red  blood 
corpuscles,  let  us  briefly  consider  their  origin,  at  least  so  far  as  is 
known,  for  there  is  no  doubt  their  life  is  of  limited  duration. 
Abundant  evidence  of  the  disintegration  of  the  red  blood  corpuscles 
is  seen  in  diiferent  parts  of  the  economy,  their  coloring  matter  more 


Fig.  60. 


Tyjiical  cliuraetiT 


f  vortL'brata.     (Kiekes.) 


or  less  broken  down  is  found,  for  example,  in  the  liver  and  spleen, 
and  which  we  shall  see  hereafter,  gives  rise  to  the  biliary  and  uri- 
nary pigments.  There  appears  to  be  but  little  doubt  that  in  the 
adult  the  formation  of  red  corpuscles  or  ha?matopoiesis,  as  the  pro- 
cess is  called,  takes  place  in  the  red  marrow  of  the  cancellous  tissue 
of  bones,^  the  corpuscles  being  developed  out  of  the  colorless 
nucleated  cells  of  the  latter. 

The  erythroblasts,  as  these  cells  are  called,  are  supposed  to  mul- 
tiply by  karyokinesis,  the  daughter  cells  so  produced,  then  elabo- 

^  Xeumann,  Archiv  der  Heilkunde,  Zelmter  Jahrgang,  1869,  s.  220.     Bizzozero, 
Centralblatt  fiir  die  Medicinischen  "Wissenschaften,  Seclister  Jahrgang,  1868,  s.  885. 


190  THE  BLOOD. 

rate  hsemoglobin  in  their  cj^toplasm,  and  subsequently  in  losing 
their  nucleus  become  red  corpuscles,  which,  in  turn,  pass  into  the 
general  circulation.  In  the  foetus,  however,  the  liver  and  spleen 
take  an  active  part  in  htematopoiesis.  It  is  quite  probable,  there- 
fore, that  they  may  still  in  the  adult  exert  some  influence  in  the 
production  of  red  blood  corpuscles,  as  well  as  the  red  marrow.  It 
may  be  mentioned  in  this  connection  that  at  the  end  of  the  third 
month  of  ftetal  life  three-fourths  of  the  red  blood  corpuscles  are 
still  nucleated.  As  development  advances,  however,  the  latter 
steadily  diminishes  in  number  until  they  finally  disappear,  being 
replaced  by  the  non-nucleated  ones  of  adult  life.  As  the  proper- 
ties of  the  red  blood  corpuscles  that  still  remain  to  be  described 
depend  upon  the  hremoglobin  that  they  contain,  their  further  no- 
tice will  be  deferred  until  the  subject  of  hsemoglobin  is  especially 
considered. 


CHAPTER  XI. 

THE  BLOOD.— {Continued.) 

The  white  corpuscles  discovered  by  Hewson  '  about  1 770,  as  their 
name  implies,  are  of  a  grayish,  whitish  color,  of  a  round  form,  and 
consist  of  a  mass  of  protoplasm  containing  granules.  A  cell  wall 
cannot  be  said  to  exist.  Chemically  the  wdiite  corpuscles  are  com- 
posed of  proteid  substances,  lecithin,  glycogen,  salts,  fat,  choles- 
terin.^ 

*When  the  blood  is  maintained  at  the  temperature  of  the  body 
the  form  of  the  white  corpuscle  is  seen  under  the  microscope  to  be 
constantly  changing,  alternately  protruding  and  retracting  its  body 
substance  in  an  amoebiform  manner  (Fig.  61).     By  adding  finely 


Fig.  61. 


Various  forms  assumed  by  the  white  corpuscles  of  the  blood.  Tlie  upper  row  represents  the 
white  corpuscles  of  man  ;  the  lower  row,  white  corpuscles  from  the  newt,  showing  changes  effected 
in  fifteen  minutes.     (Cakpexter.) 

powdered  indigo  to  serum  containing  white  corpuscles  the  manner 
in  which  they  feed  can  be  observed,  the  indigo  being  drawn  into 
the  body  of  the  corpuscle  by  the  retraction  of  its  amoeba-like  arms 
and  then  o-raduallv  absorbed  and  assimilated. 

The  white  blood  corpuscles  not  only  have  the  poAver  of  protrud- 
ing and  retracting  their  arms,  but,  like  the  amoeba  itself,  can  move 
from  place  to  place,  and  at  times  may  even  pass  through  the  walls 
of  the  blood  capillaries  into  the  surrounding  tissues,  hence  the  name 
of  "wandering  cells,"  sometimes  given  to  them. 

The  white  corpuscle  is  larger  than  the  red  one,  measuring  on  an 
average  the  -yi-Q  of  a  millimeter  (23V0  ^^  ^^  inch).  The  white  cor- 
puscles are  far  less  numerous  than  the  red  ones,  being  found  usually 
1  Works,  p.  282.  ^  HQppe.geyler,  Untei-suchungen,  Band  iv.,  s.  441. 


192 


TEE  BLOOD. 


Fig.  62. 


in  the  proportion  of  one  white  corpuscle  to  between  300  and  500 
red  ones.  This  proportion,  as  we  learn,  however,  from  the  obser- 
vations of  Hirst,^  varies  according  to  the  state  of  digestion  :  thus 
before  breakfast  the  proportion  being  about  1  to  1800,  one  hour 
after  breakfast  it  was  1  to  700,  before  dinner  1  to  1500,  after  din- 
ner, 1  o'clock,  1  to  400,  two  hours  later  1  to  1475,  after  supper,  8 
p.  M.,  1  to  550,  at  midnight  about  1  to  1200.  The  white  corpus- 
cles diflFer  also  in  many  other  respects  from  the  red  ones  :  thus  in 
the  manner  in  which  they  are  affected  by  various  reagents,  and  in 

the  way  in  which  they  adhere  to 
the  walls  of  the  vessels  in  which 
they  are  circulating  (Fig.  62),  the 
red  corpuscles  keeping  in  the  mid- 
dle of  the  stream. 

The  white  corpuscles  are  found 
also  in  lymph,  chyle,  pus,  and 
other  fluids  as  well  as  in  the  blood  ; 
the  more  general  name  of  leu- 
cocytes is  often  therefore  given  to 
them.  It  should  be  mentioned 
that  many  histologists  consider  the 
leucocytes  or  white  blood  corpus- 
cles as  being  of  three  kinds.  It 
is  claimed  by  those  holding  this 
view  that  the  white  corpuscles  dif- 
fer from  each  other  in  the  manner 
in  which  they  stain  A\itli  acid,  ba- 
sic, and  neutral  dyes,  or  according 
to  the  number  of  the  nuclei  they  may  contain,  or  to  the  amount  of 
amcebiform  movement  they  may  exhibit.  It  is  very  probable, 
however,  that  the  three  different  kinds,  so  called,  are  only  different 
stages  of  development  of  one  kind  of  white  corpuscle,  and  for  the 
present,  at  least,  they  will  be  so  regarded.  The  white  blood  cor- 
puscles originate  apparently  in  the  lympliatic  glands  and  in  the 
lymphoid  tissue  of  the  body,  generally,  whence  passing  into  the 
lymph  they  are  carried  into  the  blood.  As  a  confirmation  of  this 
view,  attention  may  be  called  to  the  fact  that  in  disease  of  the 
spleen  and  lymphatic  glands  the  white  corpuscles  may  increase  in 
number  to  such  an  extent  as  to  form  a  third  or  even  a  half  of  the 
corpuscular  part  of  the  blood.  Hence  the  light  color  of  the  blood 
in  such  circumstances  and  the  name  of  the  disease — leucocythemia. 
To  a  certain  extent  at  least,  however,  the  white  blood  corpuscles 
appear  to  be  reproduced  in  the  blood  itself  by  karyokiuesis.  At 
one  time  it  was  supjwscd  that  the  white  coiijuscles  in  the  course  of 
development  elaborated  red  coloring  matter  within  their  protoplasm, 
lost  their  nuclei,  and  finally  became,  very  much  in  the  same  man- 

'MuUer's  Archiv,  1856,  s.  174.     Lilienfeld.     Du  Bois  Eeymond,  Archiv,  1893, 
s.  560. 


A  small  venous  trunk,  a,  from  the  web  of 
the  frog's  foot,  h,  b.  Cells  of  pavement-epi- 
thelium, containing  nuclei,  d.  White  corpus- 
cles,   e.  Red  corpuscles.     (Carpenter.) 


WHITE  CORPUSCLES. 


193 


Fig.  63. 


ner  as  the  ervtliroblasts,  red  eorpuscles.  Much  indeed  might  still 
be  said  in  favor  of  this  view,  many  of  the  facts  of  comparative  an- 
atomy, embryology,  and  pathology  apparently  supporting  it.  It 
must  be  admitted,  however,  that  as  yet  we  do  not  know  positively 
what  becomes  of  the  M'hite  corpuscles,  whether  they  are  transformed 
into  some  other  kind  of  corpuscles,  or,  having  played  their  part  in 
the  economy,  simply  disintegate.  Various  functions  have  been  as- 
signed to  the  leucocytes  generally.  It  has  been  held  that  they 
promote  the  ab.sorptiou  of  fats  and  peptones  from  the  intestine,  that 
they  constitute  one  source  of  supply  of  proteid  material  to  the 
blood,  and  of  the  fibrin  ferment,  one  of  the  supposed  factors  in  the 
coagulation  of  the  blood,  that  they  are  phagocytes  and  in  feeding 
upon  pathogenic  bacteria  protect  the 
body  from  the  attacks  of  the  same,  etc. 
Until,  however,  the  life  history  of  the 
white  blood  corpuscles  is  known  from 
beginning  to  end,  their  uses  must  be 
to  a  great  extent  as  much  a  matter  of 
speculation  as  their  fate. 

It  has  already  been  mentioned  that 
the  white  corpuscles  are  not  confined 
to  the  blood,  being  also  found  in  the 
lymph,  chyle,  solitary  and  lymphatic 
glands,  and  in  the  spleen. 

The  solitary  glands,  as  we  have  suS^S^-^Cofi^^pi^tST?: 
already  noticed,  are  distributed  all  ^^S^,^^^' ^,1^^^^ 
through    the    alimentarv   canal:    the    ated  bv  the  lymph  and  formiug  the 

_^          '-J  i-i"               '            f  superficial  Ivmph-path  of  Frer.     c.  rvu- 

Feyer  S  l^atcheS,     which     consist    of     a  cleus  or  medullary  i.ortion  of  the  gland, 

1  n         T                 -.         -,              •,      T     ,  ill  the  center  of  which  the  section  of  a 

number  Ot    solitary  glands    united    to-  blood  vessel   may   be   seen.    The  path 

getlier,  are,  however,  limited  to  the  so- 
called  jejunum  and  ileum.  When  a 
section  of  one  of  these  solitary  or 
simple  lymphatic  glands  is  examined  microscopically  (Fig.  63)  it 
is  seen  to  consist  of  a  capsule  of  connective  tissue  from  which  pass 
inwardly  strands  forming  a  meshwork,  in  the  interior  of  which 
is  contained  the  so-called  adenoid  or  cytogenous  tissue.  These 
strands  of  connective  tissue  serve  to  support  the  capillary  blood 
vessels.  In  the  meshes  are  found  lymph  corpuscles  and  sometimes 
molecular  granules  and  small  oil  globules.  The  lymphatic  differs 
from  the  solitary  gland  in  that  its  meshwork  being  denser  in  the 
middle  than  at  its  sides,  the  distinction  of  the  medullary  and  corti- 
cal parts  is  better  marked  (Fig.  64).  Further  the  meshes  in  the 
lymphatic  gland  are  only  incompletely  filled  by  the  pulp,  free 
spaces  being  left  between  the  pulp  and  the  strands.  These  spaces 
communicate  on  the  one  hand  with  the  lymphatic  vessels  enter- 
ing the  gland,  and  on  the  other  with  the  lymphatics  leaving  it 
at  the  hilus.  The  afferent  and  efferent  lymphatic  vessels  and  these 
spaces  can  be  injected.  Probably  this  is  the  explanation  of  the 
13 


pursued  by  the  lymph  through  the  me- 
dullary portion  constitutes  the  deep  or 
secondary  lymph-path  of  Frey.  (Car- 
penter. ) 


194  THE  BLOOD. 

gland  appearing  after  injection  as  a  mass  of  vessels,  a  rete  mira- 
bile  between  and  continuous  with  the  lymphatics  passing  in  and 
out  of  it.  The  pulp  consists  principally  of  lymph  corpuscles,  these 
being  most  numerous  in  the  medullary  parts  of  the  gland,  Avhere 
the  blood  vessels  are  also  freely  distributed. 

The  lymph  or  chyle  passes  from  the  afferent  vessels  into  the 
spaces  left  between  the  pulp  and  the  strands,  and  comes  in  contact 

Avitli  the  lymph  corpuscles  and 

Fig.  64.  the   blood,  more    particularly 

in  the  medullary  parts  of  the 

gland  ;    after   circulating 

t  h  r  o  u  g  h    these    spaces    the 

"    \         I  V      lymph  or  chyle  passes  out  of 

^,.   '  '    '        ■  14-^     ^^^®  gland  at  the  hilus  by  the 

l|r  'f^\         efferent  lymphatic  vessels,  and 

^       so   passes   on   to  the  thoracic 

' -^  J  J  duct. 

'J  ;:-.   f).  The    researches    of  Klein,^ 

[i-  :  :* 'v'_  j  -  von  Recklinojhausen,"  and  oth- 

e  ^  ers  have  shown  that  the  walls 

Section  of  lymphatic  gland,  showing  o,  ff,  the  fi-  of    the     SCrOUS     SaCS,     like     the 
brous  tissue  which  forms  its  exterior.    6,  fc.  Super-  ^•,  i  ,         ^r>n 

ficial  vasa  infereutia.  c,c.  Larger  alveoli,  near  the  peritOUeum,  pieuia,  ClC,  COn- 
surface.    (i,  d.  Smaller  alveoli  of  the  interior,    e,  e.        -gi.    i„    „    nnneirlprnKlp  pvfpnt 

Fibrous  walls  of  the  alveoli.     (Caepenter.)  hlhl.,   LO    d    COllblueiauiC  tJALeiiL, 

of  the  adenoid  or  cytogenous 
tissue  just  mentioned,  which  enters  into  the  formation  of  the  solitary 
and  lymphatic  glands,  and  that  these  serous  sacs  communicate  by 
openings  or  stomata  with  the  lymphatics.  The  tonsils  also  appear 
to  consist  essentially  of  nodular  masses  of  lymphoid  tissue  em- 
bedded in  the  submucosa  of  follicles  of  the  mucous  membrane. 

We  have  already  seen  that  the  lymph  differs  from  the  blood 
quantitatively,  rather  than  qualitatively,  and  that  the  chyle  is  lymph 
with  the  products  of  digestion  added  to  it,  more  especially  of  the 
emulsified  fats  and  oils.  The  lymph  and  chyle  corpuscles,  which 
are  indistinguishaljle  from  the  white  (!orpuscles  of  the  blood,  seem 
to  consist  at  first  of  fatty  nuclei,  whicli,  acquiring  an  envelope 
through  diffusion  in  an  albuminous  fluid,  gradually  become  white 
corpuscles.  In  examining  the  chyle  of  the  lacteals  in  the  villi,  in 
the  mesenteric  glands,  and  in  the  thoracic  duct,  it  was  noticed  that 
the  so-called  molecular  base  of  tlic  chyle  consisted  largely  of  fatty 
matter,  and  that  the  chyle  corpuscles  were  probably  due  to  an  ag- 
gregation of  the  minute  bodies  forming  the  base  of  the  chyle.  It 
seems  probable,  therefore,  that  the  chyle  corpuscles,  or  white  cor- 
puscles of  the  l)lood,  are  elaborated  in  the  lymphatic  glands. 

In  addition  to  containing  white  corpuscles,  the  chyle  resembles 
an  early  stage  of  the  blood  in  other  respects,  thus  between  the  mes- 
enteric glands  and  thoracic  duct  it  will  coagulate — that  is,  separate 
into  clot  and  serum,  while  the  chyle  of  the  thoracic  duct  exhibits  a 
reddish  color. 

^Anatomy  of  the  Lymphatic  System,  1873.         ^Strieker's  Histology,  p.  215. 


THE  SPLEEX. 


195 


Spleen. — In  examinino;  the  structure  of  the  spleen  one  cannot  but 
be  impressed  with  its  great  similarity  to  a  lymphatic  gland.  Like 
the  lymphatic  gland,  the  spleen  (Fig.  65)  consists  externally  of  a 
fibrous  capsule,  from  which  pass  inward  numerous  strands,  consti- 
tuting the  so-called  trabecuhe,  in  the  meshes  of  which  is  contained 
the  splenic  pulp.  This  consists  of  white  blood  corpuscles,  of  red 
corpuscles  in  various  stages  of  development  or  disintegration,  of 
granular  matter  of  a  reddish-brown  hue,  blood  crystals,  iron,  etc. 
The  only  difference  between  the  spleen  and  a  lymphatic  gland  con- 
sists in  the  fact  that  the  cells  found  in  the  spleen  pass  directly  into 
the  blood. 


Fig 


Vertical  section  of  a  small  superficial  portion  of  the  bumaii  spleen.  Low  power.  A.  Peritonea 
and  fibrous  covering,  ft.  TrabecuUe.  c,  <■.  Malpighian  corpuscles,  in  one  of  which  an  artery  is 
.seen  cut  transversely,  in  the  other  longitudinally.    (/.   Injected  arterial  twigs,    e.  Sijleen-pulp 

(KOLLIKEE.) 

That  the  spleen  is  essentially  a  lymphatic  gland  seems  confirmed 
by  the  fact  that  when  it  is  small  in  man  or  an  animal,  the  lym- 
phatic glands  are  large,  and  vice  verm.  Xot  only  is  this  inverse 
ratio  observed  in  the  same  animal  but  also  in  different  species. 
Thus,  among  other  instances  observed  by  the  author,  in  the  manatee 
the  spleen  is  very  small  M^hile  the  glands  are  very  large,  M'hereas, 
in  the  sea  lion,  the  reverse  obtains.  This  view  of  the  nature  of 
the  spleen  is  confirmed  by  the  fact  that  it  can  be  removed  from 
animals  with  impunity,  the  lymphatic  glands  then  enlarging  and 
through  vicarious  action  apparently  performing  its  function,  and 
also  that  the  spleen  is  absent  in  the  lowest  of  vertebrates,  the  am- 
phioxus.  On  the  other  hand,  with  hypertrophy  of  the  spleen,  we 
have,  coincidently,  disease  of  the  bones  indicating  the  relationship, 
functionally,  between  the  two.     Indeed,  recent  observations^  render 

'  Laudenbach,  Cent  rail  )latt  fiir  Physiologie,  1896,  Band  ix.,  s.  1. 


196 


THE  BLOOD. 


it  probable  that  the  spleen  produces  red  blood  corpuscles  as  well  as 
leucocytes  which  becomes  intelligible  when  it  is  remembered  what 
has  already  been  said  as  to  the  influence  of  the  marrow  in  hsemato- 
poiesis. 

One  of  the  most  strikino;  peculiarities  of  the  spleen  is  its  great 
vascularity.  Not  only  does  a  large  quantity  of  blood  flow  into  the 
organ,  but  the  distribution  is  remarkable  inasmuch  as  capillaries  in 
certain  parts  are  absent,  the  blood  of  the  splenic  artery  passing 
then  directly  into  the  interstices  of  the  pulp  to  be  taken  up  by  the 


Fio.  m. 


Front  view  of  tlie  right  kidney  and 
suprarenal  body  of  a  fiill-growu  i'cetus. 
r,  V.  The  renal  vein  and  artery.  «.  The 
ureter,  a'.  The  .suprarenal  capsule,  the 
letter  i,s  placed  near  the  .sulcus  in  which 
the  large  veins  (;')  are  seen  emerging 
from  the  interior  of  the  organ.  (Allen 
Thomson.  ) 

veins,  a  type  of  circulation  that 
obtains  in  the  invertebrates.  It 
may  be  mentioned  in  this  con- 
nection that  the  so-called  Mal- 
pighian  corpuscles  attached  to 
the  branches  of  the  splenic  artery 
in  the  spleen  do  not  appear  to 
differ  essentially  in  their  minute 
structure  fr<jm  tliatof  the  solitary 
glands.  It  is  well  known  that 
during  digestion  the  spleen  slow- 
ly increases  in  size,  the  maximum 
being  attained  about  five  hours 
after  taking  food,  the  organ  then  slowly  shrinking  to  its  previous 
size.  It  has  also  been  shown  ^  that  the  spleen  contracts  and  re- 
laxes in  animals  in  a  rhythmical  manner  about  once  in  a  minute, 
the  movements  being  apparently  due  to  the  muscular  tissue  of  the 
capsule  and  trabeculie.  These  facts,  while  interesting,  do  not  throw 
any  light,  however,  upon  the  function  of  the  spleen.  The  spleen 
'C.  S.  Roy,  Journal  of  Physiology,  1881,  Vol.  iii.,  p.  203. 


Acrtieal  scetinn  of  suprarenal  capsule  of  man. 
1.  ('(irtex.  2.  .Medulla,  a.  Capsule.  6.  Layer  of 
external  cell-masses,  c.  Columnar  layer  (zona 
fasciculata).  d.  Layer  of  the  internal  cell- 
masses,  e.  Medullary  substance.  /.  Section  of 
a  vein.     (Cakpkntek.) 


SUPBAREXAL  CAPSULES.  197 

is  richly  supplied  by  branches  from  the  splanchnic  nerves  which 
appear  to  contain  both  vaso  constrictor  and  dilator  fibers/ 

Suprarenal  Capsules. — These  bodies  (Fig.  66),  often  also  called 
adrenals,  resemble  in  many  respects,  in  their  intimate  structure, 
lymphatic  glands.  Like  the  latter,  they  consist  (Fig.  67),  to  a 
great  extent,  of  trabecule,  in  the  ovoid  meshes  of  Avhich  are  im- 
bedded cells,  with  and  without  nuclei,  containing  granules,  oil,  and 
pigmentary  matter.  The  immense  number  of  nerves  distributed  to 
the  adrenals  is  one  of  their  most  remarkable  peculiarities.  The 
suprarenal  capsules  appear  to  be  essential  to  the  nutrition  of  the 
human  economy,  since  their  removal  in  animals  causes  death  in  a 
day  or  two,  or  even  in  a  few  horn's."  The  symptoms  preceding 
death  in  these  cases,  such  as  great  prostration,  muscular  weakness, 
loss  of  vascular  tone,  closely  resemble  those  of  Addison's  disease  in 
man,  due  to  pathological  changes  arising  in  the  adrenals.  From 
the  fact  that  removal  of  the  suprarenal  capsules  in  animals  is  fol- 
lowed by  death  and  that  Addison's  disease  in  man  is  benefited,  to 
some  extent  at  least,  by  the  use  of  adrenal  extracts,  it  has  been 
inferred  that  the  suprarenal  capsules  elaborate  some  material,  an 
internal  secretion,  which,  passing  into  the  blood,  profoundly  influ- 
ences nutrition.  Recent  researches^  render  it  probable  that  the 
material  so  elaborated  acts  more  especially  upon  the  vascular  and 
muscular  system,  stimulating  lioth  striated  and  unstriated  muscular 
fibers.  Injections  of  the  medullary  part  of  the  suprarenal  capsules 
into  the  veins  of  an  animal,  for  example,  prolong  the  contractions 
of  the  heart,  increase  blood  pressure  by  constricting  the  arterioles, 
and  stimulate  the  muscles  generally  to  great  activity. 

Thyroid  Body. — The  functions  of  the  thyroid  glands,  or  the  thy- 
roid ])ody  as  it  is  often  called  in  man,  on  account  of  the  glands  be- 
ing- united  in  the  latter  bv  a  band  or  isthmus  Iving;  in  front  of  the 
trachea,  may  be  appropriately  considered  in  this  connection,  as  they 
appear  to  influence,  to  some  extent  at  least,  ha?matopoiesis.  The 
thyroid  glands,  relatively  larger  in  the  fa?tus  and  in  the  infant  than 
in  the  adult,  measure  in  the  latter  condition  about  50  millimeters  (2 
inches)  in  length  and  30  millimeters  (1.2  inches)  in  breadth.  They 
consist  of  closed  vesicles  of  variable  size,  imbedded  in  a  connective 
tissue  which  supports  a  network  of  blood  vessels  and  lymphatics. 
The  vesicles  (Fig,  68)  are  lined  with  a  single  layer  of  cuboidal  epi- 
thelial cells,  and  appear  to  secrete  the  glairy  colloidal  fluid  found  not 
only  within  the  cells,  but  between  them.  It  is  well  known  that  the 
profound  disturbance  in  luitrition  following  the  removal  of  the  thy- 
roid glands  in  man  or  of  the  thyroid  accessory,  thyroid  and  parathy- 
roid glands  in  animals  *  is  so  great  as  to  soon  cause  death.     It  ap- 

'Schaefer,  Proc.  Koval  Societv,  1896,  Vol.  lix.,  Xo.  355. 

^  Brown  Sequard,  Comptes  rendiis  de  I'Ac.  des  Sciences,  Tome  xliii.,  1856,  pp. 
422,  5-12.     Szymonowicz,  Pfliiger's  Archi\\  Band  Ixiv.,  18%,  s.  97. 

^G.  Oliver  and  E.  A.  Schiifer,  Journal,  of  Physiology,  xviii.,  1895,  p.  ix.  Cy- 
bulski  and  Szvmonowicz,  Jahresberichte  tlber  Die  Forttchritte  der  Thier  Chemie, 
1895,  s.  379.  ' 

*Schifti  Untersucliungen  iiber  Die  Zuckerbildung  In  der  Leber,  etc.,  AViirzburg, 


198 


THE  BLOOD. 


Fig.  08. 


Group  of  glaud-vesicles  from  the  thyroid  gland 
of  a  child,  u.  Connective  tissue,  b.  Membrane  of 
the  vesicles,    c.  Epithelial  cells.     (Carpestek.  ) 


pears  to  hs  well  established  that  the  spasms,  convulsions,  emaciation 
following  extirpation  of  the  thyroids,  the  symptoms  of  myxoedema, 
cretinism,  cachexia,  thyreopriva  and  thyreoidectomica  cannot  only 
be  greatly  relieved,  but  death  averted  by  injecting  thyroid  extracts, 
feeding  with  the  fresh  gland  or  even  by  grafting  part  of  the  gland 

under  the  skin.^  Such  being 
the  case  it  would  appear  that 
tlie  thyroid  glands  richly  sup- 
plied with  blood  elaborate  from 
the  latter  a  material  which, 
passing  into  the  lymph  and 
thence  into  the  blood,  promotes 
the  general  nutrition  of  the 
body,  possibly  by  increasing 
the  number  of  red  corpuscles,^ 
or  by  destroying  some  toxic 
substance,  the  accumulation  of 
which  in  the  system  gives  rise 
by  autointoxication  to  the 
symptoms  following  thyreoidec- 
tomy and  cachexia  thyreopriva. 
While  the  composition  of  the 
colloidal  secretion  of  the  thy- 
roid glands  is  as  yet  only  im- 
perfectly known,  recent  researches  render  it  highly  probable  that 
its  most  active  constituent  is  thyroiodin,  or  iodothyrin  as  it  is  also 
called,-^  which  exists  in  the  glands  in  combination  with  proteid 
material,  and  is  characterized  by  the  great  resistance  it  oifers  to  the 
action  of  ordinary  chemical  agents.  To  this  colloidal  substance 
thyroiodin  must  bo  attributed  to  a  great  extent  at  least,  the  benefit 
derived  from  thyroid  extracts,  etc.,  as  administered  in  thyroid 
therapy.*  That  the  thyroid  glands  have  the  function  of  elaborating 
an  "  internal "  '  secretion  essential  to  nutrition,  as  held  by  the  older 
physiologists,"  is  rendered  also  probal>le  from  the  fact  as  we  have 
seen  of  the  liver  and  pancreas  elal)orating  internal  secretions  such 
as  glycogen,  urea,  and  a  glycolytic  ferment  respectively. 

1859,  s.  61.  Gley,  Archives  de  Phvsiologie  Normal  et  Pathologique,  5  Serie,  Tome 
iv.,  1892,  pp.  135,  311,  664.  Christiani,  Ibid.,  1893,  p.  39.  Vasale  et  Generali, 
Archives  Ituliennes,  De  Biologie,  Tomexxv. ,  1896,  Fas.  III.,  p.  459. 

1  Koclier,  Bucher,  ITorsley,  Murray,  Howitz  referred  to  by  Lauzon,  Klinische 
Yortnige,  1894. 

^Chittenden,  Science,  June,  1897,  p.  5. 

^  Baumann  und  Roos,  Zeitschrift  fiir  Phvsiol.  Chemle,  Band  21,  1896,  s.  319, 
s.  481,  Jiand  22,  1896,  s.  1.  Hutchinson,  Journal  of  Physiology,  Vol.  20,  1896, 
p.  474. 

*  Ewald,  Verhandlungen  des  Congresses  fiir  innere  Medecin,  1896,  s.  101. 

5  Bernard,  Rapport  sur  les  progres  et  la  marche  de  la  Phvsiologie  generale  en 
France,  1867,  p.  <5!>-  .         . 

^  Haller,  Elementa  Physiologiie,  Tomus  iii.,  1766,  p.  400:  "  Liquorem  peculi- 
arem  in  ea  glandula  parari,  qui  receptns  venulis  sanguini  reddatur,  qupe  etiam 
lienis  tS:  thymi  sit  utilitas,  ipse  Ruysciiius  .Vutumavit." 


THE  THYMUS  GLAXD. 


199 


The  Thymus  Gland. — The  thymus  gland  appears  in  the  embryo 
first  as  a  solid  body,  but  soon  becomes  a  tube  closed  at  both  ends 
and  filled  with  granular  matter.  From  this  tube  (Fig.  68)  there 
bud  out  at  intervals,  on  either  side,  hollow  lobular  processes,  the 
cavities  of  which  communicate  with  that  of  the  central  axis.  The 
thymus  in  the  adult  consists  of  a  series  of  such  oifshoots  or  lobules 
united  by  connective  tissue  and  opening  into  the  central  tube,  to 
which,  however,  there  is  no  outlet.     Each  lobule  (Fig.  69)  consists 

Fig.  60. 


Section  of  loi'ulc  of  thymus. 


of  an  external  fibrous  capsule  which  sends  prolongations  into  its 
interior  consisting  of  acini,  in  the  meshes  of  which  are  seen  the 
thymus  substance.  This  contains  lymph  corpuscles,  spheroidal 
granular  bodies,  and  concentric  corpuscles.  In  the  expressed  thy- 
mus juice  are  found  corpuscles  which  are  indistinguishable  from 
those  of  the  fluids  of  the  lymphatic  glands.  The  th^^uus  gland,  in 
its  whole  structure,  resembles  very  much  a  Peyer's  patch.  The 
functions  of  the  thymus  gland  are  unknown.  It  is  possible  that  it 
elaborates,  like  other  ductless  glands,  an  internal  secretion  that  in 
some  way  promotes  nutrition,  and  especially  in  early  life,  since  it 
diminishes  in  size  after  puberty. 

The  blood  contains,  as  already  mentioned,  in  addition  to  the 
red  and  white  corpuscles,  other  formed  elements,  the  blood  plates  of 
Hayem.^  These  are  minute  bodies,  though  attaining  sometimes  a 
size  of  the  ^i^  of  a  mm.  (45V0"  ^^  '^°  inch)  in  diameter,  circular  in 
form  and  homogeneous  in  structure.  Much  difference  of  opinion 
still  prevails  among  histologists  as  to  the  nature  of  the  blood  plates. 

1  Comptes  Rendiis,  T.  86,  p.  58,  1878. 


200  THE  BLOOD. 

Some  regard  them  as  a  distinct,  third  kind  of  corpuscle,  others  as 
only  the  nuclei  of  the  disintegrated  leucocytes.  The  latter  view  is 
based  not  only  upon  morphological  grounds  but  upon  the  fact  of  the 
blood  plates  containing  the  same  kind  of  nucleo-albumin  ^  as  the 
nucleus  of  the  leucocytes.  Apart  from  contributing  nucleo-albu- 
min to  the  blood  whose  significance  is  speculative  and  of  the  sup- 
posed use  in  the  production  of  tlie  fibrin  ferment,  the  function  of 
the  blood  plates  is  entirely  unknown. 

1  Lilienfeld,  Du  Bois  Eeymond,  Archiv  fiir  Physiologie,  1893,  s.  560. 


CHAPTER    XII. 

THE  Bl.OO'D.— {Continued.) 

One  of  the  most  interesting  properties  of  the  blood  is  its  power 
of  coagulation,  that  is  of  separating  into  clot  and  serum.  Before 
coagulation  the  blood  consists  of  the  liquor  sanguinis  or  plasma 
and  the  corpuscles ;  after  coagulation  it  ^vill  be  found  that  the  cor- 
puscles are  entangled  in  a  fine  network  consisting  of  the  meshes  of 
the  coaguated  fibrin,  the  two  constituting  the  clot  or  crassamen- 
tum,  while  the  proteids,  salts,  and  water  remain  together  as  the 
serum.  It  is  important  to  notice  that  the  liquor  sanguinis,  or  tlie 
plasma,  is  not  identical  with  serum,  liquor  sanguinis  being  serum 
with  the  addition  of  fibrinogen,  serum  liquor  sanguinis  without 
fibrinogen.  Serum  differs  also  from  what  are  known  as  serous 
effusions,  which  are  due  to  transudations,  not  to  coagulation. 


Blood. 


Before  coagulation. 

r  Water 
J    Salts 
1    Proteid 


Liquor 
sauffuini 


Corpuscles 


[  Fibrinogen 


After  coagTilation. 

Serum. 
I    Clot. 


When  the  blood  is  allowed  to  flow  into  a  tolerably  deep,  smooth 
vessel,  according  to  Xasse/  in  from  about  one  minute  and  forty-five 
seconds  to  six  minutes  a  gela<tinous  layer  will  be  seen  to  form  on 
its  surface  ;  in  from  two  to  seven  minutes  the  sides  of  the  vessel  are 
covered  with  a  similar  layer,  and  in  from  seven  to  sixteen  minutes 


Fig.  70. 


Fig.  71. 


Bowl  of  recently  coagulated  blood,  showing 
the  whole  mass  uniformly  solidified.     (Dal- 

TON.) 


Bowl  of  coagulated  blood,  after  twelve^ours 
showing  the  clot  contracted  and  floating  in  the 
fluid  serum.     (Daltox.) 


the  whole  of  the   blood   becomes  .jelly-like  (Fig.    70) ;   gradually 
there  exudes  from  the  contracting  jelly-like  mass,  drop  by  drop,  a 

'Wagner,  Physiologie,  184*2,  Band  i.,  s.10-1. 


202 


TSE  BLOOD. 


fluid,  the  serum,  and  in  from  ten  to  twelve  hours  the  coagulation  is 
complete — that  is,  the  separation  of  the  blood  into  clot  and  serum 
(Fig.  71).  The  contracted  jelly-like  red  mass,  the  clot,  being 
heavier  (specific  gravity  of  corpuscles,  1.088),  usually  falls  to  the 
bottom  of  the  straw-colored  or  reddish  liquid,  the  serum  (specific 
gravity,  1.028),  surrounding  it,  and  which  has  exuded  from  it. 

Usually,  according  to  Milne  Edwards,^  the  clot  retains  about  one- 
fifth  of  the  entire  volume  of  the  serum  ;  this  should  be  remembered 
when  the  proportion  of  clot  to  serum  is  estimated  ;  it  being  generally 
stated  that  they  are  equal.  When  the  coagulation  has  been  slow, 
the  clot  will  be  found  to  be  firm ;  on  the  other  hand,  when  the  co- 
agulation has  been  rapid  the  clot  is  soft.  When  the  blood  coagu- 
lates slowly,  and  so  remains  fluid  for  some  time,  the  red  corpuscles, 
on  account  of  their  weight,  sink  and  settle  at  the  bottom  of  the 
clot ;  the  upper  part  of  the  clot  will  be,  therefore,  much  lighter  in 
color  than  the  lower,  and,  when  white,  is  known  as  the  buffy  coat 
(Fig.  72) ;  it  is  almost  always  seen  in  the  blood  of  the  horse,  which 
coagulates  slowly,  while  it  is  absent  in  the  pigeon,  in  which  the 
blood  coagulates  almost  instantaneously. 


Length  of  Time  of  Coagulation. 


Animal. 

Man 

Horse 

Ox 

Dog 

Sheep 

Hog 


Minutes. 

Animal. 

Minutes. 

.2    to  16 

Rabbit 

•    J  to  1^ 

.5    to  13 

Lamb 

.   ^  to  1 

.2    to  12 

Duck 

.   J  to  2 

.     ^  to    3 

Fowl 

.   J  to  IJ 

.     ^to    U 

Pigeon 

.  almost 

instantaneously. 

.     h  to    U 

When  contraction  of  the  clot  takes  place  most  rapidly  at  the 
edges,  these  curl  up  and  the  upper  surface  becomes  concave  or  cup- 
ped (Fig.  73).     For  many  years  it  was  supposed  that  the  buflpy  coat 


Fig.  72. 


Fig.  73. 


Vertical  section  of  a  recent  coagulum,  show- 
ing the  greater  accumulation  of  blood  globules 
at  the  bottom.     (Dalton.) 


Bowl  of  coagulated  blood,  showing  the  clot 
bulled  and  cujiped. 


was  characteristic  of  inflammation,  whereas  it  is  now  known  that 
the  buffy  coat  is  also  present  in  diseases  of  a  totally  opposite  char- 
acter— in  clilorosis,  for  example,  it  depending  here  upon  a  diminu- 

1  Physiologic,  Tome  i.,  p.  124. 

^Tluikrah,  Inquiry  into  the  Nature  of  Blood,  1819,  p.  29. 


COAGULATION  OF  THE  BLOOD.  203 

tion  of  the  blood  corpuscles.  It  is  obvious  that  bleeding-  in  such 
cases  would  only  increase  the  bufFy  coat  by  diminishing  still  further 
the  corpuscles,  and,  when  it  is  remembered  that  bleeding  was  once 
the  sovereign  remedy  for  inflammation,  one  can  readily  appreciate 
the  number  of  lives  that  must  have  been  sacrificed  through  the  mis- 
taken idea  of  the  buify  coat  being  invariably  due  to  inflammation. 

Indeed,  the  formation  of  the  buffy  coat,  as  shown  by  the  re- 
searches of  Polli,^  appears  to  be  simply  a  question  of  time,  depend- 
ing upon  the  coagulation  being  retarded  or  accelerated. 

It  is  well  known  that  there  are  various  circumstances  which 
modify  the  coagulation  of  the  blood.  Thus,  blood  flowing  from  a 
small  orifice  coagulates  more  quickly  than  when  flowing  from  a  large 
one,  and  more  quickly  when  it  is  received  in  a  shallow  rough  vessel 
than  when  in  a  deep  smooth  one.  Blood  coagulates  more  rapidly 
in  a  vacuum  than  in  the  air.  Kapid  freezing  prevents  the  coagu- 
lation of  the  blood  ;  this  will  take  place,  however,  after  careful  thaw- 
ing.    This  fact  is  of  importance  from  a  medico-legal  point  of  view. 

Elevation  of  temperature  between  0°  C  and  60°  C.  (32°  and 
140°  F.)  increases  the  rapidity  of  coagulation.  Chemical  sub- 
stances, like  solutions  of  sodium  and  magnesium  sulphate,  when 
mixed  with  blood  will  retard  its  coagulation,  while  sodium  or  potas- 
sium oxalate  when  added  to  saturation,  as  we  shall  see  presently, 
will  prevent  coagulation  altogether.  Menstrual  blood,  while  clot- 
ting in  the  uterus,  is  kept  in  a  more  or  less  fluid  condition  in  the 
vagina,  by  the  mucus  of  the  latter.  In  this  connection  may  be 
mentioned  also  the  well-known  fact  as  yet,  however,  unexplained, 
that  human  blood  will  remain  in  the  alimentary  canal  of  the  leech 
for  days  and  weeks  without  coagulating. 

The  blood  not  only  coagulates  outside  the  body,  but  also  after 
death  within  it ;  less  rapidly,  however,  and,  as  a  rule,  in  from 
twelve  to  twenty-four  hours  after  death.  It  is  not  unusual,  also, 
during  life  to  find  clots  in  the  heart  and  other  parts  of  the  vascular 
system.  As  it  is  often  important  to  be  able  to  distinguish  an  ante- 
mortem  from  a  post-mortem  heart-clot,  it  may  be  stated  that  the 
former  are  whiter,  denser,  and  adhere  more  closely  to  the  walls  of 
the  heart  than  the  latter.  Coagula  are  also  found  when  an  artery 
is  ligated,  in  the  enlarged  veins  of  hemorrhoids,  in  the  varicose 
veins  of  the  extremities.  Usually  the  blood  coagulates  when  ef- 
fused into  the  areolar  tissue  or  the  cavities  of  the  body.  It  is  an 
interesting  fact,  however,  that  the  blood  may  remain  fluid  in  the 
serous  cavities  for  days  and  weeks  at  a  time.  When  coagula  are 
formed  in  the  heart,  and  being  swept  into  the  circulation  are  carried 
thence  into  the  small  vessels  of  the  brain,  etc,  they  constitute  what 
are  known  as  emboli.  When  the  blood  coagulates  in  the  economy 
it  acts  as  a  foreign  body,  but  is  usually  absorbed,  though  this  may 
take  a  long  time.  The  corpuscles  first  disappear,  then  the  fibrin 
softens,  breaks  down,  and  is  finally  carried  away. 

'Annali  Universali  di  Medicina,  1843,  p.  249. 


204  THE  BLOOD. 

The  coagulability  of  the  blood  is  nature's  cure  for  hemorrhage, 
and  when  this  power  is  diminished  or  wanting  we  have  the  hem- 
orrhagic diathesis,  where  the  slightest  wounds  are  followed  by 
severe,  and  sometimes  fatal,  hemorrhage. 

From  time  immemorial  various  explanations  have  been  offered  of 
the  coagulation  of  the  blood.  A  favorite  one  has  been  that  of  the 
blood  being  maintained  in  the  body  in  a  liquid  condition  through 
the  influence  of  life.  Apart  from  this  being  no  ex]>lanation  at  all, 
•  but  simply  a  statement  of  the  phenomena  to  be  explained,  it  is  not 
even  a  fact,  as  Ave  have  seen  that  the  blood  coagulates  in  the  living 
body.  In  the  last  century  it  was  generally  held  that  what  we  call 
fibrin  was  produced  in  some  way  at  the  expense  of  the  corpuscles, 
which  run  together  in  coagulation,  etc.  Petit,  Da  vies,  and  Hewson,^ 
however,  held  that  coagulation  was  due  to  some  distinct  substance 
independent  of  either  the  corpuscles  or  the  serum,  and  Hewson  per- 
formed several  experiments  to  prove  that  coagulation  was  due  to 
the  fibrin.  For  example,  Hewson  -  added  a  little  sodium  sulphate 
to  fresh  blood,  which  prevented  coagulation.  After  the  mixture 
had  remained  standing  some  time  the  corpuscles  sank  to  the  bottom, 
the  clear  fluid  which  remained  on  top  was  then  decanted,  twice  its 
quantity  of  water  was  then  added  to  this,  when  the  fibrin  coagulated. 
On  another  occasion,  this  most  able  observer^  tied  the  jugular  veins 
at  the  sternum  of  a  dog  just  dead,  and  hung  his  head  over  the  edge 
of  a  table,  so  the  ligatures  might  be  higher  than  the  head.  The  upper 
part  of  the  vein  became  transparent,  the  red  corpuscles  sinking  ;  he 
then  tied  the  vein,  separating  the  clear  from  the  red  part,  and  let  the 
clear  part  out,  which  was  fluid,  but  coagulated  soon  after.  These 
experiments  showed  that  the  coagulation  was  due  to  the  fibrin,  but 
they  did  not  demonstrate  that  this  fibrin  did  not  come  from  the 
corpuscles,  which  was  the  view  that  prevailed  at  that  time.  To  do 
this  it  was  necessary  to  show  that  the  corpuscles  were  unaffected  to 
coagulation. 

With  reference  to  determining  this  point,  Johannes  Miiller,^  the 
great  Berlin  physiologist,  in  1832  experimented  in  the  following 
ways  :  He  added  a  little  solution  of  sugar  to  frog's  blood,  which  re- 
tarded the  coagulation,  and  then  filtered  the  mixture ;  the  cor- 
puscles, which  are  very  large,  were  retained  in  the  filter,  and  the 
clear  fluid  which  passed  through  coagulated.  Milller  then  showed 
that  in  blood  which  was  defibrinatcd  by  whipping,  and  therefore 
incoagulable,  that  the  corpuscles  were  not  altered  in  any  appreciable 
manner ;  and  further,  that  when  blood  to  wdiich  had  been  added 
serum  (which  separated  the  corpuscles  from  each  other)  was  ob- 
served under  the  microscope  coagulating,  the  corpuscles  were  seen 
to  remain  intact. 

Inasmuch  as  the  white  stringy  substance  appearing  at  the  moment 

1  Milne  Edwards,  op.  cit.,  Tome  i.,  p.  119. 

2  Works,  p.  12.  3 Ibid.,  p.  32. 
*  Physiology  translated  by  Baly,  1840,  Vol.  1st,  p.  123. 


COAGULATION  OF  THE  BLOOD.  205 

of  coagulation,  Avhicli  we  call  filnnu,  cviJently  does  not  exist  as 
such  in  the  blood  before  coagulation,  it  remains  to  be  determined,  if 
possible,  under  what  form  it  then  does  exist.  If  blood  be  drawn 
into  a  concentrated  solution  of  sodium  sulphate  to  prevent  its  co- 
agulation, and  sodium  chloride  be  added  to  the  mixture  in  the  pro- 
portion of  ten  per  cent.,  a  whitish,  pasty  substance  is  thrown  down, 
amounting  to  about  25  parts  per  lUOO  of  the  blood  used,  and  called 
by  Denis/  who  first  described  it,  plasmin,  and  which,  together  with 
serin,  constitutes  blood  albumin.  Xow,  when  plasmin  is  redis- 
solved  in  water,  the  solution  splits  into  fibrinogen  3  parts,  and  para- 
globulin  22  parts,  the  former  coagulating,  the  latter  remaining 
liquid.  It  would  appear,  therefore,  that  fibrin  exists  in  the  blood 
combined  with  paraglobulin,  as  plasmin  or  some  form  closely  allied 
to  it ;  and  further,  as  with  the  withdrawal  of  the  plasmin  from  the 
blood,  the  latter  loses  its  power  of  coagulating,  the  serin  remaining 
liquid,  that  coagulation  of  the  blood  consists,  first,  in  the  splitting 
of  albumin  into  serin  and  plasmin,  and  secondly,  in  the  latter 
splitting  into  fibrin  and  paraglobulin,  or  of  the  breaking  up  of  al- 
bumin directly  into  serin,  fibrin,  and  paraglobulin. 

On  the  other  hand,  the  observation,  made  many  years  ago  by 
Buchanan,^  that  two  fluids,  like  that  of  hydrocele  and  ascites,  or  of 
ascites  and  pleurisy,  when  added  together,  coagulate,  though  when 
separate  show  no  such  tendency,  has  led  many  to  infer  that  the 
production  of  fibrin  is  rather  due  to  the  union  of  substances  in 
the  blood  than  to  the  decomposition  of  the  same,  as  just  explained. 
Indeed,  according  to  Schmidt,^  two  such  principles  actually  do  exist 
in  the  blood,  a  fibrinoplastic  sul)stance,  paraglobulin,  and  a  fibri- 
nogenous  one,  fibrinogen,  whose  union  brought  about  by  the  pres- 
ence of  a  ferment  at  the  moment  of  coagulation  constitutes  fibrin. 

Paraglobulin  can  be  readily  obtained  from  the  serum  of  the 
blood  through  precipitation  by  the  addition  of  sodium  chloride  in 
excess,  and  fibrinogen  in  the  same  way  free  from  the  liquor  san- 
guinis, in  which  coagulation  has  been  prevented  l)y  the  addition  of 
magnesium  sulphate,  and  the  corpuscles  have  been  removed  by 
filtration. 

Xow,  while  it  is  an  interesting  fact  that  if  paraglobulin  in  a 
saline  solution  be  added  to  eitlier  fibrinogen  or  hydrocele  fluid,  or  if 
fibrinogen  as  obtained  either  from  the  liquor  sanguinis  or  hydrocele 
fluid  be  added  in  saline  solution  to  serum,  fibrin  will  be  produced, 
it  does  not  necessarily  follow  that  such  a  union  as  that  of  para- 
globulin and  fibrinogen  actually  takes  place  in  the  blood  at  the 
moment  of  coagulation.  Indeed,  it  is  yet  to  be  proved  that  para- 
globulin exists  as  such  in  the  clot,  seeing  that  if  we  obtain  it  from 
the  serum  it  must  be  assumed  that  it  exists  in  excess  partly  in  the 
serum  and  partly  in    the  clot.     Again,  as  under  certain  circum- 

^  Annales  des  Sciences  Xaturelles  (iv. ),  p.  25. 
^Proc.  of  Glasgow  Philos.  Soc,  1845. 

"Du  Bois  Eevmond,  Archiv,  1861,  s.  545;  1802,  s.  428.  Pfliiger's  Aa-chiv, 
1872,  s.  413  ;  1875,  s.  291  ;  1876,  s.  515. 


206  THE  BLOOD. 

stances,  parao:lobulin  when  mixed  witli  fibrinogen  does  not  produce 
fibrin,  it  is  still  further  assumed  that  the  presence  of  a  ferment  is 
necessary  to  eiFect  the  union  of  the  two  filn'in  factors.  As  a  matter 
of  fact,  an  aqueous  extract  can  be  obtained  from  the  serum  by  co- 
agulating the  latter  with  alcohol,  allowing  the  mixture  to  stand, 
drying  and  pulverizing  the  clot,  and  then,  adding  water  and  filter- 
ing, which,  when  added  to  fibrinogen  will  cause  the  coagulation  of 
the  latter  like  a  ferment.  According  to  Schmidt,  such  a  ferment  is 
derived  from  the  disintegration  of  the  white  corpuscles,  the  latter, 
as  is  well  known,  being  always  present  in  sj)ontaneously  coagulable 
fluids  and  very  abundant  if  the  coagulation  is  marked. 

It  was  soon  demonstrated,  however,  that  the  Schmidt  theory  of 
coagulation  was  untenable,  Fredericq/  Hammarsten,^  among  others, 
proving  that  the  clot  was  due  to  the  coagulation  of  the  fibrinogen 
in  the  presence  of  a  ferment,  the  paraglobulin  not  entering  into  the 
formation  of  the  clot  at  all. 

It  has  been  shown,  however,  in  recent  years,  by  Arthus  and 
Pages,^  that  if  potassium  or  sodium  oxalate  be  added  to  freshly 
drawn  blood  in  sufficient  quantities  to  precipitate  its  calcium  salts, 
coagulation  A\ill  be  prevented,  but  that  with  the  addition  again  of 
a  soluble  calcium  salt  coagulation  will  take  place  immediately. 
The  Schmidt-Hammarsten  theory  has  been,  therefore,  still  further 
modified  so  as  to  take  into  account  the  influence  exerted  by  the  cal- 
cium salts  in  the  production  of  coagulation.  Thus,  according  to 
Pekelharing,^  after  the  blood  has  been  shed  a  fibrin  ferment  is 
formed  through  the  union  of  a  nucleo-albumin  derived  from  leuco- 
cytes and  blood  plates  with  calcium.  At  the  moment  of  coagulation 
the  calcium  leaves  the  nucleo-albumin  and  unites  with  the  fibrinogen 
or  part  of  it  to  form  an  insoluble  calcium  compound,  fibrin.  This 
view  is  based  upon  the  fact  that  coagulation  will  take  place  if 
nucleo-albumin,  together  with  calcium  salts,  be  added  to  fibrinogen 
solutions,  but  will  not  take  place  if  nucleo-albumin  or  calcium  salts 
be  added  alone.  A  still  more  recent  theory,  that  of  Lilienfeld,^ 
regards  the  fibrinogen  as  giving  rise  under  the  influence  of  leuco- 
nucleiu  to  thrombosin,  which  combining  Avith  calcium  forms  the 
fibrin,  the  leuco-nuclein  being  derived  from  a  proteid  substance, 
nucleo-histon,  obtained  from  the  leucocytes  and  blood  plates.  It 
would  appear,  therefore,  that  the  phenomena  of  coagulation  is  essen- 
tially that  of  the  union  of  calcium  with  fibrinogen,  through  the  influ- 
ence of  a  third  factor.  Either  a  nucleo-albumin  unites  with  calcium, 
and  the  latter  then  unites  with  fibrinogen,  or  a  nucleo-albumin 
develops  out  of  fibrinogen  thrombosin,  and  the  latter  unites  with 
calcium.     It  may  be  added  that,  according  to  these  theories,  blood 

1  Hoppe-Seyler  :  Physiologie  Chemie,  1879,  s.  416. 
2PHii}<er'.s  Archiv,  Band  xix.,  s.  503. 

3  Archives  de  Physiologie  Normal  et  Pathologique,  5  S^rie,  Tome  2,  1890,  p. 
739. 

*  Untei-suchungen  iiber  Das  Fibrin  ferment.     Amsterdam,  1892,  s.  15. 
5  Du  Bois  Reymond's  Archiv  fiir  Pliysiologie,  1893,  s.  560. 


COAGULATION  OF  THE  BLOOD.  207 

does  not  coao;nl ate  durin<i'  life  within  the  vessels,  because  the  ferment 
being  continually  destroyed  or  changed  does  not  exist  at  any  one 
moment  in  sufficient  quantity  to  produce  this  effect.  When  blood 
is  shed,  however,  a  relatively  large  amount  of  ferment  being  formed, 
coagulation  takes  place.  Apart,  however,  from  the  insufficiency 
of  the  explanation,  there  still  remains  the  fact  entirely  unaccounted 
for,  that  the  blood  under  certain  circumstances  does  coagulate  dur- 
ing life  within  the  vessels.  Admittiuo-  that  either  or  both  of  these 
theories  be  true,  for  they  differ  but  little,  it  cannot  be  said  that  the 
cause  of  coagulation  is  explained.  At  best,  they  only  establish 
what  takes  place  during  coagulation,  not  its  cause. 


CHAPTER    XIII. 

THE    BhOOB.— {Continued.) 

We  have  seen  that  the  blood  contains,  either  directly  or  indirectly, 
all  the  proximate  principles  of  which  the  body  is  composed,  includ- 
ing also  the  excrementitious  matters,  and  that  the  food  furnishes 
the  materials  out  of  which  the  vital  fluid  is  elaborated. 

As  the  composition  of  the  blood  must  therefore  vary  in  different 
individuals,  and  even  in  the  same  person  from  day  to  day  and  from 
hour  to  hour,  anything  more  than  an  approximate  analysis  cannot 
be  expected.  The  discrepancies  as  offered  by  the  analyses  of  dif- 
ferent chemists  are  due  not  only  to  this  cause,  but  to  the  various 
methods  made  use  of  by  them. 

As  the  object  of  an  analysis  of  the  blood  from  a  physiological 
point  of  view  is  to  show  not  only  the  ultimate  chemical  elements 
entering  into  its  composition,  but  the  manner  in  which  these  exist 
in  the  blood,  it  will  be  readily  understood  that  the  investigation  is 
an  extremely  difficult  one. 

While  it  is  not  necessary  to  describe  in  detail  the  analyses  of  the 
blood  that  have  been  made  by  different  chemists,  it  seems  proper 
that,  at  least,  attention  should  be  called  to  the  general  methods  of 
investigation  made  use  of  at  the  present  day. 

During  the  last  and  preceding  century  a  number  of  observations 
were  made  by  which  it  was  shown  that  the  blood  consisted  of  dif- 
ferent principles.  Thus  Harvey  discovered  the  proteid,  Malpighi 
and  Ruyscli  the  fibrin,  Guglielmini  and  Menghini  some  of  the  salts, 
Badia  the  iron,  Rouelle  the  soda,  etc. 

Passing  over  these  early  and  isolated  observations,^  it  may  be 
said  that  Macquer,  a  little  more  than  a  century  ago,  made  the  first 
analysis  of  the  blood  as  a  whole.  With  improved  methods  of 
chemical  investigation  the  blood  was  more  successfully  analyzed  by 
Berzelius  in  1808.  Some  years  later,  1823,  Prevost  and  Dumas  ^ 
published  the  results  of  their  elaborate  researches  upon  the  consti- 
tution of  the  blood,  and  as  their  investigations  have  served  as  the 
starting-point  for  later  analyses  let  us  briefly  review  the  method 
employed  by  these  eminent  chemists. 

The  blood  to  be  analyzed  is  received  into  two  equal  vases,  that 
of  one  vase  is  whipped  so  as  to  obtain  the  fibrin,  which,  when  en- 
tirely separated,  is  weighed.  Tlie  blood  in  the  other  vase  is  set 
aside  to  coagulate — that  is,  to  separate  into  clot  (fibrin  and  corpus- 
cles) and  serum  (proteids,  salts,  water).     The  clot  and  scrum  are 

'Milne  Edwiirds,  Physiologic,  Tome  i.,  p.  141. 

2  Ann.  de  Chemie  et  de  Physique,  1823,  Tome  xxiii.,  p.  50. 


ANALYSIS  OF  THE  BLOOD. 


209 


then  separated  aud  desiccated  so  as  to  obtain  the  amount  of  water 
in  them,  and  therefore  in  the  blood  of  the  second  vase.  As  the 
clot  consists  of  fibrin  and  corpuscles,  if  we  subtract  from  the  clot 
the  fibrin  obtained  from  the  blood  of  the  first  vase,  the  remainder 
will  give  the  quantity  of  the  corpuscles  in  the  blood  of  the  second 
vase,  or  one-half  the  quantity  in  the  whole  blood  examined.  Hav- 
ing determined  then  the  fibrin,  water,  and  corpuscles,  there  remains 
the  desiccated  serum  of  the  second  vase  to  ])e  analyzed  for  the  pro- 
teids  and  the  salts  ;  the  latter  are  determined  by  ordinary  chemical 
analysis.  Becquerel  and  Rodier  determined  the  amount  of  proteids 
by  treating  the  desiccated  scrum  with  boiling  water,  which  separates 
the  undetermined  extractive  matters  and  soluble  salts,  and  then  with 
alcohol,  which  dissolves  the  fats,  the  remainder  being  the  proteids.^ 
Figuier^  suggested  the  improvement  of  estimating  the  corpuscles 
by  adding  to  the  defibrinated  blood  twice  its  volume  of  a  solution 
of  sodium  sulphate  and  then  filtering,  the  saline  retaining  them  on 
the  filter ;  any  sodium  sulphate  that  remains  on  the  filter  being  re- 
moved by  boiling  water.  Figuier's  method  of  estimating  the  cor- 
puscles can  also  be  used  as  confirmatory  of  that  of  Dumas,  the 
quantity  of  the  corpuscles  being  estimated  in  their  dry  condition. 


Composition  of  the  Blood, 


Water 

Globules 

Proteids 

Fibrin 

Serolin 

Cholesterin 

Sodium 

Potassium 

Sodium 

Magnesium 

Sodium 
Potassium 


Free  Soda 
Magnesium 


f  Oleate 

<  Margarate 
(  Stearate 

-  Chloride 

(  Carbonate 

<  Sulphate 

[  Phosphate 


781.600 

135.000 

70.000 

2.500 

0.025 

0.125 

1.400 


3.500 


I  Sulphate 
I  Phosphate 

Calcium  phosphate   . 

Iron      .... 

Extractives  undetermined' 


.850 


0.550 
2.450 


1000.000 


The  general  results  of  an  analysis  of  the  blood  by  such  a  method 
as  that  just  given  may  be  seen  from  that  taken  from  Becquerel  and 
Rodier's  work,  and  which  undoubtedly  gives  a  very  fair  idea  of  the 

'  Traite  de  chiraie  de  pathologique,  p.  20.     Paris,  1854. 
2  Ann.  de  Chemie,  et  de  Phys.,  1844,  3me  serie,  Tome  xi.,  p.  506. 
'Eecent  analyses  have  shown  that  these  extractives  consist  of  traces  of  dextrose, 
urea,  lecithin,  cholesterin. 

14 


210  THE  BLOOD. 

average  composition  of  the  blood  from  a  purely  chemical,  and,  in- 
deed, to  a  certain  extent,  from  a  physiological  point  of  view  also. 
It  will  be  noticed  at  once,  however,  that  in  this  analysis  of  1000 
jjarts  of  blood,  there  are  present  only  135  parts  of  corpuscles; 
whereas,  anyone  who  is  familiar  with  the  appearance  of  living 
blood  under  the  microscope  knows  that  the  corpuscles  bear  a  much 
larger  proportion  to  the  plasma,  the  latter  being  to  the  corpuscles 
in  the  proportion  of  about  two  to  one.  This  discrepancy  is  per- 
fectly accounted  for  when  we  remember  that,  by  the  method  of 
Becquerel  and  Eodicr,  the  clot  from  which  the  corpuscles  are  esti- 
mated is  dried  and  their  water  therefore  driven  off;  the  135  parts 
of  corpuscles  represent,  therefore,  dry  ones  and  not  the  living  cor- 
puscles, which,  when  united  with  their  370  parts  of  water,  will 
amount  to  nearly  500  parts  in  the  1000  of  blood  analyzed. 

Judging,  also,  from  the  boiled  serum,  we  should  expect  to  find 
a  greater  quantity  of  proteids  than  70  parts  per  1000  of  blood. 
In  the  analysis  just  given  the  serum  from  which  the  albumin  is 
determined  is  dried  like  the  clot,  hence  the  water  present  in  living 
albumin  is  not  given.  When  the  water,  however,  is  taken  into 
consideration,  the  proteid  will  then  amount  to  more  than  300 
parts  in  1000  of  blood.  As  the  object  of  the  physiologist  is  to 
ascertain  if  possible  the  quantity  of  proteids,  fibrin,  and  corpuscles, 
as  they  exist  in  living  blood,  and  as  in  this  condition  water  is  an 
indispensable  element  of  their  composition,  it  becomes  a  matter  of 
importance  to  determine  the  quantity  of  these  principles  in  a  moist 
as  well  as  in  the  dry  condition.  For  these  reasons  Prof.  Flint,^ 
suggests  that,  while  the  fibrin  be  oljtained  in  the  usual  manner  of 
whipping — with  broom-corn,  for  example — and  the  corpuscles  by 
Figuier's  filtering  method,  both  these  principles  should  be  estimated 
in  their  moist  condition,  and  not  after  desiccation  ;  and  that  in  de- 
termining the  proteid  from  the  serum,  this  should  be  treated  as 
described  above,  but  in  the  condition  that  it  is  found  after  coagula- 
tion— that  is,  with  its  water. 

The  difference  between  the  results  of  an  analysis  of  the  blood'by 
the  method  of  Prof.  Flint  and  that  of  MM.  Becquerel  and  Rodier 
depends,  therefore,  upon  the  proteids,  etc.,  being  estimated,  as  com- 
bined with  or  without  water,  as  shown  by  the  following  example  : 


Composition  or  ' 

THE  Blood 

I{ec(|ucrfl  and 

Difterence  is 

Flint. 

JJodier. 

in  water. 

Water 

.     154.870 

790.070 

635.200 

Proteids 

.     329.820 

71.530 

258,290] 

Fibrin 

8.820 

2.500 

6.320 

Corpuscles     . 

.     495.590 

125.000 

370.590  ] 

Remaining  matters,  salts, 

etc.      10.900 

10.900 

00.000 

635.200 


1000.000       1000.000 
1  Physiology,  Vol.  ii.,  p.  133. 


COMFOSITIUX  OF  THE  BLOOD.  211 

We  say  the  method  of  Becquerel  and  Hodier,  not  their  actual 
analysis,  for  the  quantities  of  proteids,  fibrin,  and  corpuscles  iriven 
under  the  method  of  Becquerel  and  Kodier,  were  experimentally 
obtained  by  Professor  Flint  by  weighing  the  dry  residue  after  des- 
iccating these  principles  obtained  by  his  method.  It  is  very  satis- 
factory, however,  to  see  that  the  difference  between  the  quantities 
of  dry  proteid  and  corpuscles  given  Ijy  Prof.  Flint  and  Becquerel 
and  Kodier  are  very  slight,  and  that  the  quantity  of  fil)rin  is  the 
same  according  to  both.  The  remaining  matters  of  the  blood  are 
determined  in  the  same  manner  by  these  and  other  authorities  by 
t]ie  ordinary  methods  of  chemical  analysis. 

Of  these,  the  larger  proportion  are  the  inorganic  prinei})les,  and 
from  a  purely  chemical  point  of  view  have  been  very  satisfactorily 
determined,  both  quantitatively  and  qualitatively ;  but  of  the  exact 
manner  in  which  they  exist  in  the  living  blood  little  is  known  be- 
yond a  few  general  statements  to  l)e  noticed  shortly. 

The  analyses  of  Prevost  and  Dumas,  Andral  and  Gavarret, 
Lehmann,  Becquerel  and  Rodier,  Simon,  Denis,  Gorup  Besanez, 
Schmidt,  etc.,  while  differing  in  detail,  agree  substantially  in  show- 
ing; that  the  blood  consists  of  water  in  molecular  combination  with 
or  holding  in  solution  albuminous  substances,  fats  and  sugars,  and 
saline  matters.  It  is  interesting  to  observe  in  this  connection  that 
milk  and  eggs,  the  food  of  the  young  animal  and  embryo,  consist 
of  a  mixture  of  water,  proteids,  fats,  sugars,  and  salines,  approxi- 
mating closely  in  their  composition  to  that  of  the  blood ;  the  value 
of  such  articles  of  food  at  all  stages  of  life  will  be  therefore  readily 
understood. 

We  have  seen  that,  under  natural  circumstances,  the  diet  of  man 
is  a  mixed  one,  and  that  beyond  a  limited  period  of  time  no  single 
article  of  food,  solid  or  liquid,  will  sustain  life.  As  the  Ijlood  is 
elaborated  from  the  food  it  becomes  impossible,  therefore,  to  say 
positively  that  any  one  of  its  constituents  is  more  indispensable  to 
life  than  another.  It  is  immaterial,  therefore,  with  which  we  com- 
mence in  describing  their  quantitative  relations.  We  will  follow, 
then,  the  order  in  which  they  present  themselves  in  the  analysis 
given  by  Becquerel  and  Rodier. 

The  absolute  amount  of  water  found  in  the  blood,  according  to 
this  analysis,  amounts  to  781.600  in  the  1000;  of  this  we  have 
seen  in  life  that  over  600  parts  enter  into  molecular  combination 
with  the  proteids,  fibrin,  and  corpuscles,  forming  an  integral  part 
of  their  composition.  As  the  great  use  of  water  to  the  system  has 
already  been  pointed  out,  it  will  not  be  necessary  to  dwell  further 
on  the  importance  of  the  large  proportion  in  which  it  is  present  in 
the  blood,  merely  stating  that  while  the  quantity  varies  within  slight 
limits,  any  excess  that  may  be  taken  in  as  food  is  rapidly  eliminated 
by  the  skin,  kidneys,  etc.,  and  that  a  deficiency  in  any  amount  mate- 
rially alters  the  character  of  the  blood. 

Although  water  forms  three-fourths  of  the  blood,  and  however 


212 


THE  BLOOD. 


indispensable  it  may  be  to  health,  yet  the  researches  of  Prevost  and 
Dumas  showed  Ions;  since  that  there  exists  an  intimate  relation  be- 
tween  the  richness  of  the  blood  in  organic  matters  and  the  vital 
activity  of  the  organism. 

Thus,  while  the  quantity  of  water  is  large  in  all  vertebrates,  there 
is  more  water  in  the  blood  of  the  comparatively  inactive  fishes  and 
batrachia  than  in  birds  and  mammals,  and  that  in  those  mammals 
which  hibernate,  implying  a  low  order  of  vitality,  the  blood  con- 
tains more  water  than  in  the  ordinary  members  of  this  class.  As 
regards  the  quantity  of  solid  matters  contained  in  the  blood  of  ver- 
tebrates, the  birds,  M'hose  vital  activity  is  very  high,  come  first,  the 
mammals  next,  and  finally  the  cold-blooded  batrachia  and  fishes. 


Proportion  of  Water,  etc.,  in  1000  parts  of  Blood  of 
Vertebrates.' 


Animal. 

Water. 

Clot. 

Proteid  and  salts 

Chicken 

780 

157 

63 

Pigeon 

797 

156 

47 

Duck 

765 

150 

85 

Kaven 

797 

146 

56 

Heron 

308 

132 

59 

Monkey 

776 

146 

78 

Man 

784 

129 

87 

Ouinea-pig 

785 

128 

87 

Dog 

812 

124 

65 

Cat 

795 

102 

84 

Goat 

814 

103 

83 

Calf 

826 

91 

83 

Rabbit 

838 

94 

68 

Horse 

818 

92 

89 

Sheep 

836 

86 

77 

Eel     . 

846 

94 

60 

Frog  . 

884 

69 

46 

Trout 

864 

64 

72 

Lota 

886 

48 

66 

It  will  be  observed  in  the  above  that  the  corpuscles  and  fibrin 
are  estimated  together  as  clot.  It  should  be  mentioned,  however, 
as  showing  the  connection  between  the  number  of  corpuscles  and 
vital  power,  that  it  is  the  amount  of  corpuscles  which  varies  in  the 
diflFerent  vertebrates,  that  of  the  fibrin  being  about  the  same.  The 
amount  of  protcids,  like  that  of  the  corpuscles,  varies,  but  mthin 
much  narrower  limits. 

Let  us  turn  now  to  the  consideration  of  the  composition  of  the 
blood  corpuscles  and  more  particularly  to  their  haemoglobin.  AVhen 
blood  is  exposed,  drop  by  drop  to  a  cold  of  about  —13.3°  C.  (8°  F.) 
and  then  quickly  Avarmed  to  20°  C.  (08°  F.),  it  will  be  observed  that 
the  corpuscles  gradually  lose  their  color,  though  they  retain  for  a 
time  their  form  and  elasticity  and  that  the  serum  becomes  stained. 
1  Prevost  et  Dumas,  Ann.  de  Phy.  et  Chim.,  1823,  T.  23,  p.  64. 


H^MOGL  OBIX.  2 1 3 

This  is  owing  to  the  corpuscles  consisting  of  a  colorless  protoplasmic 
material,  the  stroma  to  which  their  shape  is  due  and  of  a  coloring 
matter,  the  hemoglobin.  The  latter  constitutes  about  94.3  per  cent. 
of  the  solid  matter  of  the  corpuscles.  It  appears  to  exist  according 
to  Hoppe-Seyler  ^  within  the  corpuscle  in  a  state  of  combination  the 
nature  of  which,  however,  is  unknown.  When  hemoglobin  is  set 
free  as  in  the  manner  just  mentioned  and  dissolves  in  the  plasma, 
the  blood  not  only  changes  its  color  but  becomes  transparent  at 
least  in  their  layers  and  is  then  said  to  be  ''  laky."  This  condition 
of  the  blood  can  be  brought  about  not  only  by  alternate  freezing 
and  thawing  but  by  the  addition  of  bile,  ether,  chloroform,  excess 
of  water  and  by  other  means.  It  may  be  recalled  in  this  connec- 
tion that  it  is  the  sodium  chloride  of  the  blood  existing  in  isotonic 
amount  that  prevents  the  blood  corpuscles  from  absorbing  water  in 
excess,  discharging  their  hemoglobin  and  of  so  giving  rise  to  a  laky 
condition  of  the  blood.  According  to  Hoppe-Seyler  the  red  cor- 
puscles consist  chemically  of  hemoglobin  in  combination  with  oxy- 
gen or  oxyhemoglobin  (94.3  per  cent.),  proteid,  together  with 
nuclein  (5.1  per  cent.),  and  of  lecithin  and  cholesterin  in  traces 
(0.7  per  cent.).  Just  as  we  have  seen  that  the  red  corpuscle  con- 
sists of  stroma  and  hemoglobin  so  it  can  be  shown  by  appropriate 
means  that  the  hemoglobin  consists  of  globulin  and  hemochromogen. 
It  is  to  the  peculiar  chemical  constitution,  however,  of  the  latter 
substance  that  the  hemoglobin  owes  its  spectrum  and  the  readiness 
with  which  it  combines  with  oxygen.  Inasmuch,  however,  as 
hemochromoffen  throuo-h  oxidation  becomes  at  once  hematin  it 
may  be  said  that  hemoglobin  practically  consists  of  globulin,  a  pro- 
teid, and  hematin,  a  pigment,  the  latter  containing  the  iron  of  the 
blood,  the  globulin  constituting  96  per  cent.,  the  hematin  4  per 
cent.  Such  being  the  case  the  red  corpuscles  will  consist  of  stroma 
5  per  cent.,  of  globulin  90.5  per  cent.  (94.3  x  .96  =  90.5),  of 
hematin  3.8  per  cent.  (94.3  x  0.4  =  3.8). 

The  coloring  matter  of  the  red  corpuscles,  the  hemoglol)in,  can  be 
readily  obtained  in  the  form  of  crystals  in  several  ways.  Among 
other  methods  that  might  be  mentioned,  that  of  Preyer,-  is  as  fol- 
lows :  Add  enough  water  to  a  small  quantity  of  defibrinated  blood 
to  make  a  clear  solution  and  evaporate  under  a  thin  cover  glass  in 
a  cool  place.  Should  this  plan  fail  add  a  little  alcohol  solution  and 
place  it  in  a  freezing  mixture.  Usually  crystals  will  at  once  form. 
These  crystals  are  more  readily  obtained  from  some  animals  than 
others — with  greater  facility,  for  example,  from  the  blood  of  the 
dog,  horse,  and  guinea-pig,  than  from  that  of  man,  and  only  with 
difficulty  from  that  of  the  bat,  mole,  and  mouse.  The  form  of  these 
blood  crystals  varies  also  in  diiferent  animals.  Thus  they  are  pris- 
matic in  form  in  man  (Fig.  74),  tetrahedral  in  the  guinea-pig  (Fig. 
75),  hexagonal  in  the  squirrel  (Fig.  76). 

^Zeitschrift  fiir  physiologisclie  Chemie,  Band  xiii.,  1889,  s.  477. 
^Preyer,  Die  Blutcrystalle.      Jena,  1871,  s.  18. 


214 


THE  BLOOD. 


From  whatever  source  they  are  obtained  they  are  transparent  and 
doubly  refracting,  and  when  oxygenated  exhil)it  the  color  of  the 
blood  from  which  they  were  obtained.     When  deoxidized,  however, 


Fig.  75. 


Prismatic  crystals  from  blood  of  man.  Tetrahedral  crj  ^tal-  from  blood  of  giiiuea-pig. 


Fro.  76. 


they  alternate  in  color  from  red  to  purple  or  green.  They  are  sol- 
uble in  water,  alkalies,  and  most  acids  ;  insoluble  in  alcohol,  and 
will  remain  unchanged  for  some  time  in  urine,  bile. 

It  is  an  interesting  fact  that  although  hasmoglobin  crystallizes  it 
does  not  dialyze  readily,  resembling  in  this  respect  colloidal  bodies. 

Oxyhfemoglobin  from  the  dog 
consists  chemicallv,  according  to 
Hoppe-Seyler,'  of  C  53.85,  H 
7.32,  N  16.17,  O  21.84,  S  0.39, 
Fe  0.43. 

The  exact  molecular  formula 
of  hi;emoglol)in  has  not  yet  been 
established.  If,  however,  the 
fonnula  Q,Jl,,^^,,;Ff>p,,„  as 
estimated  by  Hi'ifner "  for  dogs' 
hsemoglobin,  be  accepted  as  cor- 
rect, the  molecular  weight  will 
be  14001,  and  therefore  very 
great.  The  amount  of  hfemoglo- 
bin  present  in  a  given  quantity 
of  Idood  can  be  determined  from 
the  amount  of  iron  by  coloro- 
metric  methods  and  by  the  spectroscope.  The  iron  method  is  based 
upon  the  fact  that  dry  (100°  C.)  hemoglobin  contains  0.42  per 
cent,  of  iron.     Knowing  the  amount  of  the  latter  in  the  blood  the 


Hexagonal  crystals  froni  blood  of  squirrel. 


'Med.  Chem.  Unters.,  s.  370. 
^ Harnmai-sten,  op.  pit.,  p.  09. 


H^MOGLOBIXOMETEB . 


215 


amount  of  hsemoglobin  can  be  at  once  calculated  by  the  following 
equation  : 

,    100  Fe 
100   :  0.42  ::  a:  :  Fe.  x  equals ---r^ , 

in  which  x  is  the  unknown  quantity  of  haemoglobin,  Fe  the  known 
quantity  of  iron  in  the  blood,  and  0.42  the  per  cent,  of  iron  in  100 
parts  of  hsemoglobin.  To  obtain  the  amount  of  iron  in  the  blood 
whose  hsemoglobin  is  to  be  determined,  a  known  quantity  of  blood 
is  calcined,  the  ash  is  then  treated  with  hydrochloric  acid  to  obtain 
ferric  chloride,  which  is  then  transformed  into  ferrous  chloride  by 
boiling  with  zinc  until  the  liquid  is  colorless.  The  liquid  being  di- 
luted, the  amount  of  iron  in  it  is  determined  volumetrically  ^  by 
adding  from  a  burette  permanganate  of  potassium  in  standard  solu- 
tion until  the  rose  color  becomes  permanent  after  agitation,  0.0056 
gramme  of  iron  being  present  for  each  centimeter  of  standard  solu- 
tion used.  The  hsemoglobin,  as  determined  from  the  quantity  of 
iron,  amounts,  according  to  Preyer,-  in  human  blood  to  about  12.34 
per  cent. 

The  colorometric  method  depends  upon  the  comparison  of  the 
tint  of  the  blood  to  be  investigated  with  that  of  a  standard  solu- 
tion. In  determiuino-  the  amount  of  hajmoirlobin  in  this  wav  we 
make  iLse  of  the  hsemoglobinometer  of  Gowers.     This  consists  (Fig. 

Fig.  77. 


A.  Pipette  bottle  for  distilled  water.    P..  Capillary  pipette.     C.  Graduated  tube.    D.  Tube  with 
standard  dilution.    F.  Lancet  for  pricking  the  finger. 

77)  of  two  glass  tubes  (D  and  C)  of  exactly  the  same  size.  Into 
D  are  placed  20  cubic  mm.  of  blood  diluted  with  2000  mm.  of 
water;  the  strength  of  the  solution  is  therefore  1  per  cent.  C  is 
graduated,  the  scale  of  100  degrees  extending  over  a  space  equal  to 

1  Sutton,  Yolnmetric  Analysis,  4th  ed.,  pp.  88,  94.  ^Qp.  cit.,  s.  117. 


216  THE  BLOOD. 

that  in  D  containing  the  1  per  cent,  dihited  blood.  The  manner  of 
using  the  apparatus  is  as  follows  :  Into  C  are  placed  20  cubic  mm. 
of  the  blood  to  be  examined,  which  is  then  diluted  until  its  color  is 
the  same  as  that  in  D.  Suppose,  for  example,  that  we  have  to  add 
to  the  blood  to  be  investigated  placed  in  C  only  30  degrees  of  water 
(600  mm.)  in  order  to  obtain  the  same  tint  of  color  as  that  in  D, 
instead  of  as  in  the  latter  case  100  degrees  of  water  (2000  mm.),  it 
follows  that  the  blood  in  C  contains  only  30  per  cent,  of  the  nor- 
mal quantity  of  haemoglobin.  Further,  if  the  number  of  corpuscles 
in  the  investigated  blood  has  also  been  shoAvn  to  be  only  60  per 
cent,  of  the  normal  amount,  we  have  a  fraction  |^  =  i,  the  nume- 
rator being  the  per  cent,  of  the  haemoglobin  and  the  denominator 
the  per  cent,  of  corpuscles,  giving  the  average  value  of  each  corpus- 
cle, or  half  the  normal  amount. 

A  still  more  delicate  method  of  determining  the  amount  of  haemo- 
globin is  by  spectrum  analysis.  This  method  is  based  upon  the  fact 
as  shown  by  Preyer  ^  that  the  red,  yellow,  and  first  bands  of  the 
green  of  the  spectrum  can  be  seen  through  an  0.8  per  cent,  solution 
of  haemoglobin  and  that  such  a  solution  can  be  taken  as  a  standard 
of  comparison.  A  known  amount  of  the  blood  whose  haemoglobin 
is  to  be  determined  is,  therefore,  diluted  until  the  same  bands  are 
seen  with  the  spectroscope  as  with  the  standard  solution.  That 
being  accomjjlished,  the  amount  of  hoemoglobin  can  be  determined 
by  the  following  equation  : 

X  -.k  :  -.b  +  c  -.h 

xb  =  k{b  +  c) 

0 

in  which 

X  =  unknown  quantity  of  hsemoglobin. 
A-:=per  cent,  of  htemoglobin  in  solution  (0.8). 
6  =  volume  of  blood. 
c=  volume  of  distilled  water. 

Thus  suppose,  for  example,  that  2  c.c.  of  blood  required  30  c.c. 
of  water  to  give  an  absorption  spectrum  similar  to  that  of  the 
standard  spectrimi,  the  percentage  of  which  is  0.8  ;  then 

(2  +  30) 
X  =  0.8  — — -      ^^  =  12.8  per  cent,  of  oxyhtfimoglobin. 

To  appreciate  the  manner  in  which  spectrum  analysis  is  applied  in 
the  determination  of  haemoglobin,  or  in  the  study  of  the  blood 
generally,  let  us  endeavor  to  explain  briefly  the  principles  of  this 
method  of  investigation. 

As  is  well  known,  when  sunlight  is  transmitted  through  a  prism, 
as  in  Fig.  78,  it  is  decomposed  into  the  seven  colors,  violet,  indigo, 
blue,  green,  yellow,  orange,  and  red.  This  is  called  the  solar  spec- 
trum.    In  the  early  part  of  this  century  Fraunhofer  described  cer- 

iQp.  cit.,  s.  124. 


SPECTRUM  ANALYSIS.  217 

tain  lines  situated  in  these  colors,  and  which  since  then  have  been 
knowTi  as  Fraunhofer's  lines  (Fig.  79,  7),  and  which  in  all  prob- 
ability are  due  to  the  presence  of  certain  chemical  elements  exist- 
ing in  the  form  of  vapor  around  the  sun  and  which  prevent  the 
passage  of  certain  rays  emitted  by  the  solar  nucleus,  it  having  been 
demonstrated  that  a  vapor  absorbs  rays  of  light  having  the  same 

Fig.  78. 


Scheme  of  a  spectroscope  for  observing  the  spectmm  of  blood.  A.  Tube.  S.  Slit.  r/im.  Laver 
of  blood  with  flame  in  front  of  it.  P.  Prism.  JI.  Scale.  B.  Eve  of  observer  looking  through  a 
telescope,    r  r.  Spectrum. 

refrangibility  as  that  which  it  emits.  Tliu~  a  liright  vellow  line 
in  the  spectrum,  due  to  incandescent  sodimn,  will  be  replaced  by  a 
dark  one  if  the  liglit  from  the  burning  metal  be  intercepted  by  the 
vapor  of  the  same.  Since  then  it  has  been  shown  by  Brewster, 
Herschell,  and  Miiller  that  various  colored  solutions  prevent  the 
passage  of  certain  of  the  rays  of  light,  dark  bands  appearing  in  the 
spectrum  in  tlie  place  of  the  rays  or  colors  arrested.  In  the  same 
manner  the  inlluence  of  blood  upon  the  passage  of  light  through  it 
was  investigated  spectroscopically  (Fig.  78),  more  particularly  by 
Hoppe-Seyler,^  Stokes,-  and  Sorby,^  and  it  was  shown  by  these 
observers  that  when  dilute  arterial  blood  is  used  two  dark  bands 
appear  (Fig.  79,  1)  between  the  Fraunhofer  lines  D  and  E — that 
is,  in  the  yellow  of  the  spectrmn,  whereas  if  venous  blood  is  used 
only  one  dark  band  (Fig.  79,  3)  appears  in  the  yellow  near  the 
line  D.  Further,  it  was  demonstrated  that  this  difference  between 
arterial  and  venous  blood  was  solelv  due  to  whether  the  coloringr 
matter  or  the  haemoglobin  was  oxygenated  or  not,  and  that  the  fact 
of  the  arterial  blood  l^eing  red  or  scarlet,  and  of  venous  blood  being 
blue  or  purple,  was  owing  to  oxyhtemoglobin  being  of  a  red  hue  and 
hsemoglobin  of  a  bluish  one.  That  the  difference  between  arterial 
and  venous  blood  spectroscopically,  and  as  regards  color,  is  due 
simply  to  the  hcemoglobin  being  oxvgenated  in  the  former  case  and 

I  VirchoTT's  Archiv,  1862,  Band  xxiii.,  s.  446. 

^Proc.  of  Eoval  Societv  London,  1863,  1864,  Vol.  xiii.,  p.  .3-55. 

*  Quarterly  Journal  of  Science,  1865,  Vol.  ii.,  p.  198. 


218 


THE  BLOOD. 


unoxygenated  in  the  latter,  can  be  readily  demonstrated.  Thus,  if 
some  reducing  agent  like  ammonium  sulphide  or  an  alkaline  solu- 
tion of  ferrous  sulphate,  kept  from  precipitation  by  tartaric  acid,  be 
added  to  arterial  blood  or  the  M'ashings  from  a  blood  clot,  the  oxy- 
gen, being  loosely  combined  ^^At\\  haemoglobin,  is  at  once  seized  with 
avidity  by  the  reducing  agent,  the  two  dark  absorption  bauds  dis- 
appear, being  replaced  by  the  one  dark  band  characteristic  of  venous 
blood,  and  the  color  changes  from  red  to  blue.  On  the  other  hand, 
Avith  the  exposure  of  venous  blood  or  a  solution  of  haemoglobin  to 
oxygen,  or  air  containing  such,  the  one  dark  band  will  disappear, 
being  replaced  by  the  two  dark  bands  so  characteristic  of  arterial 
blood,  and  the  color  will  chano^e  from  blue  to  red  arain. 


Fig.  79. 


Red.  Orange.  Yellow.         Green. 


w 

fill 


C 


^/  i       ^ 


WIT 

I  ill    I II  111 

y 


I I l""i'°T 


«  ^  ^  *         io        il       J^        J3        i4- 


Oxyhsemoglobin  and 
NOo-Hsemoglobin. 


CO-lIsemoglobin. 


!      Eeduced  Hfemoglobin. 


Hsematin  in  acid  solu- 
tion. 


Hsematin  in  alkaline 
solution. 


Reduced  Hoematin. 


Solar  spectrum  with 
P'raunhofer's  lines. 


It  will  be  observed  as  shown  by  Fig.  79,  that  the  band  situated 
toward  the  red  end  of  the  spectrum,  often  called  the  "  a.  band,"  is 
narrower,  darker  and  more  defined  than  the  band  toward  the  green 
end,  the  "  [i  band,"  the  single  band  of  venous  blood  being  called 
the  "  y  band."  It  should  be  mentioned  that  the  situation  of  these 
absorption  l^ands  is  often  described  by  stating  the  wave-lengths  of 
those  portions  of  the  spectrum  between  which  the  bands  are  situated. 
Thus,  for  example,  if  the  solution  made  use  of  in  the  investigation 
be  one  centimeter  thick  and  contain  0.09  per  cent,  of  oxyhsemoglobin, 
the  "  a  band  "  is  said  to  ])e  situated  (Fig.  80)  between  the  wave- 
length 1  Yo^of  o"o  *^^  ^  millimet(>r  and  /  -^-^W-^-^  of  a  millimeter,  the 
"  [i  band  "   between  /  -jof  fo-Q  of  a  millimeter  and  /  yof  f  q-q  of  a 


SPECTRUM  ANALYSIS. 


219 


millimeter.  To  make  use  of  this  method,  however,  the  spectroscopes 
should  be  provided  Avith  a  scale  so  disposed  as  to  enable  the  ob- 
server to  read  off  directly  wave-lengths  of  any  part  of  the  spectrum. 
According  to  the  amount  of  oxy haemoglobin  present  in  the  blood, 
or  solution  of  oxyhsemoglobin  used,  the  dark  bands  will  vary  in 
extent.  Thus,  in  a  concentrated  solution  the  two  bands  run  into 
one,  there  being  a  general  absorption  at  the  blue  and  red  ends  of 
the  spectrum,  also  the  light  then  passing  through  only  the  green  and 
red  parts.     With  a  still  further  increase  in  the  strength  of  the  so- 


FlG. 


70      65 


60 


53 


B  C 


D 


50 


E  b 


45 


G 


Diagrammatic  representation  of  spectrum  of  oxyluemoglobin.  The  wave-lengtlis  are  indicated 
in  hundred-thousandths  of  a  millimeter  by  the  numbers,  the  important  Fraunhofer  lines  by  the 
letters,  the  a  band  by  the  dark  band  to  the  right  of  i*,  the  /3  band  by  that  to  the  left  of  ^'.  After 
ROLLETT,  in  Hermann,  Band  iv.,  s.  47,  Fig.  5. 

lution  light  will  be  transmitted  through  only  the  red  portions  of 
the  spectrum,  lience  its  red  color,  as  seen  by  transmitted  light.  It 
is  hardly  necessary  to  add  that  the  red  rays  are  the  last  to  disappear. 

The  extreme  delicacy  of  spectrum  analysis,  as  applied  to  the  de- 
termination of  the  presence  of  blood,  may  be  appreciated  from  the 
fact  of  the  two  bands  appearing  in  the  spectrum  of  light  trans- 
mitted through  a  layer  1  centimeter  thick  of  a  solution  containing 
only  1  gramme  (15.4  grains)  in  10,000  c.  cm.  (20  pints)  of  water, 
or,  in  round  numbers,  about  1  grain  of  haemoglobin  in  a  pint  and 
a  third  of  water.  This  is  an  important  fact,  since,  under  certain 
circumstances,  in  medico-legal  cases,  for  example,  the  quantity  of 
the  suspected  substance  being  exceedingly  small,  spectrum  analysis 
would  he  the  only  means  by  which  it  could  be  determined  whether 
it  was  Ijlood  or  not.  Indeed,  substances  already  decomposed  and 
putrid,  solutions  made  by  washing  with  water,  old  stains  upon  iron, 
wood,  linen  that  may  have  lain  aside  unnoticed  for  years,  can  be 
shown  by  the  spectroscope  to  contain  haemoglobin,  and  necessarily, 
therefore,  to  have  been  derived  from  blood,  since  no  other  known 
substance  affects  light  as  haemoglobin. 

Even  if  the  spectrum  obtained  was  that  of  carbon  monoxide, 
or  haemoglobin  (acid  haematin),  characterized  by  two  and  one  ab- 
sorption bands  respectively  (Fig.  79,  2,  4),  as  in  the  case  of 
arterial  and  venous  blood,  this  need  be  no  source  of  confusion, 
since  the  absorption  bands  of  these  substances  are  not  situated  in 
exactly  the  same  part  of  the  spectrum  as  those  of  arterial  and 
venous  blood,  and  even  if  a  doubt  existed  as  to  the  exact  locality 
of  the  bands,  there  could  be  none  with  reference  to  the  presence  of 


220 


THE  BLOOD. 


blood,  as  it  is  the  hsemoglobiu  in  each  case  which  is  the  cause  of 
the  appearinjr  of  the  bands.  It  should  be  mentioned  in  this  con- 
nection that  spectrum  analysis,  like  all  other  means  at  present  at 
our  command,  enables  us  only  to  determine  that  a  substance  is 
blood,  but  not  necessarily  human  blood.  In  examining  the  blood 
spectroscopically,  while  the  ordinary  spectroscope  can  be  used,  the 
microspectroscope  will  be  found  more  convenient,  and  especially 
the  form  described  by  Vierordt.^ 

It  may  be  mentioned  here  as  well  as  elsewhere  that  there  are 
several  other  compounds  or  derivatives  of  haemoglobin,  many  of 
which  have  a  characteristic  spectrum  and  are  of  more  or  less  in- 
terest as  well  as  that  of  oxyh^emoglobin.  Thus,  for  example, 
there  are  substances  :  methoemoglobin,  differing  only  from  oxy- 
hsemoglobin  in  that  its  oxygen  is  more  stable  ;  hsemochromogen 
derived  from  the  decomposition  of  haemoglobin  in  the  absence  of 
oxygen  ;  luematin  on  the  contrary  in  the  presence  of  the  latter  ; 
hsemotoidin  obtained  from  the  haemoglobin  of  extravasations  such 
as  apoplectic  clots,  corpora  lutea,  etc.  Histio-hsematins,  pigments 
found  in  the  tissue  and  supposed  to  be  derivative  of  haemoglobin, 
of  which  myohtematin  already  referred  to  is  an  example.  H^ma- 
toporpliyrin  or  iron-free  hsematin  obtained  through  the  action  of 
sulphuric  acid  upon  hsematin.  Hsemin  through  the  action  of  hy- 
drochloric acid  upon  the  same.  Hsemin  being  of  especial  interest 
from  a  medico-legal   point  of  view,  its  chemical   composition,   and 

principal  properties  and  method  of 
obtaining  will  be  briefly  noticed. 
Hffimin  as  shown  by  its  chemical 
composition  (C.,^H3.Np,HCl)  is 
a  htematin  hydrochlorate  and  can 
be  obtained  l)y  the  addition  of 
hydrochloric  acid  to  haemoglobin, 
100  parts  of  the  latter  yielding 
about  4  parts  of  hannin.  Hiemin 
is  insohible  in  alcohol  and  water, 
but  soluble  in  acids  and  alkalies, 
and  can  be  obtained  from  a  very 
minute  portion  of  blood  by  the 
following  method  :  Triturate  the 
suspected  substance  with  a  little 
common  salt  and  add  glacial 
acetic  acid,  then  warm  the  mix- 
ture till  bul)bles  appear,  and  then 
cool  it.  If  the  su})!stance,  thus 
treated,  contain  hfemin,  the  latter  will  appear  (Fig.  81)  as  crystals, 
in  tlie  form  of  rhombic  tablets  disposed  sometimes  as  stars  or  crosses 
of  a  red  or  brown  color.     If  oxygen  be  added,  the  color  of  the  crys- 

'  Die    Quantitative  Spectral   Analyse   in   ihrer    Anwendiing   auf    Physiologie. 
Tubingen,  1876. 


Fig.  81. 


Khomliif  crystals  of  luciuin  fir  hydrochlorate 
ofhiematiii. 


GASES  OF  BLOOD.  221 

tals  assumes  a  violet  hue,  while  under  the  influence  of  carbon 
dioxide  the  crystals  lose  their  transparency.  In  medico-legal  ques- 
tions where  there  may  be  a  very  small  quantity  of  material  to 
be  examined,  the  presence  of  haemin  crystals  will  settle  the  ques- 
tion as  to  whether  the  suspected  material  is  or  is  not  blood.  Hence, 
the  importance  of  the  method  just  given  from  this  point  of  view. 
It  should  be  mentioned,  however,  that  the  obtaining  of  hiemin  as 
well  as  of  haemoglobin  crystals  by  whatever  method  only  proves 
that  the  material  from  which  they  were  extracted  was  l)lood,  but 
not  necessarily  human  blood. 

In  the  fact  of  the  oxygen  of  the  blood  existing,  for  the  most  part, 
in  a  state  of  loose  chemical  combination  with  the  Inemoglobin  lies 
the  explanation  of  the  manner  in  which  blood  absorbs  or  gives  off 
oxygen.  Did  the  oxygen  exist  simply  in  a  state  of  solution  in  the 
blood  then  the  amount  absorbed,  or  given  oif,  would  depend  upon 
the  amount  of  pressure  present.  That  such  is  not  the  case,  how- 
ever, can  be  shown  by  exposing  venous  blood,  containing  little  or 
no  oxygen,  to  a  succession  of  atmospheres  containing  increasing 
quantities  of  oxygen.  At  first  there  is  a  very  rapid  absorption  of 
oxygen,  but  afterward  this  diminishes  or  ceases  altogether.  On  the 
other  hand,  if  arterial  blood,  containing  a  considerable  quantity  of 
oxygen,  be  exposed  to  successively  diminishing  pressures,  at  first 
little  oxygen  is  given  ofP,  but  afterward  the  escape  is  sudden  and 
rapid.  The  amount  of  oxygen  taken  up  or  given  off  by  blood  is 
not,  therefore,  dependent  upon  pressure,  except  so  far  as  the  latter 
influences  the  passage  to  or  from  the  plasma,  l)ut  upon  chemical 
affinity  ;  the  oxygen  absorbed  or  given  up  by  the  hemoglobin  is 
therefore  a  constant  (piantity.  The  amount  of  oxygen  absorbed  by 
dogs'  haemoglobin,  for  example,  is  1.59  c.  cm.  per  gramme,  the 
temperature  being  0°  C,  and  the  barometric  pressure  TGOmm.,^  one 
molecule  of  haemoglobin  absorbing  one  molecule  of  oxygen.  It  is 
generally  supposed  that  the  property  of  absorbing  oxygen  exhibited 
by  haemoglobin  depends  upon  the  iron  that  it  contains,  one  molecule 
of  oxygen  being  taken  up  for  each  atom  of  iron  in  the  molecule  of 
haemoglobin.  The  amount  of  oxygen  that  will  be  absorbed  by  the 
blood  in  any  instance  can  therein  be  estimated  from  the  amount 
of  iron  as  Avell  as  from  the  hiemoglobin  present.  It  may  not  be  in- 
appropriate to  mention  that  the  oxygen  absorbed,  or  given  off  by 
the  haemoglobin,  has  nothing  to  do  with  the  oxygen  entering  into 
its  molecular  composition,  and  as  already  given  in  its  chemical 
formula. 

That  the  haemoglobin  is  that  part  of  the  blood  which  absorbs  and 
gives  up  the  greatest  part  of  the  oxygen  there  can  be  no  doubt, 
since,  if  serum  freed  of  the  corpuscles,  and  therefore  of  haemoglobin, 
(the  latter  constituting  90  per  cent,  of  the  former),  be  experimented 
with  instead  of  blood,  little  or  no  oxygen  is  absorbed,  or  given  oflP, 
perhaps  ^  per  cent,  of  the  entire  blood,  of  which  the  serum  was  a 
'  Hilfner,  Zeits.  fiir  phys.  Chemie,  Band  ii.,  1877-78,  s.  389. 


222  THE  BLOOD. 

part,  and  that  proportional  to  the  pressure.  It  is,  therefore,  to 
their  haemoglobin  that  the  red  corpuscles  owe  their  function,  as  we 
have  seen,  of  being  oxygen  carriers  and,  since  the  hemoglobin  at 
low  pressure  readily  gives  up  its  oxygen,  the  functional  significance 
of  this  substance,  in  respiration,  becomes  very  evident. 

It  may  be  mentioned  in  this  connection  that  the  carbon  dioxide 
present  in  the  blood  is  not  simply  dissolved  there,  but  exists  princi- 
pallv  in  the  form  of  sodium  carbonate  and  bicarbonate  since  the 
absorption  and  giving  up  of  carbon  dioxide  by  the  blood  is  not  de- 
pendent upon  pressure.  It  is  generally  hold  that  these  salts  are  de- 
composed and  the  carbon  dioxide  set  free  by  the  haemoglobin  of  the 
red  blood  corpuscles,  the  latter  being  supposed  to  act  as  an  acid. 
That  such  is  the  case,  is  shown  by  the  fact  that  more  carbon  diox- 
ide can  be  obtained  from  blood  than  from  serum,  and  that  after 
all  the  carbon  dioxide  has  been  extracted  from  the  serum  that  is 
possible  by  the  gas  pump,  two  to  five  per  cent,  more  can  be  obtained 
by  adding  acid.  It  is  quite  possible  that  the  acid  action  of  the 
hfemoglobin,  just  referred  to,  may  be  aided  to  some  extent  by  the 
serum-albumin  and  primary  acid  phosphate  of  the  blood. 

According  to  the  recent  investigations  of  Bohr,^  how^ever,  it  ap- 
pears that  if  hremoglobin  be  exposed  to  a  mixture  of  oxygen  and 
carbon  dioxide,  it  will  absorb  carbon  dioxide  as  well  as  oxygen,  the 
former  combining  possibly  with  the  globulin  and  the  latter  with  the 
hsemochromogen.  If  such  be  the  case  hemoglobin  must  be  re- 
garded to  some  extent  at  least  as  a  carrier  of  carbon  dioxide  as  well 
as  aiding  in  the  decomposition  of  the  alkaline  carbonates  and  of  so 
setting  free  carbon  dioxide. 

The  small  amount  of  nitrogen  that  the  blood  contains  appears  to 
exist  there  in  a  simple  state  of  solution,  the  blood  absorbing  but 
little  less  nitrogen  than  that  absorbed  by  water ;  the  amount  de- 
pending, at  least,  within  limits  upon  the  law  of  pressure. 

The  gases  of  the  blood,  as  has  just  been  incidentally  mentioned, 
can  be  obtained  by  subjecting  the  blood  to  the  mercurial  vacuum. 
For  this  purpose  we  make  use  of  Grehant's  gas  pump.  This  con- 
sists (Fig.  82)  of  a  glass  reservoir  (B),  which  can  be  lowered  or 
raised  by  a  rack  and  pinion,  and  which  communicates  by  the  flex- 
ible tul)e  b  with  the  vertical  glass  tube  c,  which  is  firmly  secured 
to  the  stand.  The  vertical  tube  expands  into  the  oval-shaped  dila- 
tation A,  which  is  continued  upward  as  the  narrow  tube  f,  and 
whose  cavity  by  means  of  the  stopcock  R,  can  be  put  in  communi- 
cation either  with  that  of  the  lateral  tube  h,  or  of  the  tube  i  ter- 
minating above  in  the  cup  C,  or  cut  off  from  either.  The  lateral 
tube  h  is  connected  through  tubing  (h')  with  the  stem  e  of  the  bulb 
D,  into  which  is  inserted  a  flexible  tube  (1)  furnished  with  a  stop- 
cx)ck  (r),  for  the  transference  of  the  blood  whose  gases  are  to  be 
determined.  Tlic  stopcock  (R)  being  in  the  position  1,  Fig.  82 — 
that  is,  all  communication  between  the  cavity  of  the  vertical  tube  c 
'  Skandinavisches  Archiv  fiir  Physiologic,  Leipzig,  1891,  Band  3,  s.  47. 


GASES  OF  BLOOD. 


223 


being  completely  cut  oiF  from  that  of  the  lateral  and  terminal  tubes 
h  and  i,  mercury  is  poured  through  the  reservoir  B  until  it  not 
only  rises  to  the  level  of  the  stopcock,  but  completely  fills  the 
reservoir  itself  The  reservoir  being  then  lowered  the  mercmy  will 
fall  in  the  vertical  tube  c,  a  vacuum  being  produced  in  consequence 

Fig.  82. 


Grehaut-Alverguiat  gas  pump. 

above  it.  If  the  stopcock  he  now  turned  into  the  position  2  (Fig. 
82),  the  air  will  pass  in  from  the  lateral  tube  and  its  appendage 
into  the  vertical  tube  c,  and  the  mercury  will  foil  still  lower.  The 
stopcock  being  now  returned  into  the  position  1  (Fig.  82),  the 
reservoir  is  then  elevated,  and  the  mercury  with  the  included  air 


224 


THE  BLOOD. 


Fig.  83. 


will  ascend  into  the  oval  dilatation  A.  The  stopcock  being  now 
turned  into  the  position  3  (Fig.  82),  the  air  that  was  just  drawn 
into  the  vertical  tube  c  from  the  lateral  tube  h  passes  out  of  the 
tube  i  into  the  atmosphere.  The  stopcock  is  then  returned  to  the 
original  position  (Fig.  82,  1).  By  depressing  and  elevating  the 
reservoir  B,  and  manipulating  the  stopcock  R  in  the  manner  just 
explained,  in  a  very  short  time  a  good  vacuum  is  produced  in  the 
lateral  tube  h  h'  e,  and  its  appendage  D.  A  tube  having  been  in- 
serted into  the  artery  or  vein,  the  blood  to  be  analyzed  is  then 
transferred  from  the  vessel  in  the  living  animal  to  the  vacuum  in 
the  following  manner  :  A  tube  (M)  of  known  capacity,  say  50  c.c, 
tapering  off  at  one  end  (G),  and  guarded  by  a  stopcock  (B)  at  the 
other,  is  filled  with  mercury  by  aspiration.  The  tube  is  then  at  the 
end  G  put  in  communication  with  the  blood  vessel,  by  means  of  a 
rubber  tube  readily  slipping  over  the  canula  previously  inserted 
into  the  vessel,  which  is  closed  by  a  clip.  The  stopcock  being 
now  opened,  and  the  clip  removed,  the  blood  is  allowed  to  flow 
away  for  a  moment,  and  then  (connection  being  made  by  the  tubing) 
into  the  tube  M,  driving  out  of  the  latter  the  mercury,  which  can 
be  received  into  a  convenient  receptacle.  As  soon  as  the  tube  is 
filled  with  blood,  the  stopcock  being  closed,  connection  is  broken 

with  the  vessel,  and  the  tube  re- 
versed in  position,  so  that  its 
tapering  end  G  (Fig.  88)  may  be 
inserted  into  the  small  mercury 
trough  U,  previously  placed  in 
the  large  trough  N  containing  ice- 
water,  to  retard  the  coagulation  of 
the  blood  in  the  tube.  The  glass 
tube  is  then  joined  by  the  end 
B  to  the  rubber  tube  I)  provided 
with  a  stopcock  (e)  containing  boiled  distilled  water,  and  previously 
placed  over  the  tube  t  (Figs.  82,  83),  the  latter  being  furnished 
with  a  stopcock  (Fig.  82,  r)  and  leading  to  the  vacuum.  Both 
stopcocks  (B  and  r)  being  now  opened,  the  blood  passes  from  the 
glass  tube  (Fig.  83,  M)  into  the  vacuum  D  e  (Fig.  82),  its  place 
being  filled  with  mercury  from  the  trough  ;  the  stopcocks  are  then 
closed.  The  blood  having  passed  through  the  tube  in  the  bulb  D, 
gives  up  its  gases  readily  into  the  vacuum,  the  liberation  of  which 
is  greatly  facilitated  by  surrounding  the  bulb  with  water  (Fig.  82) 
at  a  temperature  of  about  40°  C.  (104°  F.).  As  it  is  also  desir- 
able to  keep  ])ack  the  froth  and  foam  arising  from  the  blood  as  much 
as  possible,  the  lateral  tube  e  is  surrounded  by  a  tin  one,  through 
which  ice-cold  water  flows  from  a  reservoir  (z),  and  which  effectually 
accomplishes  the  object.  The  gases  having  been  separated  from  the 
blood,  are  next  transferred  into  the  vertical  tube  c,  and  thence 
through  the  terminal  one  i  into  a  eudiometer,  standing  over  mer- 
cury in  the  cup  C,  by  depressing  the  mercurial  reservoir  B,  and 


GASES  OF  BLOOD.  225 

turning  the  stopcock  R  in  the  same  manner  as  just  explained.  The 
([uantity  of  blood  from  Avhich  the  gases  are  obtained  will,  of  course, 
depend  upon  the  size  of  the  tube  transmitting  the  blood  from  the 
vessel  to  the  vacuum,  the  vessel  being  clamped  as  soon  as  the  tube 
is  full  of  blood. 

In  order  to  determine  the  nature  and  amount  of  the  gases  given 
off  from  the  blood  we  make  use  of  an  eudiometer  in  the  usual  way 
or  of  a  Hem  pel's  apparatus,  wdiich  enables  us  to  conveniently  trans- 
fer the  mixture  of  gases  successively  into  a  solution  of  caustic  pot- 
ash and  pyrogallic  acid,  etc.,  and  of  so  determining  by  absorption 
the  amount  of  carbon  dioxide  and  oxygen  present,  the  gas  remain- 
ing over  being  usually  regarded  as  consisting  of  nitrogen.  The 
volume  of  the  gas  obtained  must  be  reduced,  of  course,  to  standard 
pressure  760  mm.  mercury,  and  standard  temperature  0°  C,  which 

can  be  done  by  the  following  formula  :   V  =  _,.,.  ,\ ,\  in  which 

•^  ^  760  (1  -I-  at) 

Fis  the  required  volume  at  standard  temperature  0°  C.  and  stand- 
ard pressure  760  mm.,  T"'  the  volume  at  the  observed  temperature 
and  pressure,  h  the  observed  pressure,  ])  the  tension  of  the  aqueous 
vapor,  a  the  coefficient  of  expansion,  a  constant  (.00366),  and  t  the 
observed  temperature. 

The  formula  is  derived  as  follows.  Firstly,  with  reference  to 
the  correction  of  the  given  volume  for  temperature  : 

l  +  «/  :  1    :  :    P   :    For  V=—^- 

1  -T-  at 

And  secondly,  for  pressure  : 

V^  V  ^  (h—v) 

V  :  — — .   :  :  {h—p)  :  760  or  V=^^.,;.    %(• 

1  +  at         ^       '^  '  760  (1  +  at) 

As  an  illustration  of  the  manner  of  using  the  formula,  let  us 
suppose  that  30  c.  cm.  of  nitrogen,  or  F',  were  collected  at  15°  C, 
740  mm.  barometric  pressure,  12.677  mm.  being  the  aqueous  ten- 
sion, then  F,  or  the  required  volume,  would  be,  at  0°  C,  and  760 
barometric  pressure,  27.23  c.  cm. 

30(740  —  12.677)  30X727.323       21819.690 

V^= ^ —  =  — ~ = ^  27  ''S  c  cm 

760(1 +.00366X15)       760X1.0549  801724  -'•-^^•'^"^• 

It  will  be  found  on  an  average  that  for  100  vol.  of  blood  used 
there  wall  be  extracted  by  means  of  the  mercurial  pump  about  60 
vols,  of  gas,  the  barometric  pressure  being  760  mm.  (30  cub.  in.) 
and  the  temperature  0°  C.  (32°  F.),  and  that  the  composition  of 
this  gas  will  be  according  to  the  kind  of  blood  examined,  as  follows  : 

Oxygen.        CarlJou  dioxide.  Nitrogen. 

Arterial  blood     .         .  20  vol.       39  vol.  1  to  2  vol. 

Venous  blood      .         .  8  to  12     "         46     "  1  to  2     " 

15 


226  THE  BLOOD. 

The  amount  of  oxygen  accords  with  the  fact  ah'eady  mentioned 
that  1  gramme  of  haemoglobin  combines  with  1.59  c.c.  of  oxygen, 
since  if  it  be  admitted  that  100  c.c.  of  blood  contain  lo  grammes  of 
haemoglobin,  then  100  c.c.  of  blood  should  contain  23.85  vols,  per 
cent,  of  oxygen,  the  excess  of  oxygen  over  that  actually  found  being 
due  to  the  ftict  that  the  haemoglobin  of  the  blood  is  not  saturated. 

The  proteid  material  of  the  plasma  of  the  blood  consists  of  three 
substances,  serum-albumin,  paraglobulin,  and  fibrinogen.  The 
principal  properties  and  reactions  of  these  three  proteids  having 
been  already  noticed,  but  little  remains  to  be  said  of  them  in  this 
connection.  Owing  to  the  property  ]:)0ssessed  by  paraglobulin  and 
fibrinogen  of  being  precipitated  when  Ijlood  is  saturated  with  mag- 
nesium sulphate  (^IgSO^),  a  means  is  therel:)y  offered  of  separating 
the  serum-albumin  from  the  other  two  proteids.  Serum-albumin 
exists  in  human  blood  to  an  amount  of  45.20  parts  per  thousand. 
Although  the  peptones  and  proteoses,  or  the  digested  proteid  food, 
differs  in  many  respects  from  serum-albumin,  the  latter  must  be 
derived  in  the  long  run  from  the  proteid  material  of  the  food.  The 
transformation  of  peptone,  etc.,  appears  to  take  jjlace,  however,  not 
within  the  alimentary  canal,  but  during  absorption,  as  the  peptone, 
■etc.,  passes  through  the  walls  of  the  alimentary  canal  into  the  blood. 
Just  as  the  proteid  substances  of  the  food  are  the  sources  of  the 
serum-albumin  of  the  blood,  so  the  latter  is  the  source  of  the  pro- 
teid material  of  the  tissues.  It  should  be  mentioned,  however,  that 
the  tissues  do  not  derive  their  supply  of  proteid  material  directly 
from  the  blood,  l>ut  rather  from  the  lympli  l)y  which  the  cells  of  the 
tissues  are  loathed.  Paraglobulin  exists  in  human  blood  to  an  amount 
of  31  parts  per  thousand.  It  has  been  stated  that  there  is  more 
paraglobulin  in  serum  than  in  an  equal  amount  of  plasma,  the  ex- 
cess of  paraglobulin  being  accounted  for  on  the  supposition  that  it 
is  derived  from  the  substance  of  the  leucocytes  disintegrated  during 
coagulation.  However  this  may  be,  the  fact  of  paraglobulin  ex- 
isting in  such  an  amount  in  the  plasma,  renders  it  probable  that, 
like  serum-albumin,  it  is  derived  from  nitrogenous  food  and  is  a 
considerable  source  of  the  proteid  material  of  the  tissues.  Apart 
from  these  meagre  statements,  and  what  has  been  said  elsewhere, 
nothing  definite  is  known  either  as  to  the  origin  or  uses  of  para- 
globulin. Fibrinogen,  the  third  proteid  of  the  plasma,  exists  in 
human  blood  only  in  small  amounts,  from  2-4  parts  per  thousand. 
It  differs  in  several  respects,  as  already  mentioned,  from  paraglob- 
ulin. Apart  from  the  theory  already  referred  of  fibrinogen  being 
the  source  of  the  fibrin  of  the  blood,  nothing  is  positively  known  as 
to  its  use  in  the  economy,  still  less  as  to  its  origin. 

The  fatty  matters  that  are  found  in  the  plasma  consist  of  choles- 
terin,  phosphorized  fats,  and  saponified  principles  like  the  marga- 
rates,  oleates,  oleic  acid  existing  sometimes  in  a  free  state.  The 
fatty  sul)stances  exist  only  in  small  quantities  in  the  blood,  and 
•often  depend  upon  the  kind  of  diet.     Thus  fatty  food  increases  the 


SALTS  OF  THE  BLOOD.  227 

amount  of  fat  in  the  blood.  The  use  of  these  fatty  substances  in 
the  blood  is  not  exactly  understood. 

The  saline  materials  of  the  plasma  consist  of  sodium,  potassium, 
and  magnesium  chlorides,  some  free  soda,  of  sodium  and  potassium 
carlx)nates,  of  sodium,  potassium,  and  magnesium  sulphates,  of 
sodium,  potassium,  magnesium,  and  calciimi  phosphates  ;  in  a  word, 
three  chlorides,  free  soda,  two  carbonates,  three  sulphates,  four 
phosphates.  It  is  possible  that  these  salts  do  not  always  exist  in 
the  blood  in  the  above  form,  that  arrangement  being  due  perhaps  to 
the  difficult  and  complicated  processes  incidental  to  their  analysis. 
It  is  well  known  that  a  considerable  quantity  of  the  earthy  phos- 
phates is  molecularly  united  with  the  fibrin  and  part  of  the  sodium 
chloride  with  the  albumin.  The  natural  relation  of  these  salts  as 
well  as  that  of  the  others  must,  therefore,  to  a  certain  extent,  at 
least,  be  disarranged  in  an  analysis. 

The  importance  of  these  salts  is  seen  not  only  in  the  nutrition  of 
the  tissues,  the  calcium  and  magnesium  phosphates,  for  example, 
supplying  material  for  the  production  of  bone,  but  they  are  also  in- 
dispensable in  maintaining  the  blood  in  its  proper  chemical  and 
physical  condition.  Thus  the  alkalinity  of  the  blood  is  due  to  its 
sodium  carbonate,  while  the  sodium  phosphate  dissolves  the  albumi- 
nous principles  and  inorganic  matters  which  are  insoluble  in  pure 
water.  The  earthy  phosphates  are  held  in  solution  in  the  serum 
through  the  presence  of  this  salt,  and  to  it  is  due  the  fact  that  so 
much  carbon  dioxide  is  dissolved  in  the  blood. 

The  existence  of  the  corpuscles  depends  on  the  presence  of  sodium 
chloride  and  other  salts  in  the  serum,  which,  existing  in  isotonic 
amounts  absorb  any  superfluous  water,  and  prevent  their  disso- 
lution. According  to  ^lilne  Edwards,  the  coloring  matter  of  the 
corpuscles  is  very  soluljle  in  water,  but  not  so  in  water  to  which 
have  been  added  albimiin  and  sodium  chloride,  both  of  which  are 
found  in  the  serum.  While  probable,  yet  it  cannot  be  stated  posi- 
tively that  age  or  sex  influences  the  quantity  of  these  salines. 
There  is  no  doubt,  however,  that  these  principles  vary  in  quantity 
according  to  the  kind  of  food.  An  exclusively  animal  or  vegetable 
diet  will  affect  the  amount  of  alkaline  phosphates  respectively. 
Thus  the  former  are  most  abundant  in  the  blood  of  the  carnivora, 
the  latter  in  that  of  the  herbivora.  The  proportion  of  the  saline 
principles  of  the  blood  is  also  known  to  vary  in  disease  ;  but  the 
limited  data,  however,  that  have  been  collected  are  of  more  interest 
at  present  to  the  pathologist  than  to  the  physiologist.  One  of  the 
most  important  substances  found  in  the  blood  is  iron.  Indeed, 
when  it  is  deficient  the  red  corpuscles  diminish  in  number.  The 
normal  standard  is  soon  regained,  however,  when  iron  is  adminis- 
tered. The  iron  exists  in  the  blood  combined  with  the  coloring 
matter  of  the  corpuscles  ;  the  color  of  the  latter,  though,  does  not 
depend  upon  the  iron,  as  was  once  supposed,  for  the  color  M-ill  re- 
main after  the  iron  is  removed,  while  the  blood  of  certain  inverte- 


228  THE  BLOOD. 

brates  like  the  Limulus  (horseshoe  crab)  is  colorless,  though  iron  is 
present. 

From  the  description  of  the  blood  just  given,  it  will  be  seen  to 
consist  of  water,  corpuscles,  proteids,  inorganic  salts,  and  extractives. 

If  the  composition  of  the  corpuscles  be  now  compared  with  that 
of  the  liquor  sanguinis,  it  will  be  found  that  the  corpuscles  contain 
the  phospiiorized  fats,  the  liquor  the  fatty  acids.  The  potash  salts 
are  confined  almost  entirely  to  the  corpuscles,  the  soda  salts  to  the 
liquor ;  the  latter  containing  about  four  times  as  much  soda  as  the 
former.  All  of  the  iron  in  the  blood  is  contained  in  the  corpuscles, 
the  greater  part  of  the  earthy  phosphates,  on  the  contrary,  in  the 
liquor.  The  relative  densities,  quantity  of  water,  solid  matters, 
proportion  of  salts  in  the  corpuscles,  and  liquor  sanguinis,  are  given 
somewhat  in  detail  in  the  following  table  : 

Blood,  in  1000  Parts  Each.' 


Coriniscles,  .513.                        L 

iquor  sangiiinii 

Density 

Water 

1.0885 
,     681.63 

1.028 
901.51 

Solid  matters 

.     318.37 

98.49 

loooToo 

lOOOTOO 

Haematin 

15.02     Fibrin 

8.06 

Globulin 

.     296.07     Extractives 

81.92 

Inorganic  salts     . 

7.28 
318.37 

8.51 

98.49 

Sodium  chloride  . 

5.546 

Potassium  chloride 

3.679 

0.359 

Potassium  phosphate   . 

2.343 

Potassium  sulphate 
Sodium  phosphate 
Soda    .         .         . 

0.132 
0.633 
0.341 

0.281 
0.271 
1.532 

Calcium  phosphate 
Magnesium  phosphate 
Iron     .... 

0.094 

0.060 

.    undetermined 

7.281 

0.298 
0.218 

8.505 

In  concluding  our  account  of  the  blood  a  few  words  may  be  said 
in  reference  to  transfusion,  though  this  subject  is  usually  considered 
as  belonging  to  therapeutics.  About  the  middle  of  the  seventeenth 
century  experiments  were  performed  which  showed  that  life  could 
be  saved  in  an  animal  dying  from  a  copious  hemorrhage,  for  ex- 
ample, by  introducing  into  its  vessels  fresh  blood  from  an  animal 
of  the  same  species.  Application  was  soon  made  of  this  fact  in  the 
treatment  of  human  beings,  and  the  wildest  enthusiasm  was  excited, 
great  hopes  being  entertained  that  old  age  could  be  rejuvenated, 
etc.  Several  fatal  cases  of  transfusion,  however,  occurring,  the 
practice  was  prohibited  in  many  places  by  law.  It  was  revived  in 
the  early  part  of  this  century,  and  with  success.  There  being  a 
'  Schmidt,  in  Eanke  Physiologic,  s.  350.     Leipzig,  1875. 


TRANSFUSION  OF  THE  BLOOD.  229 

number  of  cases  on  record  ^  which  would  have  undoubtedly  proved 
fatal  had  not  transfusion  been  used. 

In  recent  years,  however,  it  has  been  shown  in  the  case  of  cer- 
tain animals,  at  least  the  dog  and  rabbit,  for  example,  that  if  the 
serum  of  the  former  be  introduced  into  the  blood  of  the  latter 
animal,  its  blood  corpuscles  will  be  disintegrated  and  the  blood 
rendered  laky.  This  deleterious  effect  of  the  serum,  together  with 
intravascular  clotting,  due  to  the  introduction  of  fibrin  ferment, 
have  been  assigned  as  causes  of  the  mortality  following  transfusion 
and  used  as  arguments  for  the  discontinuance  again  of  the  practice. 
It  has  been  recommended,  therefore,  in  cases  of  severe  hemorrhage, 
demanding  transfusion,  that  an  isotonic  solution  of  sodium  chloride 
(0.6  per  cent.)  be  introduced  instead  of  blood  or  serum,  which  will 
not  injure  the  corpuscles,  but  by  increasing  the  bulk  and  velocity 
of  the  circulating  fluid  and  preventing  stagnation,  will  make  them 
more  efficacious  as  oxygen  carriers. 

Having  studied  the  composition  and  properties  of  the  blood  gen- 
erally, let  us  now  turn  to  the  consideration  of  its  circulation. 

1  Berard,  Physiologie,  Tome  iii.,  p.  219.     Paris,  1851. 


CHAPTER    XIV. 

CIECULATION  OF  THE  BLOOD. 

The  Heart. 

We  have  seen  that  the  use  of  the  food  is  to  repair  the  waste 
of  the  tissues,  to  supply  fuel  for  the  production  of  energy,  and 
that  the  food  is  digested,  absorbed  and  gradually  elaborated  into 
blood.  To  supply  the  wants  of  the  system,  to  furnish  the  tissues 
T\'ith  material  for  their  maintenance  and  repair,  to  carry  away  that 
which  has  become  worn  out  and  effete,  the  blood  must  move  freely 
through  all  parts  of  the  economy.  It  must  circulate.  By  the  cir- 
culation of  the  blood  is  meant  that  the  blood  moves  in  a  circle — 
that  is,  if  we  follow  its  course,  for  example  (Fig.  84),  after  it  passes 
from  the  left  ventricle  of  the  heart  to  the  aorta  we  shall  see  that 
the  blood  flows  from  the  aorta  into  the  arteries,  thence  into  the 
capillaries,  from  there  into  the  veins,  from  the  latter  by  the  vena 
cava  into  the  right  side  of  the  heart,  from  tlie  right  side  of  the 
heart  through  the  lungs  back  to  the  left  side  of  the  heart  to  the  left 
ventricle,  where  it  started. 

Usually  the  passage  of  the  blood  from  the  right  auricle  of  the 
heart  through  the  lungs  and  left  ventricle  is  known  as  the  lesser,  or 
pulmonary  circulation,  while  the  route  from  the  left  ventricle 
through  the  arteries,  capillaries,  and  veins  to  the  right  auricle  is 
distinguished  as  the  greater  or  systemic  circulation.  Using  the 
word  circulation  in  the  sense  in  which  it  is  ordinarily  accepted,  the 
terms  lesser  and  greater  circulations  are  not  appropriate,  and  may 
mislead,  inasmuch  as  we  have  seen  that  the  blood  does  not  pass 
directly  back  from  the  lungs  to  the  right  auricle  of  the  heart, 
whence  it  came,  but  indirectly,  first  coursiug  through  the  system, 
and  that  the  blood  flo^ving  from  the  left  ventricle  only  returns 
there  after  having  passed  through  the  luugs.  There  is,  in  this 
sense,  then,  only  one  circulation,  however  conveniently  the  latter 
may  be  divided  into  the  so-called  lesser  and  greater  circulations. 
In  another  sense,  however,  there  are  innimiera1)le  circulatious, 
greater  and  lesser,  since  the  blood,  after  leaving  the  heart  (Fig.  84), 
may  go  either  to  the  head,  or  viscera,  or  extremities  before  return- 
ing to  the  heart. 

As  the  motion  of  the  blood  is  in  a  circle,  it  is  immaterial  at  what 
part  of  the  vascular  system  we  begin  its  study.  We  shall  see, 
however,  that  in  exposing  any  of  the  great  functions  of  the  body, 
if  we  follow,  as  far  as  practicable,  the  order  in  which  the  facts  were 
actually  discovered,  and  the  phenomena  generalized  by  the  human 
mind,  that  the  subject  will  be  presented  in  the  most  natural  logical 


TEE  HEART. 


231 


sequence.  We  will  begin,  therefore,  the  study  of  the  circulation 
of  the  blood,  with  the  demonstration  of  the  structure  and  function 
of  the  heart. 


Fkj.  84. 


Fig.  85. 


./■ 


Lull,- 


r.  a.        r.  r.   a.    r.  a.        I.  r. 
Heart  and  luugs  of  man.     (>[ilse  Edwaeds.) 

The  heart  is  a  hollow  pear-shaped 
muscular  organ.  It  is  situated  in  the 
thoracic  cavity,  and  lies  between  the 
lungs,  with  which  it  is  connected  by 
the  great  blood  vessels  arising  from  its 
base  (Fig.  85).  The  heart  is  loosely 
enclosed  in  a  sac,  the  pericardium. 
This  sac,  having  the  form  of  the  heart, 
and  of  a  bluish-white  color,  consists  of 
two  layers.  The  external  fibrous  layer, 
continuous  with  the  external  coat  of 
the  great  blood  vessels,  consists  of  fi- 
brous tissue,  and  is  a  strong,  inexten- 
sible  membrane.  The  internal  delicate 
serous  layer  does  not  differ  essentially 
in  its  general  character  from  that    of 

Diagram  of  the  circulation.  1.  Heart.  SCrOUS  nicmbraue.  It  SUrrOUuds  thc 
2.  Lungs.  S.  Head  and  upper  estrenn-  Kp^rt  closclv  adheriuo;  tO  it  and  IS  thcU 
ties.    4.  Spleen.     5.  Intestine.     6.  Kiu-  J  c  .      r  i.\ 

ney.  7.  Lower  extremities.  8.  Liver,  reflected  ovcr  the  Commencement  01  tne 
^^*'''™''-^  great   blood  vessels   and   thc   interior 

surface  of  the  external  fibrous  membrane.  The  cavity  of  the 
pericardium  contains  about  a  drachm  or  two  of  a  serous  fluid, 
through  the  presence  of  which  the  opposed  internal  surfaces  of  the 


232 


CIRCULATION  OF  THE  BLOOD. 


Fir; 


pericardium  glide  smoothly  over  each  other,  the  movements  of  the 

heart  being  thereby  facilitated. 

The  pericardium  is  attached  by  connective  tissue  to  the  pleura  on 

each  sicle,  and  the  tendinous  center  of  the  diaphragm  below.     It  is 

not  necessary  to  give  a  de- 
tailed, minute  description  of 
the  disposition  of  the  mus- 
cular fibers  of  the  heart, 
Avhich  is  quite  complex,  a 
general  account  in  connec- 


tion with  the  present  subject 
being  sufficient.  The  auri- 
cles, or  upper  cavities  of  the 
heart  (Fig,  t^ii,  d,  e),  are  en- 
circled by  a  thin  layer  of 
muscular  fibers,  common  to 
l)oth  tliese  cavities,  and  sur- 
rounding the  auricular  ap- 
pendages, the  entrance  of 
the  vena  cava,  the  coronary 
and  pulmonary  veins.  Be- 
neath this  superficial  layer 
are  the  fibers  of  the  deep 
layer  attached  to  the  fibrous 
rings  of  the  aurieulo- ven- 
tricular orifices,  and  dis- 
posed in  an  annular  and  loop-like  manner.  The  muscular  fibers  of 
the  ventricles,  like  those  of  the  auricles,  are  also  arranged  in  two 
sets,  superficial  and  deep.  The  superficial  fibers  (Fig.  86,  a,  b), 
which  are  common  to  both  ventricles,  run  from  base  to  apex,  and  at 
this  point  pass  into  the  interior  of  the  ventricle 
in  the  form  of  a  whorl  or  spiral,  some  of  the 
fibers  terminating  in  the  columnse  carnese  and 
papillary  muscles,  others  returning  after  a 
twisting  course  to  the  point  from  which  they 
started.  The  fibers  of  the  deep  set  (Fig.  87) 
surround  each  ventricle  separately,  and  are 
disposed  in  a  circular  or  transverse  manner 
between  the  external  and  internal  layers  of 
the  superficial  fibers,  and  are  much  better  de- 
veloped in  the  left  ventricle  than  in  the  right. 
Microscopically  the  muscular  substance  of 
the  heart  consists  of  transverse  striated  muscu- 


Aiiteridi-  view  ot'lie;ivt.     ((Juain.) 


Fig.  87 


Left  ventriele  of  bullock's 

lar  fibers.     These  fibers,  however,  differ  from  ]lS.  ''(^^i.)*^  ^*^'p 
the  ordinary   fibers   of  voluntary   muscles   in 
several    particulars.      They  are    destitute    of   sarcolemma,    much 
smaller  and   more  granular,  not  collected    into  bundles,  and  are 
separated  by  comparatively  little  connective  tissue.     The  most  in- 


VALVES  OF  THE  HEART, 


233 


Fir: 


teresting  peculiarity,  however,  about  these  libers,  is  their  anasto- 
mosing or  inoscuhition  with  each  other  (Fig.  88),  which,  no  doubt, 
favor  the  contraction  of  the  heart  and  the  thorough  expulsion  of 
the  blood  from  its  cavities. 

If  a  longitudinal  section  be  carried  through  the  heart  from  base  to 
apex,  its  interior  will  be  seen  from  such  a  section  to  consist  of  four 
cavities  :  two  auricles,  so  called  from  their  auricular  appendages, 
and  two  ventricles  ;  that  the  right  auri- 
cle communicates  with  the  venoe  cavie 
and  with  the  right  ventricle,  and  the 
left  auricle  with  the  pulmonary  veins 
and  the  left  ventricle  ;  there  is  no  com- 
munication, however,  between  the  two 
auricles  or  between  the  two  ventricles  ; 
the  rio-ht  or  venous  side  of  the  heart 
being  completely  separated  from  the 
left  or  arterial  side  by  the  septum  of 
the  heart,  which  is  imperforate. 

In  certain  mammals,  in  the  dugong 
(Halicore)  and  manatee  (]\Ianatus)  for 
instance,  this  distinction  of  the  right 
from  the  left  side  of  the  heart  is  to  a 
certain  extent  visible,  even  externally, 
the  ventricles  at  the  apex  being  sep- 
arated by  quite  an  interval. 

We  have  just  seen  that  the  heart  is 
covered  with  the  serous  layer  of  the  pericardium.  It  will  be  ob- 
served that  the  interior  of  the  heart  is  also  lined  by  a  thin  trans- 
lucent membrane,  the  endocardium,  which  is  continuous  with  the 
internal  coat  of  the  blood  vessels  and  consists  of  a  fibrous  elastic 
and  epithelial  layer.  Just  at  the  point  where  the  auricles  pass  into 
the  ventricles,  the  endocardium  projects  into  the  cavity  of  the  heart 
from  the  wall  of  the  heart  on  one  side,  and  from  the  septum  on  the 
other.  This  portion  of  the  endocardium  is  strengthened  by  the  ad- 
dition of  fibrous  tissue.  It  is  these  projections  that  serve  to  divide 
the  auricles  from  the  ventricles.  The  interval  left  between  these 
projections  constitutes  the  auriculo-ventricular  orifices.  The  fibro- 
elastic  tissue  in  this  situation  forms  a  slight  ring,  to  which  is  at- 
tached on  the  right  side  of  the  heart  the  tricuspid  valve  (Fig.  89, 
Fig.  91,  5,  5',  5"),  three  membranous  folds,  which  consist  of  dou- 
blino^s  of  the  endocardium  thickened  bv  the  included  fibrous  tissue. 
By  means  of  these  curtains  or  valves,  the  auriculo-ventricular  orifice 
can  be  closed,  the  edges  of  the  valves  being  then  pressed  together 
(Fig.  91),  as  we  shall  see,  by  the  blood,  and  are  kept  stretched  by 
the  tendinous  cords  as  the  sail  of  a  boat  is  kept  stretched  against 
the  wind  by  the  sheet  line. 

The  chordffi  tendinea?  are  tendinous  cords  inserted  into  the  valve, 
and  arise  either  directly  from  the  walls  of  the  ventricle  or  are  con- 


ilui<cular  til 


(.UlAIN. 


234 


CIM.CULATION  OF  THE  BLOOD. 


nected  with  it  by  the  papiUary  muscles.  Of  these  latter  many  pass 
directly  again  into  the  substance  of  the  heart  and  are  then  known 
as  the  fleshy  columns  or  column^e  carnea?.  During  the  repose  of 
the  ventricle  the  auriculo-ventricular  orifice  is  open,  the  valves  then 
lying  loosely  against  the  walls  of  the  ventricle.  The  same  disposi- 
tion, such  as  we  have  just  described,  obtains  essentially  in  the  left 


Fig.  89. 


The  right  auricle  and  veutricle  opened,  and  a  part  of  their  right  and  anterior  walls  removed 

<(»  a<  tn  shfiW  thpir  lllti>rior.       i/^_       fOTIATN.'l 


(QUAIN.) 


side  of  the  heart.  The  mitral  valve,  however  (Fig.  90  and  Fig.  91, 
6,  6'),  by  which  the  left  auriculo-ventricular  orifice  is  closed,  con- 
sists of  two  membranous  folds  instead  of  three,  as  is  the  case  in  the 
tricuspid  valve,  and  is  stronger  than  the  latter. 

It  will  be  observed  that  the  tricuspid  and  mitral  valves  open 
from  the  auricle  to\vard  the  ventricle,  but  do  not  project  from  the 
ventricle  into  the  auricle.  At  the  anterior  angle  of  the  base  of  the 
right  ventricle  (Fig.  91,  7),  may  be  seen  an  orifice  guarded  by 
three  crescentic  membanous  folds,  the  semilunar  valves.  Through 
this  orifice  the  right  ventricle  communicates  with  the  pulmonary 
artery.  The  semilunar  valves  consist  of  doublings  of  the  endocar- 
dium, strengthened  by  fibrous  tissue.     The  convex  border  of  each 


VALVES  OF  THE  HEART. 


235 


valve  is  attached  to  the  ed^e  of  the  ring-like  orifice  of  the  pulmo- 
nary artery,  the  free  edge  projecting  into  the  latter.  Behind  each 
semilunar  valve  the  artery  is  dilated  into  a  pouch,  the  sinus  of  Val- 
salva. This  sinus  prevents  the  valve  when  open  from  adhering  to 
the  walls  of  the  artery,  and  enables  the  blood  to  get  behind  each 
valve  and  press  it  down  so  that  the  three  valves  meet  (Fig.  91,  7), 
and  so  close  the  orifice,  but  readily  separate  when  the  flow  is  from 


Fir:.    <.10. 


The  left  auricle  and  ventricle  oi)ened  and  a  part  of  their  anterior  and  left  -n-alls  removed  so  as  to 
show  their  interior.  3/^.  The  pulmonary  artery  has  heen  divided  at  its  commencement  so  as  to 
show  the  aorta  ;  the  opening  into  the  left  ventricle  has  been  carried  a  short  distance  into  the  aorta 
between  two  of  the  segments  of  the  semilunar  valves  ;  the  left  part  of  the  auricle  with  its.appen- 
dix  has  been  removed.    The  right  auricle  has  been  thrown  out  of  view.     (Quaix.) 

the  ventricles  toward  the  great  vessels,  preventing  a  reflux  from  the 
great  vessels  back  into  the  ventricle. 

At  the  middle  of  the  free  border  of  the  semilunar  valves  may  be 
seen  a  little  nodule  of  fibrous  tissue.  These  nodules,  or  corpora 
Arantii  serve  as  a  common  central  point  of  contact  when  the  valves 
are  closed.  The  semilunar  valves  of  the  aorta  (Fig.  91,  8)  do  not 
differ  in  their  structure  or  function  from  those  of  the  pulmonary 
artery,  and,  like  the  latter,  act  when  in  contact  in  closing  the  orifice 


236 


CIRCULATION  OF  THE  BLOOD. 


of  commuuication  between  the  left  ventricle  and  the  aorta.  The 
manner  in  which  the  tricuspid  and  mitral  valves  act  can  be  readily 
demonstrated  by  filling  the  ventricles  with  water  by  means  of  a 
funnel  introduced  into  the  orifices  of  the  pulmonary  artery  and 
aorta ;  the  water  rising  up  between  the  walls  of  the  ventricles  and 
the  valves  will  float  the  valves  up  until  their  edges  are  approxi- 
mated, so  closing  the  auriculo-ventricular  orifices.  By  pouring 
water  into  the  pulmonary  artery  and  aorta  it  will  be  seen  that  the 
water  gets  in  between  the  wall  of  the  vessel  and  the  valve,  into  the 

Fig.  91. 


View  of  the  base  of  the  ventricular  part  of  the  heart,  sliowing  the  relative  position  of  the  ar- 
terial and  auriciilo-veatricular  orittces.  %.  The  muscular  fibers  of  the  ventricles  are  exposed  by 
the  removal  of  the  pericardium,  fat,  blood  vessels,  etc.;  the  pulmouar}-  artery  and  aorta  have 
been  removed  by  a  section  made  immediately  beyond  the  attachment  of  the  semilunar  valves,  and 
the  auricles  have  been  removed  immediatelj"  above  the  auriculo-ventricular  orifices. 


sinus  of  Valsalva,  and  so  forces  the  free  edges  of  the  semilunar 
valves  toward  each  other,  thus  effectually  closing  the  orifices  at  the 
mouths  of  the  great  vessels.  • 

Such  being  the  general  structure  of  the  heart,  let  us  consider  now 
the  course  that  the  blood  takes  in  passing  through  it.  In  watching 
the  heart  beating  in  a  living  animal,  a  mammal,  for  example,  it 
will  be  observed  that  at  tlie  same  moment  the  right  auricle  is  di- 
lated by  the  venous  blood  flowing  from  the  system  through  the 
venae  cavse,  the  left  auricle  is  dilated  by  the  arterial  blood  flowing 
into  it  through  the  pulmonary  veins  from  the  lungs.  This  syn- 
chronous dilatation  of  the  auricles  is  known  as  the  auricular  diastole. 
Suddenly,  and  succeeding  this  auricular  diastole,  or  filling  up  of  the 
auricles,  both  auricles  simultaneously  contract,  the  venous  blood 
passing  from  the  right  auricle  into  the  right  ventricle,  the  arterial 
blood  from  the  left  auricle  into  the  left  ventricle,  regurgitation  to 
any  extent  into  the  veuie  cavte  or  pulmonary  veins  being  prevented 
by  the  muscular  fibers  encircling  these  vessels  and  the  pressure  of 
the  blood.  This  synchronous  contraction  of  the  auricles  is  called 
the  auricular  systole.     As  in  the  experiment  just  performed  with 


VALVES  OF  THE  EEABT.  237 

the  water,  so  the  blood  within  the  ventricles  of  the  heart  of  the  liv- 
ing animal  gets  in  between  the  walls  of  the  ventricles  and  the  flaps 
of  the  tricuspid  and  mitral  valves  and  floats  the  edges  of  the  valves 
up  until  the  auriculo-ventricular  orifices  are  closed.  At  this  mo- 
ment, the  ventricles  Ijeing  fully  dilated  simultaneously  contract, 
with  the  effect  of  still  more  thoroughly  approximating  the  tricus- 
pid and  mitral  valves  than  is  the  case  at  the  end  of  the  auricular 
systole,  and  so  of  more  completely  closing  the  auriculo-ventricular 
orifices.  The  papillary  muscles  contracting  at  the  same  time  as  the 
walls  of  the  ventricles  and  acting  through  the  chordae  tendinese 
upon  the  valves  stiffen  them  and  prevent  their  inversion  into  the 
auricles.  The  synchronous  filling  up  and  contraction  of  the  ven- 
tricles is  known  as  the  diastole  and  systole  of  the  heart,  but  more 
properly  as  the  ventricular  diastole  and  ventricular  systole.  Dur- 
ine:  the  ventricular  svstole  the  auricles  are  receiving  blood  from 
the  ven£e  cavse  and  the  pulmonary  veins. 

Inasmuch  as  regurgitation  backward  from  the  ventricles  into 
the  auricles  is  prevented  through  the  auriculo-ventricular  orifices 
being  closed  by  the  approximation  of  the  tricuspid  and  mitral  valves 
during  the  ventricular  systole,  the  venous  blood  passes  from  the 
right  ventricle  through  the  pulmonary  artery  to  the  lungs,  and  the 
arterial  blood  from  the  left  ventricle  through  the  aorta  to  the  system. 
Immediately  after  the  ventricular  systole  or  contraction  of  the 
ventricles  follows  their  relaxation.  During  this  period  the  heart  is 
in  repose.  The  auriculo-ventricular  orifices  are  again  open,  the 
venous  and  arterial  blood  that  has  accumulated  in  the  right  and  left 
auricles  respectively  during  the  contraction  of  the  ventricles  and 
while  the  auriculo-ventricular  orifices  were  closed,  now  flows  into 
the  ventricles,  Avhile  this  blood  is  replaced  by  the  venous  blood 
flowing  into  the  right  auricle  from  the  vense  cavse,  and  the  arterial 
blood  flowing  from  the  pulmonary  veins  into  the  left  auricle. 
Toward  the  end  of  the  ventricular  systole  the  venous  and  arterial 
blood,  forced  respectively  into  the  pulmonary  artery  and  the  aorta, 
gets  in  between  the  walls  of  the  vessels  and  the  semilunar  valves  in 
the  sinuses  of  Valsalva,  and  forces  their  free  edges  toward  each 
other  as  in  the  experiment  just  performed  with  the  water.  At  the 
end  of  the  ventricular  systole,  the  semilunar  valves  being  closely 
approximated  and  the  orifices  of  the  great  vessels  closed,  through 
the  elastic  recoil  of  the  arteries  on  their  contents,  the  blood,  being 
unable  to  regurgitate  backward  from  the  pulmonary  artery  and 
aorta,  is  forced  on  to  the  lungs  and  the  system.  It  will  be  seen 
from  the  phenomena  just  described  that,  while  the  right  side  of  the 
heart  containing  venous  blood  is  entirely  distinct  from  the  left  con- 
taining arterial,  nevertheless,  the  two  sides  of  the  heart  act  as  one — 
the  venous  blood  flowino;  into  the  ri":ht  auricle  as  the  arterial  blood 
flows  into  the  left,  the  synchronous'  filling  up  and  emptying  of  the 
auricles  being  followed  by  the  synchronous  dilatation  and  contrac- 
tion of  the  ventricles,  at  the  same  time  the  blood  forced  out  of  the 


238  CIRCULATION  OF  THE  BLOOD. 

latter  passing  to  the  lungs  and  the  system  through  the  pulmonary 
artery  and  aorta  respectively. 

The  beating  of  the  heart,  as  we  have  endeavored  to  describe  it, 
in  an  animal,  a  dog  or  a  rabbit,  for  example,  has  been  shown  to  be 
essentially  the  same  in  man,  at  least  so  far  as  comparison  has 
been  possible.  As  might  be  expected,  cases  of  ectopia  cordis  are 
very  rare,  but  there  has  been  a  sufficient  number  of  such  cases  to 
demonstrate  that  the  manner  in  which  blood  flows  through  the  heart 
in  man  does  not  diifer  from  that  of  the  mammal. 

While  the  action  of  the  tricuspid  valve  and  semilunar  valves  of 
the  pulmonary  artery  is  essentially  the  same  as  that  of  the  mitral 
valve  and  semilunar  valves  of  the  aorta,  nevertheless  the  valves  on 
the  right  side  of  the  heart  do  not  close  their  respective  orifices  as 
perfectly  as  those  on  the  left  side  of  the  heart,  there  being  some 
little  regurgitation  possible  back  from  the  pulmonary  artery  to  the 
right  ventricle,  and  from  the  right  ventricle  to  the  right  auricle. 
The  effect  of  this  insufficiency  of  the  valves  on  the  right  side  of  the 
heart  is  obviously  of  advantage ;  were  it  otherwise,  an  excess  of 
blood  driven  from  the  right  ventricle  through  the  pulmonary  artery 
to  the  lungs  might  rupture  those  delicate  organs.  This  danger  is 
avoided  through  the  imperfect  closure  of  the  pulmonary  and  the 
right  auriculo-ventricular  orifices,  since,  when  resistance  is  offered 
by  the  pulmonary  capillaries,  the  blood  will  regurgitate  backward 
through  the  pulmonary  artery  to  the  ventricle  and  thence  to  the 
auricle.  There  is  no  insufficiency,  however,  on  the  left  side  of  the 
heart,  the  auriculo-ventricular  and  aovtic  orifices  being  completely 
closed  by  the  mitral  and  semilunar  valves  respectively.  It  mil  be 
observed  also  that  the  walls  of  the  left  ventricle  are  three  or  four 
times  as  thick  as  those  of  the  right.  This  is  due,  as  might  have 
been  anticipated,  to  the  fact  that  the  contraction  of  the  left  ventricle 
forces  the  blood  to  all  parts  of  the  system,  whereas  the  right  ven- 
tricle forces  the  blood  only  to  the  lungs.  For  the  same  reason  the 
walls  of  the  auricles  are  thinner  than  those  of  the  ventricles,  little 
force  being  required  to  drive  the  blood  from  the  former  cavities  into 
the  latter. 

The  muscular  substance  of  the  heart,  like  that  of  muscles  gener- 
ally, is  therefore  developed  according  to  the  amount  of  muscular 
force  to  be  expended. 

As  the  period  which  elapses  in  mammals  during  a  cardiac  revo- 
lution or  cycle — that  is,  the  time  during  which  all  the  cavities  of 
the  heart  fill  and  empty  themselves — is  only  about  one  second, 
actually  0.8  sec.  in  man,  it  is  evident  that  close  and  careful  observa- 
tion is  necessary  in  order  to  distinguish  the  successive  phenomena 
that  we  have  endeavored  to  describe  in  the  beating  heart.  It  is 
well,  therefore,  to  begin  the  study  of  the  action  of  the  heart  by 
observing  the  phenomena,  first,  as  they  present  themselves  in  the 
lower  vertebrates,  for  example,  in  frogs,  snakes,  turtles,  and  alli- 
gators.     Such  animals  are  not  only  readily  procurable,  but  are  par- 


DURATION  OF  MOVEMENTS  OF  THE  HEART.  239 

ticularly  suitable  for  the  purpose,  siuce  in  them  the  cardiac  revohi- 
tions  succeed  each  other  much  more  slowly  than  is  the  case  in 
mammals,  and  in  the  frog  especially  there  is  an  appreciable  interval 
between  the  systole  of  the  auricle  and  that  of  the  ventricle,  whereas, 
in  most  mammals  the  systole  of  the  auricle  runs  so  into  that  of  the 
ventricle  that  it  is  impossible  to  say  exactly  where  the  first  ends 
and  the  second  begins,  the  muscular  contraction  running  as  a  con- 
tinuous wave  over  auricle  and  ventricle  from  base  to  apex.  Further, 
the  heart  of  the  frog  has  only  one  ventricle,  and  while  there  are  two 
such  cavities  in  the  heart  of  the  turtle,  nevertheless,  they  communi- 
cate, the  septum  being  but  little  developed.  In  these  animals,  then, 
the  single  ventricle  acts  like  the  two  ventricles  of  the  mammalian 
heart,  and  familiarizes  one  with  the  synchronous  action  of  the 
ventricles  when  two  such  cavities  are  present.  Again,  these  animals 
oifer  through  their  mode  of  breathing  another  advantage,  in  that  the 
heart  will  continue  beating  even  after  the  thorax  has  been  opened, 
there  being  no  necessity  of  keeping  up  artificial  respiration.  We 
shall  see,  however,  when  we  wish  to  study  the  action  of  the  heart 
in  mammals,  tliat  artificial  respiration  must  be  maintained,  for  with 
the  opening  of  the  chest  the  lungs  collapse,  respiration  ceases,  and 
the  circulation  stops.  Notwithstanding  that,  in  mammals,  a  cardiac 
revolution  occupies  such  a  small  period  of  time — about  one  second — 
nevertheless,  the  relative  parts  of  the  second  elapsing  during  which 
the  auricular  and  ventricular  systole  take  place  and  the  heart  is  in 
repose,  have  been  experimentally  determined,  as  in  the  horse,  for 
example,  by  Marey  and  Chauveau.^  The  general  results  of  their 
observations  are  embodied  in 

Duration   of   Movements  of  Heart  ix  Horse. 

Auricular  systole.  Ventricular  systole.  Repose. 

0.2  sec.  0.4  sec.  0.4  sec. 

from  which  it  will  be  observed  that  the  auricular  systole  lasts  two- 
tenths  of  a  second,  the  ventricular  systole  four-tenths  of  a  second, 
and  the  repose  of  the  heart  four-tenths  of  a  second,  one  second  be- 
ing supposed  to  elapse  during  an  entire  cardiac  revolution. 

The  apparatus  necessary  for  the  above  determination  of  the 
rhythm  of  the  heart's  movements  as  they  occur  in  the  horse,  as 
used  by  Marey,  consists  essentially  of  a  sound  (Fig.  92)  to  be  in- 
troduced through  the  jugular  vein  into  the  heart  of  the  animal. 
The  sound  is  divided  into  two  tubes,  one  of  which  is  a  distinct 
tube,  the  other  being,  however,  only  the  space  arotnid  the  tube. 
The  tube  terminates  at  one  end  in  a  little  elastic  bag  (r),  to  be  in- 
serted into  the  ventricle,  and  at  the  other  end  in  a  drum  provided 
with  a  registering  lever  (Jr).  The  space  surrounding  the  tube  com- 
municates on  the  one  hand  with  a  similar  elastic  bag  (o)  to  be  inserted 
into  the  auricle,  and  at  the  other  end  with  a  tube  passing  into  a 

^Comptes  rendus  Soc.  Biol.,  Paris,  1861.  Comptes  rendus  Acad.  Sciences, 
Paris,  1862. 


240 


CIRCULATION  OF  THE  BLOOD. 


drum  provided  with  a  second  similar  recording  lever  (/o).  The 
object  of  the  elastic  bags  o  and  v  is  that  the  successive  contractions 
of  the  auricle  and  ventricle  in  -which  they  are  placed  will  be  trans- 
mitted through  them  to  the  registering  levers  lo  and  Iv,  and  as  the 
auricle  contracts  before  the  ventricle  it  is  evident  that  the  lever  lo 


Fk;.   !)2. 


connected  with  the  elastic  bag  (o)  in  the  auricle  will  move  before 
the  lever  (Iv)  connected  with  the  bag  {v)  in  the  ventricle.  If  the 
registering  levers  are  placed  in  contact  with  a  recording  surface 
(AE)  moving  at  a  uniform  rate,  and  if  this  surface  be  marked  by 
vertical  parallel  lines,  each  intervening  space  representing  the  one- 
tenth  of  a  second,  the  lengths  of  time  during  which  the  auricular 
and  ventricular  systole  and  the  repose  of  the  heart  last  will  be 
graphically  recorded  (Fig.  93).  The  cardiac  revolution  in  this  in- 
stance lasted  twelve-tenths  seconds. 

In  order  to  divide  the  surface  of  the  recording  cylinder  into  a 
number  of  spaces  each  equal  to  the  one-tenth  of  a  second,  a  vibrat- 
ing reed  (A)  and  an  electro-magnet  (B,  Fig.  94)  are  used.  The 
reed  clamped  under  the  electro-magnet  by  one  end  to  a  stand  (C), 
the  other  end  dipping  into  mercury  (D),  is  connected  on  the  one 
hand  with  a  battery  (E),  and  on  the  other  with  another  small  elec- 
tro-magnet (F).  Such  being  the  disposition,  at  the  moment  that 
the  current  is  made,  the  electro-magnet  (B),  being  magnetized,  will 
attract  the  reed,  drawing  it  out  of  the  mercury ;  but  the  current 
being  thereby  broken,  the  electro-magnet  being  then  demagnetized, 
will  cease  to  attract,  and  the  reed  will  fall  back  into  the  mercury, 
remaking  the  current ;  the  reed  will  then  be  again  raised,  the  cur- 
rent broken,  and  the  reed  fall  again  into  the  mercury,  the  number 
of  these  alternate  elevations  and  depressions  per  second  depending 
upon  the  number  of  vibrations  of  the  reed  in  that  time.  Inas- 
much, however,  as  the  small  electro-magnet  (F)  is  magnetized  and 


THE  VIBRATOR. 


241 


demagnetized  iu  the  same  manner  as  the  large  one,  the  bar  attached 
to  it  and  carrying  the  pen  (P)  ^\\\\  approach  and  recede  from  it  syn- 
chronously with  the  vibrations  of  the  reed.     By  placing  the  pen  in 


Fig.  93. 


aui-iclo. 


Tentricle. 


Tracing  the  variations  of  pressure  in  the  right  auricle  and  ventricle,  and  of  the  cardiac  impulse, 
in  the  horse.     (To  he  read  from  left  to  right.)     (JIarey.) 

Fig.  94. 


Vibrator. 


contact  A\'ith  the  recording  cylinder,  a  trace  is  obtained  in  which 
the  equal  spaces  between  the  vertical  lines  made  by  the  marker  are 

16 


242 


CIRCULATION  OF  THE  BLOOD. 


equal  to  the  one-tenth  of  a  second,  the  reed  used  vibrating  at  that 
rate.  By  substituting  reeds  or  tuning  forks  vibrating  at  the  rate 
of  15,  20,  50,  or  100  times  a  second,  we  get  traces  in  which  the 
equal  spaces  represent  the  corresponding  fractional  parts  of  a  sec- 
ond. Usually,  there  is  also  a  third  registering  lever  (Fig.  90,  le) 
below  the  ventricular  one,  connected  by  tubing  M-ith  a  cardiograph 
(c),  the  object  of  which  is  to  transmit  the  cardiac  impulse  caused  by 
the  beating  up  of  the  heart  against  the  chest.  This  impulse  is 
shown  to  be  absolutely  synchronous  with  the  ventricular  beat  as 
recorded  by  the  second  lever  [h). 

From  the  observations  of  Franck,^  made  upon  a  woman  with 
ectopia  cordis,  there  is  no  reason  to  doubt  upon  the  supposition  that 
the  cardiac  cycle  lasts  0.8  seconds,  that  the  duration  of  the  auricular 
and  ventricular  systole  and  the  repose  of  the  heart  are  relatively 
the  same  in  man  as  in  the  horse,  as  shown  in 


Duration  of  Movements  of  Heart  in  Man. 


Auricular  systole. 

0.16  sec. 


Ventricular  systole. 

0.32  sec. 


Repose. 

0.32  sec. 


Inasmuch  as  it  is  by  the  contraction  of  the  ventricles  that  the 
blood  is  driven  through  the  lungs  and  the  system  and  as  the  ven- 
tricles recover  themselves,  so  to  speak,  during  the  repose  of  the 
heart  it  might  be  naturally  supposed  that  when  the  number  of  the 
heartbeats  are  increased  above  the  normal  the  duration  of  the  repose 
of  the  heart  would  be  shortened  rather  than  that  of  the  ventricular 
systole.  That  such  is  the  case  appears  to  have  been  shown  experi- 
mentally both  in  man  and  animals.  Thus  it  has  been  ascertained 
in  man,  by  auscultation,-  that  the  period  elapsing  between  the  first 
and  the  second  sound  of  the  heart,  or  the  period  corresponding,  as 

Fig.  95. 


Double  myograph. 


we  shall  see,  to  the  ventricular  systole,  varies  much  less  in  duration 
than  that  of  the  repose,  with  a  varying  heartbeat.     Indeed,  with  a 

'Travaux  der  Lab.  de  Marey,  Tome  iii.,  1877,  p.  311. 

^F.  C.  Donders,  Nederlandsch  Archief  Voor  Genees  eu  Xatuurkunde,  Tweede 
Jaargang,  I8G0,  p.  139. 


THE  DOUBLE  MYOGRAPH.  243 

very  rapidly  beating  heart  the  duration  of  the  repose  may  be  so 
brief  that  the  contraction  of  the  auricles  practically  follow  that  of 
the  ventricles. 

Experiments  made  by  registering:  levers  pressed  upon  the  skin 
overlying  an  artery  in  man  ^  or  upon  the  exposed  heart  in  animals ' 
confirm  the  above  conclusions.  Thus,  for  example,  with  the  heart 
beating  in  a  man  at  the  rate  of  47  per  minute  the  ventricular  sys- 
tole lasted  0.34  seconds,  the  repose  0.93  seconds,  whereas  with  the 
heart  beating  at  the  rate  of  128  per  minute,  the  ventricular  systole 
lasted  0.25  seconds,  the  repose  only  0.21  seconds.  A  convenient 
method  of  demonstrating  the  time  elapsing  during  the  contractions 
of  the  auricles  and  the  ventricles  and  the  repose  of  the  heart  in  a 
living  animal,  a  fi'og  or  a  turtle  for  example,  is  by  means  of  the 
double  myograph  (Fig.  95).  This  instrument  consists  of  two  levers, 
to  which  are  attached  delicate  rods,  ending  in  aluminium  plates, 
which  rest  upon  the  auricle  and  ventricle  of  the  heart  of  the  animal 
examined.  The  levers  can  be  shortened  or  lengthened,  their  pressure 
diminished  or  increased  by  appropriate  mechanical  arrangements, 
and  the  movements  of  the  auricle  and  ventricle  transmitted  l)y  them 
are  recorded  upon  a  cylinder  moving  at  a  uniform  and  known  rate, 
by  which  the  time  elapsing  can  be  determined. 

'  E.  Thureton,  Journal  of  Auat.  and  Plivs.,  Vol.  x.,  1876,  p.  494. 
2X.  Baxter,  Du  Bois  Eeymond's  Archiv,  Band,  1878,  s.  122. 


CHAPTER    XV. 

CIECULATION  OF  THE  BhOOJ).— (Continued.) 
CARDIAC  IMPULSE. 

In  examining  the  heart  in  a  living  animal,  as  described  in  the 
last  chapter,  it  Avill  be  observed  that  with  each  ventricular  systole 
the  heart,  as  a  whole,  moves  forward  and  upward,  the  apex  more 
particularly  beating  up  against  the  chest,  and  so  giving  rise  to  what 
is  known  as  the  cardiac  impulse.  If  a  finger  be  placed  -svithin  the 
thoracic  cavity  of  a  living  animal,  between  the  heart  and  the  side 
of  the  chest,  with  every  contraction  of  the  ventricle  the  finger  will 
be  pressed  against  the  chest  by  the  apex.  Pathological  cases,  like 
that  of  the  Viscount  ^Montgomery,  so  graphically  described  by 
Harvey,^  have  given  physiologists  the  opportunity  of  showing  that 
the  cardiac  impulse  is  produced  in  men  as  in  animals  by  the  striking 
of  the  heart  against  the  chest. 

In  man  the  cardiac  impulse  is  most  distinctly  felt  in  the  fifth  left 
intercostal  space,  about  two  inches  below  the  left  nipple,  and  one 
inch  to  its  sternal  side.  The  force  and  extent  to  which  the  cardiac 
impulse  may  be  perceived  varies  very  much  in  different  individuals, 
and  in  the  same  individual,  according  to  circumstances.  Thus,  it 
is  more  perceptible  in  emaciated  than  in  fat  persons,  during  expira- 
tion than  in  inspiration,  in  one  lying  upon  the  left  side  than  in  one 
lying  upon  the  right,  etc.  The  movement  of  the  heart  forward  and 
upward  j^roducing  the  cardiac  impulse  seems  to  be  due  to  several 
causes.  Thus,  the  sudden  distention  of  the  great  elastic  vessels  at 
its  base  would  throw  the  entire  organ  forward,  the  recoil  of  the 
ventricles,  as  they  discharge  their  contents,  further  aiding  the 
movement.  The  disposition  of  the  muscular  fibers  is  also  such  that 
the  heart  during  its  ventricular  systole  changes  its  form,  bulging 
somewhat  forward,  the  spiral  muscular  fibers,  at  the  same  time, 
tilting  up  the  apex. 

For  ordinary  purposes  the  force  and  extent  of  the  cardiac  impulse 
can  be  sufficiently  well  appreciated  by  the  hand.  The  cardiograph, 
however,  furnishes  us  M'ith  the  means  of  a  far  more  accurate  study 
of  the  beat  of  the  human  heart  than  that  afforded  by  the  sense  of 
touch  alone.  The  cardiograph  (Fig.  96)  consists  of  a  disk-shaped 
box,  one  side  of  which  is  formed  by  an  elastic  membrane.  In  the 
center  of  the  latter  is  inserted  an  ivory  knob  (^1),  which  is  applied 
to  the  chest  over  the  place  where  the  cardiac  impulse  is  greatest. 
The  box,  or  tympanum,  communicates  by  an  elastic  tube  (/)  with 
a  second  tympanum  (6),  with  which  is  connected  a  registering  lever 
'  Exercit.  de  generat.  Animalium,  p.  loG.     London,  1651. 


THE  CARDIOGRAPH. 


245 


(fZ).  It  is  evident  that  when  the  cardiograph  is  firmly  fastened  to 
the  chest  that  the  shock  of  the  cardiac  impulse  will  be  transmitted 
to  the  ivory  knob,  thence  to  the  first  tympanum  and  through  the 
column  of  air  in  the  communicating  tube  to  the  interior  of  the 
second  tympanum,  and  so,  by  means  of  the  elastic  and  movable  lid 


of  the  latter,  to  the  registering  lever.  If  the  point  of  the  lever  be 
placed  in  contact  with  a  cylinder  revolving  at  a  uniform  rate,  we 
obtain  a  graphic  representation  or  trace  of  the  heart's  impulse  (Fig. 
97).      By  such  an  apparatus  variations  in  the  heart's  beat,  which 


Fig.  97. 


Tracing  of  heart's  impulse  in  man,  taken  with  cardiograph.     To  be  read  from  left  to  right. 

are  so  slight  as  to  be  quite  inappreciable  by  the  sense  of  touch 
alone,  become  very  perceptible. 

'S\lien  it  is  desired  to  take  a  cardiographic  tracing  in  a  small 
animal,  like  a  rabbit,  guinea-pig,  or  cat,  a  very  convenient  form  of 
cardiograph  is  that  described  by  Marey^  (Fig.  i^'8).  The  instru- 
ment, as  used  by  the  author,  consists  of  two  tambours  (a,  6),  each  of 
which  contains  a  spring,  through  which  the  membrane  is  kept  pro- 
jected. The  two  tambours  are  joined  to  one  another  pincer-like, 
by  a  hinge,  and  grasp  the  cardiac  region  on  each  side  of  the  ster- 
num. A  girdle  (c)  attached  by  hooks  to  the  tambours  passes  around 
the  body  of  the  animal,  and  secures  the  apparatus  firmly.  The  com- 
pression of  the  air  in  the  tambours  due  to  the  cardiac  impulse  is 
transmitted  l)y  the  tubes  (d,  e)  to  a  second  tambour,  to  which  is  at- 
tached a  recording  lever,  like  that  represented  in  Fig,  98.  Fig.  99 
gives  the  traces  taken  by  this  instrument. 

It  will  be  remembered  that  it  was  by  means  of  the  cardiograph 

iQp.  cit.,  p.  155. 


246 


CIRCULATION  OF  THE  BLOOD. 


Fig.  98. 


and  the  sound  introduced  into  the  heart  of  the  horse  that  Marey 
and  Chauveau  demonstrated  experimentally  that  the  cardiac  im- 
pulse is  absolutely  synchronous  with  the  ventricular  systole.  What- 
ever diiference  of  opinion  may  exist  as  to 
the  relative  importance  of  the  different 
causes  assigned  for  the  production  of  the 
cardiac  impulse,  there  can  be  no  doubt, 
then,  that  its  immediate  cause  is  the  ven- 
tricular systole. 

The  spiral  arrangement  of  the  muscular 
fibers  at  the  apex  of  the  heart,  already 
alluded  to,  explains  another  phenomenon 
accompanying  the  ventricular  systole,  the 
twisting  of  the  heart.  If  the  apex  of  the 
heart  be  closely  watched,  it  will  be  noticed 
that  the  point  twists  upon  itself  from  left 
to  right  Math  the  systole,  returning  to  its 
former  position  with  the  diastole.  The 
heart,  like  a  voluntary  muscle,  which  it 
closely  resembles  in  its  substance,  also  hardens  during  contraction. 
This  becomes  very  evident  if  the  organ  be  grasped  by  the  hand 
while  beating.  Like  voluntary  muscles,  the  heart  also  shortens 
during  contraction.  This  can  be  demonstrated  by  quickly  cutting 
the  heart  out  of  a  living  animal,  pinuing  it  down  on  a  board  by 
passing  a  needle  vertically  through  its  base,  and  then  inserting  a 
second  needle  into  the  board  parallel  with  the  first,  so  that  the  apex 
of  the  heart  just  touches  the  second  needle.  With  each  systole  it 
will  be  seen  that  the  ventricles  invariably  shorten,  the  apex  dis- 
tinctly receding  from  the  second  needle.  If  the  beating  heart  be 
examined  in  situ  there  is,  on  the  contrary,  an  apparent  elongation 
of  the  heart  during  its  systole.     This  is  due,  however,  not  to  any 


Cardiograiih.     (Marey.) 


Fig.  99. 


CO. 


Vk,( 


Ch. 
Tracings  taken  with  cardiograph.     Co.   Guiuea-pig.    L.   Rabbit.     Ch.   Cat.     (Marey.) 


elongation  of  the  ventricles,  but  to  the  fact  that  at  the  moment  of 
the  cardiac  impulse,  which  is  synchronous  with  the  ventricular 
systole,  the  whole  heart,  as  we  have  seen,  is  moved  forward  and 


CHANGES  IN  FORM  OF  THE  HEART. 


247 


protruded  ;  at  this  moment  the  apex  is  apparently  elongated,  while, 
in  reality,  it  is  shortened. 

However  carefully  the  beating  heart  may  be  observed,  it  is,  nev- 
ertheless, impossible,  on  account  of  the  rapidity  of  its  movements, 
to  obtain  a  correct  idea  of  the  changes  it  undergoes  in  the  living 
animal.     Owing  to  this  fact,  plaster  casts  ^  (Fig.  100)  have  been 


ProjectioB  of  a  dog's  heart.     Shaded  portion  indicates  ajipearance  of  diastole  ;     white  portion,  of 
systole.     A.  Anterior  surface.     L.  Lateral  surface.     P.  Posterior  surface.     (McKendrick.) 

made  of  the  distended  and  contracted  heart  fixed  in  that  condition 
at  the  moment  of  death,  which  show,  approximately  at  least,  the 
changes  undergone  in  the  form  of  the  heart  in  a  living  animal,  and 
reveal  the  fact  that  the  post-mortem  form  of  the  heart  is  not  that 
of  the  living  animal  either  in  diastole  or  systole.  It  must  be  borne 
in  mind  that  the  changes  in  the  form  of  the  beating  heart  just  de- 
scribed are  such  as  occur  in  the  opened  chest,  and  necessitating  also 
in  the  case  of  the  mammal,  the  maintenance  of  artificial  respiration. 
While  there  is  no  reason  to  suppose  that  the  changes  in  the  form 

Fig.  101. 


1 


^^vf^Vv/\KA/v^^^MAAAAAANVJ\'A\AMAM/ 


1.  Cardiographic  tracing  from  a  case  of  ectopia  cordis.  (Francj'OIS  P'ranck.)  2.  Cardiographic 
tracing  from  the  exposed  heart  of  a  cat,  obtained  by  placing  a  light  lever  on  the  ventricle.  The 
tuning-fork  curve  marks  50  vibrations  per  second.     (Landois.) 

of  the  heart  observed  in  the  unopened  chest.  Fig.  101,  1,  differ  es- 
sentially from  those  in  the  opened  one.  Fig.  101,  2,  recent  re- 
searches ^  render  it  possible  that  certain  minor  differences  exist  in 

IF.  Hesse,  Du  Bois  Eeyraond's  Arcliiv(Anatomie),  1880,  s.  828. 
2  J.  B.  ITiivcraft,  Journal  of  Physiology,  V.  xii.,  1891,  p.  448.     J.  B.  Haycraft 
&  D.  R  Patel-son,  Ebenda,  V.  xix.,  1896,  p.  496. 


248  -      CIRCULATION  OF  THE  BLOOD. 

the  two  cases.  Thus,  for  example,  it  may  be  supposed  that  the  ven- 
tricles contract  more  equably  in  all  diameters,  and  that  there  is  less 
flattening  of  the  heart  in  the  antero-posterior  direction  in  the  un- 
opened chest  than  in  the  opened  one. 

Work  done  by  the  Heart. 

In  mechanics  the  work  done  by  a  machine  is  usually  estimated 
in  kilogramme  meters  or  foot  pounds,  that  is,  the  number  of  kilo- 
grammes or  pounds  the  machine  can  lift  through  one  meter  or 
foot.  In  other  words,  the  work  done  equals  the  weight  multiplied 
by  the  height.  On  the  supposition  that  at  each  systole  of  the  left 
ventricle,  180  grammes  (6.3  oz.)  of  blood,  the  so-called  "  pulse  vol- 
ume," is  ejected  into  the  aorta  under  a  pressure  of  3.21  meters 
(10.2  feet),  that  being  the  height  to  which  the  blood  would  rise  in 
a  tube  placed  in  the  aorta  of  man,'  the  left  ventricle  lifts  at  each 
systole  180  grammes  of  blood,  3.21  meters  high,  that  is,  does  578.8 
gramme  meters  of  work  (180  x  3.21  =  578.8).  If  the  578.8 
grammes  be  multiplied  by  72  on  the  supposition  that  the  heart  beats 
seventy-two  times  a  minute,  and  the  quotient  by  (30  and  24  for  the 
hour  and  day  it  will  be  seen  that  the  work  done  by  the  left  ven- 
tricle of  the  heart  in  twenty-four  hours  amounts  to  nearly  60,000 
kilogrammeters  578.8  x  72  x  60  x  24  =  59927040  gramme  meters. 
Assuming  that  the  work  done  by  the  right  ventricle  amounts  to 
one-fourth  of  that  done  by  the  left,  or  15000  kilogrammeters,  the 
pressure  of  tlie  blood  in  the  pulmonary  artery  being  one-fourth 
that  of  the  pressure  in  the  aorta,  the  work  done  by  both  ventricles 
during  twenty-four  hours  would  be  nearly  75000  kilogrammeters 
(240  foot  tons)."  It  should  be  mentioned,  however,  that  the  energy 
put  forth  by  the  ventricles  of  the  heart  is  not  only  exerted  in  lift- 
ing 180  grammes  of  blood  through  3.21  and  0.8  meters,  respectively, 
at  each  systole,  but  in  imparting  to  the  blood  the  velocity  with 
which  it  flows  in  the  aorta  and  pulmonary  artery.  Assuming  that 
the  velocity  in  the  aorta  amounts  to  0.5  meter  per  second,  we  can 
make  use  of  the  well-known  formula  T^=  s^'Igh  in  which  g  is  the 
accelerating  force  of  gravity  (9.81  meters  per  second)  to  obtain  the 
value  of  /(  or  the  height  through  which  the  1 80  grammes  of  blood 
must  be  lifted  in  order  to  acquire  by  falling  from  such  height  the 
given  velocity.     Squaring  both   sides  of   the  equation  V  =  \^2gh 

and  transposing  Ave  obtain  h  =      -  =  — —    =   0.0127  meter. 

g         2  X  9.81 

The  work  done  by  the  left  ventricle  at  each  systole  will  be  equal, 

therefore,  to  raising  180  grammes  of  blood  0.0127  meter  high,  for 

felling  from  that  height  the  blood  would  acquire  a  velocity  of  0.5 

^Haugliton,  Animal  Mechanics,  1873,  p.  137. 

^  Kilngrammctci-s  are  converted  into  foot  pounds  by  multiplying  by  7.233.  1  kilo 
(2.2  pounds  avoird. )  raised  1  meter  (3.2  feet)  higli  =  1  lb.  avoird.  raised  7.233 
high.     Foot  pounds  are  converted  into  foot  tons  by  dividing  by  2240. 


SOUNDS  OF  THE  HEART.  249 

meter.  As  the  work  done  by  the  left  ventricle  in  this  respect  is 
small,  amounting  in  twenty-four  hours  to  only  207.3  kilogramme- 
ters,  it  is  usually  neglected  together  with  that  done  by  the  right 
ventricle,  which  is  necessarily  still  less,  in  estimating  tlie  work  done 
by  the  heart.  We  shall  see  hereafter  that,  in  accordance  with  the 
theory  of  the  conservation  of  energy,  that  the  work  of  75000  kilo- 
grammeters  done  by  the  heart  in  twenty-four  hours  is  transmuted 
heat.  Such  being  the  case,  176263  heat  units  must  l)e  applied 
mechanically  by  the  heart  since  1  heat  unit  so  applied  will  lift  425.5 
grammes  1  meter  high  (176263  X  425.5  =  75000  kilogrammcters). 
Further,  as  one  gramme  of  coal  when  burned  yields  8080  heat 
units,  it  follows  that  the  heat  transformed  into  work  by  the  heart  is 
equal  to  that  which  would  be  produced  by  the  combustion  within 
the  heart  of  nearly  22  grammes  of  coal  (8080  x  21.8  =  176263). 
That  the  heat  so  transformed  into  work  by  the  heart  is  not  derived 
from  the  combustion  of  the  carbon  of  its  muscular  tissue  is  shown 
by  the  fact  that  if  so,  the  heart,  upon  the  supposition  that  it  weighs 
al30ut  300  grammes,  would  be  entirely  consumed.  It  may  be  men- 
tioned in  this  connection,  though  it  will  be  considered  hereafter, 
that  as  the  energy  exerted  by  the  heart  is  expended  in  overcoming 
the  resistance  incidental  to  the  circulation,  the  energy  that  disappears 
in  being  so  applied  reappears  as  heat. 

If  in  a  living  animal  the  ear  be  applied  to  the  precordial  region, 
and  in  man  more  particularly  to  the  third  intercostal  space  a  little 
to  the  left  of  the  median  line  of  the  chest,  accompanying  the  beat 
of  the  heart  two  successive  sounds  will  be  heard,  followed  by  a 
silence.  After  a  little  practice  it  will  be  recognized  that  these  two 
sounds  differ  from  each  other  in  their  quality,  pitch,  and  duration. 
The  first  sound  is  a  dull,  confused  one,  of  a  booming  character,  low 
in  pitch,  and  lasts  longer  than  either  the  second  sound  that  follows 
it  or  the  silence  intervening  between  the  second  sound  and  the  first 
one.  The  second  sound  as  compared  with  the  first  one,  is  a  clear 
sound,  well  defined,  sharp,  high  in  pitch.  While,  for  all  practical 
purposes,  it  may  be  said  that  the  second  sound  immediately  follows 
the  first,  there  is  quite  an  appreciable  interval  of  silence  between  the 
second  and  the  first  sound,  this  interval  of  silence  lasting  about  the 
same  length  of  time  as  the  second  sound.  On  the  supposition  that 
0.8  second  elapses  during  the  period  in  which  the  first  and  second 
sounds  are  heard  and  the  silence,  the  first  sound  will  last  0.32 
second,  the  second  sound  0.24  second,  the  silence  0.24  second.  A 
comparison  of  the  duration  of  the  movements  and  sounds  of  the 
heart  shows  that  the  period  of  0.32  second  during  which  the  first 
sound  is  heard  is  absolutely  synchronous  with  the  0.32  second  of  the 
ventricular  systole,  that  the  0.24  second  during  which  the  second 
sound  is  heard  the  heart  is  in  repose,  and  that  the  silence  is  syn- 
chronous partly  with  the  last  0.0.8  second  during  which  the  heart 
is  in  repose  and  partly  with  the  0.16  second  of  the  auricular 
systole. 


250  CIRCULATION  OF  THE  BLOOD. 

Duration  of  Movements  and  Sounds  of  Heart  during 
0.8  Second. 


Ventricular  systole. 

Repose. 

Auricular  sjstole. 

A 

__-^— ^~~~-~^ 

A 

0.32  sec. 

0.24  sec.     +     0.08  sec. 

+ 

0.16  sec. 

V 

V                       "^^ — 

______  ^ 

_- — -— ' 

First  sound. 

Second  sound. 

Silence. 

From  the  fact  of  tlie  first  sound  of  the  heart  being  composed  of 
both  a  valvuhu-  and  muflfled  character  it  might  be  naturally  supposed 
that  it  consists  of  more  than  one  component  and  that  its  production 
must  be  due  therefore  to  more  than  one  cause.  Such,  indeed,  has 
been  shown  to  be  the  case,  the  first  sound  being  made  up  in  reality 
of  two  sounds,  a  valvular  one  caused  by  the  closure  of  the  auriculo- 
ventricular  valves  and  a  muffled  one  due  to  the  contraction  of  the 
muscular  fibers  of  the  ventricles.  That  the  first  sound  is  so  pro- 
duced is  shown  by  the  fact  that  it  is  heard  during  the  period  of  the 
ventricular  systole  during  the  time  that  the  auriculo-ventric- 
ular  valves  close  and  the  muscular  fibers  contract.  That  the 
closure  of  the  auriculo-veutricular  valves  contributes  to  the  produc- 
tion of  the  first  sound  can  be  further  demonstrated  by  experiments 
like  those  of  Chauveau  and  E'aivre,^  who  either  modified  the  first 
sound  or  abolished  it  altogether  by  preventing  the  closure  of  these 
valves  by  cutting  the  chordae  tendineje,  or  introducing  a  wire  ring 
into  the  auriculo-veutricular  orifices,  and  by  the  recent  ones  of 
Wintrich  ^  who  demonstrated  by  means  of  a  resonator  and  stetho- 
scope that  the  first  sound  consisted  of  two  components  of  different 
pitch. 

Further,  pathology  shows  that,  in  man,  the  character  of  the  first 
sound  is  changed  if  the  auriculo-veutricular  valves  are  diseased,  and 
it  is  well  known,  also,  that  in  auscultation  the  first  sound  is  heard 
with  its  maximum  intensity  over  these  valves,  and  that  it  is  propa- 
gated downward  along  the  ventricles  to  ^vhich  they  are  attached 
toward  the  apex. 

That  the  muscular  contraction  of  the  heart  produces  a  sound,  can 
be  demonstrated  by  the  cardiophone  (Fig.  102),  a  distinct  sound 
being  heard  when  the  latter  is  attached  to  the  telephone,  and  that 
the  sound  so  produced  contributes  to  the  production  of  the  first  sound 
of  the  heart  can  be  proved  by  experiments  such  as  those  of  Ludwig 
and  Dogiel,^  Krehl,*  Kasem-Bek,^  in  which  the  valves  were  made 
incompetent  and  the  only  way  of  accounting  for  the  sound  still . 
heard  was  to  attribute  it  to  muscular  contraction. 

While  some  difference  of  opinion  still  prevails  as  to  the  nature 

^  Nouvelle  recherches  experiraentales  sur  les  Mouvements  du  Cceur,  etc. ,  p.  30. 
Paris,  1856. 

2  Sitz-berichte  der  phys.  med.  soc.  zu  Erlangen,  1873,  s.  1,  1875,  s.  51. 

^Berichte  u.  die  Verhandl.  d.  K.  Siicksinn,  Gessel.  der.  Wissen.  zu  Leipzig, 
1868,  s.  89. 

<  Archiv  fur  Anat.  u.  Phys.,  1889,  s.  253. 

spfliiger's  Archiv,  Band  xlvii.,  1890,  s.  53. 


THE  CAEDIOPHOXE. 


251 


of  the  sound  produced  by  cardiac  or  skeletal  muscle,  it  appears  to 
be  due  to  a  repetition  of  the  unequal  tensions  that  occur  in  a  muscle 
during  its  contraction,  rather  than  of  individual  contractions,  which 
we  shall  see  hereafter,  constitute  the  condition  of  tetanus. 

As  has  already  been  observed,  the  second  sound  differs  from  the 
first  in  being  a   clear,  well-defined  sound,  and  is  essentially  of  a 

Fig.  102. 


Cardiophone.    6.  Button  to  be  placed  upon  heart.     W,   11'.  'Wires  for  attachment  to  telephone. 

T.  Telephone. 


valvular  character.  It  is  heard  during  the  first  three-quarters  of 
the  period  in  which  the  heart  is  in  repose.  Xow,  at  this  moment 
the  semilunar  valves  of  the  pulmonary  artery  and  aorta  are  flapping 
together  through  the  blood  getting  in  between  the  valves  and  the 
walls  of  the  vessels.  The  closure  of  these  valves  -will  account  for 
the  second  sound  of  the  heart  and  its  simple  valvular  character. 
The  second  sound  of  the  heart  can  be  imitated  bv  suddenlv  closings 
the  aortic  valves  by  a  column  of  water,  as  was  first  shown  by 
Rouanet,^  and  can  be  abolished  by  hooking  back  the  semilunar 
valves  in  a  living  animal,  as  was  first  demonstrated  by  WilUams, 
and  confirmed  by  the  Dublin  Committee  in  their  report  presented 
to  the  meeting  of  the  Briti.^h  Association  in  I806.- 

We  learn  also  through  the  changes  produced  in  the  character  of 
the  second  sound  of  the  heart  from  disease  of  the  semilunar  valves, 

'  J.  Eouanet,  Analyse  Des  Bruits  Du  cceur,  These  ^'o.  252,  Paris,  1832,  p.  9. 
2  Report  of  the  Sixth  Meeting  of  the  British  Association  for  the  Advancement  of 
Science,  London,  1837,  pp.  261,  275. 


252  CIRCULATION  OF  THE  BLOOD. 

and  from  auscultation  that  the  second  sound  is  heai'd  most  distinctly 
opposite  the  semilunar  valves,  and  is  propagated  upward  along  the 
great  vessels  to  which  they  are  attached.  There  can  be  no  doubt, 
then,  that  the  second  sound  of  the  heart  is  caused  simply  by  the 
closure  of  the  semilunar  valves  of  the  pulmonary  artery  and  aorta. 

It  may  be  mentioned  in  this  connection  that  when  the  heart  beats 
more  rapidly  than  usual,  the  period  of  silence  is  shortened  rather 
than  the  periods  during  which  the  two  sounds  are  heard,  just  as 
we  saw  the  period  of  repose  of  the  heart  is  shortened  rather  than 
that  of  the  systole. 

When  it  is  considered  that  age,  sex,  food,  exercise,  etc.,  in- 
fluence the  rapidity  of  the  action  of  the  heart,  it  becomes  evident 
that  an  intimate  sympathy  must  exist  between  the  circulation  and 
the  other  great  functions  of  the  economy.  From  time  immemo- 
rial, therefore,  the  frequency  of  the  heart's  action  has  always  been 
regarded  as  one  of  the  most  important  indications  of  the  general 
health  of  the  system.  The  practical  importance,  therefore,  of  deter- 
mining, as  far  as  possible,  the  average  beat  of  the  heart  in  a  given 
time,  within  the  limits  of  health,  must  be  obvious  to  every  physi- 
cian. We  shall  see  in  the  next  chapter  that  with  each  ventricular 
systole  or  cardiac  impulse  there  is  an  expansion  of  the  arteries  due 
to  the  blood  being  forced  out  of  the  left  ventricle  into  the  aorta. 
This  expansion  of  the  arteries  or  pulse,  which  we  will  consider 
again  in  detail,  is,  for  convenience'  sake,  usually  felt  and  counted 
instead  of  the  beat  of  the  heart  itself,  and,  other  things  being  equal, 
the  result  of  such  examination  can  be  accepted  as  a  criterion  of  the 
condition  of  the  heart  and  vascular  system  generally.  It  will  be 
observed  from  the  Table  compiled  from  the  observations  of  Guy  ^ 
and  Milne  Edwards,^  that  the  average  number  of  cardiac  beats  per 
minute  varies  according  to  the  age  and  sex,  and  this  should  always 
be  remembered  when  the  pulse  is  counted  in  man.  Thus  in  the 
foetus,  while  the  number  of  pulsations  per  minute  is  140  (deter- 
mined by  listening  to  the  foetal  heart),  at  birth  the  number  falls  to 
136,  and  that  up  to  the  third  year  of  life,  while  the  pulse  is  still 
the  same  in  both  sexes,  it  now  averages  only  about  107  beats  to  the 
minute.  As  we  pass,  however,  from  infancy  to  youth,  it  will  be 
seen  that  the  number  of  pulsations  per  minute  gradually  diminishes, 
and  that  at  the  same  period  the  pulse  of  the  female  is  a  little 
quicker  than  that  of  the  male.  In  adult  life  the  average  number 
of  pulsations  in  the  male  may  be  said  to  be  from  70  to  72  per  min- 
ute, and  from  6  to  8  beats  more  in  the  female.  At  the  approach  of 
old  age  the  pulse  becomes  a  little  more  frequent,  at  eighty  years  of 
age  the  number  of  beats  usually  being  about  80  a  minute. 

As  is  well  known,  in  animals  of  different  species,  but  which  are 
closely  allied  in  tlieir  general  organization,  the  pulse  varies  with  the 
size  of  the  animal,  l)eing  slowest  in  the  largest  and  fastest  in  the 

'  Cyclopa'dia  of  Anat.  andPliys.,  Vol.  iv.,  p.  181. 
2 Pliysiologie,  Tome  iv.,  p.  62. 


Age. 


FREQUENCY  OF  HEART'S  ACTION.  253 

Frequency  of  Heart's  Action. 

Pulsations  per  minute. 


Foetal 

At  birth  . 

1  year  . 

2  years  . 

2  to  7  y 

ears 

8  "  14 

14  "  21 

21  "  28 

28  "  35 

35  "  42 

42  "  49 

49  "  56 

56  "  63 

63  "  70 

70  "  77 

Male. 

I-emale. 

140 

140 

186 

136 

128 

128 

107 

107 

97 

98 

84 

94 

76 

82 

73 

80 

70 

78 

68 

78 

70 

77 

67 

76 

68 

77 

70 

78 

67 

81 

71 

82 

77  "  84       " 

.smallest  auimals.  Thus  in  the  horse  the  number  of  beats  is  only 
40  to  the  minute,  in  the  ass  about  50,  in  the  sheep  from  60  to  80, 
the  clog  100  to  120,  in  the  rabbit  150,  and  in  some  of  the  smallest 
rodents  even  175.  The  circulation  is  also  more  rapid  in  small  in- 
sects than  in  large  ones,  and  it  has  long  been  a  matter  of  observa- 
tion that  in  man  the  pulse  is  slower  in  persons  of  large  stature  than 
in  those  of  small.  This  connection  between  the  rapidity  of  the 
pulse  and  the  size  of  the  animal  seems  to  be  a  very  general  one  in 
the  animal  kingdom,  so  far  as  has  been  observed,  and  its  signifi- 
cance will  become  apparent  when  we  study  the  production  of  ani- 
mal heat  in  the  economy,  for  we  shall  see  then  that  the  rapidity  of 
the  circulation  is  directly  correlated  with  the  production  of  energy, 
and  that,  as  a  general  rule,  the  greatest  amount  of  nervo-muscular 
activity  is  exhibited  by  the  smallest  auimals  of  any  one  order  rather 
than  by  the  largest  ones. 

This  dependence  of  the  pulse  on  the  size  may  to  a  certain  extent 
explain  the  difference  between  the  pulse  of  the  young  and  of  the 
old,  and  of  the  sexes  as  just  mentioned.  It  should  be  stated, 
however,  that  the  observations  of  Volkmann  ^  show  that  youth 
and  sex  in  themselves,  without  regard  to  size,  influence  the  rate  of 
the  pulse,  for  in  individuals  of  equal  size  the  youngest  had  the 
quickest  pulse,  and  the  pulse  of  the  woman  was  always  quicker 
than  that  of  the  man. 

It  must  not  be  forgotten,  however,  in  counting  the  pulse  that 
often  individuals  are  met  with  in  perfect  health  in  whom  the  pulse 
is  extremely  rapid,  or  just  the  reverse.  Thus,  according  to  the  late 
Professor  Dunglison,^  the  pulse  of  Sir  William  Congreve  never  fell 
below  128  beats  per  minute,  while,  as  is  well  known,  on  the  other 
hand,  tnat  of  J^s'apoleon  I.  often  did  not  exceed  40  beats  to  the  min- 

^  Die  Iltemodynamik,  s.  30,  3G.     Leipzig,  1850. 
^ Human  Physiology,  1856,  Sth  ed.,  Vol.  i.,  jj.  440. 


254  CIRCULATION  OF  THE  BLOOD. 

ute.^  Haller-  refers  to  cases  where  the  pulse  was  still  slower,  being 
only  23  beats  to  the  minute. 

As  is  well  known,  the  action  of  the  heart  is  also  influenced  by 
digestion;  according  to  Milne  Edwards,^  there  is  an  increase  of 
from  five  to  ten  beats  after  each  meal.  On  the  other  hand,  pro- 
longed fasting  diminishes  the  frequency  of  the  pulse  from  twelve  to 
sixteen  beats.  According  to  the  same  high  authority,  while  vege- 
table food  diminishes  the  action  of  the  heart  animal  food  increases 
it,  fermented  drinks  at  first  diminish  then  accelerate  the  movements 
of  the  heart.  Coffee  is,  however,  in  the  highest  degree  a  cardiac 
stimulant.  Every  one  is  familiar  with  the  fact  that  any  violent 
exercise,  like  running  or  jumping,  increases  the  action  of  the  heart. 
As  long  ago  as  the  early  part  of  the  last  century  it  was  shown,  by 
the  experiments  of  Bryan  Robinson,*  that  the  pulse  of  a  man  in 
the  recumbent  position  being  64  to  the  minute,  was  increased  to  78 
during  a  slow  walk,  and  still  further  increased  to  100  by  walking 
a  league  and  a-lialf  in  an  hour,  and  rose  as  high  as  140  to  150 
after  running  as  rapidly  as  possible.  It  is  also  well  known,  from 
the  experiments  of  Guy,^  that  if  the  number  of  pulsations  on  the 
average  be  6G  to  the  minute  in  a  man  lying  down,  the  number  will 
be  increased  to  71  if  he  sits  up,  and  will  be  still  further  increased 
to  81  if  he  stands  up.  After  what  has  just  been  said  in  reference 
to  muscular  activity  increasing  the  action  of  the  heart,  the  results 
of  Guy's  experiments  are  just  what  might  have  been  expected, 
since  muscular  force  is  developed  in  changing  the  position  of  the 
body  and  maintaining  it  in  equilibrium. 

Indeed,  it  was  in  this  way  that  many  of  the  older  physiologists 
theoretically  explained  the  acceleration  of  the  heart's  beat  observed 
in  the  change  of  posture  just  referred  to.  It  was  Guy,  however, 
who  first  demonstrated,  by  means  of  a  revolving  board  which  sup- 
ported the  person  who  was  the  subject  of  the  experiment  and  so 
relieved  him  of  the  necessity  of  supporting  himself  by  muscular 
exertion,  that  the  variations  in  the  frequency  of  the  heart,  according 
to  the  position  of  the  body,  was  dependent  upon  the  quantity  of 
muscular  force  put  forth  in  maintaining  equilibrium  in  each  of  the 
positions.  The  practical  importance  of  these  facts  for  the  physician 
<;annot  be  exaggerated,  since  it  is  obvious  that,  in  a  person  suffering 
with  heart  disease,  it  is  of  the  utmost  importance  that  any  increase 
in  the  action  of  the  heart  should  be  avoided.  The  greatest  caution, 
under  such  circumstances,  should  be  advised  in  the  taking  of  exer- 
cise ;  any  sudden  or  violent  effort,  like  quickly  lifting  up  a  trunk, 
or  running  rapidly  up  stairs,  should  be  strictly  ])rohibited,  the 
slight  acceleration  in  the  heart's  beat  from  such  an  effort  being  fre- 
quently a  cause  of  death  in  persons  affected  with  heart  disease. 

It  is  well  known  that  during  the  day  there  is  a  variation  in  the 

^Berard,  Physiolofjie,  Tome  iv.,  p.  118. 

^Elementa  Phy^iiologie,  Tome  ii.,  p.  250.  •' Physiolotjie,  Tome  iv.,  p.  79. 

*  A  Treatise  on  tlie  Animal  Economy,  p.  177.     lAiblin,  1732. 

5 Cycloptedia  of  Anat.  and  Pliys.,  Vol.  iv.,  !>.  188. 


CONDITIONS  INFLUENCING  ACTION  OF  HEART.        200 

action  of  the  heart,  and  for  a  long  time  it  was  supposed  that  the 
pulse  Avas  quicker  in  the  evening  than  in  the  morning.  According 
to  the  older  physiologists,  "Pulsus  nocturnus  multo  celerior  est."' 
When,  however,  the  action  of  the  heart  at  evening  is  considered 
uninfluenced  by  food,  exercise,  etc.,  it  has  been  found  that  the  pulse 
at  that  period  of  the  day  is  really  slower  than  in  the  morning,  and 
that  the  heart  is  less  susceptible  to  the  action  of  stimulants.  This 
condition  is  due,  no  doubt,  to  muscular  fatigue. 

In  sick  persons,  however,  it  is  otherwise,  since  at  evening  there 
is  usually  some  fever  present,  and  this  is  accompanied  by  a  quicker 
pulse.  According  to  INIilne  Edwards,"  while  sleep  tends  to  diminish 
the  action  of  the  heart,  the  number  of  pulsations  at  least  in  man, 
is  not  diminished  to  any  extent  by  that  circumstance.  In  women, 
and  especially  children,  in  that  condition,  however,  there  seems  to 
be  considerable  difference  as  compared  -with  the  wakeful  state.  The 
temperature  ot  the  surrounding  atmosphere  influences  also  the 
rapidity  of  the  action  of  tlie  heart — heat  increasing  and  cold  dimin- 
ishing the  number  of  heart  l)eats. 

De  la  Roche  ^  found  that  his  pulse  was  increased  to  160  beats  per 
minute  in  an  atmosphere  of  65.5°  C.  (150°  F.),  and  it  is  well  known 
that  the  pulse  is  quicker  in  hot  countries  than  in  cold  ones.  Among 
the  other  influences  that  accelerate  or  diminish  the  action  of  the 
heart  must  be  mentioned  that  of  respiration.  When  the  manner  in 
which  the  blood  flows  through  the  pulmonic  capillaries,  and  the 
changes  produced  in  it,  have  been  described,  the  mutual  sympathy 
existing  between  the  heart  and  limgs  will  then  be  fully  ap})reciated. 
It  would  be  anticipating  too  much  to  give  a  detailed  account  of  this 
mutual  influence  at  present,  but  it  may  be  mentioned  in  this  con- 
nection that  the  action  of  the  heart  may  be  voluntarily  arrested 
through  modifying  the  conditions  of  respiration.  Thus,  for  ex- 
ample, if  after  a  forcible  expiration  the  mouth  and  nose  are  closed 
and  then  a  powerful  inspiratory  effort  is  made,  the  heart  may  cease 
to  beat.  This  appears  to  be  due  to  the  extreme  dilatation  of  the 
heart  caused  by  the  venous  blood  flowing  so  freely  into  the  right 
side  of  the  heart  as  to  cause  engorgement  of  the  lungs  and  of  the 
left  side.  On  the  other  hand  if  exactly  the  opposite  experiment 
is  tried,  that  is,  if  after  taking  a  deep  inspiration,  and  the  mouth 
and  nose  are  closed,  a  strong  expiratory  effort  is  then  made,  the 
heart's  action  may  also  be  arrested. 

Under  these  circumstances  the  heart  is  contracted,  since  the  flow 
of  the  venous  blood  is  interrupted,  as  shown  by  the  veins  of  the  neck 
and  face  swelling  up,  while  the  arterial  blood  is  forced  out  of  the 
compressed  lungs  into  the  left  ventricle  and  thence  into  the  arteries. 
Both  of  these  experiments  are  dangerous,  and  should  not  often  be 
repeated.  It  is  well  known  that  the  late  Prof.  E.  F.  Weber,  of 
Leipsic,  was  able,  by  closing  the  glottis  and  at  the  same  time  con- 

'  Keill,  Teutamina  medico-pliysica,  p.  178.     London,  1730. 
2Physiologie,  Tome  iv.,  p.  74.  ^xhese,  Paris,  1806,  p.  33. 


256  CIRCULATION  OF  THE  BLOOD. 

tracting  forcibly  the  chest,  to  diminish  the  cardiac  beats  to  three  to 
five  a  minute,  which  were  unaccompanied  with  the  cardiac  impulse 
or  sounds,  and  with  the  result,  finally,  of  stopping  the  action  of  the 
heart  altogether.  On  one  occasion,  having  suspended  his  respira- 
tion longer  than  usual.  Professor  Weber  ^  fell  into  a  syncope.  This 
case,  concerning  the  truth  of  which  there  can  be  no  question,  confirms 
the  statements  made  by  Galen,-  and  others,'^  that  death  in  certain  indi- 
viduals had  been  caused  by  the  voluntary  suspension  of  their  breath- 
ing. One  of  the  most  interesting  and  best  authenticated  cases  of 
the  possibility  of  temporarily  arresting  the  action  of  the  heart  was 
that  of  Colonel  Towhnsend,  reported  in  the  early  part  of  the  last 
century  by  Cheyne.^  This  physician  relates  how  Colonel  Towhn- 
send could  so  arrest  the  breathing  and  the  beating  of  his  heart  that 
death  was  simulated.  In  this  condition  the  pulse  could  not  be  felt 
at  the  wrist ;  there  was  no  cardiac  impulse  ;  a  mirror  placed  in  front 
of  the  mouth  was  not  tarnished,  and,  apparently,  he  was  dead.  On 
the  occasion  reported  by  Cheyne,  Colonel  Towhnsend  remained  in 
this  condition  for  half  an  hour ;  gradually,  hoAvever,  the  respira- 
tion and  circulation  became  reestablished.  It  should  be  mentioned, 
however,  that  Colonel  Townhsend  died  later  in  the  afternoon  of  the 
same  day  that  the  facts  just  described  occurred. 

It  may  be  mentioned  in  this  connection  as  appropriately  as  else- 
where that  if  a  Avide  glass  tube  filled  with  smoke  be  inserted  into 
one  nostril,  the  other  nostril  and  mouth  being  closed,  that  the 
smoke  will  move  with  each  beat  of  the  heart.  The  "  cardio-pneu- 
matic  movement,"  as  this  movement  is  called  and  of  which  a  trac- 
ing can  be  obtained  by  appropriate  apparatus,  appears  to  be  due  to 
the  fact  that  the  heart  occupying  less  space  within  the  thorax  when 
it  contracts  air  will  pass  into  the  lungs  with  each  systole  and  out 
with  each  diastole. 

Having  described  the  motion  of  the  heart  and  the  various  influ- 
ences that  modify  it  it  remains  now  to  consider,  so  far  as  is  known, 
how  the  beat  of  the  heart  is  maintained.  When  we  come  to  the 
special  study  of  muscular  contractility  we  shall  learn  that  an  ordi- 
nary voluntary  muscle  usually  contracts  in  response  to  a  stimulus, 
the  will,  emanating  in  the  brain,  and  transmitted  through  a  nerve 
to  the  nmscle. 

While  the  heart  is  a  muscular  organ,  its  action  differs  from  that 
of  the  ordinary  muscle  in  being  involuntary  in  character.  The 
voluntary  muscle,  however,  not  only  contracts  through  the  influence 
of  the  will  or  nerve  force,  but  also  in  response  to  mechanical,  elec- 
trical or  chemical  stimuli,  and,  in  this  respect,  the  heart  does  the 
same.  Thus,  if  the  chest  of  a  living  animal  be  opened,  and  the 
heart  mechanically  irritated  by  an  instrument,  a  scalpel,  for  exam- 
ple, it  will  be  seen  to  contract  like  any  other  muscle  stimulated  in 

1  Milne  Edwards,  Physiologic,  Tome  iv.,  p.  88. 
^ffiuvres  trad,  de  Daremberg,  Tome  i.,  p.  366. 
3Muller's  Archiv,  1S51,  s.  91. 
<The  English  Malady,  p.  307.     London,  1734. 


CONDITIONS  INFLUENCING  ACTION  OF  HEART. 


On  7 


a  similar  manner.  The  same  effect  follows  the  application  of  elec- 
tricity by  means  of  the  electrodes.  The  addition  of  warm  water, 
and  exposure  to  the  air  will  also  cause  the  heart  to  contract. 

The  muscular  substance  of  the  heart,  then,  hke  that  of  any 
other  muscular  organ,  is  endowed  with  the  property  of  contractility, 
through  which  the  organ  contracts  in  response  to  various  stimuli. 
There  appears  to  be  no  doubt  that  the  contractions  of  the  heart  are 
maintained  bv  a  constant  supply  of  oxygenated  blood,  anemia  of 
the  heart,  brought  about  by  the  ligature  of  the  coronary  arteries, 
promptly  arresting  the  heart's  action,^  whereas,  as  shown  long  ago 
bv  Haller  ^  and  numerous  observers  ^  in  recent  times,  the  heart  will 
continue  to  beat  for  many  hours  if  supplied  with  blood.  As  the 
blood,  however,  is  a  highly  complex  flnid,  it  becomes  a  matter  of 
importance  to  determine,  if  possible,  the  constituent  or  constituents 
upon  Avhich  the  maintenance  of  the  muscular  contractions  of  the 
heart  more  particularly  depend.  Unfortunately,  however,  the  diffi- 
culties that  have  obtained  until  recently  in  isolating  the  mammalian 
heart  have  been  so  great  that  little  has  been  learned  as  to  the  influ- 
ence exerted  by  any  one  constituent  of  the  blood  upon  the  heart. 

The  influence  exerted  by  the  dif- 
ferent constituents  of  the  blood  upon 
the  contraction  of  the  frog's  heart 
can,  however,  be  shown  by  means  of 
a  frog-manometer,  such,  for  example, 
as  that  of  Kronecker.  This  appara- 
tus consists  (Fig.  103)  of  a  two-way 
canula  (c)  which  is  tied  into  the 
excised  heart.  The  canula  (c)  com- 
municates, by  one  limb  with  a  mer- 
curial manometer  (/h),  and  by  the 
other  ^^•ith  the  Marrio'tte  flasks  (a,  b). 
Either  a  or  h  can  be  put  in  com- 
munication with  the  interior  of  the 
heart.  The  fluid  in  one  of  the  flasks 
contains  the  substance  whose  effect 
upon  the  heart  is  to  be  studied,  the 
fluid  in  the  other,  being  an  indiffer- 
ent one,  is  used  as  a  control   fluid. 


Fig.  103. 


Scheme  of  Kronecker' s  frog-manometer. 
a,  h.    Marriotte's  flasks  for  the  nutrient 
mi  1  1    /  T\  i_    •         n     •  ^    '         fluids.    «.  Stop-cock.    c.  Canula.    m.  Ma- 

i  he  glass  vessel  («)  contains  nUlCl  in     nometer.    h.  Heart,    d.  Glass  cup  for  h. 
-  -  r\,^^    ^f    €',e.  Electrodes.   Cy/.  Revolving  cylinder. 

yjne   oi     fLANDois.) 


(Landois.) 


which  the  heart  pulsates. 

the  electrodes  (e')  is  attached  to  the 

canula,  the  other  electrode  (e)  is  inserted  into  the  fluid  in  d.    Of  the 

different    substances  studied,  such  as  oxygen,  sodium  carbonate, 

sodium  and  potassium  chloride,  salts  of  calcium,  oxygen  appears  to 

be  highly  important,  if,  indeed,  not  essential,   more  oxygen  being 

^Erichsen,  London  Medical  Gazette,  1842,  2d  Ser.,  Vol.  ii.,  p.  561. 
^Memoires  sur  la  Nature  Sensible  et  Irritable  des  Parties  du  corps  animal  a 
Laussanne,  17o6,  Tomei. ,  p.  370. 

3N.  Martin,  Phil.  Trans.,  1883,  Part  ii. 
17 


258  CIRCULATION  OF  THE  BLOOD. 

used  by  a  beating  than  a  resting  heart,  and  the  amount  of  oxygen 
consumed  being  greatest  during  work.  Sodium  carbonate  is  of 
great  value  in  maintaining  the  alkalinity  of  the  blood.  Sodium 
chloride  appears  to  be  essential  and  should  exist  in  isotonic  amount. 
Salts  of  calcium  appear  to  be  essential,  since  precipitation  of  the 
calcium  by  a  soluble  oxalate  brings  spontaneous  contraction  of  the 
heart  to  a  standstill.  In  conclusion,  it  may  be  mentioned  that  a 
mixture  consisting  of  tri-calcium  phosphate,  sodium  chloride,  potas- 
sium chloride,  and  sodium  bicarbonate,  in  proper  proportions,^  will 
maintain  the  contractions  of  the  heart  for  many  hours. 

It  is  a  matter  of  daily  observation  that  the  circulation,  like  the 
other  functions,  is  influenced  by  the  nervous  system,  but  as  the  re- 
lation of  the  nervous  system  and  the  circulatory  organs  is  quite  a 
complex  one,  the  consideration  of  this  part  of  the  subject  will  be  for 
the  present  deferred. 

In  concluding  our  account  of  the  heart  it  may  be  now  appropri- 
ately mentioned,  however,  that  while  the  action  of  the  heart  is 
greatly  influenced  by  the  nervous  system,  the  heart  itself  is  insen- 
sible. The  insensibility  of  the  heart  is  often  observed  in  cases 
where  it  has  been  wounded,  the  patient  being  unconscious  of  pain, 
or,  indeed,  of  any  feeling  at  all.  In  the  celebrated  case  of  the  Vis- 
count Montgomery,  so  often  mentioned  by  authors,  and  so  well  de- 
scribed by  Harvey,  the  opportunity  was  offered  of  directly  inspect- 
ing and  feeling  the  heart.  Harvey  tells  us,  in  the  work "  already 
referred  to,  that  this  individual  was  entirely  unconscious  of  the  ap- 
plication of  his  finger  to  the  heart. 

J  S.  Kinger,  Journal  of  Physiology,  Vol.  vli.,  1886,  p.  291. 
2  Op.  cit.,  p.  375. 


CHAPTER   XVI. 

CIRCULATION  OF  THE   B'LOOB.— {Continued.) 

THE  ARTERIES. 

We  have  seen  that  at  each  vcntricuhir  systole  the  blood  is  forced 
from  the  heart  into  the  pulmonary  artery  and  aorta.  The  manner 
in  which  the  venous  blood  passes  through  the  pulmonary  capillaries, 
and  returns  aerated  arterial  blood  to  the  heart,  will  be  described 
when  the  subject  of  respiration  is  considered ;  for  the  present  let 
us  follow  the  blood  as  it  flows  through  the  aorta  and  its  branches, 
the  arteries. 

The  arterial  system,  by  means  of  which  the  lilood  is  circulated  to 
all  parts  of  the  body,  consists  of  musculo-elastic  tubes,  which,  in 
their  general  disposition,  may  be  compared  to  a  cone  of  which  the 
heart  is  the  apex,  and  the  base  the  periphery  of  the  body,  or  to  a 
tree  of  which  the  aorta  represents  the  trunk,  and  the  arteries  the 
branches.  As  we  recede  from  the  heart  to  the  periphery  the 
branches  divide  and  subdivide,  and  anastomose,  until,  becoming 
microscopic,  they  pass  into  the  capillaries.  With  few  exceptions, 
the  combined  calibre  of  the  branches  of  an  artery  is  o-reater  than 
that  of  the  artery  itself.  There  is  a  gradual  increase,  therefore,  in 
the  capacity  of  the  arterial  system  as  we  pass  from  the  heart  to 
the  capillaries.  As  a  general  rule,  the  arteries  run  in  nearly  a 
straight  course  to  the  parts  which  they  supply  with  blood.  The 
branches  gradually  diminish  in  size,  and  comparatively  few  are 
given  off  between  the  main  trunk  and  the  capillaries.  The  aorta 
and  the  arteries,  like  the  heart,  are  not  nourished  by  the  blood  cir- 
culating in  their  cavities,  but  by  blood  from  adjacent  vessels,  the 
vasa  vasorum,  which  have  no  direct  connection  with  the  arteries 
which  they  supply.  The  vasa  vasorum,  which  include  little 
veins,  as  well  as  arteries,  are  mostly  restricted  to  the  outer  coat 
of  the  artery,  but  few  penetrating  the  middle  coat.  The  vasa 
vasorum  of  the  arteries  bear  the  same  relation  to  the  arteries  that 
the  coronary  arteries  and  veins  bear  to  the  heart  itself.  The  ar- 
teries are  also  supplied  by  nerves  derived  from  both  the  cerebro- 
spinal and  sympathetic  systems,  but  principally  from  the  latter. 
The  manner  in  wliich  these  nerves  modify  the  calibre  of  the  arteries 
Ayill  be  understood  when  their  minute  structure  has  been  studied, 
to  the  consideration  of  which  let  us  now  turn. 

The  arteries,  including  the  aorta,  consist  essentially  of  three  coats 
(Fig.  104),  an  external  fibrous,  a  middle  elastic  muscular,  an  in- 
ternal epithelial.  Each  of  these  coats,  however,  can  be  shown  to 
consist  of  several  subcoats,  or  layers,  more  or  less  developed,  ac- 
cording to  the  size  and  situation  of  the  artery. 


260 


CIRCULATION  OF  THE  BLOOD. 


The  external  or  fibrous  coat  of  the  artery  is  mainly  composed  of 
fine  bundles  of  white  connective  tissue,  the  filaments  of  which  are 
usually  disposed  in  a  spiral  manner  around  the  vessel,  and  on  the 
surface  are  often  loosely  adherent  to  surrounding  parts  ;  the  inner 
surfiice  of  the  fibrous  coat,  however,  is  intimately  blended  with  the 
middle  coat.  Between  the  bundles  of  the  connective  tissue  fibers, 
of  which  the  external  coat  consists,  are  disposed  in  various  amounts 
fine  nets  of  elastic  tissue  ;  these  nets  are  most  abundant  in  the  inner 
part  of  the  external  coat.  To  their  internal  coat  the  arteries  owe 
chiefly  their  strength.  The  middle  coat  of  the  artery  consists  of 
layers  of  elastic  and  muscular  tissue,  which  are  disposed  around  the 
vessel  in  a  circular  manner.  The  relative  amount  of  these  tissues, 
however,  varies  according  to  the  size  and  position  of  the  vessel.  In 
the  largest  arteries,  those  nearest  the  heart,  the  middle  coat  is  com- 


Transverse  section  of  the  walls  of  the  aorta,  treated  -n-ith  acetic  acid,  and  magnified.  1.  Inter- 
nal coat.  a.  Eiiithelium  and  basement  membrane.  6,  c.  Layers  of  elastic  tissue.  2.  Middle 
coat.  d.  Layers  of  clastic  tissue,  e.  Muscular  and  connective  tissue.  3.  External  coat,  com- 
po-sed  of  fibrous  tissue  and  tine  nets  of  clastic  tissue.     (Leidy.) 


posed  mainly  of  elastic  tissue,  there  being  very  little  muscular  tissue 
present,  whereas,  in  the  medium  size  arteries,  the  middle  coat  chiefly 
consists  of  muscular  tissue,  and  in  the  smallest  arteries  of  muscular 
tissue  only.  The  muscular  tissue  is  of  the  unstriated  character,  and 
consists  of  fusiform  cells,  or  bands,  with  oval  nuclei ;  they  do  not 
entirely  surround  the  artery ;  the  elastic  tissue  forms  a  more  or 
less  close  network  of  fibers,  Avhich,  from  its  membranous  perforated 
character,  is  often  known  as  the  fenestrated  membrane.  A  great 
deal  of  the  elasticity,  and  all  the  contractility  with  which  the  arteries 
are  endowed,  are  due  to  their  middle  coat. 

The  internal  coat  of  the  artery  is  essentially  a  continuation  of 
the  endocardium,  or  lining  membrane  of  the  heart,  and  consists  of 
three  layers,  an  outer  elastic  of  the  membranous  fenestrated  kind,  a 
middle  basement  membrane,  and  an  inner  endothelial  layer,  com- 
posed of  elongated  lozenge-shaped  cells.  The  outer  elastic  layer  of 
the  internal  coat  of  the  artery  is  intimately  connected  with  the 
inner  portion  of  the  middle  coat,  Avhile  the  inner  endothelial  mem- 
]>ranc  is  that  part  of  the  artery  M^hich  ultimately  becomes  the 
capillary.     AVe  have  seen  that  the  action  of  the  heart  is  intermittent 


THE  ARTERIES.  261 

in  character,  each  ventricular  systole  being  followed  by  the  diastole, 
a  period  of  repose  during  which  no  blood  flow^s  into  the  arterial 
system  from  the  heart.  If,  however,  a  large  artery  near  the  heart 
be  opened,  it  will  be  observed  that  the  blood  flows  out  of  the  artery 
continuously,  both  during  the  systole  and  diastole.  With  each  ven- 
tricular systole,  however,  the  jet  becomes  stronger ;  the  flow  in  the 
artery,  therefore,  is  not,  like  that  in  the  heart,  intermittent,  but  re- 
mittent. If  the  artery  examined  be  situated,  however,  at  a  distance 
from  the  heart,  near  the  periphery,  the  flow  of  the  blood  will  be 
found  to  be  but  slightly  remittent,  indeed  almost  uniform,  while 
finally,  as  we  shall  see  in  the  capillaries,  it  is  entirely  so.  The 
flow  of  the  blood,  then,  as  it  passes  from  the  heart  through  the 
arteries  to  the  capillaries  from  being  intermittent  becomes  remittent, 
and  finally  uniform.  It  is  to  the  property  of  elasticity,  with  which 
we  have  seen  arteries  are  endowed,  that  this  transformation  of  an 
intermittent  motion  into  a  remittent  one  is  due.  For,  during  each 
ventricular  systole,  of  the  blood  that  is  forced  into  the  arteries  a 
part  only  presses  ouAvard  the  blood  already  in  the  arteries,  the  re- 
maining part  presses  outward  the  walls  of  the  artery.  From  the 
moment,  however,  that  the  effect  of  the  systole  ceases — that  is, 
during  the  diastole — through  its  elasticity  the  walls  of  the  artery 
recoil  on  the  blood  which  has  distended  them,  and  press  it  onward 
(the  aortic  valves  preventing  any  regurgitation)  immediately  after 
the  part  of  the  blood  that  has  just  preceded — that  is,  the  part 
forced  forward  during  the  systole.  There  are  two  successive  waves 
of  blood  then  in  the  artery,  that  of  the  systole  and  that  of  the 
diastole  ;  they  follow  each  other,  however,  so  rapidly,  that  ulti- 
mately they  merge  into  one,  the  movement  of  the  blood  in  the 
capillaries  becoming  finally  uniform.  The  elasticity  of  the  artery 
favors,  therefore,  the  onward  movement  of  the  blood. 

Did  the  arteries  consist  of  rigid  tubes  the  blood  would  flow 
through  them  in  the  same  intermittent  manner  as  it  does  through  the 
heart.  With  each  ventricular  systole  blood  would  flow  from  the  arte- 
ries into  the  capillaries  in  an  amount  equal  to  that  which  flowed  from 
the  heart  into  the  aorta,  with  the  diastole  of  the  heart,  however, 
the  flow  from  the  arteries  would  entirely  cease.  The  author  is 
in  the  habit  of  demonstrating  the  difference  between  the  flow  of 
liquids  in  elastic  and  rigid  tubes  by  means  of  the  apparatus  repre- 
sented in  Fig.  105.  This  consists  of  a  reservoir  (A)  containing 
a  colored  fluid,  and  provided  with  a  stopcock  (B)  by  means  of 
which  the  delivery  of  the  fluid  can  be  regulated.  To  the  stopcock 
is  connected  a  flexible,  but,  if  possible,  a  non-elastic  tube  (C)  which 
is  connected  with  a  tin  tube  (D),  the  latter  bifurcating  so  that  the 
fluid  from  the  reservoir  can  pass  through  the  tube  G  into  the 
tubes  E  and  F,  simultaneously.  One  of  these  tubes  (E)  consists 
of  glass,  the  other  (F)  of  caoutchouc,  the  former  (E)  is  connected 
with  the  tube  D  by  caoutchouc.  At  their  distal  ends  the  tubes  D 
and  F  are  bent  downward  so  that  the  fluid  flowing:  from  them  can 


262 


CIRCULATION  OF  THE  BLOOD. 


be  conveniently  collected  in  the  jars  P  I.  The  glass  tube,  as  it 
terminates,  is  drawn  out  so  as  to  simulate  the  capillary  end  of  an 
artery,  its  orifice  having  a  diameter  of  2.5  mm.  (J^  of  an  inch). 
The  same  effect  is  accomplished,  as  regards  the  caoutchouc  tube, 
by  inserting  into  its  distal  end  a  tube  of  glass  of  the  same  length 
and  diameter  as  that  of  the  distal  end  of  the  glass  tube.  The  tubes 
E  F  are  supported  by,  and  firmly  bound  to,  the  table  K,  which  is 
painted  white,  so  that  the  colored  fluid  can  be  readily  seen  in  the 
glass  tube. 

The  reservoir  being  filled  and  the  stopcock  turned  on,  the  colored 
fluid  passes  into  the  bifurcated  tube  and  thence  through  the  elevation 
and  depression  of  the  lever  (G),  worked  by  hand,  in  an  intermit- 
tent manner,  into  the  rigid  glass  tube  and  elastic  caoutchouc  one. 
The  lever  should  be  uniformly  depressed  and  elevated  at  the  rate 
of  about  sixty  times  to  the  minute  and  the  fluid  watched  as  it 
escapes  from  the   tubes.     It  will  be  observed,  from  the  reasons 

Fig.  105. 


Apparatus  to  (.Iciuoustratf  tlie  tiow  of  a  fluid  through  rigid  and  elastic  tubes.      (Marey.) 


already  given,  that  the  flow  from  the  rigid  glass  tube  is  absolutely 
intermittent,  with  each  depression  of  the  lever  the  flow  entirely 
CL'asing.  On  the  other  hand,  the  flow  from  the  caoutchouc  tube  is 
distinctly  remittent,  the  jet  not  ceasing  but  only  diminishing  with 
the  depression  of  the  lever  and  increasing  again  with  its  elevation. 
It  is  needless  to  add  that  the  elevation  and  depression  of  the  lever 
represent  the  opening  and  closing  of  the  aortic  valves,  the  escape 
of  the  fluid  from  the  tubes  the  flow  of  blood  through  the  con- 
stricted arteries  toward  the  capillaries. 

Tliis  exporiraciit  not  only  proves  that  the  elasticity  of  a  tube  in- 
fluences the  character  of  the  movement  of  the  fluid  flowing  through 
it,  but  also  of  the  quantity  that  escapes  from  it,  for  if  the  jars  P I  be 


THE  ARTERIES.  263 

examined,  it  will  be  seen  that  the  one  collecting  the  liquid  from  the 
elastic  tube  is  almost  three  times  as  full  as  that  collecting  from  the 
rigid  one.  During  an  experiment  lasting  three  minutes,  while 
2800  c.  cm.  (3.7  pints)  of  fluid  flowed  into  the  one  jar,  only  1000 
c.  cm.  (1.7  pints)  flowed  into  the  other.  This  is  as  might  have 
been  expected  when  it  is  remembered  that  an  elastic  tube  is  capable 
of  receiving  more  fluid  than  a  rigid  one,  for  two  reasons :  first, 
there  is  not  only  the  quantity  of  fluid  which,  after  entering  the 
tube,  presses  directly  onward  and  which  corresponds  to  the  fluid 
in  the  rigid  tube,  but  also  an  additional  quantity  which  presses  the 
walls  of  the  elastic  tube  outwardly.  It  is  this  lateral  fluid,  so  to 
speak,  that  follows  and  adds  itself  to  the  part  which  presses  di- 
rectly onward  that  converts  the  intermittent  motion  into  the  remit- 
tent one,  and  by  just  so  much  as  the  walls  of  the  tube  will  give  to 
this  lateral  pressure  the  amount  of  fluid  entering  the  elastic  tube 
will  be  in  excess  of  that  entering  the  rigid  one.  Second,  it  being 
remembered  that  the  principal  obstacle  to  the  flow  of  a  liquid 
through  a  tube  is  the  friction  of  its  walls,  and  that  the  friction  is 
proportional  to  the  square  of  the  velocity  of  the  current,  it  follows 
that  as  the  effect  of  the  dilatation  of  the  artery  is  to  diminish  the 
velocity  of  the  current  through  it,  and  therefore  to  diminish  the 
amount  of  friction  according  to  the  square  of  the  velocity  of  the 
current,  the  quantity  of  fluid  delivered  from  the  elastic  tube  will, 
therefore,  be  greater  than  that  from  the  rigid  one. 

We  have  seen  that  the  arteries  are  not  only  endowed  with  elastic- 
ity, but  also  Tvdth  contractility  or  tonicity,  as  it  was  called  by  Bichat, 
and  it  has  been  shown,  experimentally,  by  Poisseuille,'  that  the  re- 
coil of  the  walls  of  the  artery  upon  the  blood  that  had  previously 
distended  it  is  greater  than  can  be  accounted  for  by  the  elasticity 
of  the  artery  alone.  Indeed,  the  tendency  of  an  artery  is  always 
to  contract,  to  empty  itself  of  its  blood.  For  this  reason  difficulty 
is  always  experienced  in  injecting  the  vessels  of  an  animal  immedi- 
ately after  death. 

If,  during  life,  the  calibre  of  the  arteries  is  about  equal  to  that 
observed  after  death,  it  is  because  the  arteries  are  during  life  dis- 
tended with  blood. 

That  the  arteries  will  contract  independently  of  the  elasticity  or 
the  recoil  following  upon  the  distention  of  its  walls  through  the 
blood  forced  into  the  vessel  by  the  heart  can  be  demonstrated  by 
ligating  an  artery  in  two  places  and  in  a  part  of  its  course  where 
no  branches  are  given  off,  so  as  to  exclude  the  influence  of  the  gen- 
eral circulation,  and  then  opening  the  artery  at  a  point  situated  be- 
tween the  ligatures.  Under  such  conditions,  although  the  artery  is 
uninfluenced  by  the  action  of  the  heart,  etc.,  the  blood  will  jet  out 
with  force,  and  the  artery  will  be  almost  completely  emptied. 
When  it  is  remembered,  as  we  have  seen,  that  in  the  smallest  arte- 
ries the  middle  coat  consists  entirely  of  muscular  fibers,  there  being 
^Journal  de  Magendie,  T.  ix.,  p.  44. 


264  CIRCULATION  OF  THE  BLOOD. 

no  elastic  tissue  present,  it  becomes  evident  that  the  contractiHty,  in 
such  cases  at  least,  must  be  due  entirely  to  the  action  of  the  muscu- 
lar fibers.  Hence  the  distinction  clearly  made  by  John  Hunter,^ 
that  in  the  large  arteries  the  recoil  of  the  walls  was  due  almost  en- 
tirely to  the  elasticity ;  in  the  smallest  arteries,  on  the  contrary,  to 
the  contractility.  The  physiological  significance  of  this  distinction 
was  also  seen.  Hunter  attributing  to  the  elasticity  the  conversion  of 
the  intermittent  action  of  the  heart  into  the  remittent  one  of  the 
arteiy,  to  the  contractihty  the  regulating  of  the  calibre  of  the  ar- 
teries, and,  therefore,  the  supply  of  the  blood  to  the  system.  In- 
asmuch as  arteries  therefore  contract  in  virtue  of  their  contractility 
as  well  as  of  their  elasticity,  and  as  after  death  the  contractility 
disappears,  as  might  be  expected,  the  amount  of  contraction  is 
greater  in  the  living  artery  than  the  dead  one.  The  contractility 
of  the  arteries  can  be  easily  demonstrated  by  the  application  of 
various  stimuli,  mechanical,  chemical,  electrical,  exposure  to  air,  ap- 
plication of  cold,  etc.  Thus  the  mere  scraping  of  the  walls  of  an 
artery  or  the  pricking  of  a  needle  Avill  cause  them  to  contract. 
Various  chemical  substances,  such  as  sulphuric  acid,  ammonia,  alum, 
and  ergot,  are  among  the  most  powerful  stimuli  to  muscular  con- 
tractility. Indeed,  the  usefulness  of  haemostatics  in  arresting 
hemorrhage  depends  upon  this  property. 

The  smallest  arteries  readily  contract  under  the  influence  of  both 
the  direct  and  indirect  electrical  currents.  Simple  exposure  of  the 
arteries  to  air  suffices  to  produce  a  slow  but  permanent  constriction 
of  the  vessel.  The  local  application  of  cold — ice,  for  example — in 
stopping  bleeding  after  wounds,  is  well  known  to  the  uneducated, 
the  effect  being  due  to  contractility.  The  stimulus  of  great  heat 
produces  the  same  result. 

We  have  already  seen  that,  through  nervous  influence,  the  ar- 
teries contract.  In  speaking  of  the  structure  of  the  arteries,  it  was 
mentioned  that  the  muscular  fibers  are  supplied  by  nerves  derived 
from  the  sympathetic  and  cerebro-spinal  systems.  The  stimulation 
by  electricity  of  these  vasomotor  nerves,  as  they  are  called,  is  fol- 
lowed by  contraction  of  the  arteries  they  supply,  while  division  or 
paralysis  of  these  nerves  is  followed  by  a  dilatation  of  the  vessels. 
The  phenomena  of  blushing,  of  sudden  pallor  in  the  face,  are 
familiar  examples  of  the  influence  of  the  vasomotor  nerves  in  modi- 
fying the  amount  of  blood  in  a  part ;  in  the  one  case  the  vessels 
dilating,  in  the  other  contracting.  When  it  is  remembered  that 
more  blood  is  demanded  by  an  organ  at  one  time  than  another,  a 
gland  when  secreting,  for  example,  requiring  more  arterial  blood 
than  when  quiescent,  it  becomes  evident  that  there  must  be  some 
means  in  the  economy,  by  which  the  amount  of  blood  supplying 
any  organ  can  be  varied.  It  is  through  the  vasomotor  filaments 
that  the  nervous  system  modifies  the  calibre  of  the  arteries,  and,  in 
that  way,  regulates  the  amount  of  blood  distributed  to  diflerent 
iWoiJjs,  Vol.  iii.,  p.  194. 


CONTRACTILITY  OF  THE  ABTEEIE-i.  265 

parts  of  the  body.  The  origin  and  distribution  of  tlie  vasomotor 
nerves  ^11  be  considered  in  detail  hereafter. 

While  it  must  be  admitted  that  the  contractility  of  the  arteries 
favors  somewliat  the  onward  flow  of  the  blood  within  them,  ^-ithont 
doubt  the  principal  eifect  of  their  contractility  is  the  recriilation  of 
the  supply  of  blood  through  the  modification  of  their  calibre.  It 
should  be  mentioned,  as  regards  this  contractility,  that,  by  what- 
ever means  it  is  induced,  whether  the  stimuli  be  mechanical,  chem- 
ical, or  electrical,  that,  unlike  ordinary  striate<l  muscle,  it  does  not 
immediately  follow  the  application  of  the  stimidus,  more  or  less 
time  interveninof,  accordincr  to  the  stimulus  used.  It  is  also  to  be 
noticed  that  a  temporary  relaxation  usually  follows  a  contraction, 
and,  if  the  stimidus  be  very  intense,  the  contraction  is  followed  by 
a  dilatation,  as  if,  for  the  moment,  the  contractility  had  been  ex- 
hausted in  producing  its  effect. 

We  have  seen  that  during  each  ventricular  systole  the  aorta  and 
arteries  generallv  become  distended  with  the  blood  forced  into  them 
by  the  heart,  and  as  the  pressure  of  the  blood  is  exerted  both  lat- 
erallv  and  lono-itudinallv,  the  arterv  must  therefore  enlarge  in  both 
these  directions.  The  longitudinal  enlargement  of  the  artery  is, 
however,  so  much  more  apparent  than  the  transverse  one,  as  will 
be  explained  presently,  that  the  latter  is  usually  masked  or  obscured. 
So  much  so,  indeed,  is  this  the  case,  that  for  a  long  time  it  was  de- 
nied by  physiologists  that  there  was  any  transverse  dilatation  of  the 
artery.  While  Harvey,^  it  is  true,  states  that  when  an  artery  is  di- 
vided, and  held  at  the  cut -end  by  the  fingers,  the  dilatation  is  appar- 
ent, it  must  be  admitted,  however,  that,  to  the  ordinary  eye,  this 
is  far  from  evident.  The  proof  of  the  transverse  dilatation  of  the 
artery,  however,  does  not  rest  on  the  mere  assertion  of  a  physiolo- 
gist, however  celebrated,  but  can  be  readily  demonstrated,  either  as 
shown  by  Flourens,-  by  placing  around  a  living  artery  a  watch- 
spring,  the  ends  of  which  just  meet  during  the  relaxation  of  the 
vessel,  and  which  separate  during  the  lateral  distention,  or,  by  Pois- 
seuille's  ^  method,  which  consists  in  enclosing  an  artery  in  a  li\"ing 
animal  within  a  tube  filled  with  water  (the  ends,  of  course,  being 
closed),  and  the  interior  of  which  communicates  with  a  capillary 
tube,  ser^'ing  as  an  indicator,  in  which  the  water  rises  or  falls,  ac- 
cording as  the  water  is  forced  out  of  the  tube  by  the  lateral  disten- 
tion or  transverse  chlatation  of  the  artery,  or  is  sucked  back  again 
by  the  recoil  of  the  wall  of  the  vessel,  due  to  its  elasticity.  The 
longitudinal  expansion  of  the  artery,  or  the  elongation,  is  more 
easily  demonstrated  than  the  expansion  in  the  transverse  direction. 
As  also  shown  by  Flourens  it  is  very  evident,  if  the  artery  exam- 
ined be  slightly  colored,  and  a  needle  as  a  guide  be  immovably 
placed  on  one  side  of  the  vessels  with  each  ventricidar  systole  and 
diastole  the  colored  point  on  the  artery  will  be  observed  to  advance 

and  recede  in  a  longitudinal  direction.     The  elongation  of  the  ar- 
cs o 

lExercitatio  altera  ad  J.  Eiolanum  Opera  Omnia,  175'3,  p.  112. 

^Annates  des  Sciences  ]Sat.,  1837,  T.  vii.,  p.  106.         "Op.  cit.,  T.  ix.,  p.  46. 


266  CIRCULATION  OF  THE  BLOOD. 

tery  is  also  very  apparent  in  the  vessels  of  the  stump  of  an  ampu- 
tated extremity,  and  becomes  quite  evident  in  a  vessel  in  which  the 
blood  flowing  meets  vdih  an  obstacle,  as  where  the  artery  bifurcates, 
or  runs  in  a  tortuous  course  rather  than  a  straight  one.  During 
the  elongation  of  an  artery  the  vessel  frequently  rises  up  out  of  its 
bed,  experiencing  considerable  displacement ;  this  is  known  as  the 
locomotion  of  the  artery,  and  is  often  seen  in  the  temporal  and 
radial  arteries  of  old  and  emaciated  persons. 

On  account  of  the  extent  of  the  vessel  exposed  during  the  elon- 
gation, the  longitudinal  expansion  is  for  more  evident  than  the 
transverse  one,  and,  as  we  have  already  observed,  quite  obscures  it. 
The  increase  of  capacity  due  to  the  longitudinal  expansion  of  the 
artery  is,  however,  less  than  that  due  to  the  transverse  one,  for,  as 
is  well  known,  the  capacity  of  the  tube  increases  as  regards  the 
length,  in  a  simple  ratio  only,  whereas,  the  capacity  of  the  tubes  in 
the  transverse  direction  increases  not  in  a  simple  ratio,  as  the  diam- 
eters, but  as  the  squares  of  the  diameters. 

The  elongation  and  transverse  dilatation  of  the  arteries  due  to  the 
distention  of  their  walls  by  the  blood  forced  into  them  by  the  heart 
at  each  ventricular  systole  constitute  the  pulse.  It  will  be  observed 
that  the  pulse,  or  the  expansion  of  the  artery,  is  synchronous  "svith 
the  contraction  of  the  ventricle  of  the  heart,  not  with  the  heart's 
expansion,  as  was  thought  by  Galen,  and  the  ancients  generally. 
Although  this  truth  seems  to  have  been  known  to  a  writer  who 
lived  during  the  early  part  of  our  era,  it  remained  for  Harvey  to 
demonstrate  it  in  modern  times.  Ordinarily,  neither  the  elongation 
nor  transverse  dilatation  of  an  artery  or  its  pulse  is  visible  to  the 
naked  eye,  or  appreciable  even  by  touch  alone.  It  is  for  this  reason 
that  the  observer  presses  with  his  finger  more  or  less  the  artery 
examined,  thereby  constricting  the  vessel  and  so  increasing  the 
velocity  of  the  l)lood,  it  flowing  faster  as  the  artery  becomes  smaller, 
the  same  amount  of  blood  passing  through  in  a  given  time  ;  this,  as 
we  have  seen,  increases  friction,  and  so  causes  an  obstacle  to  the 
flow,  which,  within  limits,  increases  the  force  of  the  heart,  and, 
therefore,  the  distention  of  the  artery,  and  so  makes  the  beating  of 
the  vessel  or  the  pulse  more  apparent. 

Production  of  the  Pulse. 

No  artery  in  man  can  be  directly  measured,  either  as  regards  its 
expansion  or  its  pressure.  In  feeling  the  pulse,  however,  the 
endeavor  is  made  to  measure  both  by  the  sense  of  touch  alone. 

While  the  experience  of  every  physician  shows  to  what  an  extent 
slight  variations  in  the  pulse  can  be  appreciated  by  the  tactus 
eruditus  alone,  nevertheless  it  is  only  by  means  of  the  graphic 
method  that  the  conditions  on  which  the  production  of  the  pulse 
and  its  variations  depend  can  be  successfully  investigated.  By  the 
graphic  method,  as  we  have  seen,  a  pictorial  representation,  a  trace 
of  some  kind  of  the  phenomena  occurring,  can  be  obtained  and  pre- 


THE  SPHYGMOGBAPH. 


267 


served,  by  means  of  which  slight  variations,  due  to  change  of  con- 
ditions, become  at  once  evident  that  would  be  entirely  unappreciable 
by  the  eye  or  touch  unaided. 

The  advantage  of  such  an  experimental  investigation  of  the  pulse, 
the  practical  application  that  can  be  made  of  it  in  investigating  the 
cause  of  disease,  will  be  at  once  appreciated  after  the  sphygmograph 
and  the  arterial  schema,  the  apparatus  we  use  in  studying  the  pulse, 
has  been  described,  and  the  results  obtained  by  it  shown. 

The  Sphygmograph. 

The  object  of  the  sphygmograph  {aifoyixoc,  a  trace,  and  ycjo.ipco,  to 
write)  is  to  measure  the  succession  of  the  alternate  dilatations  and 
contractions  of  an  artery  due  to  the  blood  forced  into  it  by  the  beat- 
ing heart,  to  magnify  these  movements,  and  to  register  them  on  a 
surface  moving  at  a  uniform  rate  by  clock-work. 

Fig.  106. 


Mechanical  arrangement  of  the  sphygmograph.     (Sanderson.) 

The  sphygmograph  was  originally  invented  by  Vierordt,  and 
afterward  greatly  improved  by  Marey.  The  instrument  (Fig. 
106)  consists  of  a  brass  frame  (O  R),  the  under  surface  of  w'hich 
is  covered  with  ebonite,  and  which  can  be  applied  to  the  outer  edge 
of  the  volar  aspect  of  the  forearm  so  that  it  rests  immovably  in 
this  position  with  reference  to  the  radius  and  wrist-bones,  particu- 

FiG.  107. 


Marey's  sphygmograph  applied  to  arm.     (Marey.) 

larly  the  scaphoid.  The  pulsations  of  the  radial  artery  are  received 
by  an  ivory  button  (K),  placed  at  the  free  end  and  under  the  sur- 
face of  the  steel  spring  I ;  the  other  fixed  end  of  the  spring  is  at- 
tached to  the  brass  work  at  P.     By  means  of  the  ivory  button  and 


268 


CIRCULATION  OF  THE  BLOOD. 


Fig.  108. 


spring  the  pulsations  of  the  artery  are  transmitted  to  the  vertical 
screw  T,  which  passes  through  the  brass  bar  N,  whose  center  of 
motion  is  at  E,  above  the  attachment  of  the  steel  spring  I ;  the 
free  end  (B)  of  the  brass  bar  is  bent  upward  at  right  angles,  and 
carries  a  knife-edge  (D),  Fig.  106.  The  elevation  of  the  screw  T, 
through  the  pulsations  of  the  artery,  raises  the  brass  bar  N,  carry- 
ing the  knife-edge  D,  the  latter,  in  turn,  elevating  the  registering 
lever  A,  of  which  one  end  (C)  is  supported  by  a  horizontal  rod 
passing  through  it  and  connecting  the  sides  of  the  brass  frame, 
while  the  other  movable  end  (A)  terminates  in  a  metal  joint,  which 
registers  the  motion  of  the  pulsation  on  a  piece  of  paper  (Fig.  107) 
blackened  by  passing  it  to  and  fro  through  the  flame  of  a  kerosene 
lamp.  The  paper  is  fastened  to  a  copper  plate,  which  is  moved  at 
a  uniform  rate  by  the  clock-work  (Fig.  107).  As  the  distance  be- 
tween the  supporting  rod  C  and  the  knife-edge  D  is  much  less  than 
the  length  of  the  lever,  the  vibrations  of  the  extremity  of  the  lever 
(A)  are  far  more  extensive  than  the  vertical  movement  of  the  spring 
I  and  screw  T.     By  means  of  the  screw  T  the  distance  between 

the  steel  spring  I  and  the  register- 
ing lever  A  can  be  varied  at  will 
without  interfering  with  the  mech- 
anism by  which  the  movement  is 
transmitted.  The  distance  between 
the  brass  frame  and  the  ebonite  sur- 
face can  also  be  increased  or  dimin- 
ished, according  to  the  direction  in 
which  the  screw  Y  is  turned,  and, 
in  this  way,  the  pressure  on  the 
artery  may  be  varied  ;  the  variation 
in  the  pressure  is  measured  by  the 
scale  (Fig.  108),  which  has  been 
experimentally  graduated  by  turn- 
ing the  instrument  upside  down, 
and  successively  placing  a  series  of 
weights  on  what  would  be  ordi- 
narily the  lower  surface  of  the 
spring,  but  which  is  now  the  upper 
surface,  and  observing  the  extent  of 
its  deflection  and  marking  the  scale 
correspondingly.  Finally,  by  means 
of  a  movable  clamp,  there  can  be  adapted  to  the  sphygmograph, 
when  desirable,  a  delicate  tympanum,  with  registering  lever,  in 
connection  with  a  cardiograph,  so  that  the  traces  of  the  cardiac  and 
arterial  pulsation  can  be  registered  simultaneously  on  the  black- 
ened surface. 

To  take  a  trace  with  the  sphygmograph  of  the  radial  artery,  which 
is  the  vessel  usually  examined,  the  forearm  should  be  supported  on 
something,  a  table,  for  example,  the  back  of  the  wrist  resting  on  a 


Scale  for  determining  pressure  excited  by 
artery.     (Sanderson.) 


SPHYGMOGRAPHIC  TRACINGS. 


269 


cushion  or  padding,  so  that  the  dorsal  sui'face  of  the  hand  "svill  be 
inclined,  vdih.  reference  to  the  forearm,  at  an  angle  of  20  to  30  de- 
grees. The  instrument  must  be  so  placed  on  the  wrist  that  the 
block  rests  upon  the  trapezium  and  scaphoid,  while  the  extremity'  of 
the  spring  is  opposite  the  styloid  process  of  the  radius,  the  general 
direction  of  the  sphygmograph  will  then  be  parallel  with  that  of 
the  radius.  In  making  an  observation  it  is  best  to  begin  by  ad- 
justing the  instrument  so  that  the  ivory  button  on  the  under  surface 

Fig.  109. 


Sphygmographic  tracing  from  radial  artery  of  a  man  set.  twenty-five. 

Fig.  110. 


?phygmograpliic  tracing  from  radial  artery  of  a  man  set.  thirty. 

Fig.   111. 


Sphygmographie  tracing  from  femoral  artery  of  a  man  iet.  thirty. 
Fig.  112. 


Sphygmographie  tracing  from  radial  artery  of  a  woman  set.  sixty-fire.    Atheromatous  arteries. 

Fig.  113. 


Sphygmographie  tracing  from  radial  artery  of  a  man  set.  seventy.    Atheromatous  arteries. 

of  the  spring  is  at  such  a  distance  from  the  bone  that  the  artery  is 
pressed  upon  during  its  entire  expansion,  and  yet  not  so  compressed 
as  to  obliterate  at  any  moment  its  cavity. 

To  those  unfamiliar  with  the  use  of  the  sphygmograph,  perhaps 
it  will  be  well  to  begin  by  arranging  the  spring  so  that  it  will  exert 
a  pressure  sufficient  to  flatten  the  artery  against  the  radius  and  then 


270 


CIRCULATION  OF  THE  BLOOD. 


to  diminish  the  pressure  until  the  eifects  of  such  compression  dis- 
appear, and  thus  to  take  traces  of  the  maximum  and  minimum 
pressures,  and  one  then  of  an  intermediate  character. 

Having  described  the  sphygmograph  and  the  manner  of  using  it, 
the  following  figures  will  illustrate  the  character  of  the  traces  taken 


0.20 


0.80 


0.20  < 


0.20< 


0.20  < 


Pulse-curves  described  by  a  series  of  Sphygmographic  Levkrs— placed  at  intervals  of 
20  em.  from  each  other  along  an  elastic  tube  into  which  fluid  is  forced  by  the  suddeu  stroke  of  a 
pump.  The  pulse-wave  is  travelling  from  left  to  right,  as  indicated  by" the  arrows  over  the  pri- 
mary (a)  and  secondary  (6,  c)  pulse-waves.  The  dotted  vertical  lines  drawn  from  the  summit  of 
the  several  primary  waves  to  the  tuning-fork  curve  below,  each  complete  vibration  of  which 
occupies  1-.50  second,  allow  the  time  to  be  measured  which  is  taken  up  by  the  wave  in  passing 
along  20  cm.  of  the  tubing.  The  waves  a'  are  waves  rcfltcted  from  the  closed  distal  end  of  the 
tubing ;  this  is  indicated  by  the  direction  of  the  arrows.  It  will  be  observed  that  in  the  more 
ilistant  lever  VI.  the  reflected  wave,  having  but  a  slight  distance  to  travel,  becomes  fused  with  the 
primary  wave.     (FromMAREY.) 


by  it.  Thus,  for  example.  Figs.  109,  110,  and  111  are  obtained 
from  the  radial  and  femoral  arteries  in  a  healthy  man  of  about 
thirty  years  of  age.     Figs.  112  and  113  are  from  the  radial  of  a 


SPHYGMOGBAPHIC  TRACINGS.  271 

woman  ?et.  sixty-five  and  of  a  man  ?et.  seventy  respectively,  in  both 
of  which  cases  the  arteries  were  in  an  atheromatous  condition. 

If  sphymographic  tracings  from  arteries  such  as  shown  in  Figs. 
109-113  be  compared  with  those  obtained  from  an  india-rubber 
tube,  Fig.  114,  through  Avhich  water  is  forced  by  a  pump  and  upon 
which  sphygmographs  are  applied  at  equal  intervals,  the  tracings 
will  be  seen  to  present  in  both  cases  the  same  general  characters. 
In  both,  the  same  kind  of  movements  succeed  each  other  in  the 
same  order.  "With  the  expansion  of  the  artery  and  the  tube  the 
levers  rise,  with  the  contraction  they  fall,  then  the  secondary  eleva- 
tion or  dicrotic  j)ulse  occurs,  then  finally  the  descent  again.  As 
in  the  case  of  the  natural  heart,  so  in  that  of  the  pump  it  will  be 
observed  that,  as  long  as  the  heart  and  pump  act,  the  respective 
valves  being  open,  the  artery  and  tube  expand,  and  the  levers 
ascend,  and  with  the  cessation  of  the  flow  of  liquid  from  behind 
the  artery  and  tube  contract  and  the  levers  descend. 

Inasmuch  as  the  curves  obtained  from  the  artery  and  the  india- 
rubber  tube  by  sphygmographic  methods  are  essentially  of  the  same 
character  it  may  be  reasonably  inferred  that  they  are  produced  in 
the  same  way.  It  is  for  this  reason  that  tracings,  such  as  are  rep- 
resented in  Fig.  114,  may  be  used  as  illustrating  the  conditions 
upon  which  the  production  of  the  natural  pulse  depends.  It  is 
obvious  that  what  we  call  the  pulse  is  due  not  to  a  movement  of  the 
blood  itself  which  is  one  of  translation  and  slow  but  to  the  expan- 
sion of  the  wall  of  the  artery  following  the  systole  of  the  heart,  and 
which  beginning  at  the  aortic  orifice  progresses  wave  like  towards 
the  capillaries.  "  Unda  non  est  materia  progrediens  sed  forma 
materia?  progrediens."  ^  It  need  hardly  be  mentioned  that  a 
sphygmographic  tracing  is  not  a  representation  of  a  pulse  wave 
since  the  ascending  part  of  the  curve  only  indicates  that  the  pulse 
wave  is  passing  under  the  sphygmograph,  the  descendiug  part  that 
the  wave  has  passed  by.  It  will  be  observed  that  the  ascending- 
part  of  sphygmographic  tracing  or  curve  is  steep,  the  descending  part 
gradual.  The  steep  ascent  is  due  to  the  sudden  expansion  of  the 
wall  of  the  artery  following  the  ejection  of  blood  by  the  heart,  the 
gradual  fall  to  the  recoil  of  the  arterial  wall  due  to  its  elasticity  not 
being  instantaneous.  The  lever  remains,  therefore,  momentarily  at 
the  height  to  which  it  has  been  elevated  by  the  pulse  wave,  this 
period  being  prolonged  in  j^roportion  as  the  elasticity  of  the  artery 
is  diminished.  Hence,  in  old  persons  in  whom  the  arteries  are  not 
very  elastic  the  curve  at  the  summit  is  rounded  oif  and  the  descent 
is  a  gradual  one.  It  wdll  also  be  observed  from  an  inspection  of 
successive  sphygmographic  traces,  such  as  are  represented  in  Fig. 
114,  that  the  ascending  part  of  the  curve  becomes  less  steep  in  pro- 
portion as  the  position  of  the  sphygmographs  recede  from  that  of 
the  pump  or  heart.  This  is  also  in  accordance  with  the  explanation 
of  the  manner  in  which  the  pulse  wave  is  produced  just  given. 

1 E.  H.  Weber,  De  pulsu  in  omnibus  arteriis  plane  non  svnchronico,  Annot  Acad. 
Leipzig,  1834. 


97  9 


CIRCULATION  OF  TEE  BLOOD. 


It  was  shown  by  Weber  that  the  pulse  wave  is  transmitted  at  a 
rate  of  about  9  meters  (28.8  feet)  a  second.  Weber  ^  determined 
this  velocity  by  observing  with  chronometers  the  difference  in  time 
of  the  beat  of  the  facial  and  dorsalis  pedis  arteries,  measuring  the 
distance  of  the  facial  artery  from  the  heart  as  accurately  as  possible, 
and  the  distance  of  the  dorsalis  pedis  from  the  facial,  and  subtract- 
ing the  first  distance  from  the  second,  the  difference  of  distance  the 
pulse  wave  passed  over  in  the  second  case,  as  compared  with  the 
first,  will  account  for  the  difference  in  the  time  of  the  beats,  and 
give  approximately  the  distance  passed  over  by  the  pulse  wave  in 
one  second.  Supposing  that  the  ventricular  systole  lasted  four- 
tenths  of  a  second,  the  length  of  the  pulse  wave  would  be  -^^  of  9 
meters  =  3.6  meters  (11.5  feet),  and  there  would  be,  therefore,  two 

and  a-half  waves  in  a  second   I  .^—  =  2.5  j  •     Consequently  the 

anterior  end  of  a  pulse  wave  would  have  reached  the  extremities  be- 
fore the  posterior  end  had  left  the  left  ventricle.  It  would  appear, 
however,  that  this  estimate  of  the  length  of  the  pulse  wave  is  some- 
what exaggerated,  it  having  been  shown  by  the  photosphygmograph 
that  the  pulse  wave  is  about  1.5  meters  (4.7  feet)  long,  requiring, 
therefore,  about  one-sixth  of  a  second  to  pass  from  the  heart  to  the 
foot.  As  a  certain  length  of  time  elapses  during  the  transmission 
of  the  pulse  wave  from  the  heart  to  the  capillaries,  it  is  obvious 
that  the  pulse  will  be  felt  in  arteries  near  the  heart  sooner  than  in 
those  far  from  it.  This  is  well  shown  in  the  successive  sphygmo- 
graphic  traces  of  Fig.  114,  a  considerable  interval  of  time  elapsing 
between  the  elevation  of  lever  1,  placed  near  the  pump  and  lever 
6,  at  some  distance  from  it.  Any  one  can  readily  convince  himself, 
in  his  own  person,  that  there  is  a  gradual  retardation  of  the  pulse 
from  the  heart  to  the  periphery,  by  feeling  the  left  carotid  artery 
with  the  thumb  and  index  finger  of  the  left  hand,  and  the  left  radial 
with  those  of  the  right.  The  beat  of  the  radial  artery  will  be  felt 
later  than  that  of  the  carotid,  the  difference  in  the  time  of  the  beat 
being  quite  appreciable. 

When  it  is  remembered  that,  as  the  blood  is  propelled  forward 
into  the  arterial  system,  it  is  being  continually  diverted  laterally 
through  the  distensibility  of  the  walls  of  the  arteries,  and  that  as 
the  (juantity  of  blood  forced  forward  at  each  ventricular  systole  is 
limited  in  quantity,  it  must  follow,  as  we  recede  from  the  heart  to 
the  periphery,  that  there  will  be  less  and  less  blood  forced  forward. 
The  blood  having  been  progressively  absorbed,  so  to  speak,  by  these 
lateral  distentions  in  the  proximal  portion  of  the  arteries,  there  will 
be  less,  therefore,  to  distend  the  distal  parts.  The  pulse  being  due 
to  this  distention,  must,  therefore,  be  weaker  in  the  arteries  at  a  dis- 
tance from  the  heart  than  in  those  near  it,  and  must  ultimately  dis- 
appear in  the  smallest  arterioles  altogether.  As  a  fact,  the  pulse  is 
rarely  felt  in  arteries  having  a  diameter  less  than  J  of  a  mm.  (y^^  of 
iMuUer's  Archiv,  1851,  s.  537. 


SPHYGMOGRAPHIC  TRACINGS. 


273 


Fig. 


Apd   C  J   D 


Pulse  Teacisg  from  the  Radial  Artery  of  Max. 
The  vertical  curved  line,  L,  gives  the  tracing  which 
the  recording  lever  made  when  the  blackened  paper 
was  motionless.  The  curved  interrupted  lines  show 
the  distance  from  one  another  in  time  of  the  chief 
phases  of  the  pulse-wave,  viz.,  x  =  commencement 
and  A  end  of  expansion  of  artery,  p,  pre-dicrotic 
notch.  ,7,  dicrotic  notch.  C,  dicrotic  crest.  D,  Post- 
dicrotic  crest.  /,  the  post-dicrotic  notch.  These  are 
explained  in  the  text  later  on.  ^  (Foster.) 


an  inch).     It  is  for  this  reason  that  in  the  case  of  an  aneurism,  the 
lateral  distention  being  here  greatly  exaggerated,  that  the  pulse  is 
often  absent  in  that  portion  of  the  artery  situated  beyond  the  seat 
of  the  disease.     In  the  case 
of  aneurism  of  the  aorta,  the 
pulse  may  be  absent  in  all  of 
the  arteries  of  the  body. 

From  the  very  nature, 
therefore,  of  the  production 
of  the  pulse  it  must  not  only 
be  postponed,  but  sooner  or 
later  extinguished.  It  will 
be  seen  from  an  examination 
of  the  pulse  tracing  of  the 
I'adial  artery  of  man  that  the 
lever,  after  having  descended 
some  distance  from  its  maxi- 
mum elevation,  rises  again 
and  then  descends  finally. 

The  secondary  crest  C 
(Fig.  115)  superimposed 
upon  the  primary  curve  con- 
stitutes, as  already  mention- 
ed, the  dicrotic  crest,  and  the 

pulse  giving  rise  to  it  the  dicrotic  pulse.  When  two  extra  crests 
appear,  which  is  sometimes  the  case,  the  pulse  is  said  to  be  tricrotic, 
and  when  several  are  seen,  polycrotic.  Usually,  when  extra  crests 
appear,  one  or  more,  they  are  situated  upon  the  descended  part  of 
the  curve,  and  the  latter  is  then  spoken  of  as  being  katacrotic.  In 
some  cases,  however,  as  in  aneurism  of  the  aorta  (Fig.  116),  for 
example,  the  primary  crest  does  not  appear  at  the  highest  part  of 
the  curve,  but  upon  its  ascending  part,  the  curve  being  then  called 
anacrotic. 

It  may  be  mentioned  in  this  connection  that  in  well  marked  cases 
of  dicrotic  pulse  the  dicrotic  crest  is  not  only  well  defined,  but  also 
the  pre-dicrotic  and  dicrotic  notches  pre- 
ceding it,  and  the  po.st-dicrotic  crest  and 
notch  following  it  as  shown  in  Fig.  115. 
Difference  of  opinion  still  prevails  among 
physiologists  as  to  the  exact  manner  in 
which  the  dicrotic  pulse  is  produced.  Ac- 
cording to  some  investigators  it  is  due  to 
the  pulse  Avave  being  reflected  back  from 
the  capillaries  or  small  arteries  to  the  heart. 
If  this  were  the  case,  however,  the  dis- 
tance between  the  dicrotic  and  primary  crests  ought  to  be  less  in 
arteries  far  from  the  heart  than  in  those  near  to  it,  since  the  dis- 
tance passed  over  by  the  retrograde  wave  will  be  less  in  the  former 
18 


Anacrotic  sphygmograph  trac- 
ing from  the  ascending  aorta 
(Aneurism.)     (Fo  ster.) 


274  CIRCULATION  OF  THE  BLOOD. 

than  in  the  latter.  As  it  has  been  shown,  however,  by  measure- 
ment that  tlie  distance  between  the  dicrotic  and  primary  crests 
is  the  same  in  both  the  peripheral  and  proximate  arteries,  which 
is  inconsistent  with  the  theory  of  the  dicrotic  pulse  being  due  to 
a  retrograde  wave,  it  is  obvious  that  the  latter  must  be  produced 
in  some  other  wav.  At  the  present  day  the  dicrotic  pulse  is  usu- 
ally supposed  to  be  due  to  a  secondary  wave  which,  being  gener- 
ated at  the  aortic  valves,  is  thence  propagated  towards  the  periph- 
ery, the  wave  being  produced  in  the  following  manner :  At 
the  end  of  the  ventricular  systole,  the  pressure  in  the  ventricle  be- 
ing less  than  in  the  aorta,  the  blood  flows  back  towards  the  heart 
and  closes  the  semilunar  valves,  the  latter  through  their  resistance 
thereby  give  rise  to  the  secondary  wave,  which,  following  in  the 
wake  of  the  pulse  wave,  gives  rise  to  the  dicrotic  pulse.  In  con- 
nection Avith  the  production  of  the  dicrotic  jiulse  it  may  be  men- 
tioned that  the  conditions  favoring  it  are  an  elastic  extensible 
arterial  wall,  a  low  mean  pressure  permitting  readily  the  action  of 
the  arterial  wall  and  a  quick  contraction  of  the  ventricle  with  the 
ejection  of  a  comparatively  large  quantity  of  blood. 

AVliile  the  description  of  the  pulse  in  disease  belongs  rather  to 
works  on  medicine  and  therapeutics,  it  may  not  appear  superflu- 
ous to  mention  that  pathology  confirms  the  views  that  have  just 
been  offered  as  to  the  production  of  the  natural  pulse.  Thus,  in 
an  ossified  artery,  there  is  no  pulse,  because  dilatation  is  impossible. 
When  the  arteries  near  the  heart  are  rigid,  the  pulse  is  jerky,  and 
the  flow  of  blood  is  intermittent,  not  remittent.  We  see  the  same 
kind  of  pulse  when  the  walls  of  the  arteries  are  relaxed,  unable  to 
recoil  thoroughly  on  their  contents.  If  the  artery  be  irritable,  and 
at  the  same  time  distensible,  the  pulse  will  be  exaggerated,  and  can 
be  seen  by  the  naked  eye  when,  otherwise,  it  is  usually  impercep- 
tible. The  character  of  the  pulse  is  profoundly  affected  by  the 
conditions  of  the  system,  modified  by  general  disease.  Thus  the 
large  compressible  pulse  of  fever,  the  hard  pulse  of  Bright's  dis- 
ease, the  small  pulse  of  peritonitis,  the  soft  pulse  of  collapse,  etc., 
are  well  known  to  the  physician. 

Finally,  it  has  been  shown  by  Vierordt  and  Aberlc  ^  that  there 
is  a  daily  variation  in  the  calibre  of  the  arteries  that  must  influence 
somewhat  the  character  of  the  pulse,  the  radial  artery,  for  example, 
being  larger  in  the  evening  than  in  the  morning. 

lArcliiv.  f.  physiol.  Ileilkundo,  1856,  B.  xy.,  s.  574. 


CHAPTER   XVII. 


Fi(i.  ii: 


CTRCULATIOX   OF   THE    B'LOOB.— {Continued.) 

PRESSURE  AND  VELOCITY  OF  THE  BLOOD  IN  THE  ARTERIES. 

By  blood  pressure,  ^vhether  it  be  cardiac  or  arterial,  etc.,  is  meant 
the  pressure  or  force  that  is  exerted  by  the  blood  upon  the  surface 
of  the  vessel  containing  it,  or,  what  is  the  same  thing,  the  force 
that  is  required  to  be  put  forth  by  the  walls  of  the  vessels  in  order 
to  sustain  the  column  of  blood  within  them.  Before  showing  the 
manner  in  which  the  blood  pressure  is  determined  in  a  living  ani- 
mal, let  us  first  endeavor,  however,  to  illustrate,  by  a  few  simple 
experiments,  the  manner  in  which  the  pressure  of  liquids  in  general 
is  determined. 

It  is  well  known,  as  first  shown  by  the  distinguished  geometri- 
cian Pascal,  that  the  pressure  exerted  anywhere  upon  a  mass  of 
liquid,  assuming  the  latter  to  be  perfectly  fluid 
and  uninfluenced  by  gravity,  is  transmitted  undi- 
minished in  all  directions,  acting  with  the  same 
force  on  all  equal  surfaces,  and  in  a  direction  at 
riffht  ang-les  to  those  surfaces.  That  the  force  ex- 
erted  upon  the  mass  of  a  liquid  is  transmitted  in 
all  directions,  and  at  right  angles  can  be  readily 
shown  by  means  of  the  apparatus  represented  in 
Fig.  117.  This  consists  of  a  cylinder  provided 
with  a  piston  fitting  into  a  hollow  sphere  pierced 
with  numerous  holes,  into  which  are  fitted  small 
cylindrical  jets  placed  perpendicularly  to  the  sides. 
The  sphere  and  cylinder  being  filled  with  water, 
and  the  piston  depressed,  the  water  will  be  ob- 
served to  spout  out  from  all  of  the  jets,  and  not 
simply  from  the  one  opposite  the  piston.  In  order 
to  show  that  the  pressure  is  transmitted,  not  only 
in  all  directions,  but  equally,  we  make  use  of  an  apparatus  very 
similar  to  the  one  just  described,  and  represented  in  Fig.  118,  it 
differing  only  in  that  the  perpendicular  jets  projecting  from  the 
sphere  contain  closely  fitting,  but  easily  movable  pistons,  each  pis- 
ton having  the  same  area.  The  sphere  being  filled  with  water,  the 
latter,  by  virtue  of  its  weight,  will  press  equally  upon  the  surface 
of  all  the  pistons.  Xeglecting  the  influence  exerted  by  the  weight 
of  the  water,  and  the  friction  of  the  pistons,  it  will  be  observed 
that  if  a  given  pressure  (P)  be  exerted  upon  the  piston  A  the  water 
will  transmit  the  same  pressure  to  tlie  other  pistons  (B  C  D),  which 
will  move  outwardly,  unless  they  are  each  subjected  to  an  equal  and 


Apparatus  to  demon- 
strate the  equality  of 
jiressure  in  all  direc- 
tions. 


276 


CIRCULATION  OF  THE  BLOOD. 


opposite  pressure  (P).  It  is  evident,  therefore,  that  the  pressure 
(P)  exerted  upon  A  is  not  only  transmitted  in  a  straight  line  upon 
B,  but  equally  upon  C  and  D — that  is,  equally  in  all  directions.  If 
now  the  axes  of  the  jets  BCD  be  disposed  parallel  to  each  other, 
and  made  to  approach  until  they  form  one,  and  for  the  three  pis- 
tons a  single  one  be  substituted,  as  in  Fig.  119,  the  conditions  of 
the  pressure  are  in  nowise  changed,  but  it  becomes  at  once  evident 
that  the  pressure  exerted  upon  the  piston  A,  and  transmitted  by 
the  fluid,  is  proportional  to  both  the  number  and  area  of  the  pis- 
tons, whether  existing  separately  as  B,  C,  and  D,  or  combined  as 
B  C  D.  That  is  to  say,  if  a  weight  of  one  pound  be  placed  upon 
the  piston  A,  the  three  pistons  B,  C,  D,  or  the  one  piston  BCD,  will 
be  pressed  outward  by  the  pressure  transmitted  through  the  liquid, 
unless  a  weight  of  one  pound  be  placed  upon  each  of  the  pistons 
B,  C,  or  D,  or  of  three  pounds  upon  the  piston  B  C  D.  Suppose, 
however,  that  the  apparatus  be  constructed  of  the  form  represented 


Fig.  lis. 


Apjiaratus  to  demonstrato  pressure. 

in  Fig.  120,  in  which,  as  before,  the  large  piston  B  has  three  times 
the  area  of  the  small  one  A,  and  carries  three  times  as  heavy  a 
weight,  it  will  be  observed  that  while  the  small  piston  A  with  a 
weight  of  one  pound  and  an  area  of  one  inch  descends  through 
three  inches,  the  large  piston  B,  with  an  area  of  three  inches,  and 
with  a  weight  of  three  pounds,  ascends  through  only  one  inch,  equi- 
librium being  then  established,  just  as  a  lever  whose  arms  have  a 
length  respectively  of  three  and  one  inches  Mill  be  balanced  by  sus- 
pending a  one-pound  weiglit  at  the  end  of  the  long  arm,  and  a  three- 
pound  M'eight  at  the  end  of  the  short  one.     It  is  perfectly  evident 


PRESSURE  OF  LIQUIDS. 


2V  / 


that  in  neither  case  is  there  any  absohite  gain  of  power,  for  Avhat  is 
gained  in  weight  is  lost  in  height  or  distance. 

In  practical  mechanics  the  Bramah  press  is  a  beantifnl  applica- 
tion of  the  principle  just  enunciated,  in  which  a  pressure  of  300 
pounds  exerted  upon  a  piston  corresponding  to  A  will  exert  a  pres- 
sure of  30,000  pounds  upon  a  piston  BCD,  supposing  the  sectional 
area  of  the  latter  to  be  100  times  that  of  the  former.  It  must  not 
be  forgotten,  however,  that  in  the  Bramah  press,  as  in  the  simple 
apparatus  just  described,  and  in  the  case  of  the  lever  Avith  unequal 
arms,  that  the  greater  weight  is  elevated  only  a  fractional  part  of  the 
distance  through  which  the  lesser  weight  has  descended,  and  that 
what  is,  therefore,  gained  in  weight  is  lost  in  distance.  The  signifi- 
cance of  this  important  truth  in  the  study  of  Ijlood  pressure  will 
very  soon  become  evident. 

Xow,  on  reflection,  it  will  become  evident  from  what  has  just 
been  said  with  reference  to  the  transmission  of  pressure  through 
fluids,  that  the  pressure  exerted  by  the  particles  of  water  against 
each  other  must  be  estimated  in  exactly  the  same  manner  as  we 
have  estimated  the  pressure  P  transmitted  to  the  base  of  the  piston 
B  (Fig.  120).  It  follows,  therefore,  that  if  the  weights  and  pistons 
be  removed  from  the  apparatus  (Fig.  120),  that  the  water  will  rise 
to  the  same  level  in  both  of  its  limbs  (Fig.  121),  proving  that  the 
pressure  exerted  by  the  water  in  A  and  B  must  be  equal  and  op- 
posite,  notwithstanding   that  the  limb  B  contains  three  times   as 


Fig.  120. 


Fig.  121. 


n 


III 


Principle  of  the  hydraulic  jire^^. 

much  water  as  the  limb  A,  for  if  the  pressure  exerted  by  the  water 
in  B  were  greater  than  that  in  A  the  level  of  the  water  would  rise 
higher  in  the  latter  than  in  the  former.  It  follows,  therefore,  from 
the  principle  of  Pascal,  or  the  equality  of  pressure,  that  the  pres- 
sure exerted  by  a  fluid  is  independent  of  the  quantity  of  the 
fluid,  and  of  the  form  of  the  vessel  containing  it,  but  is  depen- 
dent for  the  same  fluid  on  the  area  of  the  base  upon  which  the 
pressure  is  exerted,  and  the  height  of  the  column  of  liquid  above 
it.     For  let    us    suppose    that    the  vessel,  whose  liquid    contents 


278 


CIRCULATIOX  OF  TEE  BLOOD. 


press  upon  the  bottom,  be  of  a  taperiiiji;  form,  such  as  is  repre- 
sented in  Fig.  122,  and  that  the  bottom  D  E  l)e  divided  into 
eight  areas  of  a  size,  equal  to  that  of  the  mouth  F.  From  what 
has  been  said  of  the  pressure  being  transmitted  equally  in  all  direc- 
tions, it  follows  that  the  weight  of  a  small  liquid  layer,  say  half  an 
inch  thick  at  the  top,  will  be  transmitted  undiminished  to  the  eight 
areas  of  the  bottom,  producing  the  same  pressure  as  if  eight  of  such 
layers  of  lic[uid  were  separately  placed  upon  them.  In  the  same 
manner,  a  layer  half  an  inch  thick,  but  situated  as  much  lower 
down  in  tlie  liquid,  so  as  to  have  twice  the  area  of  F,  will  produce 
the  same  pressure  upon  the  bottom  as  if  four  such  liquid  layers 
were  laid  there — that  is,  the  same  as  the  pressure  due  to  the  eight 
small  layers.  It  follows,  therefore,  that  each  horizontal  layer  of  the 
same  thickness,  no  matter  where  it  lies  in  the  liquid,  produces  the 
same  pressure,  the  amount  depending  upon  its  thickness  and  the 
area  of  its  base.  The  total  pressure  of  the  liquid  upon  the  bottom 
must  depend,  therefore,  on  the  area  of  the  base,  and  its  vertical 
height  or  thickness — that  is,  equal  to  a  column  of  liquid  having 
the  same  ])ase  and  the  same  vertical  heig-ht.     The  truth  of  the  theo- 


Fk;.  122. 


Fig.  123. 


To  illustrate  the  pressure  exerted  by 
liquids. 


Apparatus  to  demonstrate  that  the  ])ressure  is 
iudejieudent  of  shape  and  size  of  vessel, 


rem  so  deduced  is  experimentally  verified  by  the  experiment  just 
performed,  since  the  pressure  exerted  by  the  columns  of  liquid  in  A 
and  B  (Fig.  121)  are  the  same,  because  they  have  tlie  same  base 
and  the  same  height  of  liquid  above  it.  That  the  shape  of  the  ves- 
sel has  no  more  influence  with  regard  to  the  pressure  exerted  by 
the  water  it  contains  than  that  exerted  by  the  amount  will  become, 
perhaps,  more  evident  if  the  apparatus  (Fig.  123)  be  tilled  with 
water.  The  level  to  which  the  water  rises  being  the  same  in  all 
the  tubes,  though  of  very  different  shape,  proves  that  the  pressure 
exerted  by  the  water  must  Ijc  the  same  in  all  of  them.  On  account, 
liowever,  of  the  ])ractical  importance  of  the  law  of  the  j)ressure  of 
liquids,  and  of  the  necessity  of  keeping  clear  in  tlie  mind  the  dis- 


PRESSUBE  OF  LIQUIDS. 


279 


tinction  between  the  pressure  exerted  by  the  liquid  and  its  weight, 
let  us  illustrate  the  principle  involved  a  little  more  in  detail  by- 
means  of  the  apparatus  represented  in  Fig.  124. 

This  consists  of  a  balance,  in  one  of  whose  scale  pans  (A)  a  known 
weight  is  placed,  while  to  the  other  (B)  a  wire  is  attached,  termi- 
nating in  a  flat  disk  (C),  which  is  so  exactly  applied  to  the  lower 
opening  of  the  supporting  cylinder  (D)  that  it  practically  consti- 
tutes its  bottom,  being  tightly  drawn  up  by  the  counterpoising 
weight  in  A.  A  known  weight  being  now  added  to  that  already  in 
A,  and  water  being  gradually  poured  into  the  cylinder,  by  degrees 
the  pressure  of  the  liquid  on  the  disk  or  bottom  increases,  and  when 
the  pressure  so  exerted  equals  the  counterpoising  weight  in  A  the 
least  excess  of  water  detaches  the  disk — that  is,  the  bottom  of  the 
cylinder  falls  out,  and  the  water  flows  out ;  but,  as  the  pressure  is 
at  once  diminished  by  the  outflow,  the  disk  is  drawn  up  again  and 
adheres  closely  to  the  cylinder.  The  pointer  touching  the  surface 
of  the  water  marks  its  level  at  the  moment  of  equilibrium. 

Fig.  124. 


Pressure  of  a  lii|uid  on  the  l)ottom  of  the  vessel  which  contains  it. 

In  this  experiment  it  is  obvious,  as  might  have  been  expected, 
that  the  pressure  exerted  by  the  water  upon  the  bottom  is  precisely 
equal  to  its  weight,  which  was  two  pounds.  Suppose,  now,  we  sub- 
stitute for  the  cylinder  a  conical-shaped  vessel  (F),  with  the  same 
sized  orifice  at  the  bottom,  but  with  a  much  wider  one  at  the  top, 
and,  therefore,  capable  of  containing  more  Avater ;  nevertheless,  if 
we  experiment  with  the  conical  vessel  as  we  did  before  with  the 
cylinder,  notwithstanding  that  the  former  contains  three  times  as 
much  water  as  the  latter,  the  pressure  exerted  by  the  Avater  upon 
the  bottom,  as  we  see,  is  the  same,  being  only  two  pounds,  whereas 
the  water  weighs  six  pounds.      In  the  experiment  with  the  conical 


280 


CIRCULATION  OF  THE  BLOOD. 


vessel  the  pressure  exerted  l)y  the  water  upon  the  bottom  is,  there- 
fore, less  than  its  weight,  and  the  reason  is  very  obvious,  since  it  is 
only  that  part  of  the  water  within  the  dotted  lines  tl^at  exerts  pres- 
sure upon  the  bottom,  the  pressure  of  the  remaining  extra  water,  so 
to  speak,  being  exerted  upon  the  walls  of  the  vessel,  and  not  upon 
its  bottom. 

Finally,  if  we  make  use  of  a  conical  vessel  (Fig.  1 24,  G),  or  of 
one  (Fig.  125)  consisting  of  two  cylindrical  parts  of  unequal  di- 
ameters, of  which  the  lower  one  has  the  same  sized  orifice  at  the 
bottom  as  obtains  in  the  two  vessels  just  used,  and  holding  less 
water  than  either  of  the  latter,  we  shall  still  find,  experimentally, 
in  the  same  way,  that  the  pressure  exerted  upon  the  bottom  is  un- 
diminished by  that  circumstance,  being  two  pounds,  though  the 
water  weighs  only  one  pound.  This  must  be  so,  since  the  pressure 
exerted  upon  the  bottom  is  due  to  a  column  of  water  having  the 
same  vertical  height  and  base  as  the  column  of  water  included  be- 
tween the  two  dotted  lines  D  and  G  (Fig.  125) — that  is,  the  pres- 


FiG.  125. 


Fig.  126. 


Fig.  127. 


Hydrostatic 
paradox. 


To  demonstrate  the  upward  pressure 
exerted  bv  water. 


sure  of  the  column  of  water  on  the  principle  of  the  pressure  being 
exerted  efjually,  and  in  all  directions,  is  not  only  exerted  upon  E  F 
(Fig.  125),  or  the  part  of  the  bottom  directly  underneath  it,  but 
also  upon  the  remaining  part  of  the  bottom  on  both  sides  of  E  and 
F.  The  total  pressure  exerted  upon  the  bottom  is,  therefore,  the 
same  as  if  there  were  two  extra  columns  of  water  (D,  G)  pressing 
downward  in  addition  to  that  upon  E  F  actually  present.  It  will 
be  observed  in  this  experiment  that  the  pressure  exerted  by  the 
water  upon  the  bottom  is,  therefore,  greater  than  its  weight.  At 
first  sight,  this  result  may  appear  paradoxical,  it  being  perhaps 
difficult  to  compreliend  Avhy,  if  the  water  in  the  vessel  exerts  a 
pressure  upon  the  ])ottom,  that  when  the  vessel  is  placed  in  the 
scale-pan  of  the  balance  that  its  weight  should  be  only  equal  to  the 


PRESSURE  OF  LIQUIDS.  281 

weight  of  the  water  and  vessel.  The  reason,  however,  becomes  at 
once  clear  when  it  is  remembered  that  the  pressure  of  the  water  is 
exerted  in  all  directions,  upward  as  well  as  downward,  and  that 
when  the  vessel  is  placed  in  the  scale-pan  (Fig.  125),  tliat  part  of 
the  pressure  exerted  upward  against  the  surface  of  the  vessel  in  the 
direction  of  the  arrows,  being  opposed  in  direction  to  the  force  of 
gravity,  does  not  appear  as  weight ;  consequently,  the  weight  is 
simply  equal  to  the  weight  of  the  vessel  and  of  the  water  it  con- 
tains. If,  however,  this  upward  pressure  be  balanced  by  an  equal 
downward  pressure,  obtained  by  an  extra  quantity  of  water,  equal 
in  amount  to  the  volume  included  between  the  dotted  lines,  then 
the  pressure  and  weight  of  the  water  would  be  identical — that  is, 
the  conditions  would  be  the  same  as  in  the  first  experiment. 

That  the  pressure  of  the  water  is  transmitted  upward  as  well  as 
downward  can  be  readily  demonstrated  by  the  following  simple 
experiment.  A  large  open  glass  tube  (A,  Fig.  12()),  one  end  of 
which  is  ground,  is  fitted  with  a  thin  card  (B),  to  the  center  of 
which  is  attached  a  string  (C)  by  which  it  can  be  held  against  the 
bottom  of  the  tube.  The  whole  is  then  immersed  in  ajar  of  water, 
and,  although  the  string  be  allowed  to  hang  over  the  side  of  the 
jar,  the  card  will  still  adhere  to  the  mouth  of  the  jar,  it  being  kept 
in  this  position  by  the  upward  pressure  of  the  water. 

If  now  water  be  slowly  poured  into  the  tube  the  disk  will  still 
adhere  to  the  latter,  not  sinking  until  the  height  of  the  water  in- 
side the  tube  is  equal  to  the  height  outside.  Hence  it  follows  that 
the  upward  pressure  is  equal  to  a  column  of  water  whose  area  is 
that  of  the  tube  (A),  and  whose  height  is  the  distance  from  the 
disk  to  the  outer  surface  of  the  liquid.  The  upward  pressure  is, 
therefore,  governed  by  the  same  law  as  the  downward  pressure. 

The  hydrostatic  bellows  (Fig.  127)  is  an  interesting  instrument 
in  this  connection,  as  illustrating  the  principle  of  Pascal,  and  the 
manner  in  which  we  propose  to  study  blood  pressure.  It  consists 
of  a  narrow  tube  (A)  eight  feet  in  length,  with  a  sectional  area  of 
one-fourth  of  an  inch,  inserted  into  a  square  bellows  (C)  having  a 
superficial  area  of  one  hundred  and  forty-four  inches.  The  appa- 
ratus having  been  filled  with  water,  it  follows  that,  as  the  water  in 
the  tube  weighs  fourteen  ounces,  and  as  the  superficial  area  of  the 
top  of  the  bellows  (144  inches)  is  576  times  that  of  the  sectional 
area  of  the  tube  (one-fourth  of  an  inch),  the  bellows  (D,  D)  should 
balance  a  weight  of  fourteen  ounces  multiplied  by  576,  equals  8064 
ounces,  equals  504  pounds,  which,  as  a  matter  of  fact,  it  does.  At 
first  sight  this  result  may  appear  as  paradoxical  as  in  the  experi- 
ment with  the  cylindrical  vessel ;  it  will  be  observed,  however,  that 
the  distance  through  which  the  504  pounds  upon  the  bellows  are 
elevated  is  but  the  one-sixth  of  an  inch,  a  fractional  part  only  of  the 
ninety-six  inches  through  which  the  pressure  was  exerted.  It  is 
only  another  illustration  of  what  we  gained  in  weight  we  lost  in 
height,  or  of  a  small  force  acting  through  a  great  height  being  equal 


1282 


CIRCULATION  OF  THE  BLOOD. 


to  a  large  force  acting  through  a  short  one,  fourteen  ounces  falling 
through  ninety-six  inches,  being  equal  to  80(34  ounces,  or  504 
pounds,  ascending  through  the  one-sixth  of  an  inch.  It  follows, 
therefore,  that  the  pressure  even  of  a  small  quantity  of  water,  if  ex- 
erted from  a  sufficient  height,  will  be  very  great ;  indeed,  Pascal 
succeeded  in  bursting  a  strongly  made  cask  by  means  of  a  narroAv 
thread  of  water  forty  feet  high,  and,  in  this  manner,  demonstrated 
his  principle  of  the  equality  of  pressure. 

In  considering  the  pressure  exerted  by  two  columns  of  liquid 
such  as  obtains  in  the  apparatus  (Fig.  121),  it  will  be  remembered 
that  only  one  liquid — water — was  used.  It  is  needless  to  say,  how- 
ever, that  if  two  liquids  of  diflPerent  densities,  such  as  water  and 
mercury,  were  experimented  with,  the  level  of  the  water  would 
stand  13.5  times  higher  than  that  of  the  mercury,  the  latter  being 
that  much  heavier,  the  altitudes  of  the  liquids  being  inversely  as 
their  densities.  In  other  respects,  what  has  been  said  of  the  pres- 
sure exerted  by  water  will  apply  equally  to  mercury  or  other  liquids, 
and  inasmuch  as  we  will  make  use  of  a  mercurial  column  as  a 
measure  of  the  pressure  exerted  by  the  blood,  it  will  not  be  super- 
fluous to  illustrate  first  the  manner  in  which  we  measure  by  mer- 
cury the  pressure  exerted  by  any  liquid  ;  this  we  do  by  means  of 

Fig.  128. 


I  laldat's  apparatus. 

Haldat's  apparatus  (Fig.  128).  This  consists  of  a  tube  {A  B  C) 
bent  at  both  ends  at  right  angles,  one  of  which  is  provided  with  a 
stopcock  {A)  on  which  can  be  screwed  vessels  (7),  E,  F,  etc.),  of 
the  same  height,  but  differing  in  shape  and  capacity.  The  tube 
A  B  C  is  filled  Avith  mercury  until  it  reaches  the  level  P.  The 
vessel  E  is  first  screwed  on,  for  example,  to  the  end  at  A  and  water 


BLOOD   PRESSURE.  283 

is  poured  into  it  until  it  reaches  the  level  (l,  this  level  is  registered 
by  the  movable  rod  H.  The  pressure  of  the  water  in  the  vessel  E 
upon  the  surface  of  the  mercury  in  the  limb  A  will  cause  the  mer- 
cury to  rise  in  the  tube  C  up  to  the  level  /,  and  is  there  registered 
by  a  mova])le  collar..  The  stopcock  A  is  then  opened,  which  allows 
the  water  to  run  out  of  the  vessel  E,  which  is  then  removed  and  is 
replaced  by  the  vessels  D  and  F',  these,  in  turn,  are  filled  with 
water  up  to  the  level  G,  Avhen  it  will  be  observed  that  the  mercury 
which  had  in  the  meantime,  in  each  case,  fallen  to  its  original  level 
in  limb  A,  rises  again  to  the  level  /  the  same  as  before,  thus  prov- 
ing that  the  pressure  exerted  by  the  water  upon  the  mercury  is,  as 
we  have  already  seen,  independent  of  the  quantity  of  the  water  and 
of  the  shape  of  the  vessel,  but  is  equal  to  the  weight  of  a  column  of 
water  whose  base  is  the  surface  of  the  mercury  M  beneath  the  stop- 
cock in  limb  A,  and  whose  altitude  is  the  height  [A  (i)  of  the  level 
of  the  water  above  the  surface  of  the  mercury,  that  is,  the  pressure 
of  the  water  (P)  equals  altitude  [A  (t)  multiplied  by  area  {M). 
The  height  of  the  Avater  being  the  same  in  D  F  and  E,  and  the 
surface  of  the  mercury  (J/)  representing  the  area  in  each  case,  the 
product  of  ^i  G  X  M  must  give  the  pressure  exerted  by  the  water 
in  all  three  vessels,  which  we  have  just  seen  is  the  case,  the  column 
of  mercury  being  the  same  in  both  experiments. 

The  column  of  mercury  is  then  the  measure  of  the  pressure 
exerted  by  the  water  in  D,  F,  or  G  sustaining  it.  It  is  obvious 
that  we  must  double  P I  as  the  mercury  is  proportionally  depressed 
in  the  other  limit  of  the  tube.  It  is  by  means  of  the  hydrostatic 
principles  that  we  have  illustrated  somewhat  in  detail  that  Stephen 
Hales,  in  the  early  part  of  the  last  century,  first  determined  the 
cardiac  blood  pressure  in  a  living  animal  with  anything  like  accu- 
racy, and  estimated  what  it  would  probably  be  in  man.  Hales's 
method  ^  of  experimenting  was  as  follows  :  A  living  animal,  a  horse, 
for  example,  having  been  firmly  secured,  a  large  artery,  like  the 
femoral  or  carotid,  Avas  exposed,  and,  after  having  been  ligated,  was 
opened.  A  brass  tube  was  then  inserted  into  the  vessel,  to  which 
was  adapted  a  glass  tube  ten  feet  long.  The  connection  between 
the  brass  and  the  glass  tube  was  made  by  a  brass  pipe,  and  in  some 
cases  by  a  portion  of  the  trachea  of  a  goose,  the  latter  being  used 
on  account  of  its  pliancy  so  that  no  disarrangement  would  ensue 
through  the  strus^gles  of  the  animal.  The  tube  havino-  been  in- 
serted  into  the  femoral  artery,  for  example,  the  blood  was  observed 
to  rise  in  the  glass  eight  feet  three  inches  above  the  level  of  the  left 
ventricle  of  the  heart.  In  the  case  of  the  carotid  artery  the  l)lood 
rose  even  higher,  attaining  a  height  of  nine  feet  six  inches,  or  114 
inches.  In  order  to  estimate  the  pressure  or  force  sustaining  such 
a  column  of  blood,  just  as  in  the  case  of  the  experiment  with  the 
water  and  the  mercury,  or  with  the  bellows,  the  altitude,  114  cubic 
inches,  must  be  multiplied  by  the  internal  surface  of  the  left  ventri- 

1  Statical  Essays,  Vol.  ii.,  pp.  1,  2,  14,  15,  19,  20,  21,  39,  40.     London,  1740. 


284  CIRCULATION  OF  THE  BLOOD. 

cle  of  the  horse's  heart,  or  the  area.  Hales  determined  the  area  of 
the  left  ventricle  of  the  horse's  heart  by  injecting'  it  with  hot  wax, 
then  the  wax,  when  cold,  was  removed  and  small  pieces  of  paper 
properly  cut  were  placed  upon  it  until  the  wax  was  perfectly 
covered  ;  the  small  pieces  of  paper  were  then  removed  to  a  sheet  of 
paper  which  was  ruled  oif  into  squares,  and  in  this  way  it  was  esti- 
mated that  the  inner  surface  of  the  ventricle,  or  the  area  needed 
for  the  calculation,  was  equal  to  26  inches,  deducting  1  inch  for  the 
orifice  of  the  aorta.  The  pressure  or  the  force  of  the  liquid,  in 
this  case  the  blood  in  the  carotid  artery,  being  independent  of  the 
quantity  and  the  shape  of  the  vessel  containing  it,  but  equal  to  the 
altitude  of  the  column  of  the  blood  multiplied  by  the  area  or  its 
base,  the  product  of  114  inches  by  20 — that  is,  2,964  inches  of 
blood — will  be  the  pressure  or  force  which  the  ventricle  sustains  at 
the  moment  of  its  systole.  Now,  as  a  cubic  inch  of  blood  weighs 
267.7  grains,  the  pressure  of  the  blood  amounts  to  267.7x2964, 
or  793462.8  grains,  which  is  a  little  over  113  pounds,  there  being 
7,000  grains  to  the  pound.  On  the  supposition  that  the  blood 
would  rise  7J  feet  high  in  a  tube  inserted  into  the  carotid  artery  of 
a  man,  and  that  the  internal  area  of  the  left  human  ventricle  is 
equal  to  15  square  inches.  Hales  estimated  by  the  method  just 
mentioned,  that  the  pressure  on  the  left  ventricle  at  the  moment  of 
contraction  w^ould  amount  to  51.2  pounds.  This  estimate  is  too 
low,  as  the  later  investigations  of  Poisseuille,  Volkmann,  etc.,  to 
be  described  presently,  have  shown  that  the  blood  would  probably 
rise  in  a  tube  placed  in  a  carotid  artery  of  a  man  as  high  as  in  that 
of  the  horse,  there  being  but  little  difference  probably  in  this  re- 
spect as  regards  these  mammals.  Indeed,  Volkmann  ^  has  demon- 
strated that  even  in  the  chicken  the  blood  rises  as  hio;h  in  some 
instances  as  in  the  dog  and  the  horse.  Further,  Haughton,^  by  a 
different  method  from  that  of  Hales,  calculated  that  the  cardiac 
blood  pressure  in  man  ought  to  be  about  the  same  as  that  observed 
in  the  horse,  his  method  being  based  upon  a  knowledge  of  the  dis- 
tance to  which  a  divided  artery  will  spurt,  which  in  the  case  of  man 
was  learned  by  Haughton  through  a  surgical  operation,  the  force 
with  which  the  heart  contracts  to  produce  such  an  effect  being  de- 
duced from  his  data. 

Modern  investigation,  as  we  shall  see,  has  shown  that  the  blood 
pressure  is  influenced  by  conditions  unknown  to  Hales,  neverthe- 
less his  original  experiment  is  to  this  day  the  most  striking  way  of 
demonstrating  it,  and  his  application  of  hydrostatical  principles  in 
measuring  it  is  the  method  since  so  successfully  made  use  of  by 
Poisseuille,  Volkmann,  Ludwig,  and  others. 

It  is  not  so  much,  however,  the  pressure  that  the  heart  sustains 
wliich  the  physiologist  wishes  to  determine  as  the  actual  force  with 
which  the  heart  drives  the  blood  into  the  aorta  at  each  ventricular 

'  Die  Hicraodynaniik,  s.  177. 

2  Animal  Mecliauics,  p.  40.     London,  1873. 


THE  n.EMODYNAMOMETER.  285 

systole.  The  diifereuce  between  the  action  of  the  heart  and  that  of 
the  hydrostatic  apparatus  we  have  shown,  in  which  the  large  glass 
tube  and  bellows  represent  the  aorta  and  heart,  is  that  the  heart, 
like  any  other  muscle,  exerts  itself  according  to  the  resistance  to  be 
ov^ercome.  Thus,  if  we  raise  a  pound  -svitli  our  hand,  the  muscles 
of  the  extremity  make  a  greater  effort  than  when  we  raise  a  feather, 
so  according  to  the  resistance,  for  example,  offered  by  the  capil- 
laries to  the  efflux  of  the  blood  into  them  from  the  arteries,  will  the 
heart  contract  more  forcibly,  and  the  blood-pressure  will  rise.  It 
is  evident,  then,  that  the  possible  force  of  the  heart  and  the  actual 
force  usually  exerted  may  differ  very  much  in  amount.  Before 
demonstrating  this  experimentally  let  us  describe  the  hsemodyna- 
mometer,  the  apparatus  by  means  of  which  blood  pressure  is  usually 
studied  at  the  present  day,  and  then  compare  the  arterial  with  the 
cardiac  pressure.  The  hsemodynamometer,  so  called  from  the 
Greek  words  alim,  blood,  u'r^ainz,  power,  and  iitznov,  measure,  is 
essentially  a  mercurial  manometer  adapted  to  measure  the  blood 
pressure,  hence  the  name  given  to  the  instrument  by  Poisseuille,^ 
who  first,  in  1828,  made  use  of  it  for  this  purpose.  The  apparatus 
that  we  shall  use  (Fig.  129)  is  the  same  as  Poisseuille's,  with  some 
modifications.  It  consists  of  a  U-shaped  glass  tube  (B  C  D  E),  of 
which  the  distal  or  ascending  limb  (D  E)  is  longer  than  the  proxi- 
mal or  descending  one  (B  C).  From  the  proximal  branch  B  is 
given  off  a  short  horizontal  one  A,  by  means  of  which  the  manom- 
eter is  put  in  communication  ^^^th  the  artery  whose  blood  pressure 
we  wish  to  determine,  and  which,  in  this  case,  will  be  the  carotid 
artery  of  the  rablnt.  The  U-shaped  tube  being  clamped  in  a 
vertical  position,  perfectly  clean  and  dry  mercury  is  poured  into 
it  until  the  mercury  reaches  a  given  level  in  the  two  limbs.  To 
prevent  the  blood  coagulating  that  which  will  come  from  the  artery 
a  saturated  solution  of  sodium  carbonate  is  allowed  to  flow 
from  the  pressure-bottle  P  through  the  tube  h  b  into  the  proxi- 
mal end  B  of  the  manometer,  and  through  its  horizontal  branch 
(A),  to  which  is  connected  by  a  short  piece  of  tubing  a  glass  tube, 
or  leaden  pipe  (c),  the  latter  being  stopped  temporarily  by  the  fin- 
ger, or  by  a  cork.  To  avoid  the  inconvenience  of  inserting  the 
horizontal  branch  of  the  manometer  A,  or  its  continuation  the  pipe 
c,  into  the  artery,  and  whicli  would  be  impossible  in  the  case  of  the 
rabbit,  the  vessel  being  so  small,  a  pointed  and  bevelled  glass  canula 
is  first  inserted  into  the  artery,  the  vessel  having  been  previously 
ligated  at  its  distal  end,  and  clamped  at  its  proximal  end.  The  in- 
sertion of  the  canula  will  be  greatly  facilitated  if  a  small  piece  of 
card  be  placed  under  the  vessel  to  support  it,  and  by  making  the 
opening  for  the  canula  Y-shaped.  The  canula  is  secured  in  the 
artery  by  a  ligature,  and  is  connected  with  the  pipe  c  by  a  small 
piece  of  tubing.  The  arterial  canula  is  filled  with  the  solution  of 
sodium  bicarbonate  by  means  of  a  syringe,  and  the  same  solution 

'  Journal  de  physiologic  de  Magendie,  Tome  viii.,  p.  272,  1828. 


286 


CIRCULATION  OF  THE  BLOOD. 


allowed  for  a  moment  to  flow  from  the  pressiire-l)ottle  into  the 
proximal  limb  of  the  manometer,  and  through  its  horizontal  branch 
and  the  pipe  c,  so  that  all  the  air  shall  be  driven  out.  The  arterial 
canula  and  the  pipe  c  are  then  connected  as  quickly  as  possible,  and 
the  tube  {h  h)  leading  from  the  pressure-bottle  to  the  jjroximal  limb 

Fig.  1-29. 


The  mercurial  kymograph,  a.  Vulcanite  rod  of  floating  piston,  h.  Tube  which  communi- 
cates with  the  pressure  bottle,  c.  Tube  which  communicates  with  the  artery,  d.  Feeding  cylin- 
der. 1.  First  axis,  which  revolves  once  in  a  minute.  2.  Second  axis,  which  revolves  once  in  ten 
seconds.  'A.  Third  axis,  in  a  second  and  a  half.  The  instrument  is  furnished  with  other  cylin- 
ders suitable  for  the  reception  of  single  bands  of  glazed  iiaper,  the  surface  of  which  can  be  black- 
ened after  they  are  lixcd  on  to  the  cylinders,  by  causing  the  latter  to  revolve  over  the  flame  of  a 
l)etroleum  lamp. 

of  the  manometer  clamped.  On  removing  the  clamp  from  the 
artery  the  blood  will  jet  out,  pressing  forward  against  the  soda  solu- 
tion, M'hich,  in  turn,  will  press  against  the  mercury  in  the  proximal 
end  of  th(!  manometer,  forcing  it  downward,  the  mercury  in  the  dis- 
tal limb  being  proportionally  elevated,  and  which  having  reached  a 


ARTERIAL  PRESSURE.  287 

certain  level  Avill  then  oscillate  above  and  below  the  same  with 
each  beat  of  the  heart.  It  will  be  observed  that  during  the  systole 
the  force  of  the  heart  not  only  expends  itself  in  elevating  the  col- 
umn of  mercury,  but  also  in  distending  the  walls  of  the  artery. 
The  effect  of  the  latter  is  that  during  the  diastole  through  the 
elastic  recoil  of  the  arterial  Avails  the  mercurial  column  is  kept  ele- 
vated, though  not  as  high  as  during  the  systole.  It  may  be  men- 
tioned incidentally  in  this  connection,  that  the  pressure  due  to  the 
elastic  recoil  of  the  walls  of  the  artery  is  usually  designated  arte- 
rial pressure,  as  distinguished  from  the  direct  pressure  due  to  the 
contraction  of  the  heart  and  known  as  cardiac  pressure.  It  must 
be  borne  in  mind,  however,  in  making  this  distinction  between  arte- 
rial and  cardiac  pressure  that  the  former  is  only  the  delayed  eifect  of 
the  latter,  since  the  cardiac  pressure  exerted  during  the  systole  in 
distending  the  arterial  walls  is  restored  during  the  diastole  as  the 
elastic  recoil  of  those  walls  or  the  arterial  pressure.  It  is  evident 
from  the  hydrostatical  principles  just  illustrated  that  the  pressure 
of  the  blood  in  the  artery  will  be  measured  by  the  weight  of  the 
column  of  mercury,  whose  base  or  area  is  a  circle,  having  the  same 
diameter  as  that  of  the  artery,  and  whose  altitude  is  the  height  of 
the  column  of  mercury — that  is,  the  difference  between  the  two 
levels  F  and  G,  and  which,  in  this  particular  experiment,  it  will  be 
observed,  amounts  to  90  millimeters  (3.6  inches).  The  arterial 
pressure  can  be  briefly  and  conveniently  expressed  then  by  the 
formula  P  equals  TzR-h  W,  in  which  P  equals  the  pressure,  ~Il^  the 
area  of  the  artery,  h,  the  height  of  the  mercury,  and  TFits  weight, 
it  being  understood  that  the  symbol  -  is  the  ratio  of  the  circumfer- 
ence to  the  diameter,  and  If  the  square  of  the  radius  of  the  circum- 
ference of  the  artery,  and  that  the  product  of  -  by  K'  gives  the  area. 
To  illustrate  the  manner  in  which  this  formula  can  be  made  use 
of  let  us  determine,  at  least  approximately,  by  its  means  the  pres- 
sure exerted  l^y  the  blood  upon  the  semilunar  valves  of  the  aorta 
in  man.  Let  us  assume  ^  that  the  diameter  of  the  aorta  at  the  level 
of  the  semilunar  valves  in  a  man  aged  twenty-nine  years  was  34 
millimeters.  The  radius  R  being  17  millimeters,  and  its  square  289 
millimeters,  the  area  of  the  aorta  would  be  equal  to  289  millimeters 
multiplied  by  3.1416  {-)  or  907.9  millimeters.  The  latter  or  the 
area  being  multiplied  by  200  the  probable  height  to  which  the 
mercury  would  be  elevated  in  millimeters,  could  the  manometer 
tube  be  inserted  into  the  human  aorta,  gives  181580  millimeters, 
or  2453  grammes  (one  cubic  millimeter  of  mercury  weighing  ^-^ 
of  a  gramme)  as  the  pressure  sustained  by  the  aortic  valves  in  man. 
Or,  more  briefly,  by  substituting  in  the  general  formula  the  partic- 
ular values 

P=R'X'Xhy^W 

Pressure  =  28!)  )<  3.14  <  200  X  t*.  gramme  =  2.453  kilogrammes 
1  Poisseuille,  op.  cit.,  p.  304. 


288  CIRCULATION  OF  THE  BLOOD. 

It  may  be  said  then  that  the  actual  pressure  under  which  the  blood 
is  driven  into  the  aorta  at  each  ventricular  systole  may  amount  to 
2,4  kilogrammes  (5.2  pounds).  As  a  general  rule,  however,  the  blood 
pressure  is  estimated  by  simply  measuring  the  height  to  which  the 
mercury  is  elevated  in  the  distal  limb  of  the  manometer,  and  doub- 
ling the  result,  without  the  area  of  the  artery  or  the  weight  of  the 
mercury  being  taken  into  consideration.  By  that  method  the  aortic 
pressure  would  be  estimated  as  amounting  to  200  millimeters. 

The  disadvantage  of  such  a  manner  of  estimating  blood  pressure 
is  due  to  the  fact  already  mentioned  that  the  difference  between 
animals  as  regards  the  height  to  which  the  mercury  will  rise  in  the 
manometer  is  not  as  great  as  perhaps  might  have  been  at  first  im- 
agined. Since  the  blood  pressure  depends  not  only  on  the  height 
of  the  mercury  in  the  manometer,  but  also  on  the  area  of  the  artery, 
we  should  expect  to  find,  as  indeed  is  the  case,  that  while  the  height 
of  the  mercury  is  about  the  same  in  different  species  of  animals, 
that  the  blood  pressure  may  be  absolutely  very  different,  though 
relatively  the  same  per  unit  of  area.  As  the  aortic  blood  pressure 
is  equal  to  the  height  of  the  mercurial  column  multiplied  by  the 
area  of  the  aortic  orifice  it  is  evident  that  the  pressure  will  be  pro- 
portional to  the  size  of  this  orifice,  and  will,  therefore,  be  greatest, 
other  things  equal,  in  that  animal  which  has  the  largest  aorta. 
Thus  the  aortic  blood  pressure  of  man  as  estimated  simply  in 
millimeters  of  mercury  differs  but  little  from  that  of  the  horse ;  on 
the  other  hand,  the  aortic  pressure  in  the  horse,  as  estimated  in  the 
above  manner,  is  greater  than  that  in  man. 

In  estimating  blood  pressure  a  fact  must  be  taken  into  considera- 
tion which  is  usually  neglected,  and  that  is,  that  the  solution  of  so- 
dium carbonate  having  weight  must  exert  a  certain  amount  of  pres- 
sure upon  the  mercury  in  the  manometer.  The  licight  to  which  the 
mercury  is  elevated  is  then  due  to  the  pressure  of  the  blood  and  of 
the  solution.  To  obtain  the  former  we  must  therefore  deduct  the 
latter  from  the  observed  altitude  of  the  mercury.  As  10  millime- 
ters (I  in.)  of  the  soda  solution  are  equal  to  1  mm.  of  mercury  for 
every  10  mm.  of  the  soda  solution  in  the  proximal  limb  of  the 
manometer  we  must  deduct  then  1  mm.  of  mercury  from  the  alti- 
tude of  the  mercury  in  the  distal  limb  of  the  manometer.  As  a 
general  rule,  the  amount  of  the  soda  solution  in  the  proximal  limb 
of  the  manometer  is  so  small  that  the  effect  of  its  weight  upon  the 
mercury  need  not  be  considered.  Thus,  in  determining  the  blood 
pressure  in  the  carotid  artery  of  the  rabbit  it  Mill  be  noticed  that 
the  solution  of  soda  amoimts  to  only  5  mm.  (1  in.),  and  therefore 
only  I  mm.  must  be  subtracted  from  the  90  mm.,  or  the  observed 
altitude  of  the  column  of  mercury,  to  obtain  the  arterial  pressure. 
In  using  certain  kinds  of  manometer,  however,  as  we  shall  see,  the 
amount  of  tlie  soda  solution  being  greater  the  influence  of  its  pres- 
sure becomes  more  appreciable.  It  will  be  observed,  also,  that  the 
pressure  bottle  containing  the  solution  of  sodium  carbonate  is  sus- 


CARDIAC  PRESSURE.  289 

pended  at  a  height  of  about  2  meters  (6.4  feet)  above  the  manome- 
ter, aud  that  it  can  be  elevated  or  depressed  as  desirable.  The  ob- 
ject of  this  is  that  having  learned  by  experience  to  about  what 
height  the  mercury  will  be  elevated  by  the  arterial  pressure,  we 
make  use  of  the  soda  solution  not  only  to  prevent  the  coagulation 
of  the  blood,  but  also  to  exert  pressure  upon  the  mercury  to  the 
same  extent  as  the  arterial  blood  will  do.  As  soon  as  the  clamp  is 
removed  from  the  carotid  artery  the  blood  at  once  then  exerts  its 
pressure  upon  the  soda  solution,  but  advances  only  a  little  way  in 
the  tube  c  (Fig.  129),  loss  of  blood  as  well  as  coagulation  being 
thereby  prevented.  The  pressure  of  the  blood  is  then  transmitted 
to  the  soda  and  thence  to  the  mercury ;  if  the  pressure  bottle  has 
not  been  sufficiently  elevated,  then  the  level  of  the  mercury  will  rise 
in  the  distal  limb  of  the  manometer,  and  if  too  much  elevated  the 
reverse  will  be  the  case.  The  effect  of  the  arterial  pressure  \a\\ 
therefore  be  the  same  as  if  exerted  directly  upon  the  mercury. 

In  speaking  of  the  connecting  tube  c  (Fig.  129),  it  was  men- 
tioned that  it  should  be  of  glass  and  preferably  of  lead.  The  rea- 
son of  this  is  now  very  evident.  Did  the  tube  consist  of  an  exten- 
sible material  the  pressure  of  the  blood  would  be  exerted  to  a  great 
extent  upon  the  walls  of  the  tube  rather  than  upon  the  soda  solu- 
tion, and  therefore  not  upon  the  mercury. 

We  have  just  seen  that  the  pressure  of  the  blood  upon  the  aortic 
valves  in  man  may  amount  to  2.4  kilogrammes  (5.2  lbs.).  Now, 
since  the  pressure  exerted  upon  the  mass  of  a  liquid  is  transmitted 
undiminished  equally  and  in  all  directions  and  acts  with  the  same 
force  upon  all  equal  surfaces,  according  to  the  principle  of  Pascal 
to  obtain  the  cardiac  pressure  we  have  only  to  multiply  the  aortic 
pressure  (2.4  kilogrammes)  by  the  ratio  of  the  aortic  area  (907.9 
millimeters)  to  the  internal  area  of  the  left  ventricle  (100  square 
centimeters),  which  gives 

2.4  kilogrammes  X  k~7^^  =  26.4  kilogrammes  =  58  pounds 

=  cardiac  pressure 

This  estimate  of  cardiac  pressure  is,  of  course,  somewhat  greater 
than  that  obtained  by  Hales  (51.2  pounds),  since  the  latter  assumed 
that  the  blood  would  be  elevated  7.5  feet  (175  mm.  of  mercur}^), 
instead  of  8.5  feet  (200  mm.  of  mercury). 

If,  now,  the  hydrostatic  bellows  (Fig.  127)  be  compared  with  the 
heart  and  aorta,  it  is  obvious  that  the  small  force  acting  through  a 
great  height  in  the  narrow  tube,  corresponds  to  the  aortic  pressure, 
and  the  great  force  acting  through  the  small  heisfht  in  the  bellows, 
corresponds  to  the  cardiac  pressure. 

A  great  advance  was  made  by  Ludwig,^  in  1848,  in  the  manner 
of  investigating  blood  pressure,  by  his  invention  of  the  kymograph 
(Fig.  129).  This  consists  of  a  mercurial  manometer  like  that  of 
Poisseuille,  in  the  distal  limb  of  which  is  placed  a  vertical  rod  (a), 

iMuUei-'s  Archiv,  1847,  s.  242. 
19 


290  CIRCULATION  OF  THE  BLOOD. 

the  lever-end  of  which  terminates  in  a  concave  cup-shaped  float, 
and  rests  npon  the  convex  surface  of  the  mercury,  while  the  upper 
end  of  the  vertical  rod  projects  out  of  the  upper  open  end  of  the 
distal  limb  of  the  manometer,  and  carries  a  delicate  sable  brush, 
wetted  with  ink,  or  a  pen  of  glass,  the  point  of  which  rests  against 
the  cylinder  e.  The  vertical  rod  is  kept  in  the  perpendicular  by 
the  support  s,  through  which  it  passes,  and  the  brush  or  pen  in  con- 
tact with  the  cylinder  by  the  weighted  string  o.  The  cylinder  e  is 
covered  with  either  white  or  smoked  paper.  With  every  oscillation 
of  the  mercury  in  the  distal  limb  of  the  manometer,  the  rod  a  is 
elevated  or  depressed,  and  a  vertical  line  is  made  upon  the  cylinder 
by  the  brush  or  pen.  If  now  the  cylinder  is  made  to  revolve  at  a 
uniform  rate,  the  vertical  mark  will  become  a  curve,  like  that  rep- 
resented in  Fig.  130,  and  we  obtain  a  graphic  representation  of  the 

Fig.  130. 


Trace  of  blood  pressure  in  rabbit. 

blood  pressure,  hence  the  name  kymograph  given  to  the  instrument 
— from  yjj[J.a,  a  wave,  and  Y[)a(foj,  to  write.  It  may  be  mentioned 
that  the  idea  of  the  recording  pen,  etc.,  was  suggested  to  Ludwig 
by  a  similar  contrivance  made  use  of  by  Watt  for  registering  pres- 
sure in  the  steam  engine.  The  immense  importance  of  Ludwig's 
invention  cannot  be  exaggerated,  for,  by  means  of  the  kymograph, 
the  study  of  blood  pressure  became  far  more  exact  than  had  been 
possible  previously. 

Slight  variations  in  the  oscillation  of  the  mercury,  for  example, 
which  were  entirely  inappreciable  in  the  hjemadynometer,  became 
perfectly  apparent  when  graphically  recorded  upon  the  revolving 
cylinder.  The  great  merit  of  Ludwig's  invention  did  not  consist 
simply  in  the  application  of  the  kymograph  to  the  study  of  the 
blood  pressure,  but  the  application  of  the  graphic  method  in  the  in- 
vestigation of  the  circulation  of  the  blood  generally,  and  indeed,  of 
all  physiological  phenomena.  In  truth,  it  is  not  saying  too  much 
that  the  study  of  physiology  experimentally  has  been  revolutionized 
by  it,  results  having  been  obtained  by  the  graphic  method,  as  we 
have  already  seen,  which  had  been  considered  impossible  by  the 
physiologists  of  the  preceding  generation. 

As  the  mercurial  manometer  of  the  kymograph,  with  its  acces- 
sories, the  pressure  bottle,  connecting  tubes,  etc.,  is  the  same  as  that 
already  described,  it  is  only  necessary  to  say  that  the  mercurial 
manometer,  when  used  as  part  of  the  kymograph,  is  firmly  clamped 
to  the  table  (T,  Fig.  129)  supporting  the  cylinders,  the  latter 
being  moved  by  clock-work  contained  in  the  box  H,  and  the 
motion  made  uniform  by  the  Foucault  regulator  (7^).  This  consists 
of  two  fans,  which,  when  the  velocity  is  increased  through  the  fric- 


THE  KYMOGRAPH.  291 

tion  engendered,  expand  and  so  retard  the  motion,  and  when  the 
velocity  diminishes  contract  again,  and  so  offering  less  resistance  it 
increases  again,  the  fans  being  approximated  and  separated  by  an 
elastic  spring.  There  are  three  axes  (1,  2,  3)  connected  with  the 
clock-work,  and  according  to  the  one  on  which  the  cylinder  is  placed 
the  rate  of  its  revolution  can  be  varied. 

When  the  cylinder  used  is  that  covered  \ni\\  smoked  paper,  it  is 
held  on  the  axis  connected  with  the  clock-work  by  a  vertical  rod 
passing  from  its  center  upward  into  the  frame,  and  which  is  screwed 
on  to  the  box.  By  means  of  this  vertical  rod  the  cylinder  can  also 
be  elevated  or  depressed  through  a  height  of  several  centimeters. 
When,  however,  a  trace  is  taken  upon  white  paper,  and  it  is  de- 
sirable that  the  observation  shall  extend  over  as  long  a  period  of  time 
as  possible,  then  a  somewhat  different  arrangement  is  made  from 
that  just  described.  Two  cylinders  are  then  used  (Fig.  129,  <?,  (J), 
one  of  which  (e)  is  to  record  the  trace,  and  which,  resting  upon  the 
axis  connected  with  the  clock-work,  is  supported  from  above  by 
a  frame,  not  represented  in  the  figure,  which,  like  the  other  frame, 
can  also  be  scrcAved  on  to  the  box.  The  other  cylinder  (c)  is  covered 
with  white  paper  rolled  around  it  by  machinery,  and  in  quantity 
sufficient  to  last  for  several  hundred  observations.  This  cylinder 
acts  as  a  feeder  to  the  recording  one,  for,  as  the  latter  revolves,  it 
unwinds  the  white  paper  around  the  former,  the  paper  being  kept 
smooth  by  two  little  ivory  wheels  on  the  frame  (not  represented  in 
Fig.  129).  Having  explained  the  construction  of  the  kymograph, 
let  us  consider  now  the  traces  of  blood  pressure  of  the  cat,  turtle, 
frog,  for  example,  as  recorded  by  it,  and  point  out  some  of  the  re- 
sults obtained  by  their  study,  and  which  would  have  been  impos- 
sible had  the  study  of  blood  pressure  been  limited  to  the  use  of  the 
mercurial  manometer  only.  By  an  examination  of  Fig.  131,  illus- 
trating the  kymographic  trace  of  the  blood  pressure  in  tlie  cat,  re- 
corded upon  the  smoked  paper,  and  preserved  by  varnishing,  it  Avill 
be  observed  that  the  trace  consists  of  a  number  of  large  curves, 

Fi(}.  131. 


Trace  of  blood  pressure  iu  cat. 

each  of  which  is  made  up  of  smaller  ones.  The  large  curves  ex- 
tending from  crest  to  crest  of  the  wave,  being  to  a  certain  extent 
respiratory  in  origin,  their  relations  to  inspiration  and  expiration 
will  be  considered  hereafter.  For  the  present,  however,  it  may  be 
said  that  during  a  part  of  the  period  of  inspiration  the  blood  pres- 
sure is  increased  and  during  a  part  diminished,  and  that  in  the  same 
way  the  blood  pressure  is  both  diminished  and  increased  during 
expiration. 


292 


CIRCULATION  OF  THE  BLOOD. 


As  respiration  is  far  less  active  in  the  turtle  and  frog  than  in  the 
rabbit,  it  will  be  seen,  as  might  have  been  expected,  that  respira- 
tion does  not  influence  in  these  animals,  to  any  great  extent,  the 
form  of  the  curve  of  blood  pressure.  Indeed,  the  respiratory  curves 
are  absent  in  the  traces  of  the  blood  pressure  of  the  turtle  and  frog 
(Figs.  132,  133),  the  curves  in  the  latter  traces  being  cardiac  in 
origin  and  corresponding  to  the  small  curves  of  Fig.  131, 


Fig.  132. 


Trace  of  blood  pressure  in  turtle. 
Fig.  133. 


Trace  of  blood  pressure  iu  frog. 

The  small  curves  in  the  mammal  being  cardiac  in  origin,  each 
small  curve  corresponds  to  a  heart-beat,  the  elevation  being  caused 
by  the  systole,  the  depression  by  the  diastole.  If  the  pen  be  watched 
during  these  oscillations,  it  will  be  noticed  that  there  is  an  average 
height  above  and  below  which  the  pen  is  elevated  and  depressed 
with  each  cardiac  beat.  This  average  height  represents  the  mean 
cardiac  pressure.  On  the  other  hand,  the  average  vertical  distance 
or  ordinate  between  the  horizontal  line  or  abscissa,  representing  the 
height  at  which  the  pen  is  sustained  by  atmospheric  ])ressure  only, 
and  the  horizontal  line  representing  the  height  at  wdiich  the  pen  is 
sustained  through  the  elastic  recoil  of  the  arterial  walls,  represents 
the  mean  arterial  pressure.  To  obtain  either  the  mean  cardiac  or 
mean  arterial  pressures  the  respective  ordinates  must  be  added  and 
the  sum  divided  by  the  number  of  ordinates  and  the  quotient  mul- 
tiplied by  two.  The  cardiac  or  arterial  pressure,  however  is  de- 
termined at  any  one  moment  in  millimeters  of  mercury  by  simply 
observing  the  difference  between  the  levels  of  the  mercury  in  the 
proximal  and  distal  limbs  of  the  manometer.  Very  great  differ- 
ences are  found,  also,  among  animals,  as  regards  the  proportion  of 
the  cardiac  to  the  arterial  pressures.  In  the  rabbit,  for  example, 
the  force  of  the  left  ventricle  exceeds  but  little  that  of  the  aorta, 
whereas,  in  the  liorse,  the  excess  of  the  cardiac  pressure  as  com- 
pared with  the  arterial  is  very  marked.     Thus,  by  means  of  his 


CARDIAC  AND  ARTERIAL  PRESSURE. 


29a 


cardiometer,  Bernard  ^  has  shown  that  the  arterial  pressure  in  the 
rabbit,  being  95  mm.  (3.8  inches),  with  each  ventricular  systole  the 
mercury  rose  to  100  mm.  (4  inches),  the  cardiac  pressure  being  only 
5  mm.  greater  than  the  arterial.  On  the  other  hand,  in  the  horse, 
the  arterial  pressure  being  110  mm.  (4.4  inches),  the  cardiac  pres- 
sure was  65  mm.  greater,  the  mercury  rising  to  175  mm.  (7  inches) 
with  the  systole. 

Just  as  we  have  seen  the  pulse  gradually  disappearing  as  we  re- 
cede from  the  heart,  so,  for  the  same  reason,  we  should  expect  to 
find  this  excess  of  cardiac  over  arterial  pressure  becoming  less  and 

Fig.  134. 


40 


30 


20 


10 


JQ- 


X 

Blood-pressure  curve  of  the  carotid  of  a  dog  obtained  with  a  mercurial  manometer.  0-x  =  line 
of  no  pressure,  zero  line,  or  abscissa ;  y-y'  is  the  blood-jiressure  tracing  with  small  waves,  each 
one  caused  by  a  heart-beat,  and  the  large  waves  due  to  the  respiration.  A  millimeter  scale  shows 
the  height  of  the  pressure  in  millimeters  of  mercury.     (Landois.  ) 


less  as  we  pass  toward  the  periphery.  Experiment  confirms  in  this 
respect  what  theory  would  lead  us  to  expect.  Thus,  Volkmann  - 
has  shown  that,  while  in  the  carotid  artery  of  the  dog  the  excess  of 
the  cardiac  pressure,  as  compared  Avith  the  arterial,  amounts  to  37 
mm.  (1.4  inches),  in  the  metatarsal  artery  the  excess  amounts  to 
only  1  mm.  (,}^  of  an  inch). 

The  cardiomcter,  made  use  of  in  demonstrating  the  difference  be- 
tween cardiac  and  arterial  pressure  (Fig.  135),  consists  of  a  metallic 
vessel  containing  water,  within  which  is  suspended  an  elastic  cap- 
sule (INI),  communicating  at  one  end  (T)  with  the  artery  whose  pres- 
sure is  to  be  determined,  and  at  the  other  end  with  a  delicate  mer- 

^  Systeme  Nerveux,  Tome  i.,  pp.  283,  286. 
^  Die  Hwmodynamik,  s.  167. 


294 


CIRCULATION  OF  THE  BLOOD. 


curial  manometer  (B)  for  registering  the  pressure.  The  upper  part 
of  the  vessel  is  closed  with  a  cork  through  which  passes  a  glass 
tube,  into  which  the  water  rises,  and  which  transmits  to  the  regis- 
tering tambour  R  the  distention  of  the  capsule  M  due  to  the  vary- 
ing cardiac  pressure.  The  arterial  pressure,  however,  when  once 
attained,  remains  constant,  the  constriction  at  the  bottom  of  the 
mercurial  manometer  B  offering  such  a  resistance  to  the  rise  of  the 
mercury  that  the  intermittent  action  of  the  heart  is  not  felt. 

Fig.  135. 


p  //   R 


Cardiometer.      (Marky.) 

Not  only  does  the  cardiac~vary  in  relation  to  the  aortic  pressure, 
but  the  cardiac  pressure  varies  itself.  Thus,  it  has  been  shown  by 
means  of  the  Goltz-Gaule  manometer  (Fig.  1.'>G)  that  there  is  in 
the  dog,  for  example,  a  maximum  and  a  minimum  intra-ventricular 
pressure,  amounting  to  140  and  —50  millimeters  of  mercury  re- 
spectively.^ The  latter  being  a  negative  pressure  that  is  lower  than 
that  of  the  atmosphere,  the  blood  will  be  forced  into  the  heart  as 
we  shall  see  more  particularly  hereafter.  The  instrument  just  re- 
ferred to  by  which  variations  in  the  intra-ventricular  pressure  is 
usually  determined,  consists  essentially  (Fig.  135)  of  two  parts, 
one  of  which  (a)  acts  as  an  ordinary  manometer,  the  other  as  a 
maximum  or  minimum  manometer  according  to  the  position  of  the 
valve  (v)  the  part  (a)  being  then  clamped.  The  valve  (y)  is  of  a 
cup  and  ball  variety,  and  when,  as  in  Fig.  138  permits  the 
passage  of  the  fluid  from  the  heart,  but  not  towards  it.     Since  the 

^Fr.  (ioltz  u.  J.  Gaule,  Pfliif^er's  Archiv,  Band  xvii.,  1878,  s.  100  ;  S.  de  Jager, 
Ebenda,  Band  xxx.,  1883,  s.  491. 


MANOMETERS. 


295 


column  of  fluid  that  passes  the  valve  can  not  return,  the  mercury 
will   remain  at  the  o^reatest  lieio;ht  to  which  it  has  been  elevated, 


Fig.  136. 


The  maximum  manometer  of  Goltz  and  Gaule. 


the  instrument  then  acting  as  a  maximum  manometer.     By  revers- 
ing the  valve  the  manometer  is  then  converted  into  a  minimum  one. 
Slight  variations   in  the  iutra-auricular,  ventricular,  and  aortic 
pressures  can  be  much  better  demonstrated,  however,  by  means  of 


Fig.  137. 


Fig.  138  T^ 


Diagram  to  illustrate  the  essential  parts  of  Hiir- 
thle's  membrane  manometer. 


Curve  of  pressure  in  the  left  ven- 
tricle of  the  dog,  Hiirthle's  mem- 
brane manometer.     (Foster.) 


Fig.  138  A. 


Curve  of  pressure  in  aorta  of  dog. 

(FOSTEK.) 


membrane  manometers  than  mercurial  ones,  the  inertia  of  the  mer- 
cury in  the  latter  being  too  great  to  be  much  affected.     Among  the 


296 


CIRCULATION  OF  THE  BLOOD. 


Fig.  139. 


membrane  manometers  or  tonometers,  as  they  are  also  called,  made 
use  of  for  this  purpose  that  of  Hiirthle  ^  is  a  convenient  form. 
This  consists  essentially  of  a  very  small  metal  hemispherical  drum 
(Fig.  137,  a),  the  upper  end  of  which  is  covered  with  a  delicate 
elastic  membrane  (e),  bearing  upon  its  center  a  thin  metal  disc  (c?), 

connected  by  a  short  upright  (e)  with 
a  recording  lever  (l),  the  lower  end 
terminating    as  a  tube  (6). 

A  catheter  filled  Avith  sodium  car- 
bonate solution  having  been  intro- 
duced through  the  jugular  vein  into 
the  right  auricle  (^4)  or  ventricle  ( T^), 
or  through  the  carotid  artery  into  the 
aorta,  and  so  into  the  left  ventricle, 
connection  is  made  with  the  mano- 
meter, the  latter  being  usually  filled 
wdth  the  same  solution  as  that  in  the 
catheter.  Such  being  the  disposition 
of  the  apparatus,  it  is  obvious  that  any 
variations  in  the  pressure  exerted  by 
the  heart  cavities  will  be  transmitted 
through  the  fluid  of  the  catheter  and 
drum  to  the  elastic  membrane  of  the 
latter,  and  in  turn  transmitted  thence 
to  the  recording  lever.  It  will  be  ob- 
served that  the  curve  (Fig.  138  V) 
of  the  pressure  of  the  left  ventricle  in 
the  dog  obtained  by  the  Hiirthle  mano- 
meter, as  well  as  that  of  the  right  ven- 
tricle of  the  horse  obtained  by  a 
Marey  sound  (Fig.  93),  agree  in  the 
following  features  :  the  pressure  rises 
at  the  very  beginning  of  the  systole 
very  rapidly,  soon  reaches  a  maximum, 
which  is  maintained  at  nearly  the  same 
height  for  some  time,  that  part  of  the 
curve  constituting  the  "  systolic  plateau,"  then  rapidly  falls  to  the 
line  of  atmospheric  pressure,  or  even  below  it,  and  remains  at  the 
base  line  till  the  next  cardiac  beat.  It  must  be  mentioned,  however, 
in  this  connection,  that,  according  to  some  observers,  the  production 
of  the  so-called  "  systolic  plateau  "  is  due  to  the  friction  of  the  tube, 
ill-placed  canula,  etc.,  the  highest  point  of  pressure  being  naturally 
peaked,  not  flattened.  By  introducing  two  catheters  into  the  heart 
of  a  dog  so  that  the  end  of  one  will  lie  in  the  ventricle  (Fig.  139  V), 
the  end  of  the  other  in  the  aorta  (.1),  and  then  connecting  the  other 
ends  of  the  catheters  with  two  membrane  manometers,  the  pressure 
of  the  ventricle  and  auricle  can  be  simultaneously  recorded. 
iPfliiger's  Archiv,  Band  xliii.,  1888,  s.  399. 


Diagram  illustrating  the  method  of 
recording  simultaneously  the  pressure 
in  the  left  ventricle  and  at  the  root  of 
of  the  aorta.     (Hukthle.) 


DIFFERENTIA  L  MANOMETER. 


207 


An  examiuatiou  of  the  two  curves  (Figs.  138  T'and  138  ^1)  shows 
that  at  (o),  Fig.  138  V,  the  beginning  of  the  ventricular  systole,  no 
effect  is  produced  upon  the  blood  of  the  aorta,  the  latter  being  cut 
off  from  the  influence  of  the  ventricular  pressure  by  the  closing  of 
the  aortic  valves,  A  little  later,  however,  as  at  (1),  Fig.  138  J., 
the  aortic  valves  being  now  open  the  effect  of  the  ventricular  pres- 
sure is  felt  and  the  pressure  in  the  aorta  begins  to  rise.  The  sim- 
ultaneous changes  in  the  pressure  of  the  ventricle  and  aorta  just 
described  can  also  be  demonstrated  by  means  of  the  differential 
manometer  of  Hiirthle^  (Fig.  140).  It  may  be  stated  as  the  result 
of  experiments  made  with  different  kinds  of  manometers  that  the 
average  pressure  of  the  right  ventricle  is  about  one-third  that  of  the 

Fig.  140. 


^         '•      )    ^) 

f.    - 

i 

o             1     ^'                ''' 

di \                             'J- )c^ 

^  ^   J.L  _„  L        -;'  .^  J  [^^4^  U 

ti  O  ir^U  V  ^  ir 

o     i      a 

T  T, 

Piagram  of  the  diflferential  manometer  of  Hiirthle.  (Foster.)  T,  Ti.  The  tambours  of  two 
membrane  manometers,  the  mouths  of  the  tubes  opening  into  each  being  shown  in  section,  d, 
rfj.  Central  disks  of  tambours,  working  on  a  balance  above  them,  the  latter  remainiug  horizontal 
a.s  long  as  the  pressure  in  the  tambours  is  equal,  but  moving  upward  or  downward  with  any  dif- 
ference in  pressure,  and,  in  working  against  the  spring  ^  by  means  of  e  and  ei,  moves  the  lever  I. 

left,  and  as  the  pressure  of  the  right  auricle  is  only  one-tenth  that 
of  the  rin-lit  ventricle,  it  would  be  onlv  one-thirtieth  that  of  the  lefb 
ventricle. 

While  the  flow  of  the  blood  through  the  arterial  system  gener- 
ally is  influenced  by  the  length  of  the  vessel,  friction,  etc.,  the 
capillary  system,  as  we  shall  see,  is  the  constant  source  of  resis- 
tance. In  proportion  to  the  fulness  of  the  capillaries  a  greater  or 
less  obstacle  is  offered  to  the  flow  of  the  arterial  blood.  The  force 
that  the  heart  exerts  must  then  vary  according  to  the  resistance  to 
be  overcome. 

Arterial  pressure  is  due,  therefore,  not  only  to  the  force  exerted 
by  the  heart  from  behind,  vis  a  tcrgo,  but  to  the  resistance  of- 
fered by  the  capillaries  in  front,  vis  a  frontc.  This  is  readily 
sllO^^•n  by  means  of  the  Coats-  or  Marey''  apparatus,  but,  as  both 
these  methods  involve  taking  the  heart  out  of  the  animal,  and  as 
it  is  desirable  to  show  the  phenomena,  the  heart  being  in  situ,  the 
author  usually  makes  use  of  Brubaker's  frog  manometer  (Fig.  141). 
This  consists  of  a  mercurial  manometer  J/  like  that  we  have  used 
in  determining  the  blood  pressure  in  the  rabbit,  only  that  it  is 
smaller.     The  arterial  canula  differs,  however,  from  the  one  used 

iPfliigers  Archiv,  Band  xlix.,  1891,  s.  29. 

2 Sanderson,  Handbook  Pliy .biological  Laboratory,  p.  268.  ''Op.  cit.,  p.  70. 


298 


CIRCULATION  OF  THE  BLOOD, 


in  that  experiment.  In  this  instance  the  end  a  of  a  _L-shaped  glass 
tube  is  inserted  into  the  bulbus  arteriosus  of  the  frog,  the  end  h 
being  adjusted  to  the  proximal  end  of  the  manometer,  while  the 
stem  c  is  connected  by  the  tube  d  with  a  funnel  e  containing  a  so- 
lution of  sodium  carbonate.  The  funnel  corresponds  to  the  pres- 
sure bottle  in  the  experiment  with  the  rabbit.  The  frog  is  secured 
to  a  piece  of  cork,  which  rests  within  the  stand  supporting  the 
manometer ;  the  stand  can  be  raised  or  lowered  upon  the  vertical 
rod  ;  the  latter  also  supports,  by  the  horizontal  rod  the  funnel. 
Having  first  determined  the  normal  blood  pressure,  it  will  then  be 

Fig.  141. 


Brubaker's  frotr  manometer. 


observed  that  as  the  tube  d  is  compressed,  an  obstacle  being  thereby 
interposed  to  the  flow  of  blood  from  the  aorta,  the  pressure  will  be 
increased,  the  mercury  rising  in  the  distal  limb  of  the  manometer, 
thus  showing  that  the  force  which  the  heart  exerts  is  proportional 
to  the  resistance  to  be  overcome. 

It  is  hardly  necessary  to  state  that  the  constriction  of  the  tube  in 
the  last  experiment  would  represent  a  capillary  obstruction  in  the 
living  animal.  Theory  and  experiment,  therefore,  agree  in  show- 
ing that  the  amount  of  force  which  the  heart  usually  exerts  is  far 
less  than  the  possible  force  that  can  be  put  forth  if  occasion  de- 
mands it.  Assuming  that  the  blood  flows  through  tlie  arteries, 
according  to  hydraulic  laws,  we  should  expect  to  find  the  pressure 


BLOOD  PRESSURE  IN  DIFFERENT  ARTERIES. 


299 


diminishing  as  we  recede  from  tlie  heart  to  the  periphery.  Thus, 
if  we  watch  the  colored  fluid  as  it  flows  from  the  reservoir  (a,  Fig. 
142)  through  the  liorizontal  tube  h,  it  will  be  observed  that  the 
height  to  which  the  fluid  rises  in  the  vertical  tubes  c^  and  c,  in- 
serted into  the  horizontal  one  gradually  diminishes  as  we  recede 
from  the  first  (c^)  to  the  sixth  tube  (c).     In  the  present  experiment, 


Fig.  142. 


l)ecrease  of  pressure  in  tubes  of  equal  caliber. 

where  the  colored  fluid  rose  in  the  first  tube  to  a  height  of  27  cm. 
(10.8  inches)  in  the  sixth  to  a  height  of  only  9  cm.  (3.6  inches),  the 
level  of  the  fluid  in  the  remaining  tubes  (2,  3,  4,  5)  being  inter- 
mediate between  these  extremes.  This  difference  in  the  level  of 
the  fluid  in  the  vertical  tubes  is  caused  by  the  resistance  due  to 
friction  which  the  fluid  encounters  as  it  flows  from  the  reservoir 
through  the  horizontal  tube,  and  as  the  resistance  encountered  at 
the  first  tube  gradually  diminishes  as  we  approach  the  sixth  the 
height  of  the  fluid  or  the  pressure  is  proportionally  diminished  in 
the  tubes  as  we  pass  from  the  reservoir  to  the  outlet.  Poisseuille  ^ 
failed  with  his  mercurial  manometer  to  detect  any  difierence  in  the 
blood  pressure  of  arteries  situated  at  different  distances  from  the 
heart,  such  as  theory  indicated  should  have  been  found.  Indeed, 
the  difference  in  the  blood  pressure  of  two  arteries,  seen  even  when 
one  is  situated  at  a  considerable  distance  from  the  heart,  is  too  slight 
to  be  appreciable  by  the  mercurial  manometer  alone.  Volkmaun,^ 
however,  showed  by  means  of  the  kymograph,  that  there  was  a  dif- 
ference of  7  mm.  (0.2.S  inch)  mercury  between  the  blood  pressure 
in  the  carotid  and  metatarsal  arteries  of  the  dog,  the  pressure 
amounting  in  the  first  case  to  172  mm.  (6.8  inches),  and  in  the 
latter  to  165  mm.  ['o.Q  inches).  In  the  rabbit  the  difference  be- 
tween the  l)lood  pressure  in  the  carotid  and  femoral  arteries  is  only 
about  5  mm.  (i  of  an  inch);  in  the  calf,  however,  the  difference 
amounts  to  26  mm.  (1.04  inches). 

It  is  not  only  desirable  to  determine  whether  there  exists  any 
difference  in  the  ])lood  pressure  of  two  arteries  like  the  carotid 
and  metatarsal,  but  also  if  the  pressure  in  two  arteries  like  the  two 


^Op.  cit.,  p.  37. 


2 Op.  cit.,  s.  167. 


300 


CIRCULATION  OF  THE  BLOOD. 


carotids  or  the  two  criirals  is  equal  or  different.  With  tliis  object 
as  well  as  of  determining  the  difference  between  the  pressure  in 
an  artery  and  a  vein,  the  carotid  and  the  jugular  vein,  for  example, 
we  make  use  of  the  differential  manometer  of  Bernard  ^  (Fig.  143). 
This  consists  of  a  U-shaped  glass  tube  firmly  supported  upon  a 
stand  which  carries  a  graduated  scale,  and  by  means  of  which  the 


Differential  manometer  of  Bernard. 

tube  is  filled  with  mercury  to  a  certain  level.  The  two  ends  of  the 
U-tube  are  adapted  to  lead  pipes  which  are  connected  with  the  pres- 
sure bottle  containing  the  solution  of  soda,  and  at  e  e  with  arterial 
canulffi  to  be  inserted  into  the  vessels  to  be  examined.  By  means 
of  the  stopcocks  either  one  or  both  the  vessels   can  be  placed  in 

'  Systeme  Nerveux,  Tomei.,  p.  281. 


THE  KYMOGRAPS. 


301 


communication  with  the  manometer.  Suppose,  for  example,  the 
two  ends  of  the  manometer  have  been  inserted  by  means  of  the 
arterial  canuls  into  the  carotids  of  a  rabbit.  Having  opened  both 
stopcocks  and  removed  the  clamps  from  the  arteries  and  allowed 
the  blood  to  press  against  the  solution  of  soda,  it  will  be  observed 
that  the  level  of  the  mercury  remains  imchanged,  showing,  there- 
fore, that  the  blood  pressure  in  the  two  arteries  is  the  same.  If  now 
one  of  the  stopcocks  be  closed,  at  once  the  mercury  will  rise  in  the 
limb  of  the  tube  of  the  corresponding  side,  and  by  doubling  the 
height  to  which  the  mercury  is  elevated,  and  deducting  1  mm.  for 

Fig.  144. 


Fick's  spring  kymograph,  a.  C-spring.  x.  Support,  d.  Eod  which  communicates  the  move- 
ments of  the  spring  to  the  lever  I,  and  thus  to  the  writing-needle  G.  c.  Leaden  tube  by  which 
the  cayity  of  the  spring  is  in  communication  with  the  artery. 


every  10  mm.  of  solution  ol  sodium  carbonate  used,  the  blood  pres- 
sure of  the  artery  on  the  side  v.here  the  stopcock  remained  opened 
is  obtained. 

Admirable  an  instrument  as  the  kymograph  undoubtedly  is,  and 
however  accurately  it  fulfils  its  purpose,  it  must  not  be  forgotten 
that  the  trace  recorded  on  the  cylinder  is  due  to  the  oscillations  of 
the  mercury,  and,  therefore,  only  indirectly  to  the  pressure  of  the 
blood.  On  account,  however,  of  the  inertia  of  the  mercury  and  the 
suddenness  of  the  expansion  of  the  artery,  the  oscillations  of  the 
mercury,  though  caused  by  the  pressure  of  the  blood,  are  not  an  ex- 
act measure  of  it,  since  by  the  time  the  mercury  has  risen  to  its 


302  CIRCULATION  OF  THE  BLOOD. 

highest  elevation  the  artery  has  collapsed.  If  the  heart  is  beating 
very  quickly  the  extent  of  the  oscillations  of  the  mercury  is  rela- 
tively too  small,  and  if  the  interval  between  the  pulsations  is  pro- 
longed the  excursion  of  the  manometer  is  too  great.  The  use  of  the 
mercurial  kymograph  is,  therefore,  limited  to  the  study  of  the  mean 
pressure  and  of  variations  in  pressure,  such  as  occur  at  sufficiently 
long  intervals  to  prevent  the  oscillations  being  mixed  up  witli  those 
proper  to  the  instrument.  In  order  to  study  the  variations  of  blood 
pressure  in  the  exact  order  in  which  thoy  occur,  and  as  regards 
their  duration  and  degree,  etc.,  we  make  use  of  Fick's  spring  kymo- 
graph, which  is  so  constructed  that  it  transmits  the  movements 
communicated  to  it  witliout  obscuring  them  by  any  movement  of  its 
own. 

The  instrument  (Fig.  144)  consists  essentially  of  a  hollow  C- 
shaped  thin  metal  spring  (a)  filled  with  alcohol  and  communicat- 
ing through  its  proximal  end  (5)  by  means  of  a  connecting  tube  (c) 
with  the  pressure  bottle  containing  the  solution  of  the  sodium 
bicarbonate  and  the  arterial  cauula.  The  proximal  end  of  the 
s^jring  being  fixed,  as  the  blood  pressure  increases  the  spring  tends 
to  straighten  itself  and  the  distal  or  free  end  makes  the  movements 
which  follow  exactly  the  variations  in  the  arterial  tension,^     These 

Fig.  145. 


Traces  in  rabbit  taken  with  Fick's  spring  kymograph. 

movements  are  most  exact,  the  slightest  variations  in  the  blood 
pressure  being  expressed  by  them.  As  they  are,  however,  very 
small  before  being  recorded,  they  are  enlarged  by  the  lever  which 
is  carried  by  the  distal  end  of  the  spring.  It  will  be  seen  from 
Fig.  145,  illustrating  a  trace  of  the  blood  pressure  in  the  carotid 
artery  of  the  rabbit,  taken  by  the  spring  kymograph,  that  the 
ascent  of  the  lever,  due  to  the  expansion  of  the  artery  caused  by 
the  ventricular  systole,  is  very  abrupt,  almost  vertical,  that  at  the 
vertex  the  direction  of  the  trace  is  horizontal,  that  the  lever  in  its 
descent  pursues  an  oblique  course  at  its  termination,  being  also 
horizontal  in  direction,  and  that  the  dicrotism  of  the  pulse  is  very 
evident.  Tlie  nature  of  these  peculiarities  we  have  already  consid- 
ered in  describing  the  pulse.  If  we  wish  to  express  in  millimeters 
of  mercury  the  absolute  blood  pressure  determined  by  the  spring 
kymograph,  the  instrument  must  first  be  graduated  by  comparison 

'  In  some  recent  forms  of  Fick's  kymograph  the  memlirane  of  a  small  air  drum 
works  against  a  horizontal  slip  of  steel  which  acts  as  a  spring. 


VELOCITY  OF  THE  BLOOD.  303 

with  a  mercurial  manometer.  This  is  done  in  the  following  way  : 
The  spring  kymograph  being  so  placed  that  it  will  write  on  the  re- 
cording cylinder,  its  connecting  tube  in  communication  with  the 
pressure  bottle  is  adapted  to  the  proximal  end  of  the  mercurial 
manometer.  The  pressure  bottle  is  first  lowered  until  the  solution 
it  contains  stands  at  the  same  level  as  that  of  the  mercury  in  the 
manometer.  The  clockwork  being  put  in  motion  the  cylinder  re- 
volves and  a  trace  is  taken  which  will  represent  the  abscissa.  The 
pressure  bottle  is  then  raised  till  the  mercury  is  elevated  in  the 
distal  limb  of  the  manometer  10  mm.  (|-  of  an  inch)  higher  than 
in  the  proximal  one,  and  a  second  tracing  taken,  and  so  on  until 
we  have  attained  a  number  of  tracings  parallel  with  the  first  one 
or  abscissa,  and  therefore  with  each  other.  The  vertical  distance 
between  the  abscissa,  and  these  lines  or  the  ordinates  measured  in 
millimeters  expresses  then  the  value  of  the  tracing  in  millimeters 
of  mercurial  pressure. 

We  have  already  alluded  incidentally  to  the  influence  of  respira- 
tion in  modifying  the  curve  of  the  blood  pressure,  and,  as  we  have 
now  seen,  how  the  latter  may  vary  according  to  the  part  of  the  vascu- 
lar system  generally.  It  is  probable,  also,  that  tlie  blood  pressure  de- 
pends, to  a  certain  extent,  upon  the  size  of  the  animal,  the  period  of 
life,  and  general  health,  cceteris  paribus,  the  blood  pressure  being 
greater  in  larger  than  in  smaller  animals,  in  those  of  middle  age  than 
in  very  young  or  very  old  animals,  in  strong,  healthy  than  in  weak, 
sickly  ones.  Inasmuch  as  the  pressure  of  the  blood  depends  upon 
the  muscular  force  of  the  heart,  and  as  the  muscular  substance  of 
the  heart,  like  all  other  muscle,  is  nourished  by  the  blood,  it  follows 
that  loss  of  blood  in  weakening  the  heart  fibers  should  diminish 
blood  pressure.  The  experiments  of  Hales  ^  and  Colin  ^  have  shown 
that  such  is  the  case,  the  blood  pressure  being  diminished  in  propor- 
tion to  the  amount  of  blood  lost.  Finally,  we  shall  see  that  the 
vasomotor  nerves,  in  modifying  the  calibre  of  the  vessels,  greatly  in- 
fluence the  blood  vessels.  In  concluding  our  account  of  the  arteries, 
there  still  remains  for  consideration  the  velocity  with  which  the 
blood  flows  through  them. 

Physiologists  at  one  time  endeavored  to  determine  the  velocity  of 
the  blood  by  means  of  the  theorem  of  Torricelli,  assuming  that  the 
velocity  with  which  a  fluid  escapes  from  a  reservoir  may  be  learned 
from  observing  the  height  to  which  it  will  flow  into  a  vertical  tube 
connected  with  the  same,  the  velocity  being  equal  to  that  which  a 
body  would  acquire  falling  in  vacuo  through  a  distance  equal  to  the 
height  which  the  fluid  attains  in  the  tube,  which  is  nearly  the  same 
as  the  level  of  the  fluid  in  the  reservoir.  Little  or  no  importance, 
however,  can  be  attached  to  this  manner  of  determining  the  veloc- 
ity of  the  blood  in  the  arteries,  since  the  cardiac  energy  is  expended 
in  not  only  imparting  a  velocity  to  the  blood  but  in  overcoming  re- 

'  Statical  Essayn:,  Vol.  ii.,  p.  16.     London,  1740. 
2 Milne  Edwards,  Physiologie,  Tome  iv.,  p.  115. 


304 


CIRCULATION  OF  THE  BLOOD. 


sistance,  and  unless  the  latter  factor  is  known  and  be  taken  into 
account  the  velocity  obtained  by  theory  will  be  a  gross  exaggera- 
tion. Assuming,  according  to  well-known  hydraulic  principles  that 
the  velocity  with  which  a  fluid,  in  a  given  time,  flows  through  a 
tube  is  equal  to  the  ratio  of  the  efflux  to  the  sectional  area  of  the 
tube,  Hales^  estimated  that  the  blood  in  the  horse  flows  from  the  left 
ventricle  into  the  aorta  at  the  rate  of  nearly  17  inches  in  a  second, 
which  we  will  see  agrees  closely  with  the  velocity  recently  deter- 
mined by  experiment. 

Passing  by  the  early  attempts  to  determine  the  velocity  of  the 
blood  such  as  those  just  mentioned,  and  which  have  now  only  a  his- 
torical interest,  let  us  endeavor  to  determine,  not  what  the  velocity 
of  the  blood  ought  to  be  in  an  artery  according  to  theory,  but  what 
the  velocity  actually  is  in  a  living  animal  by  experiment.  The 
hsemodromometer   (Figs.    146,   147),  the   instrument  invented  by 


Fig.  14G. 


Fig.  147. 


Volkmann's  hn;iiJoilri)mometer  for  measuring  the  rapidity  of  the  arterial  circulation. 


Volkmann"  for  this  purpose,  consists  of  a  metallic  tube  (c),  which  is 
united  to  the  two  ends  of  a  divided  artery,  and  through  which  the 
blood  can  flow  in  the  same  direction  as  through  the  vessel  itself 
(Fig.  146).  To  the  metallic  tube  is  attached  laterally  a  U-shaped 
glass  tube  (<:?),  containing  water.  By  turning  stopcocks  the  metal 
tube  is  put  in  communication  with  the  U-shaped  tube  in  such  a  way 

^Statical  Essays,  Vol.  ii.,  p.  46.  ^ Hfemodynamik,  s.  185. 


THE  STEOMUHR. 


;305 


(Fig.  147)  that  the  blood  cannot  pass  at  once  as  it  clid  before  from 
the  artery  through  the  metal  tube  to  the  artery  again,  but  must  first 
pass  through  the  U-shaped  tube.  The  length  of  this  tube  being 
known,  and  the  time  it  takes  for  the  blood  to  flow  through  it  being 
observed,  the  velocity  with  which  the  blood  flows  through  the  artery 
can  be  determined  approximately.  There  are  objections,  however, 
to  the  use  of  this  instrument,  as  the  blood  does  not  flow  through  the 
glass  tube  as  easily  as  it  does  through  the  artery,  both  on  account 
of  the  curvature  of  the  tube  and  of  the  difference  in  its  substance  as 
compared  with  that  of  the  artery,  and  as  the  blood  flows  from  the 
proximal  end  of  the  artery  into  the  glass  tube  it  drives  ahead  the 
water  it  contains  into  the  distal  end,  the  effect  of  which  is  to  con- 
tract the  vessels,  and  so  further  retard  the  flow. 
It  is  for   these   reasons,  that  Volkmann's  esti-  Fig.  148. 

mate  of  the  velocity  of  the  blood,  for  example, 
in  the  carotid  artery  of  the  horse  of  254  milli- 
meters (10.2  iuches)  in  a  second  is  too  low. 

By  the  invention  of  the  stromuhr,  in  1857, 
Ludwig  ^  greatly  improved  Volkmann's  method 
of  measuring  the  velocity  of  the  blood.  This 
instrument,  also  called  the  rheometer  {;i^oj,  to 
flow,  /uzTooi^,  a  measure),  consists  (Fig.  148)  of 
two  glass  bulbs  {B,  C)  of  an  ovoid  shape,  and  of 
a  known  capacity,  communicating  superiorly  by 
the  curved  tube  and  terminating  so  iuferiorly  as 
to  be  screwed  into  the  canula?  F  and  G,  which 
are  onlv  larg-e  enough  to  be  inserted  into  the  cut 
ends  of  the  artery  to  be  examined.  The  canulse 
having  been  ligated,  and  the  vessel  previously 
clamped,  by  means  of  the  small  tube  opening 
into  the  communicating  tube,  the  bulb  C  is  filled 
with  olive  oil  up  to  the  mark  J/,  the  bulb  B 
with  serum.  The  small  tube  is  then  closed.  The 
clamps  having  been  removed,  the  blood   flows  -    ~ 

from  the  proximal  end  of  the  artery  by  means  Ludwig's  stromuhr. 
of  the  canula  F  into  the  bulb  C,  driving  the  oil 
ahead  of  it  through  the  communicating  tube  into  the  bulb  B,  the 
serum  in  the  latter  being  driven  out  of  it  through  the  canula  G  into 
the  distal  end  of  the  artery.  So  fiir  the  method  of  experimenting 
with  the  stromuhr  is  essentially  the  same  as  that  of  the  ha?modro- 
mometer,  with  these  two  differences,  however,  that  serum  being  used 
instead  of  water  there  is  less  resistance  offered  to  the  flow  of  the 
blood,  and,  on  account  of  the  shape  of  the  bulbs,  a  greater  quantity 
of  blood  can  be  used,  which  is  also  of  advantage.  The  sreat  im- 
provement,  however,  in  Ludwig's  instrument,  as  compared  with 
Volkmann's,  consists  in  this,  that  by  turning  the  vertical  rod  H 

^  Dogiel,  Berichte  iiber  Die  Verhand.  Der  Kon  Sachsischen  Gesell.  Der  Wissen. 
Zu  Leipzig,  1867,  s.  200. 
20 


/^^- 


306  CIRCULATION  OF  THE  BLOOD. 

through  1 80  degrees,  by  a  simple  mechanical  arrangement,  the  bulb 
B  now  filled  with  oil  communicates  through  the  canula  F  with  the 
proximal  end  of  the  artery,  and  the  bulb  C  filled  with  blood  com- 
municates through  the  canula  G  with  the  distal  end.  The  blood 
still  flowing  from  the  proximal  end  of  the  artery  will  now  drive 
the  oil  out  of  B  into  C,  and  the  blood  displaced  by  the  oil  will  pass 
into  the  distal  end.  By  turning  the  rod  back  again  the  bulb  ( ' 
^nll  communicate  with  the  canula  F,  and  the  bulb  B  with  the  canula 
G.  This  operation  can  be  repeated  several  times  before  the  blood 
coagulates. 

To  illustrate  the  manner  in  which  the  velocity  of  the  blood  is 
determined  in  a  living  animal  by  the  stromuhr  we  will  suppose  that 
the  instrument  has  been  adapted  to  the  carotid  artery  of  a  rabbit. 
The  animal  having  been  firmly  secured  and  the  artery  exposed  and 
clamped  in  two  places,  the  clamps  being  separated  by  a  distance 
of  two  inches,  about  an  inch  of  the  intervening  vessel  is  cut  out. 
The  stromuhr  being  attached  to  the  vertical  stem  of  the  holder  by 
the  horizontal  rod  and  the  bulbs  having  been  previously  w^armed 
and  their  ends  screwed  into  the  canul?e  which  have  been  inserted 
into  the  cut  ends  of  the  artery,  the  bulb  C  is  then  filled  with  oil  up 
to  the  mark  31,  it  containing  then  5  c.  cm.,  and  the  bulb  B  with 
serum.  The  clamps  are  now  withdrawn  from  the  artery  and  the 
blood  from  its  proximal  end  will  be  observed  to  drive  the  oil  from 
C  into  B,  the  oil  displacing  the  serum  in  B,  which  passes  into  the 
distal  end  of  the  artery.  The  moment  that  the  blood  reaches  the 
level  of  the  mark  31  the  movable  disk  I)  is  rotated  as  rapidly  as 
possible  through  180  degrees  with  the  effect  of  putting  the  bulb  B 
filled  with  oil  in  communication  with  the  proximal  end  of  the  artery 
and  the  bulb  C  filled  with  blood  in  communication  with  the  distal 
end  of  the  vessel.  The  blood  continuing  to  flow,  the  oil  is  now 
driven  from  B  into  C,  the  disk  being  rotated  back  again  the  mo- 
ment that  the  blood  reaches  the  level  of  the  mark,  the  bulb  (',  now 
filled  with  oil,  communicates  as  at  first  with  the  proximal  end  of 
the  artery.  The  experiment  may  be  continued  in  this  way  for  a 
minute  or  more  until  the  blood  begins  to  coagulate.  Inasmuch  as 
we  learn  how  often  in  a  given  time  a  definite  quantity  of  oil  is  dis- 
placed by  tlic  blood  we  learn  how. much  blood  is  delivered  by  the 
carotid  artery  in  that  time.  Suppose,  for  example,  that  in  an  ex- 
periment 5  c.  cm.  of  blood  have  been  delivered  by  the  carotid  ar- 
tery 10  times  in  100  seconds — that  is,  50  c.  cm.,  then  1  c.  cm.  of 
blood  has  flown  from  the  artery  in  2  seconds,  or  0.5  c.  cm.,  equal 
to  500  mm.  in  1  second.  Dividing  this  amount  by  the  sectional 
area  of  the  artery  through  which  it  has  flown — that  is,  by  3.14 
mm.  (1-  X  3.14  =  3.14),  the  diameter  of  the  artery  and  the  can- 
ula being  nearly  the  same,  2  mm.,  and  the  radius,  therefore,  1 
mm.,  we  get  the  velocity,  nearly  158  mm.  (G.3  in.),  in   1   second 

I' =  158.9),  the  hydraulic  principle  involved  being  that  the 


THE  H^MODROMOMETEB. 


307 


velocity  equals  the  ratio  of  tlic  quantity  of  fluid  delivered  to  the 
sectional  area  of  the  tube. 

The  stromuhr  is  a  most  excellent  and  reliable  instrument,  as  it 
interferes  so  little  with  the  circulation,  the  flow  of  the  l)lood  being- 
only  stopped  during  the  instant  that  the  disk  is  rotated  and  the 
blood  pressure  being  little  altered  by  its  passage  through  the  instru- 
ment. This  can  be  sho^^ii  by  connecting  a  manometer  with  the 
two  tubes  which  are  in  communication  with  the  bulbs,  but  which 
are  not  seen  in  the  illustration,  the  tubes  being  placed  in  the  side 
of  the  apparatus  not  shown  in  the  flgure. 

Fig.  149. 


Hfemodromometer  of  Chauveau  and  Lortot. 


Fig.  150. 


While  the  stromuhr  is  admirably  adapted  to  determine  the  ex- 
act amount  of  blood  passing  through  nn  artery  and  the  mean  ve- 
locity of  the  flow,  it  does  not,  however,  enable  us  to  determine  the 
incessant  variations  experienced  by  the  blood  as  regards  its  velocity. 
For  this  object  physiologists  make  use  of  the  ha?modromometer  of 
Chauveau.  The  construction  of  this  instrument,  like  the  hsema- 
tachometer  of  Vierordt,^  is  based  upon  the  principle  of  measuring 
the  velocity  of  the  blood  by  observing  the  amount  of  deviation 
undergone  by  a  pendulum,  the  free  end  of 
which  is  suspended  in  the  blood  current,  the 
amount  of  deviation  being  proportional  to 
the  velocity.  It  is  essentially  the  same  kind 
of  instrument  as  the  hydrostatic  pendulum 
used  by  engineers  to  measure  the  velocity 
of  a  current  of  water.     Chauveau's  htemo- 

dromometer,  invented  in  185<S,-  consists  of  ji;tmataeh..meterofVierordt. 
a  brass  tube  (Fig.  149,  A),  which  is  in-  eu£  o'^thr^fr^iry. '"*"*''*" '"^ 
serted  into  the  cut  ends  of  a  divided  artery, 

or  into  the  slit  made  in  the  vessel  of  the  horse  and  ligated.  Part 
of  the  wall  of  the  tube  is  of  India-rubl)er  membrane  fastened  over 
a  longitudinal  opening  in  the  tube,  and  through  which  passes  a  light 
lever.      The  short  expanded  arm  of  the  lever  hangs  freely  in  the 

'  Die  Erschehuingen  und  Gesetze  der  Stromgescliwindekeit  des  Bluts,  1858,  s.  10. 
2  Journal  de  la  Pliysiologie,  Tome  ill.,  p.  095.     Paris,  1860. 


.308  CIBCULATION  OF  TEE  BLOOD. 

blood,  and  is  moved  through  a  greater  or  less  arc,  according  to  the 
force  ^vith  which  the  l)lood  rushes  against  it,  in  from  the  artery,  the 
India-rubber  membrane  acting  as  a  fulcrum.  The  movements  of 
the  long  arm  of  the  lever  H  in  the  opposite  direction  to  those  of 
the  short  one  are  measured  by  means  of  a  graduated  scale.  The 
lono-  arm  of  the  lever,  it  will  be  observed,  projects  considerably 
from  the  tube  A.  In  order  to  determine  the  actual  velocity  of  the 
flow  in  addition  to  the  varying  changes  the  instrument  must  be 
first  experimentally  graduated.  This  can  be  done  in  the  following 
wav  :  A  current  of  warm  Avater,  or,  better,  defibrinated  blood,  is 
made  to  pass  through  the  tube  of  the  htemodromometer  with  such 
a  velocity  that  the  deviation  undergone  by  the  pendulum  is  the 
same  as  when  the  instrument  was  inserted  in  the  arter}^  The  ve- 
locitv  of  the  current  can  be  easily  determined  by  receiving  the  fluid 
from  the  tube  in  a  graduated  vessel,  and  ol)serving  the  time  occupied 
in  discharging  a  given  quantity. 

AVhen  a  marker  is  attached  to  the  end  of  the  long  lever  H,  the 
movements  can  then  be  recorded  on  the  cylinder,  and  we  obtain  a 
graphic  representation  of  the  velocity  and  its  variations.  The 
hfemodromometer,  when  used  in  this  way,  becomes  the  hwmodrom- 
ograph.  Lortet^  has  modified  Chauveau's  instrument  so  that  a 
trace  of  the  blood  pressure  can  be  taken  simultaneously  with  that 
of  the  velocity.  This  is  accomplished  (Fig.  149)  by  putting  in 
communication  with  the  tube  A  the  lever  of  which  through  its 
movement  gives  a  trace  of  the  velocity  of  the  blood,  a  sphygmo- 
scope  (B),  the  blood  from  the  artery  after  passing  through  the  tube 
A,  enters  the  caoutchouc  bladder  B,  of  the  sphygmoscope,  and  ex- 
panding, it  compresses  the  air  in  the  glass,  which,  acting  through 
the  tube  D,  upon  the  recording  lever  F,  gives  the  trace  of  tlie  blood 
pressure. 

Chauveau  has  determined,  by  means  of  his  hsemodromometer, 
that  the  velocity  of  the  blood  in  the  carotid  of  the  horse  at  each 
ventricular  systole  is  about  50  cm.  {'10  in.)  in  a  second  ;  this  veloc- 
ity, however,  gradually  diminishes  until  finally  the  blood,  for  a 
moment,  stops  moving  altogether.  Immediately  following  the  sys- 
tole and  synchronous  with  the  closure  of  the  semilunar  valves,  a 
second  impulse  is  given  to  the  blood  by  the  recoil  of  the  arterial 
walls,  and  the  blood  moves  now  at  a  rate  of  about  20  cm.  (8  in.)  a 
second ;  this  velocity  gradually  diminishes,  the  average  rate  being, 
until  the  next  ventricular  systole,  about  12  cm.  (4.8  in.)  in  a  sec- 
ond. It  will  be  observed,  from  these  experiments,  that  the  veloc- 
ity of  the  blood  is  at  times  much  more  rapid  than  at  others.  This 
is,  however,  only  true  of  the  arteries  near  the  heart,  like  the  ca- 
rotid, the  acceleration  of  the  velocity,  like  the  pulse,  gradually  dis- 
appearing in  the  small  arteries,  and  for  the  same  cause,  the  gradual 
diminution  of  the  cardiac  pressure,  as  we  recede  from  the  heart  to 

^  Eecherches  sur  la  vitesse  du  coui-s  du  sang  dans  les  arteres  du  Cheval  an  moyen 
d'un  nouvel  hemodromographe,  ParLs,  1807. 


VELOCITY  OF  THE  BLOOD. 


309 


the  periphery.  While  the  velocity  of  the  blood  in  the  arteries  in 
man  can  be  experimentally  determined  from  the  experiments  made 
upon  the  horse,  approximately,  it  may  be  considered  as  not  differ- 
ing very  much  from  that  observed  in  that  animal.  The  velocity  of 
the  blood  in  the  arterial  system  is  not  only  modified,  as  we  have 
seen  by  the  cardiac  pressure,  but  is  influenced  by  other  causes. 

It  has  already  been  mentioned  that  the  capacity  of  the  arterial 
system  increases  as  we  pass  from  the  aorta  to  the  capillaries,  and  as 
fluids  move  more  slowly  in  the  wide  tubes  than  in  narrow  ones,  the 
velocitv  of  the  blood  ought  to  be  slower  in  the  peripheral  arteries 
than  in  those  near  the  heart.  Experimentally,  this  has  been  shown 
to  be  the  case  ;  according  to  Yolkmann,  the  velocity  of  the  blood  in 
the  metatarsal  artery  in  the  dog  is  only  5  cm.  (2  inches),  that  of  the 
carotid  artery  being  25  cm,  (10  inches)  in  the  second.  The  velocity 
of  the  blood  will  vary,  also,  according  to  the  resistance  offered 
to  its  flow ;  the  compression  of  an  artery,  for  example,  offering  an 
obstacle  to  the  circulation,  will  diminish  the  velocity,  and  even  stop 
the  movement  altogether.  The  amount  of  resistance  offered  by  the 
capillaries  greatly  influences  the  velocity  of  the  l)lood.  The  capil- 
lary resistance  remaining  constant,  an  increase  in  the  force  of  the 
heart  will  increase  the  velocity ;  a  diminution  in  the  cardiac  force 
will  diminish  it.  On  the  other  hand,  the  force  of  the  heart  remain- 
ing coHstant,  the  velocity  of  the  blood  will  be  either  increased  or 
diminished,  according  as  the  capillary  resistance  is  increased  or 


123  4 


1    234 


Tracings  of  variations  of  rapidity  and  of  pressure  of  blood  in  the  carotid  of  a  horse,  obtained 
by  CTiauveau  and  Lortet.  The  liner  represents  the  curve  of  the  rapidity  of  the  blood  ;  andp  the 
curve  of  arterial  pressure.  The  figures  and  vertical  lines  represent  corresponding  periods  in  the 
tracings.     (McKexdrick.) 


diminished.  It  will  be  observed  from  what  has  been  said  in  refer- 
ence to  the  pressure  of  the  blood  and  its  velocity,  that,  with  the 
increase  or  diminution  of  the  one  we  have  often  a  corresponding 
increase  or  diminution  of  the  other.  Thus,  when  the  action  of  the 
heart  is  diminished  by  stimulation  of  the  pneumogastric  nerve,  the 
velocity  and  blood  pressure  are  diminished  at  the  same  time.     The 


310  CIRCULATION  OF  THE  BLOOD. 

relation  of  the  two,  however,  may  be  an  inverse  one — that  is,  the 
velocity  may  be  diminisliecl,  and  yet  the  blood  pressure  may  be  in- 
creased ;  for  example,  if  an  artery  be  compressed  the  velocity  is 
diminished,  and  yet  the  blood  pressure  rises,  as  we  have  seen.  Any 
influence  which  increases  or  diminishes  the  force  of  the  heart,  which 
propels  the  blood  toward  the  periphery,  will  increase  or  diminish 
at  the  same  time  the  velocity  and  blood  pressure,  as  in  the  exam- 
ple just  given  of  the  effect  of  stimulation  of  the  pneumogastric 
nerve  ;  on  the  contrary,  any  influence  Avhich  will  increase  or  dimin- 
ish the  resistance  to  the  arterial  flow  will  make  the  velocity  and 
l)lood  pressure  vary  in  the  inverse  relation  toward  each  other. 
Thus,  if  the  capillary  resistance  be  very  great  the  velocity  is  dimin- 
ished })ut  the  blood  pressure  rises. 

On  account  of  this  relation  between  the  pressure  of  the  blood 
and  its  velocity,  wherever  it  is  practicable  the  two  should  be  studied 
together  (Fig.  151),  since  it  is  impossible  to  learn  from  the  eleva- 
tion of  the  mercury  in  the  manometer  alone  wliether  the  rise  in  the 
blood  pressure  is  due  to  increased  cardiac  action,  or  increased  pe- 
ripheral resistance.  If,  however,  the  trace  of  the  velocity  be  taken 
simultaneously  with  that  of  the  blood  pressure,  and  it  is  seen  that 
the  velocity  is  diminished,  then  the  rise  in  the  blood  pressure  \\'\\\ 
be  due  to  peripheral  resistance  ;  on  the  other  hand,  if  the  velocity 
be  increased,  then  it  Ls  due  to  increased  heart  action.  The  want  of 
such  comparative  observation  leaves  us  often  in  doubt  as  to  what 
the  rise  in  the  blood  pressure,  as  indicated  by  the  elevation  of  the 
mercury,  w^as  really  due  to  in  many  of  the  recorded  experiments 
upon  blood  pressure.  The  result  of  Chauveau's  observation  upon 
the  coronary  arteries  with  his  hsemodromograph  illustrates  the  im- 
portance of  this  comparative  method  of  experimentation.  It  being 
demonstrated  that,  during  the  systole  of  the  ventricle,  the  velocity 
of  the  blood  is  diminished  in  the  coronary  arteries,  the  rise  in  the 
blood  pressure  observed  must  be  due  to  peripheral  resistance,  the 
contracted  state  of  the  muscular  substance  of  the  heart  during  the 
systole  oflFering  an  obstacle  to  the  flow  of  the  blood  through  the 
coronary  arteries;  the  velocity  being  increased,  however,  during 
the  diastole,  and  the  blood  pressure  falling,  shows  that  the  obstacle 
has  been  removed,  the  muscular  fibers  of  the  heart  now  being  re- 
laxed. The  above  view  is  a  confirmation  of  what  has  been  already 
said  in  reference  to  the  circulation  of  the  blood  throusch  the  sub- 
stance  of  the  heart  itself. 


CHAPTER    XVIII. 

CIRCULATIOX    OF   THE   BhOOB.— (Con fi, wed.) 

THE  CAPILLARIES. 

The  capillaries  (Fig.  102)  discovered  by  Malpighi/  iu  1(361, 
are  the  minute  vessels  through  which  the  blood  (with  few  excep- 
tions) flows  from  the  arteries  to  the  veins.  As  an  artery  becomes 
smaller  and  smaller  it  gradually  loses  its  external  and  middle  coat, 
and,  to  a  great  extent,  its  internal  one  also,  the  endothelial  layer 
alone  remaining.  This  constitutes  a  capillary.  As  the  capillary 
approaches  the  vein  it  not  only  becomes  larger,  but  changes  the 
character  of  its  structure,  developing  gradually  three  coats,  until 
finally  the  capillary  becomes  a  vein.  Practically,  it  is  impossible 
to  say  exactly  where  the  artery  ends  and  where  the  capillary  begins, 
or  where  the   capillary  ends  and   the  vein  begins,  the  transition 

Fig.  1o2. 


Cajiillary  yilexus  in  the  portion  of  a  web  of  a  frog's  foot,  magnified  110  diameters.     1.   Trunk  of 
vein.     2.  2,  2.  Its  branches.     3.  3.  Pigment  cells.     (Carpexter.) 


from  one  to  the  other  is  so  gradual.  It  is  for  this  reason  that  a 
difference  of  opinion  prevails  among  anatomists  as  to  what  consti- 
tutes a  capillary,  and   therefore  the  description  of    these  vessels 

1  Marcelli  Malpiglii,  Opera  Omnia  Lug  Bat,  1687,  p.  328. 


312 


CIRCULATION  OF  THE  BLOOD. 


dijEfers,  according  to  the  view  taken  of  their  structure.  According 
to  some  histologists  there  are  various  kinds  of  capillaries,  differing 
from  each  other  in  the  amount  of  muscular  and  fibro-elastic  tissue 
present.  Such  vessels  we  would  regard  as  either  small  arteries  or 
veins,  considering  a  capillary  to  be  a  transparent,  apparently  homo- 
geneous, elastic  and  possibly  contractile  vessel  whose  wall  consists 
of  a  single  layer  of  flattened  endothelial  lanceolate  cells  with  oval 
nuclei,  joined  edge  to  edge  by  the  so-called  cement  substance  and 
continuous  with  the  endothelial  layer  of  the  arteries  on  the  one  hand, 
and  with  that  of  the  vein  on  the  other.  The  ^^'all  of  the  capillary 
varying  between  the  ^i^  *«  ToVo  of  a  mm.  (12^00  ^ncl  ^^J^^  of 
an  inch)  in  thickness,  is  apparently  almost  homogeneous,  it  is  only 

after  appropriate  treatment  with  silver 
nitrate  and  carmine  that  the  outlines  of 
the  cells  composing  it,  with  their  nuclei, 
become  apparent  (Fig.  153).  The  length 
of  the  capillary — that  is,  the  distance 
between  the  end  of  the  artery  and  the 
beginning  of  the  vein — varies,  on  an 
average,  between  the  J  and  -^  of  a  mm. 
(-gig-  and  y|-g-  of  an  inch),  the  average  di- 
ameter varying  between  the  -^-^  and  the 
(otAt-a  and   -t-jtW  of  an 


Fig.  1: 


T6-0,of 
inch). 


a  mm. 


000 


4000 


Fine  capillaries  from  the  mesentery. 


If  the  thickness  of  the  wall  of  the 
capillary  be  deducted  from  that  of  the 
diameter  of  the  vessel  it  will  be  found 
that  in  many  instances  the  calibre  of  the 
vessel  is  so  small  as  to  permit  of  the  red  blood  corpuscles  passing 
through  it  only  in  single  file.  Indeed,  in  some  cases  the  diameter 
of  the  red  blood  corpuscle  is  larger  than  that  of  the  lumen  of  the 
capillary,  and  in  order  to  pass  through  the  latter  it  must  change  its 
shape,  lengthening  and  narrowing  itself,  regaining,  however,  its 
proper  form  through  its  elasticity  on  passing  into  a  larger  vessel. 

The  small  size  of  the  capillaries,  both  as  regards  their  length  and 
breadth,  has  an  important  significance  in  reference  to  the  amount  of 
blood  flowing  from  them  into  the  veins.  Thus  it  is  well  known, 
from  the  researches  of  Poisseuille,^  that  the  amount  of  fluid  dis- 
charged by  a  tube  the  y^-g-  of  a  millimeter  in  diameter  (2-5V0  ^^  '"^^ 
inch)  will  be  sixteen  times  that  discharged  by  a  tube  the  ^i^-  of  a 
mm.  i^Q-Q  of  an  inch),  the  amounts  discharged  being  proportional 
to  the  fourth  powers  of  the  diameters — that  is,  1  :  x  ::  ^1-^-  :  y^-q, 
or  X  equals  2  and  2*  equals  16.  On  the  other  hand,  the  amount 
discharged  by  tu])OS  of  the  length  of  the  capillaries  will  be  inversely 
as  their  lengths — that  is,  of  two  capillaries  of  different  lengths  more 
fluid  will  l)e  discharged  from  the  short  vessel  than  the  long  one. 
It  will  be  seen,  therefore,  that  any  change  in  the  length  or  breadth 
1  Mem.  de  I'Acad.  des  Sciences  Savant  Etrang,  Tome  ix.,  p.  513. 


THE  CAPILLARIES. 


313 


of  a  capillary  will  influence  greatly  the  amount  of  blood  delivered 
to  the  veins,  and  so  increase  or  diminish  the  resistance  offered  by 
the  capillary  system  to  the  arterial  flow ;  the  significance  of  wdiich 
we  have  seen  in  considering  the  velocity  of  the  blood  and  its  pres- 
sure in  the  arteries.  The  cell-like  structure  of  the  capillaries  just 
referred  to  makes  perfectly  clear  how  it  is  possible  for  the  white 
corpuscles  to  pass  from  the  capillary  into  the  surrounding  tissues. 
The  capillaries,  unlike  the  arteries  and  veins,  constitute  a  true 
plexus  of  vessels  of  nearly  uniform  diameter,  branching  and  inos- 
culating in  every  direction.  This  inosculation  is  characteristic  of 
the  capillaries  and  the  plexus  is  developed  in  proportion  to  the 
functional  activity  of  the  part.  Thus  the  capillaries  are  very  nu- 
merous and  close  set  in  the  nervo-muscular  and  glandular  tissues, 
absorbing  surfaces,  etc.,  structures  in  which  the  molecular  changes 
incident  to  nutrition  are  peculiarly  active. 

While  the  general  character  of  the  capillaries  throughout  the  sys- 
tem is  the  same,  the  difference  in  their  disposition  as  regards  their 


Fi<;.  L-.4. 


Fk;.  1.-|.'i. 


Distribution  of  capillaries  on  tlie  surface  of 
the  skin  of  the  tiuger.     (Carpenter.) 


Distribution  of  capillaries  in  muscle. 
(Carpenter.) 


closeness  and  the  form  of  the  network  is  often  so  marked  that  the 
histologist  can  frequently  tell  from  what  part  of  the  body  a  tissue 
has  been  taken  by  an  examination  of  the  capillaries  alone.  No  one 
can  fail  to  recognize  the  difference  in  the  arrangement  of  the  capil- 
laries in  the  skin  (Fig.  154),  as  compared 
with  that  in  muscle  or  mucous  membrane 
(Figs.  155,  156).  Capillaries,  while 
found  almost  everywhere  in  the  human 
body,  are  absent  in  certain  structures  like 
cartilage,  hair,  nails,  etc.,  and  hence  such 
parts  are  often  called  extravascular.  This 
name  is  apt,  however,  to  mislead  and  is 
inappropriate,  since  all  tissues  are  extra- 
vascular  in  so  far  as  they  lie  outside  of  the 
vessel  carrying  the  blood  that  nourishes 
them.  In  the  vascular  tissues  the  nutri- 
ment osmoses  through  the  wall  of  the  capillary  into  the  tissue  im- 
mediately surrounding  the  vessel  and  thence  into  parts  more  and 
more  remote  from  it.     In  the  so-called  extravascular  tissue  the  nu- 


1)1  till  uti  net  1  11  u  L  1  ui  I 
lolhcle.--  ol  mutous  membrane. 
(Carpenter.) 


314  CIRCULATIOX  OF  THE  BLOOD. 

triment  comes  from  tlie  blood  of  a  capillary,  as  in  the  vascular 
tissue,  though  the  capillary  may  be  situated  at  a  considerable  dis- 
tance from  the  tissue  that  it  nourishes.  The  only  difference  be- 
tween the  vascular  and  extravascular  tissue  is  that  the  nutriment 
Is  conveyed  a  longer  distance  in  the  one  case  than  the  other ;  the 
difference,  therefore,  is  one  of  degree,  not  of  kind.  There  are  no 
capillaries  in  the  spleen,  erectile  tissues,  and  maternal  part  of  the 
placenta,  their  place  being  supplied  by  blood  sinuses.  When  we 
come,  however,  to  the  study  of  the  development  of  these  organs, 
we  shall  see  that  these  blood  sinuses  are  probably  enormously 
dilated  capillaries.  It  will  be  remembered  that  the  arterial  sys- 
tem was  likened  to  a  cone,  of  which  the  heart  is  the  apex  and  the 
capillaries  the  base,  and  that  the  area  of  the  branches  of  an  ar- 
tery is  usually  greater  than  that  of  the  artery  itself.  We  should 
expect,  therefore,  to  find  that  the  capacity  of  the  capillary  system 
is  far  greater  than  that  of  the  arterial.  Indeed,  the  microscopical 
examination  of  the  skin,  mucous  membrane,  muscle,  etc.,  in  which 
the  capillary  vessels  have  been  injected  gives  the  impression  that 
such  tissues  consist  of  nothing  but  capillaries.  This  is  also  true 
almost  to  the  same  extent  in  living  animals  under  certain  condi- 
tions, thus  during  digestion  the  surface  of  the  mucous  membrane 
lining  the  alimentary  canal  presents  a  light  red  appearance  through 
the  distention  of  its  capillaries  with  blood. 

The  capacity  of  the  capillary  system  must  be  immense — indeed, 
according  to  Yierordt,^  it  is  800  times  that  of  the  arterial.  This 
estimate,  though  only  approximate,  cannot  be  very  far  from  the 
truth,  being  deduced  from  the  law  that  the  velocity  with  w^hich  a 
fluid  flows  through  a  tube  is  inversely  as  the  diameter  of  the  tube. 
We  shall  soon  see,  as  an  illustration  of  this  law,  that  the  blood 
flows  much  more  slowly  in  the  capillaries  than  in  the  aorta,  the 
total  area  of  the  capillaries  being  far  greater  than  that  of  the  aorta. 
The  sectional  area  of  the  capillary  system  being  then  to  the  sec- 
tional area  of  the  aorta  as  the  velocity  of  the  blood  in  the  aorta 
is  to  the  velocity  of  the  blood  in  the  capillaries,  the 

.„     .          sec.  area  of  aorta  X  vel.  of  blood  in  aorta 
sec.  area  of  capillaries  = 


840  = 


vel.  of  blood  in  capillaries 
1X14 

i 

60 


By  dividing  the  total  sectional  area  of  the  capillaries  by  the  area 
of  one  capillary  an  approximate  estimate  of  the  number  of  capil- 
laries can  be  obtained.  It  was  in  this  way  that  Hales^  calculated 
that  there  were  over  eight  millions  of  capillaries  in  the  human 
body.     The  general  structure,  distribution,  etc.,  of  the  capillaries 

1  Die  Erscheinungen  und  Gesetze  der  StromgeyelnviiKligkeiten  des  Blutes,  s.  35. 
'^Statical  Essays,  Vol.  ii.,  p.  69. 


CAPILLARY  CIRCULATION.  315 

having  been  described,  let  us  now  consider  the  manner  in  which 
the  blood  flows  through  them. 

As  the  phenomenon  of  the  flow  of  the  blood  through  the  capil- 
laries, as  viewed  by  the  microscope,  is  one  of  the  most  beautiful 
and  striking  spectacles  in  nature,  a  few  words  as  to  the  most  con- 
venient method  by  which  it  can  be  observed  appear  necessary. 
For  this  purpose  we  generally  make  use  of  the  mesentery  of  the 
frog,  on  account  of  it  being  so  easily  exposed  and  readily  arranged 
on  the  apparatus  supporting  it,  which  is  a  very  simple  one,  consist- 
ing of  a  thin  piece  of  cork  with  an  opening  in  it  through  which 
the  light  can  pass,  and  upon  which  rests,  slightly  elevated,  a  glass 
slide,  over  which  is  placed  the  mesentery,  the  loop  of  intestine 
drawn  out  of  the  body  to  which  the  mesentery  is  attached  resting 
in  a  little  gutter  or  groove  on  the  glass  slide  surrounding  the  open- 
ing. A  few  drops  of  a  solution  of  sodium  chloride  (3  per  cent.) 
being  placed  upon  the  mesentery  and  a  slide  cover  placed  over  it, 
and  the  cork  placed  on  the  stage  of  the  microscope,  the  circulation 
can  be  observed  for  a  considerable  time  before  inflammation  sets  up. 
The  web  of  the  frog's  foot,  its  lung  and  tongue,  may  also  be  used 
for  the  demonstration  of  the  circulation.  The  tongue  of  the  frog, 
on  account  of  its  being  attached  to  the  anterior  part  of  the  lower 
jaw  and  free  posteriorly,  and  therefore  being  easily  drawn  out  of 
the  mouth  and  through  its  great  vascularity,  is  also  a  favorite  sub- 
ject of  study  with  physiologists.  When  the  tongue  is  used  it  is 
best,  however,  to  inflate  it  first  and  then  slit  it  open,  when  a  mag- 
nificent view  of  the  circulation  is  obtained.  The  tails  of  tadpoles, 
of  little  fish,  and  the  gills  of  the  salamander,  are  also  serviceable 
objects  for  the  study  of  the  circulation.  AVhen  the  salamander  is 
used  it  should  be  placed  in  a  Holman's  life  slide,  by  means  of  which 
the  animal  is  firmly  secured  without  injuring  it,  while  the  water  is 
constantly  renewed.  When  the  fish  is  used,  Caton's  fish  trough 
will  be  found  serviceable.  This  consists  of  an  oblong  box,  one  end 
of  ^vhich  transmits  the  light  through  an  opening  in  the  piece  of 
glass  upon  which  the  tail  of  the  fish  in  which  the  capillaries  are  to 
be  examined  is  secured,  the  head  and  body  of  the  fish  resting  at 
the  other  end  of  the  box.  By  means  of  a  cistern  and  tube,  a  con- 
stant current  of  water  passes  through  the  box. 

The  study  of  the  capillary  circulation  in  mammals  is  more  diffi- 
cult than  in  any  of  the  animals  just  referred  to,  since,  with  the  ex- 
ception of  the  wing  of  the  bat,  there  is  no  external  part  transparent 
enough  to  be  observed  with  the  high  power  of  the  microscope,  and 
if  any  of  the  internal  parts  are  used  the  effects  of  exposure  are  far 
more  injurious  than  in  the  frog,  for  example.  The  mesentery  and 
omentum  of  small  rodents,  like  rats  and  mice,  etc.,  have  been  often 
made  use  of  in  demonstrating  the  capillary  circulation  in  the  mam- 
malia ;  but  the  omentum  of  the  guinea-pig  is  preferable  for  many 
reasons,  on  account  of  its  transparency  and  of  its  delicate  and  simple 
structure,  consisting,  to  a  great  extent,  of  only  two  layers,  of  being 


316  CIRCULATION  OF  THE  BLOOD. 

attached  to  only  one  side  of  the  stomach,  and  little  or  no  fat  being 
present.  The  great  difficnlty  experienced  in  observing  the  capil- 
laries in  the  peritoneum  of  the  mammalia  is  due  to  the  injurious 
effects  of  exposing  the  membrane  to  the  atmosphere  and  the  risk  of 
wounding  it.  To  avoid  this,  the  omentum,  which  is  the  part  we 
use,  is  floated  into  a  glass  trough  containing  either  serum  or  a 
solution  of  sodium  chloride  ('3  per  cent.),  which  is  kept  at  the  tem- 
perature of  the  body  by  means  of  the  warm  stage,  which  we  have 
already  described.  The  guinea-pig  used  should  be  put  under  the 
influence  of  chloral,  three  grains  injected  under  the  skin  being 
sufficient  for  an  animal  weighing  one  pound,  and  then  placed  upon 
a  support  on  a  level  with  the  stage  of  the  microscope.  The  incision 
being  made  a  little  below  the  ensiform  cartilage,  and  extending 
outward  from  the  rectus  muscle,  about  an  inch  from  the  edge,  the 
omentum  is  carefully  seized  and  drawn  out  into  the  trough.  It  is 
well  to  cover  the  parts  of  the  membrane  not  immediately  under  the 
microscope  with  pieces  of  blotting-paper,  in  this  way  avoiding  un- 
necessary exposure,  and  at  the  same  time  keeping  the  omentum 
steadier  than  it  otherwise  would  be.  With  all  the  above  precau- 
tions, however,  the  view  of  the  capillary  circulation  thus  obtained 
is  far  from  satisfactory,  and  not  comparable  to  that  observed  in  the 
mesentery  of  the  frog. 

Since  the  time  of  Malpighi,  the  phenomena  of  the  capillary  cir- 
culation have  been  often  described  ;  but  language  is  inadequate  to 
give  one  any  idea  of  the  beauty  of  the  spectacle,  and  to  be  appre- 
ciated it  must  be  seen. 

We  will  suppose  the  mesentery  of  the  frog  disposed  within  the 
field  of  the  microscope  as  just  described.  Here  may  be  seen  the 
arterioles  of  the  mesenteric  artery  through  which  the  blood  flows 
with  apparently  amazing  rapidity,  dividing  and  subdividing  until 
the  blood  is  carried  to  an  exquisite  network  of  delicate  tubes  re- 
sembling a  web  of  fine  spun  glass,  the  capillaries,  in  which  the 
blood  is  separated  from  the  tissues  by  a  thickness  which  has  just 
been  stated  may  vary  between  the  ^i^-  and  -^-^-^-^  of  a  mm.  (y2"S'¥¥ 
and  2'5  o^TTTT  ^^  ^^  inch),  but  which  in  reality  is  so  thin  as  to  defy 
accurate  measurement.  It  will  be  readily  :ipprcciatcd,  therefore, 
with  what  rapidity  the  nutritive  elements  osmose  into  the  tissues 
and  the  effete  matters  be  taken  up  by  the  blood.  Indeed,  the  cap- 
illaries are  the  seat  of  all  physiological  and  pathological  nutrition 
processes.  The  arteries  and  veins  are  only  means  toward  an  end, 
the  one  set  of  vessels  carrying  the  blood  to  the  part  to  be  nour- 
ished, the  other  carrying  it  away  laden  with  the  waste  products.  It 
will  be  observed  that  the  red  blood  corpuscles  move  in  the  middle 
of  the  stream,  and  if  the  caj)illary  be  large  enough  to  admit  of 
three  corpuscles  moving  abreast,  the  middle  one  soon  advances  be- 
yond the  others,  showing  that  the  velocity  of  the  current  is  greater 
in  the  middle  than  at  the  sides  on  account  of  the  friction.  Indeed, 
the  blood  moves  so  slowly  where  it  is  in  actual  contact  ^dth  the 


CAPILLARY  CIIiCULATION.  317 

wall  of  the  capillary  that  it  appears  immovable  and  has  been  called 
for  this  reason  the  "  still  layer."  As  might  be  expected,  the  fric- 
tion so  exerted  is  less  in  a  wide  than  in  a  narrow  tube,  in  a  sluggish 
than  in  a  swift  stream.  A  red  corpuscle  is  sometimes  caught  in 
the  still  layer,  where  it  moves  slowly  for  a  time,  turning  over  and 
over  ;  sooner  or  later,  however,  it  passes  again  into  the  central 
stream  and  in  an  instant  is  whirled  out  of  sight.  The  white  cor- 
puscles, on  the  contrary,  stick  either  to  the  still  layer  or  to  the 
capillary  wall,  and  being  quite  numerous  in  the  frog,  a  number  are 
often  seen  at  one  time  in  the  same  capillary. 

The  difference  in  the  behavior  of  the  red  and  white  corpuscles  in 
this  respect  appears  to  be  due  solely  to  the  red  corpuscles  being 
heavier  than  the  white  ones,  or  the  leucocytes,  it  having  been 
shown  ^  that  if  a  fluid  holding  in  suspension  two  kinds  of  particles 
be  driven  through  capillary  tubes  the  lighter  particles  will  go  to  the 
wall,  the  heavier  ones  to  the  middle  of  the  stream.  The  corpus- 
cles often  move  in  such  a  manner  that  they  appear  as  if  they  were 
endowed  with  consciousness  and  volition.  Thus  when  the  single 
rows  of  corpuscles  flowing  in  two  capillaries  reach  a  third  vessel, 
formed  through  the  union  of  the  other  two,  and  only  large  enough 
to  admit  one  row,  one  row  will  hold  back  until  the  other  one  has 
passed  into  the  capillary  and  then  will  follow  in  its  turn.  Fre- 
quently the  corpuscles  will  flow  in  one  direction  and  meeting  some 
obstacle  will  entirely  reverse  their  course.  A  corpuscle  is  often  re- 
tarded for  some  time  by  the  angle  formed  by  the  division  of  a  cap- 
illary into  two,  and  may  be  observed  turning  over  and  over  and 
changing  its  shape  according  to  the  pressure  of  the  current  until  it 
is  swept  finally  into  the  main  stream. 

Certain  capillaries  will  be  for  a  time  quite  empty,  while  others 
near  by  are  filled  M'ith  corpuscles,  then  one  or  two  corpuscles  will 
float  into  the  empty  capillary,  in  a  moment  or  so  a  few  more,  and 
soon  a  current  is  established,  while  in  the  same  gradual  way  a  dis- 
tended capillary  may  become  empty. 

Poisseuille  ^  first  showed  that  the  law  regulating  the  flow  of 
liquids  in  tubes  was  applicable  to  such  having  as  small  a  diameter 
as  those  of  the  capillaries,  and  it  is  an  interesting  illustration  of 
the  uniformity  of  the  laws  of  nature  that  the  same  phenomenon  of 
the  rapidity  of  the  flow  of  a  stream  being  greater  in  the  middle 
than  at  the  sides  is  seen  on  a  magnificent  scale  in  the  motion  of  a 
glacier,  it  being  a  matter  of  daily  observation  to  those  passing  any 
time  on  a  glacier  to  notice  that  the  stones,  debris,  etc.,  move  more 
rapidly  in  the  middle  of  the  glacier  than  tliose  at  the  sides. 

One  of  the  most  striking  fiicts  in  the  phenomena  of  the  capillary 
circulation  is  the  uniformity  with  which  the  blood  flows  through 
these  vessels.  The  motion  is  here  perfectly  continuous ;  we  no 
longer  observe  either  the  intermittent  or  remittent  action  so  charac- 

'  A.  Schklarewsky,  Pfliiger's  Archiv,  Band  i.,  1868,  s.  603. 
^Mem.  de  L'Aead.  des  .Sciences,  Sav.  Etrang,  T.  vii.,  1835,  p.  45. 


318  CIRCULATION  OF  THE  BLOOD. 

teristic  of  the  heart  and  arteries.  We  observe  that  the  flow  of 
the  blood  in  the  capillaries  is  never  the  same  for  any  length  of 
time — indeed,  one  of  its  most  interesting  peculiarities  is  the  con- 
stant manner  in  which  the  scene  varies — influenced  as  it  is  by  so 
many  conditions.  In  endeavoring  to  follow  the  course  of  the  cor- 
puscles as  they  flow  through  the  capillaries,  one's  first  impressions, 
seeing  them  often  swept  along  as  if  in  a  torrent,  is  that  the  veloc- 
ity of  the  flow  must  be  very  great.  Reflection  at  once  suggests  to 
us,  however,  that  in  proportion  to  the  power  of  the  microscope  used 
the  velocity  is  magnified.  The  simplest  way  of  determining  the 
velocity  of  the  blood  in  the  capillaries  is  to  substitute  for  the  ordi- 
nary eye-piece  of  the  microscope  an  ocular  micrometer,  and  with  a 
reliable  watch  held  close  to  the  ear  to  determine  the  time  that  it 
takes  a  blood  corpuscle  to  pass  across  the  field  of  the  microscope,  or 
the  interval  of  space  included  between  two  or  more  divisions  of  the 
micrometer.  Weber  ^  was  the  first,  we  believe,  to  make  use  of  this 
method.  It  was  in  this  way  that  he  determined  the  velocity  of 
the  blood  in  the  capillaries  of  the  tail  of  the  tadpole  to  be  about 
the  I  of  a  millimeter  in  a  second  (the  ^L  of  an  inch).  Valentin  ^ 
estimated  the  velocity  in  the  capillaries  of  the  web  of  the  frog's 
foot  was  about  the  same — in  round  mimbers,  about  2.5  cm.  (one 
inch)  in  a  minute.  According  to  Volkmann,'  the  velocity  of  the 
blood  in  the  capillaries  of  the  gills  of  the  tadpole  is  ^  of  a  mm.,  in 
the  tail  of  a  little  fish  -jL  of  a  mm.,  and  in  the  capillaries  of  the 
mesentery  of  a  dog,  -^^  of  a  millimeter  in  a  second — in  round 
numbers,  about  5  cm.  (2  inches)  in  a  minute. 

Yierordt  ^  makes  use  of  an  apparatus  for  measuring  the  velocity 
of  the  blood  in  the  capillaries,  which  is  based  upon  the  fact  that  a 
body  moving  at  a  certain  rate  and  illuminated  l)ut  for  a  very  short 
instant  appears  immovable.  By  placing  l)etween  the  mirror  of  the 
microscope  and  the  object-glass  a  movable  disk  pierced  with  holes 
through  which  the  light  is  transmitted,  the  object  viewed  is  only 
seen  wdien  one  of  the  holes  passes  across  the  axis  of  vision.  If  the 
length  of  time  the  blood  corpuscle  is  illuminated  be  known  and  the 
blood  corpuscle  appear  immovable,  then  the  rate  at  which  it  is 
moving  can  be  inferred.  This  physiologist  has  also  calculated  the 
velocity  of  the  blood  in  the  capillaries  of  the  human  retina.  As  is 
well  known,  the  eye  after  a  time  becomes  fatigued  when  exposed  to 
a  strong  white  light ;  if  the  eye  be  now  compressed,  one  sees  the 
image  of  a  current  in  the  form  of  a  network.  This  appears  to  be 
due  to  the  passage  of  the  blood  corpuscles  through  the  capillaries 
of  the  retina.  By  calculating  the  space  passed  over  in  a  given  time 
by  the  image,  X'ierordt ''  estimates  the  velocity  in  this  situation  to 
vary  between  the  ^\^  and  -^'^  of  a  millimeter  in  a  second.  Assum- 
ing that  the  rapidity  of  the  motion  of  the  white  corpuscles  can  be 
accepted  as  a  means  of  estimating  the  velocity  of  the  still  layer,  it 

iMullei-'s  Arohiv,  18:^8,  s.  467.  ^ i^liysiologie,  Band  i.,  s.  482. 

'' Die  Hjemodynamik,  s.  184.  'Op.  cit.,  s.  85.  =0p.  cit.,  s.  112. 


CONDITIOXS  IXFLUEXCIXG  CAPILLARY  CIRCULATIOX.  319 

can  be  stated  that  on  an  average  the  current  in  tlie  middle  of  the 
stream  moves  9  to  17  times  more  rapidly  than  that  at  the  sides.  In- 
asmuch as  the  amount  of  blood  required  by  the  tissues  varies  very 
much  from  time  to  time,  we  should  expect  to  find  also  great  varia- 
tions in  the  state  of  the  capillaries  in  this  respect.  Thus  at  one 
time  the  capillaries  supplying  a  tissue  may  be  entirely  empty  or 
almost  so,  at  another  gorged  Avith  blood.  It  becomes  important, 
therefore,  to  study  the  effects  of  such  agents  as  Anil  modify  the  cal- 
iber of  these  vessels  or  accelerate  or  retard  the  flow  of  the  blood 
through  them. 

Among  the  most  important  of  these  may  be  mentioned  the  effects 
of  cold,  heat,  electricity,  certain  local  irritants,  and  changes  in  the 
physical  and  chemical  composition  of  the  blood.  Thus  a  low  tem- 
perature diminishes  the  quantity  of  blood  in  the  capillaries  and 
retards  the  circulation,  while  a  high  temperature,  on  the  contrary, 
increases  the  amount  and  accelerates  its  velocity.  The  effect  of 
cold  upon  the  cajjillary  circulation  can  be  readily  demonstrated  by 
placing  a  piece  of  ice  upon  the  part  examined,  the  web  of  a  frog's 
foot,  for  example,  or  the  mesentery.  The  circulation  will  at  once 
be  observed  to  become  much  slower,  stagnate,  and  often  cease  en- 
tirely, the  capillaries  are  emptied  and  the  small  arterioles,  those 
carrying  usually  two  or  three  rows  of  blood  corpuscles,  will  now 
admit  only  one  row.  If  the  ice  be  removed,  the  circulation  will 
become  normal  again.  If  now  the  part  examined  be  covered  ^nth 
Avater,  say  at  a  temperature  of  40°  C.  (104°  F.)  or  placed  upon  the 
warm  stage  at  the  same  temperature,  the  quantity  of  blood  in  the 
capillaries  will  be  greatly  increased  and  the  velocity  so  much  accel- 
erated, that  it  is  with  difiiculty  the  corpuscles  can  be  distinguished. 
The  circulation  can  be  at  once  arrested  by  the  stimulus  of  electrical 
currents,  the  greatest  effect  being  obtained  when  individual  currents 
are  used.  The  effect  of  the  application  of  a  local  irritant,  like  a 
solution  of  common  salt,  when  applied  to  the  arterioles,  and  pos- 
sibly also  to  the  true  capillaries,  is  at  first  to  produce  a  constriction 
and  a  diminution  in  the  velocity  of  the  current.  The  constriction 
is,  however,  soon  followed  by  a  dilatation  and  the  velocity  is  accel- 
erated. This  condition,  however,  lasts  but  a  moment,  an  oscillation 
of  the  current  begins,  the  velocity  is  diminished  again,  stagnation 
follows,  the  capillary  becomes  gorged  Avith  blood,  the  Avhite  corpus- 
cles increase  in  number,  and  an  inflammatory  state  is  set  up.^ 

It  is  Avell  known  that  the  composition  of  a  fluid  will  influence 
the  rapidity  Avith  Avhich  it  flows  through  tubes  of  small  diameter. 
Thus,  solutions  of  potassium  iodide  and  bromide,  etc.,  flow  more 
rapidly  than  solutions  of  sodium,  calcium,  and  magnesium  chloride, 
of  sodium  phosphate  and  carbonate.  One  Avould  naturally  infer 
then  that  the  presence  or  absence  of  certain  salts  in  the  blood  Avould 

'Thompson  :  Lectures  on  Inflammation,  Edinburgh,  1813,  p.  51.  AVilson  Philip, 
Med.  Chir.  Trans.,  1823,  Vol.  xii.,  p.  401.  '  "Wharton  Jones,  Guy's  Hospital  Ke- 
ports,  1851,  Vol.  vii.,  •2d  Ser.,  p.  24. 


320  CIRCULATION  OF  THE  BLOOD. 

influence  the  rapidity  with  which  it  flows  in  the  capillaries.  Such 
was  experimentally  proven  to  be  the  case  by  Poisseuille/  the  rapidity 
of  the  circulation  in  the  horse  being  diminished  by  the  introduction 
into  the  blood  of  ammonium  acetate  and  sodium  chloride.  The 
influence  of  respiration  upon  the  capillary  circulation  will  be  con- 
sidered when  the  subject  of  asphyxia  is  taken  up  ;  while  the  effect 
of  the  vasomotor  nerves  in  modifying  the  calibre  of  the  arteries, 
and  thereby  affecting  the  quantity  of  the  blood  delivered  to  the 
capillaries,  will  be  deferred  until  we  study  the  nervous  system. 

In  speaking  of  the  effect  of  irritants  when  applied  to  the  capil- 
laries, it  was  just  stated  that  a  constriction  of  tlie  arterioles,  and 
probably  also  of  the  capillaries,  was  the  first  effect.  It  has  long 
been,  however,  a  subject  of  discussion  as  to  Avhether  the  capillaries 
are  really  contractile  in  the  same  sense  as  the  arteries.  It  is  pos- 
sible that  the  cause  of  the  difference  of  opinion  that  still  prevails 
in  reference  to  this  matter,  may  be  due  to  tlic  fact  of  one  physiol- 
ogist regarding  as  a  capillary  what  another  would  consider  an 
arteriole.  The  arterioles  are,  undoubtedly,  contractile,  their  walls 
containing  muscular  fibers,  and  since  the  layer  of  nucleated  cells  of 
which  the  capillary  wall  consists  is  continuous  with  the  contractile 
tunic  of  the  arteriole,  the  capillary  may  possess  true  contractility. 
This  seems  to  be  the  case,  at  least  in  the  capillaries  of  the  embryo, 
Avhere  the  nuclei  of  the  cells  stand  out  through  the  contraction  of 
the  capillaries.  On  the  other  hand,  the  diminution  in  the  calibre 
of  the  capillary,  often  supposed  to  be  an  evidence  of  its  contrac- 
tility, is  really  due  to  a  diminution  in  the  pressure  of  the  blood, 
the  wall  of  the  capillary  recoiling  upon  its  contents  through  its 
elasticity,  from  a  previous  state  of  distention. 

When  a  tissue  Avhich  has  been  thoroughly  injected,  is  seen  under 
the  microscope,  it  appears  as  if  it  consisted  almost  entirely  of  cap- 
illaries. It  will  be  readily  understood  that  any  change,  however 
slight,  in  the  calibre  of  the  capillaries  will  considerably  influence 
the  volume  of  the  organ  containing  them.  The  changes  in  the 
volume  of  an  organ  will  serve  then  as  a  measure  of  the  amount  of 
the  contraction  and  relaxation  of  its  capillaries.  Physiology  is  in- 
debted to  Mosso  more  particularly  for  the  employment  of  this 
method  as  a  means  of  determiniup;  chanj^es  in  the  volume  of  the 
capillaries. 

The  plethysmograph  (rrh^fioz,  bulk,  jiKufco,  to  write)  devised  by 
Mosso'  for  this  purpose  consists  essentially  of  a  large  glass  jar  (A, 
Fig.  157),  in  which  an  arm  is  enclosed,  for  example,  and  commu- 
nicating by  a  tube  with  a  small  glass  jar  (B),  which  is  suspended 
in  the  water  of  the  jar  C  by  means  of  the  pulley  and  weight.  The 
jar  A  enclosing  the  arm  is  filled  with  water.  With  each  increase 
in  the  volume  of  the  arm  the  water  is  driven  out  of  the  jar  A 
through  the  tube  into  the  jar  B,  sinking  it  deeper  in  the  water  of 

'Compter  Rendus  do  I'Acad.  des  Sciences,  1843,  Tome  xvi.,  p.  60. 
2Atti  Delia  Itealc,  Acad,  delle  scienze  di  Torino,  xi.,  1875,  p.  21. 


THE  PLETHYSMOGRAPH. 


321 


the  jar  C.  With  each  diminution  in  the  volume  of  the  arm,  the 
water  is  drawn  back  into  the  jar  A,  the  jar  rising  out  of  the  water 
in  C.  A  pen  adapted  to  the  weight,  records  graphically  upon  a 
cylinder  the  elevation  and  depression  of  the  jar  B — that  is,  the 
chano-es  in  the  volume  of  the  arm  examined.  From  the  results  of 
his  experiments,  Mosso  concludes  that  the  changes  in  the  volume 
of  an  organ  are  due  not  only  to  variations  in  the  blood  pressure, 
but  also  to  changes  in  the  calibre  of  the  vessels  as  well. 

Fig.  157. 


Plethj'siuograiih  of  !Mo; 


It  will  be  remembered,  that  in  speaking  of  the  pressure  of  the 
blood  in  the  arteries,  it  was  shown  that  the  pressure  of  a  fluid  grad- 
ually diminished  as  it  receded  from  the  source  of  the  supply  to  the 
outlet,  the  diminution  being  shown  by  the  different  heights  to  which 
the  fluid  rose  in  the  vertical  tubes.  Let  us  consider  now  what  takes 
place  when  the  fluid  flows  out  of  the  apparatus  (Fig.  158),  which  is 
almost  the  same  as  that  just  referred  to,  with  the  difference  only 
that  the  diameter  of  the  horizontal  tube  instead  of  being  the  same 
throughout  its  entire  length,  for  a  short  distance  in  the  middle  (r), 
is  very  much  diminished.  We  will  consider  this  part  as  represent- 
ing the  capillaries,  the  horizontal  portion  of  the  tube  on  the  left, 
the  arteries,  that  on  the  right,  the  veins.  It  will  be  observed,  as 
in  the  previous  experiment,  that  the  pressure  diminishes  very  grad- 
ually and  regularly  in  the  tubes  1,  2,  3,  corresponding  to  the  arterial 
system,  but  that  the  pressure  in  the  tubes  4,  5,  6,  representing  the 
veins,  is  very  low,  the  blood  passing  from  the  arteries  into  the 
capillaries  with  difficulty,  but  readily  passing  out  of  the  capillaries 
into  the  veins.  Indeed,  in  the  living  animal  at  times,  while  the 
21 


322 


CIRCULATION  OF  THE  BLOOD. 


arterial  pressure  amounts  to  150  to  200  mm.  of  mercury,  the  venous 
pressure  is  almost  nothing.  Such  a  difference  in  the  pressure  im- 
plies that  the  capillary  offers  great  obstacles  to  the  tlow  of  the 
arterial  blood.  If  the  experiment  be  modified  by  substituting  a 
somewhat  larger  tube  for  the  one  representing  the  capillaries,  the 
effect  of  this  dilatation  will  be  that  the  pressure  in  the  artery,  and 

Fig.  158. 


Apparatus  to  show  decrease  of  pressure  in  tubes  of  unequal  calibre.     (Maeey.) 


in  the  arterial  end  of  the  capillary,  is  diminished,  while  the  pressure 
in  the  venous  end  of  the  capillary,  and  in  the  veins,  is  increased. 
Any  influence,  therefore,  that  favors  the  retention  of  the  blood  in 
the  arteries,  will  diminish  the  quantity  of  blood  in  the  veins,  and 
vice  versa}  The  dotted  line  (Fig.  158)  represents  the  effect  of  sub- 
stituting the  large  tube. 

It  is  an  everyday  observation  that  when  one  compresses  the  skin 
with  the  finger,  the  part  becomes  pale,  regaining  its  natural  color, 
however,  as  soon  as  the  compression  ceases,  the  blood  returning 
then  to  the  capillaries.  In  order  that  the  blood  should  be  driven 
out  of  the  vessels  of  the  skin,  the  external  force  must  be  superior  to 
the  internal  one,  or  the  pressure  of  the  blood.  If  we  know  the 
amount  of  compression  used,  then  we  can  estimate  approximately 
the  internal  force,  or  the  pressure  of  the  blood  in  the  capillaries. 

Upon  this  principle  Kries  ^  determined  the  pressure  of  the  capil- 
laries in  a  given  area  of  the  hand  to  amount  when  raised  to  24  mm. 
mercury  and  lowered  to  54  mm,  mercury,  the  instrument  (Fig.  159) 
made  use  of  consisting  of  a  glass  plate  to  which  m  as  attached  a  scale 
pan  on  which  weights  were  placed  until  the  pressure  exerted  by  the 
plate  upon  the  skin  made  it  pale. 

While  there  can  be  no  doubt  that  the  heart  is  the  main  cause  of 
the  circulation,  there  are  also  good  reasons  for  believing  that  there 
are  other  conditions  than  the  contractile  force  of  the  heart  and  the 


'Marey,  op.  cit.,  p.  357. 
^N.  V.  Kries,  Beriflite  iibcr  Die  Verbandl. 
"Wissen.  zu  Leipzig,  1875,  s.  149. 


Der  Kon.    Sachsis.   Gesells.   Der 


CAPILLARY  FORCE. 


ooo 


Fig 


V.  Kries's  ap- 
paratus for  capil- 
lary pressure.  A. 
Square  of  glass. 
(Laxdois.) 


arteries  which  influence  the  flow  of  the  blood  through  the  capil- 
laries. As  is  well  known,  in  plants,  and  in  many  of  the  lower 
animals,  the  nutrient  fluid  is  carried  to  all  parts  of  the  system  in 
the  absence  of  a  heart ;  analogy  \yould  lead  us  to  expect,  therefore, 
that  there  must  exist  in  the  higher  animals  a  similar 
force,  a  capillaiy  power,  so  to  speak,  which  may  be 
masked  by  the  influence  of  a  centralized  powerful 
heart.  This  so-called  capillary  force  appears  to  be 
inseparably  connected  with  the  nutritive  and  secre- 
tory processes,  since  what  increases  or  diminishes  the 
one  influences  in  the  same  way  the  other.  The  idea 
of  such  a  force  is  not  a  new  one,  it  is  embodied  in  an 
ancient  aphorism  of  TJbi  stimulus  ib'i  fluxus.  That 
some  such  power  exists  in  the  capillaries  of  the  higher 
animals,  independent  of  the  action  of  the  heart,  is 
shown  by  the  fact  that  the  blood  Avill  still  continue 
to  flow  in  the  capillaries  after  the  heart  has  ceased 
beating,  while,  on  the  other  hand,  the  heart  may  still 
be  acting,  and  yet  the  circulation  will  entirely  cease 
in  the  capillaries  of  certain  parts.  Local  variations 
in  the  volume  of  the  blood  flo-snng  through  the  capil- 
laries, the  reversal  of  the  current  in  the  vessels, 
changes  in  their  diameter,  so  often  observed  in  the 
healthy  living;  animal,  cannot  be  attributed  to  the 
action  of  the  heart,  but  are  evidently  due  to  an  influence  engen- 
dered in  the  walls  of  the  capillaries  themselves,  or  in  the  sur- 
rounding tissues. 

]Many  pathological  facts  might  be  mentioned  as  illustrations  of 
such  local  variations.  Thus,  in  cases  of  spontaneous  gangrene  of 
the  lower  extremities,  although  the  heart  may  be  beating,  and  the 
arteries  and  the  capillaries  entirely  pervious,  nevertheless  the  blood 
will  not  flow  through  the  capillaries,  the  stopping  of  the  circulation 
being  due  to  a  difference  in  the  capillaries  themselves,  and  the  sur- 
rounding tissues.  Again,  it  has  often  been  demonstrated,  at  least 
in  cold-blooded  animals,  that  the  flow  of  blood  through  the  capil- 
laries will  continue  even  after  the  heart  has  been  completely  ex- 
cised. While  this  cannot  be  shown  experimentally  upon  a  hot- 
blooded  animal,  the  shock  experienced  being  so  great  from  so  severe 
an  operation,  nevertheless  nature  often  does  in  a  gradual  way  what 
we  cannot  show  by  experiment.  Thus,  as  is  well  known,  after  the 
general  death  of  the  body,  urine  has  floAved  from  the  ureters,  sweat 
exuded  from  the  skin,  and  glands  have  secreted.  Such  phenomena 
can  only  be  explained  on  the  supposition  that  the  blood  has  con- 
tinued to  flow  through  the  capillaries  after  the  heart  has  ceased  to 
beat.  It  is  well  known,  since  the  observations  of  Dr.  Bennett 
Dowler  ^  upon  the  bodies  of  individuals  who  have  died  of  yelloAy 

^Researches  on  the  CapiUarv  C'iivuhition,  New  Orleans  Med.  and  Surg.  Journal, 
1849. 


324  CIRCULATION  OF  THE  BLOOD. 

fever,  that  the  veins  often  become  so  distended  with  blood  within 
a  few  minutes  after  death  that  when  opened  the  blood  will  spurt 
from  them  a  foot  or  more.  The  tonicity  of  the  arteries  can  hardly 
be  supposed  to  account  for  this  venous  jet,  or  for  the  empty  condi- 
tion in  which  the  arteries  are  almost  always  found  after  death — but 
to  some  additional  force  in  the  capillaries  themselves.  Further, 
we  shall  see,  when  we  come  to  study  the  development  of  the  circu- 
lation in  the  embryo,  that  the  blood  begins  to  move  first  in  the  area 
vasculosa,  that  is  toward  the  heart,  not  from  it,  and  that  the  heart 
itself  consists  of  cells  so  loosely  attached  together  that  it  can  be 
scarcely  supposed  to  contract  with  force  enough  to  account  for  the 
primitive  circulation.  Indeed,  in  the  case  of  twins,  it  has  been 
noticed  that  the  heart  in  one  of  the  two  has  even  never  been  de- 
veloped during  the  whole  period  of  embryonic  life,  and  yet  the 
greater  part  of  the  organs  were  well  formed.  It  might  be  supposed 
that  the  circulation  in  the  twin  in  which  the  heart  Avas  absent  was 
maintained  by  the  heart  of  the  one  in  which  it  was  present,  the 
blood  from  the  one  twin  passing  to  the  other  through  the  vessels  of 
the  placentas,  Avhich  wei'e  more  or  less  in  contact.  This  was 
shown  by  Dr.  Houston  ^  to  be  impossible,  at  least  in  the  case  re- 
ported by  him. 

In  this  connection  the  researches  of  Hyrtl "  are  interesting,  that 
anatomist  having  shown  that  the  placental  vessels  do  not  communi- 
cate in  those  cases  where  the  twins  are  of  the  opposite  sex.  The 
facts  of  comparative  anatomy,  experiment,  pathology,  embryology, 
all  harmonize  in  showing  that  there  exists  in  the  capillaries  some 
force  independent  of  the  heart's  action,  which  aids  the  flow  of  the 
blood  through  them.  It  has  often  been  supposed  that  the  contrac- 
tility of  the  capillaries  aids  the  flow  of  blood  through  them.  Ad- 
mitting that  the  capillaries  are  contractile,  this  force  could  only  be 
exerted  in  a  rhythmical  manner  by  alternate  contractions  and  dila- 
tations, a  kind  of  peristalsis  ;  but  no  such  movement  is  observed, 
the  blood  flowing  through  the  capillaries  as  if  they  were  glass  tubes. 
Further,  it  can  be  experimentally  demonstrated  that  a  diminution 
in  the  diameter  of  the  capillaries,  whether  it  be  due  to  true  con- 
tractility, or  simply  to  elasticity,  retards  the  flow  of  the  blood,  the 
blood  pressure  rising.  The  capillary  force  cannot,  therefore,  be  of 
such  a  kind. 

On  the  other  hand,  the  experiments  of  Weber  "^  and  Wharton 
Jones  *  have  shown  that  electrical  and  chemical  stimuli  modify  the 
capillary  circulation,  retarding  the  flow  of  the  blood,  and  even  pro- 
ducing complete  stagnation,  and  yet  no  alterations  in  the  diameter 
of  the  capillaries  are  observed,  the  change  being  evidently  of  a 
physico-chemical  nature.  Such  facts,  as  Mcll  as  those  already  re- 
ferred to,  show  that  there  exists  some  mutual  relation  between  the 

'Dublin  Mediful  Journal,  1S37. 

'^Die  Blutegefiisse  der  Monschlichen  Nachgeburt.     Wion,  1S70. 

3  Mailer's  Archiv,  1852,  s.  ;i61.  ^Op.  cit. 


CAPILLARY  FORCE.  o25 

blood,  on  the  one  hand,  and  the  walls  of  the  capillaries  and  the 
surrounding  tissues,  on  the  other. 

It  appears,  then,  that  while  the  heart  forces  the  blood  into  and 
through  the  capillaries,  the  rate  at  which  it  flows  through  these 
vessels  will  depend  upon  the  general  nutritive  condition  of  the 
parts  supplied  by  the  capillaries,  and  that  this  capillary  force  can, 
under  certain  conditions,  maintain  the  circulation  independently  of 
the  heart. 

Prof.  Draper  ^  suggests  that  the  capillary  force  just  referred  to, 
may  be  of  the  same  character  as  the  force  of  capillary  attraction, 
illustrating  this  view  by  the  following  experiment :  "  If  two  liquids 
communicating  with  one  another  in  a  capillary  tube,  or  in  a  porous 
structure,  have  for  that  tube  or  structure  different  chemical  affini- 
ties, movements  will  ensue,  that  liquid  which  has  the  most  energetic 
affinity  will  move  with  the  greatest  velocity,  and  may  even  drive 
the  other  liquid  before  it."  Thus,  it  will  be  noticed  that  if  a  capil- 
larv  tube,  containine;  "-um,  be  immersed  in  a  vessel  filled  with  water, 
that  the  gum  will  rise  in  the  tube,  being  displaced  by  the  water, 
the  water  having  a  greater  affinity  for  the  walls  of  the  tube  than 
the  gum.  These  experimental  conditions  are  realized  in  the  living 
body,  the  fresh  arterial  blood,  on  account  of  its  oxygen  and  other 
nutritive  elements,  having  a  greater  affinitv  for  the  tissues  than  the 
effete  venous  blood,  hence  the  arterial  blood  will  push  forward  the 
venous  blood  from  the  systemic  capillaries  toward  the  veins.  On 
the  other  hand,  in  the  pulmonary  capillaries  just  the  reverse  ob- 
tains, the  venous  blood  drives  forward  the  arterial,  since  the  former 
has  a  greater  affinity  for  the  inspired  oxygen  than  the  latter,  in 
which  the  blood  is  already  oxygenated.  According  to  the  same 
physical  principle,  the  portal  blood,  containing  the  same  elements 
out  of  which  the  bile  is  elaborated,  having  a  greater  attraction  for 
the  hepatic  cells  than  the  blood  of  the  hepatic  vein,  the  latter  will 
be  driven  out  of  the  hepatic  capillaries  into  the  hepatic  veins.  In- 
deed, there  must  be  a  continual  movement  going  on  in  every  part 
of  the  economy,  each  cell  having  a  greater  attraction  for  the  blood 
containing  its  nourishment  than  for  that  blood  which  has  nourished 
it.  Such  a  movement  undoubtedly  supplements  the  force  of  the 
heart. 

The  consideration  of  the  influence  of  the  nervous  system  upon 
the  caiiillarv  circulation,  whether  as  modifvino-  throuorh  the  vasomo- 
tor  nerves  the  calibre  of  the  arteries,  or  acting  directly  by  chang- 
ing the  nutrition  of  the  parts,  will  be  deferred  for  the  present.  In 
concluding  our  account  of  the  circulation  of  the  blood  it  remains 
for  us  now  to  describe  the  flow  of  the  blood  from  the  capillaries 
back  to  the  heart  through  the  veins. 

1  Human  Physiology,  1878,  p.  131. 


CHAPTER  XIX. 

CIECULATION  OF  THE   BLOOD.— {Continued.) 

THE  VEINS. 

Ix  observing  the  flow  of  the  blood  through  the  capillaries,  it 
will  be  seen  that  these  vessels  gradually  pass  into  larger  ones,  the 
venous  radicles,  which  in  turn  transmit  the  blood  to  the  veins,  the 
latter  gradually  uniting  form  two  large  trunks,  the  venae  cavse, 
which,  together  with  the  coronary  and  cardiac  veins  transmit  the 
blood  to  the  right  auricle  of  the  heart  while  the  pulmonary  veins 
return  it  to  the  left. 

The  venous  system  may  be  regarded  as  consisting  of  two  sets  of 
veins,  a  superficial  set  returning  the  blood  from  the  skin  and  sur- 
face generally,  and  a  deep  set  which  accompanies  the  arteries. 

The  veins  diifcr  in  their  structure  from  the  arteries  rather  in  de- 
gree than  in  kind,  consisting  essentially  like  the  latter  of  three 
coats,  an  internal  endothelial,  a  middle  elastic  muscular,  and  an  ex- 
ternal fibrous.  The  internal  coat,  consisting  of  subepithelial  and 
elastic  layers,  is  a  continuation  of  the  capillary,  which  we  have  seen 
is  a  prolongation  of  the  internal  coat  of  the  artery.  Indeed,  it  is 
practically  impossible  to  say  exactly  where  the  artery  ends  and  the 
capillary  begins,  or  where  the  capillary  ends  and  the  vein  begins, 
the  transition  from  the  one  set  of  vessels  to  the  other  is  so  gradual. 

The  middle  coat,  containing  the  vasa  vasorum,  consists  princi- 
pally of  fibrous  tissue  disposed  in  a  longitudinal  direction  with 
some  elastic  fibers,  and  of  a  circular  coat  of  elastic  and  muscular 
fibers  mingled  with  some  fibrous  tissue.  The  external  coat,  like 
that  of  the  artery,  consists  of  white  fibrous  tissue,  and  in  the  larg- 
est veins,  particularly  in  those  of  the  abdominal  cavity,  there  are  a 
few  unstriped  muscular  fibers  arranged  in  a  longitudinal  direction. 
In  the  veins  near  the  heart  a  few  striated  muscular  fibers  are  pres- 
ent, derived  principally  from  those  of  the  auricle.  These  fibers 
are  particularly  well  developed  in  the  turtle.  In  certain  situations 
in  the  cerebral  sinuses,  etc.,  the  veins  consist  of  little  more  than 
the  internal  coat  with  a  few  longitudinal  fibers.  Generally  the 
veins  adhere  much  more  closely  to  the  surrounding  tissues  than  the 
arteries.  Were  such  not  the  case,  in  many  instances  the  vessels 
would  collapse,  the  walls  not  being  strong  enough  to  resist  external 
pressure.  It  may  be  also  mentioned  that  it  is  through  the  intimate 
adhesion  of  the  wall  of  the  superior  vena  cava,  jugular,  subclavian, 
etc.,  to  the  surrounding  aponeurotic  layers  that  these  vessels  are 
kept  open  during  inspiration.^ 

Many  of  the   larger  veins  are  provided  with  valves  resembling 

1  Berard,  Physiologic,  Tome  quatrieme,  p.  9. 


VALVES  OF  VEINS. 


327 


Fig.  160. 


Diagram  showing  valves  of  veins.  A. 
Part  of  a  vein  laid  open  and  spread  out, 
witli  two  pairs  of  valves.  B.  Longitudi- 
nal section  of  a  vein,  showing  the  apposi- 
tion of  the  edges  of  the  valves  in  their 
closed  state.  C.  Portion  of  a  distended 
vein,  exhibiting  a  swelling  in  the  situation 
of  a  pair  of  valves.     (Quaix.) 


those  of  the  aorta  and  pulmonary  artery  (Fig.  160).  They  are 
usually  found  in  pairs,  and  consist  of  cresceutic  semilunar  doublings 
or  folds  of  the  intei'nal  coat  or  lining 
membrane  of  the  vein  strengthened 
with  some  included  fibro-elastic  tis- 
sue. These  valves  are  usually  situ- 
ated opposite  each  other  and  project 
obliquely  into  the  cavity  of  the  vein 
or  in  the  direction  of  the  current. 
The  convex  portion  of  each  valve  is 
attached  to  the  side  of  the  vein,  the 
concave  edge  is  free  and  points  to- 
ward the  heart.  Behind  each  valve 
the  vein  is  dilated  into  a  sort  of 
pouch  or  sinus  (Fig.  160)  which 
prevents  the  valves  adhering  to  the 
sides  of  the  vein  as  the  blood  passes 
between  them  toward  the  heart. 
When,  however,  the  blood  passes 
backward  toward  the  periphery,  as 
we  shall  see  it  does  under  certain  circumstances,  it  enters  the  sinus 
and  getting  behind  the  valves  presses  them  toward  each  other  and 
together  and  so  prevents  any  further  reflux. 

The  valves  are  so  disposed,  therefore,  that  while  they  ofibr  no 
obstacle  to  the  flow  of  the  blood  toward  the  heart,  they  efl"ectually 
prevent  to  any  extent  motion  in  the  reverse  direction. 

The  valves  are  most  abundant  in  the  upper  and  lower  extremities  ; 
the  significance  of  this  we  shall  see  presently.  The  importance  of 
the  valves  in  the  veins,  though  great  physiologically,  must  not  be 
exaggerated,  since  many  veins  have  no  valves.  Thus  in  man  at 
least,  however  it  may  be  in  other  mammals,  there  are  no  valves  in 
the  vense  cav?e,  in  the  innominate,  pulmonary,  portal,  hepatic,  renal, 
uterine,  ovarian,  spinal,  and  iliac  veins.  Further,  there  are  very 
few  valves  in  the  veins  of  birds,  reptiles,  and  fishes,  and  with  the 
exception  of  that  in  the  aorta,  so-called,  of  the  eolis,  a  small  nudi- 
branchiate  moUusk,  there  are  none  in  the  veins  of  the  invertebrata. 
It  is  evident,  therefore,  that  the  valves  are  not  indispensable  in  the 
maintenance  of  the  circulation. 

The  veins  possess  a  considerable  amount  of  elasticity.  This  is 
shown  by  the  jet  of  blood  which  follows  the  puncture  of  a  distended 
vein  made  in  a  portion  of  the  vessel  between  two  ligatures.  The 
veins  through  their  unstriped  muscular  fibers  are  also  contractile, 
their  caliber  being  slowly  and  gradually  diminished  through  the 
application  of  electrical  and  other  stimuli.  The  contractility  of 
the  veins  can  be  more  readilv  demonstrated  in  the  froa:  and  other 
batrachians  than  in  mammals.  The  veins,  like  the  arteries,  are 
supplied  and  influenced  by  the  vasomotor  nerves,  though  not  to  the 
same   extent.     The   veins,   though   much   thinner  and  apparently 


328  CIRCULATION  OF  THE  BLOOD. 

weaker,  will  usually  resist  a  greater  pressure  than  the  arteries. 
Thus  it  was  shown  in  the  last  century  by  Wintringham  ^  that  a 
greater  force  was  required  to  rupture  the  vena  cava  and  portal  vein, 
for  example,  than  the  aorta.  The  method  by  which  this  was 
determined  is  as  follows  :  An  iron  siphon  containing  a  sufficient 
quantity  of  mercury,  to  which  was  screwed  a  glass  gauge,  and 
which  communicated  freely  with  a  condensing  syringe,  was  adapted 
to  the  artery  or  vein  whose  strength  was  to  be  tested.  When  the 
air  in  the  sealed  top  of  the  gauge  was  compressed  with  a  pressure 
equal  to  158  pounds,  the  aorta  in  the  ram,  for  example,  burst,  the 
vena  cava  of  the  same  animal,  however,  resisting  until  the  pressure 
amounted  to  17(3  pounds.  The  strength  of  the  portal  vein  was 
even  greater  than  that  of  the  vena  cava.  Wintringham,  however, 
notices  that  the  arteries  of  glands  are  stronger  than  the  correspond- 
ing veins.  Thus  the  splenic  vein  burst  under  a  pressure  of  about 
34  pounds,  the  artery  supporting  a  pressure  of  150  pounds.  These 
experiments  of  AYintringham  were  very  numerous  and  extended, 
being  made  upon  the  vessels  of  men,  pigs,  sheep,  dogs,  etc.,  and  in 
the  main  have  been  confirmed  by  the  later  ones  of  Davy.^  The 
significance  of  the  greater  strength  of  the  veins,  as  compared  with 
that  of  the  arteries,  usually  observed,  becomes  at  once  apparent 
when  we  reflect  upon  the  different  amounts  of  pressure  to  which 
the  two  sets  of  vessels  are  subjected.  AVe  have  seen  that  the  pres- 
sure diminishes  gradually  in  the  arterial  system,  that  the  force  of 
the  heart  is  practically  constant,  and  that  the  arterial  pressure  is 
being  constantly  relieved  by  the  flow  into  the  capillaries.  On  the 
other  hand,  the  pressure  into  the  veins  varies  according  to  the 
amount  of  blood  delivered  to  them  by  the  capillaries,  regurgitation 
to  any  extent  is  impossible  through  the  presence  of  the  valves, 
while  the  heart  offers  a  very  restricted  outlet.  Thus  portions  of  the 
venous  system,  from  pressure  in  the  veins,  absorption  of  fluid,  ac- 
cumulation through  gravity,  etc.,  are  subject  to  very  great  varia- 
tions in  pressure  which  the  tenacity  of  their  walls  usually  enables 
them  to  resist  without  injury.  The  ill  effects  of  over-distention 
are,  nevertheless,  seen  only  too  frequently  in  varicose  veins,  etc. 
The  capacity  of  the  venous  system  is  much  greater  than  that  of  the 
arterial — according  to  Haller,^  in  the  ratio  of  2.2  to  1.  Usually  a 
vein  when  distended  contains  more  blood  than  the  adjacent  artery ; 
the  capacity  of  the  pulmonary  arteries,  however,  is  about  equal  to 
that  of  the  corresponding  veins.  Many  arteries,  like  those  of  the 
extremities,  are  accompanied  by  more  than  one  vein,  and  some,  like 
the  brachial  and  spermatic,  have  more  than  two  ;  the  superficial  veins, 
further,  have  no  corresponding  arteries.  Nevertheless,  any  estimate 
of  the  capacity  of  the  venous  system  as  compared  with  that  of  the 
arterial  can  be  only  approximate,  since  the  quantity  of  blood  flowing 

*  An  Experimental  Inquirv  on  some  parts  of  the  animal  structure,  pp.  49,  73,  96, 
159,  179,  212.     London,  1740. 

^  Ke.searolies,  Physiological  and  Anatomical,  Vol.  i.,  p.  441. 
3  Elementa  Physiologise,  Tomus  1.,  p.  1315. 


PRESSURE  OF  BLOOD  IN  VEINS.  329 

through  the  veins  must  vary  according  to  the  pressure  and  velocity 
of  the  flow,  the  amount  passing  through  the  capillaries,  the  state  of 
the  digestion  and  respiration,  etc.  Indeed,  the  most  striking  char- 
acteristic of  the  venous  system  is  the  variability  of  the  amount  of 
blood  it  contains. 

One  of  the  most  important  features  of  the  venous  system  is  the 
numerous  anastomoses  between  the  veins,  which,  it  will  be  remem- 
bered, are  exceptional  in  the  case  of  the  arteries.  There  are  always 
numerous  such  channels  by  which  the  blood  finds  a  ready  route 
back  to  the  heart,  so  that,  if  the  flow  be  obstructed  in  one  vein,  an 
equally  easy  way  is  offered  by  another.  The  anastomoses  between 
the  veins  are  very  important,  enabling  these  vessels  to  accommodate 
themselves  to  the  great  variation  in  the  quantity  of  blood  flowing 
into  them  to  which  they  are  subject.  The  anastomoses,  together 
with  the  valves,  serve  to  provide  against  any  obstacle  to  the  freedom 
of  the  capillary  flow,  the  importance  of  which  we  have  already  seen. 
In  addition  to  the  anastomotic  branches  usually  described  may  be 
mentioned  others  less  well  known,  such  as  those  connecting  the 
vena  cava  and  portal,  the  oesophageal  and  hemorrhoidal,  the  dia- 
phragmatic connecting  the  hepatic  circulation  with  the  vena  cava. 
The  importance  of  these  anastomotic  vessels  becomes  evident  when 
the  veins  usually  returning  the  blood  to  the  heart  are  obstructed. 
Under  such  circumstances,  they  become  greatly  enlarged,  as  is  well 
known  to  the  pathological  anatomist. 

When  it  is  remembered  that  the  arterial  pressure  gradually 
diminishes  as  we  recede  from  the  heart  to  the  periphery,  it  might 
be  expected  by  the  time  that  the  blood  has  passed  through  the 
capillaries  and  reached  the  veins,  that  it  would  exert  but  little  pres- 
sure in  the  latter.  This  has  been  experimentally  shown  to  be  the 
case.  Thus,  according  to  Yolkmann  ^  while  the  pressure  of  the 
blood  in  the  metatarsal  artery  of  the  calf  was  146  mm.  of  mercury 
(5.8  inches)  that  in  the  metatarsal  vein  Avas  only  27.5  mm. 
(1.1  inch).  It  has  also  been  shown  that  as  we  return  from  the 
capillaries  to  the  heart  the  pressure  in  the  veins  gradually  falls,  the 
pressure  in  the  femoral  vein  being  11.4  mm,,  in  the  brachial  4  mm., 
in  the  facial  3  mm.,  and  in  the  larger  venous  trunks  near  the  heart 
negative.  That  the  pressure  in  the  veins  near  the  heart  may  be  nega- 
tive, that  is  less  than  that  of  the  atmosphere,  is  well  shown  by  the 
experiments  of  Barry.-  This  consists  in  introducing  into  the  jugu- 
lar vein  of  a  horse  or  dog  a  bent  tube,  of  which  the  opposite  end  is 
immersed  in  a  vase  of  colored  liquor.  With  each  inspiration  the 
liquid  rises  in  the  tube,  falling  again  with  each  expiration.  While 
the  pressure  is  diminished  in  the  jugular  and  hepatic  veins  during 
inspiration,  on  the  other  hand,  in  the  remaining  abdominal  veins  it 
is  increased ;  the  latter  being   compressed  by  the   viscera  through 

1  Die  Hsemod%T3amik,  s.  173. 

^Eeclierches  experimentales  sur  les  causes  du  mouvement  du  sang  dans  les  veines. 
Paris,  lb25,  p.  17. 


330 


CIRCULATION  OF  THE  BLOOD. 


the  falling  of  the  diaphragm,  an  obstacle  is  oiFered  to  the  flow  of 
the  blood,  and  the  pressure  rises.  The  lowering  of  the  venous 
pressure  during  inspiration  is  shown  graphically  by  Fig.    161,  in 


Pr.  V.  n.    Trace  of  blood  pressure  in  hepatic  veins.    R.  Trace  of  respiration,  takcu  with  pneu- 
mograph.    (Maeey.) 

which  the  depression  of  the  upper  trace  Pr,  V.  H,  representing  the 
blood  pressure,  coincides  with  that  of  the  lower  trace  R,  represent- 
ing the  respiratory  movement.  The  increase  in  the  pressure  in  the 
abdominal  veins  during  inspiration  is  well  shown  by  Fig.  162,  in 

Fig.  162. 


Pr.VP. 


Pr.  V.  P.    Trace  of  blood  pressure  in  portal  vein.    P..  Trace  of  respiration,  taken  with  pneumo- 
graph.    (Marey.) 

which  the  depression  in  the  lower  trace  R,  due  to  inspiration,  coin- 
cides with  the  elevation  of  the  upper  trace  Pr.  Y.  P.,  due  to  the 
increase  in  the  blood  pressure.  On  the  other  hand,  during  expira- 
tion, the  pressure  in  the  abdominal  veins  is  diminished,  since  the 
vi.scera  no  longer  compress  these  vessels,  the  diaphragm  being 
elevated.  If,  however,  the  expiration  be  violent,  then  the  contrac- 
tion of  the  abdominal  walls  compresses  the  viscera  and  the  veins 
and  increases  the  pressure. 

The  weight  of  the  blood  inHucnces  the  pressure  in  the  veins. 
Thus,  the  blood  flows  more  readily  to  the  heart  in  the  veins  of  the 
upper  extremity  when  the  limb  is  elevated  than  wlien  hanging 
down.  The  varicose  condition  often  observed  in  the  veins  of  the 
lower  extremities  illustrates  the  effect  of  the  venous  pressure  due  to 
the  weight  of  the  blood.  While  the  pressure  in  the  veins  is  ordi- 
narily very  slight,  at  times  it  is  so  much  increased  as  to  give  rise  to 
a  pulsation — the  venous  pulse.  This  may  be  due  to  an  obstruction 
in  the  veins,  or  to  an  increase  in  the  quantity  of  blood  flowing  in 
these  vessels.  Thus,  if  all  the  venous  blood  in  a  part  be  forced  to 
return  to  the  heart  by  a  single  vein,  as  can  be  effected  by  ligating 
all  the  adjacent  veins,  as  in  the  experiment  of  Poisseuille,^  the  pres- 

i_Magendie,  Lefons  sur  los  plicnomem-.s  physique  do  la  vie,  Tome  iii.,  p.  181. 
Paris,  18157. 


REGURGITANT  VENOUS  PULSE.  331 

sure  on  the  vein  will  be  so  much  increased  as  to  equal  that  of  an 
artery  of  like  size,  the  force  of  the  heart  being  exerted  ujwn  the 
blood  of  a  single  vein,  and  therefore  concentrated  instead  of  as  or- 
dinarily upon  several  and,  therefore,  diffused  and  dissipated.  Dur- 
ing the  ventricular  systole,  and,  therefore,  when  the  tricuspid  valve 
is  closed,  the  flow  of  the  blood  through  the  auricle  into  the  ventricle 
is,  for  the  instant,  stopped,  the  pressure  in  the  auricle  and  vena 
cava  is  then  momentarily  increased.  If,  however,  the  beating  of 
the  heart  cease  in  diastole,  as  in  the  case  after  excitation  of  the 
pneumogastric  nerve,  the  blood  will  flow  into  the  ventricle,  which, 
being  filled,  receives  tlien  no  more  blood  from  the  auricle  ;  the 
blood  continuing  to  flow  will  fill  the  auricle  and  the  vena  cava  un- 
til  these  parts,  being  distended,  the  pressure  will  be  very  much  in- 
creased. This  can  be  experimentally  shown  in  the  frog  by  means 
of  the  double  myograph.     By  comparing  the  traces  (Fig.  163)  of 

Fig.  168. 


O.  Trace  of  auricle.    V.  Trace  of  ventricle.    S' O.  Systole  of  auricle.    £■.  Stimulation  of  the 
pneumogastric  nerve.     (Maeey.) 

the  auricle  and  ventricle,  taken  simultaneously,  it  will  be  observed 
that  the  pressure  in  the  auricle  is  increased  during  the  arrest  in 
diastole  of  the  heart's  action  through  stimulation  of  the  pneumo- 
gastric nerve. 

There  is  also  observed  at  times  in  certain  veins,  the  external  jug- 
ular, for  example,  a  regurgitant  venous  pulse.  This  is  due  to  a  re- 
flux of  blood  from  the  right  side  of  the  heart,  and  is  synchronous 
with  the  movement  of  expiration,  there  being  no  obstacle  at  the 
mouth  of  the  vein  to  the  return  of  the  blood  if  the  expiratory 
movement  be  exaggerated.  It  is  usually  evidence  of  insufficiency 
of  the  tricuspid  valve  or  some  other  pathological  condition.  We 
have  seen  that  the  veins  are  both  larger  and  more  numerous  than 
the  arteries,  and  as  the  volume  of  blood  which  passes  in  a  given 
moment  through  any  part  of  the  vascular  system  is  the  same,  it 
follows  that  the  blood  ought  to  flow  more  slowly  through  the  veins 
than  the  arteries.  If  the  venous  system  be  considered  twice  as  ca- 
pacious as  the  arterial,  then  the  blood  should  flow  half  as  slowly 
through  the  veins  as  the  arteries.  Experiment  is  in  harmony  with 
theoretical  considerations,  it  having  been  shown  by  Volkmann  ^  that 
the  blood  flows  in  the  jugular  vein  of  the  dog  at  the  rate  of  225 
mm.  (9  inches)  in  a  second,  that  of  the  carotid  artery  in  the  same 

'Op.  cit,  s.  195. 


332  CIRCULATION  OF  THE  BLOOD. 

animal  being  329  mm.  (13  inches).  The  velocity  of  the  blood  cur- 
rent diiFers,  therefore,  from  that  of  the  pressure,  since  the  velocity 
lost  in  the  capillaries  is  regained  somewhat  in  the  veins,  whereas 
the  pressure  falls  continuously,  the  pressure  of  the  capillaries  being 
less  than  that  of  the  arteries,  but  greater  than  that  in  the  veins. 
The  conditions  that  influence  the  rapidity  of  the  flow  in  the  veins, 
however,  vary,  so  that  it  is  impossible  to  fix  upon  any  average  rate. 
There  can  be  no  doubt  that  the  flow  of  the  blood  in  the  veins  is 
essentially  due  to  the  contractile  force  of  the  heart.  Thus,  accord- 
ing to  Sharpey,^  the  hepatic  veins  can  be  filled  with  an  injection  of 
defibrinated  blood  thrown  into  the  aorta  under  a  pressure  of  3.6 
cm.  (1.4  in.)  of  mercury,  which  is  only  about  half  that  of  the  nor- 
mal arterial  pressure.  The  experiment  of  Magendie,"  in  which  the 
femoral  vein  was  iigated  and  opened,  the  blood  jetting  forth,  the 
jet  and  flow  gradually  ceasing  with  compression  of  the  femoral  ar- 
tery, proved  the  competency  of  the  heart  to  force  the  blood  through 
the  capillaries  into  the  veins,  the  force  of  the  artery  causing  the  jet 
from  the  vein  being,  as  we  have  seen,  only  the  reaction  from  its  pre- 
vious distention,  due  to  the  preceding  ventricular  systole.  While 
the  heart  is  the  main  cause  of  the  venous  flow,  as  in  the  case  of 
the  capillaries,  there  are  other  causes  which  assist  in  promoting  this 
movement.  Thus,  muscular  contraction,  by  compressing  the  veins, 
forces  the  blood  in  these  vessels  toward  the  heart,  regurgitation  be- 
ing impossible  through  the  action  of  the  valves.  Hence,  the  sig- 
nificance of  the  fact  of  valves  being  so  much  more  numerous  in  the 
veins  of  the  nuiscles  than  in  the  cavities  of  the  body,  the  veins  in 
the  latter  situation  not  being  subjected  to  the  same  kind  of  com- 
pression as  those  between  and  within  the  muscles.  It  must  be 
mentioned,  however,  in  order  that  too  much  stress  be  not  laid  upon 
this  connection  bet^veen  muscular  action  and  the  presence  or  absence 
of  valves,  tliat  in  some  cases,  as  in  the  portal  vein  of  the  horse  and 
in  the  mesenteric  veins  of  the  reindeer,  for  example,  valves  do  ex- 
ist. In  order  that  muscular  contraction  shall  assist  the  flow  of  the 
blood  through  the  veins,  not  only  must  valves  exist  to  prevent  re- 
gurgitation, but  the  contractions  of  the  muscles  must  be  intermit- 
tent, as  during  the  period  of  repose  after  a  contraction  the  vein  has 
time  to  fill  up  again  with  blood  that  will  be  forced  forward  with  the 
following  contraction.  This  alternate  filling  up  and  emptying  of 
the  muscular  veins  is  also  of  advantage  from  a  nutritive  point  of 
view,  since,  as  we  shall  see,  the  activity  of  the  muscle  depends  upon 
the  free  and  rapid  circulation  of  the  blood  through  its  substance.^ 
The  influence  of  muscular  contraction  in  accelerating;  the  venous 
flow  is  well  known  to  every  surgeon,  the  jet  from  a  vein  increasing 
in  force  with  the  contraction  of  the  muscles  below  the  opening. 
The  amount  of  increase  of  pressure  in  the  veins,  due  to  muscular 

'Todd  and  I)Ownian,  Phvs.  Anat.,  1856,  Vol.  ii.,  p.  350. 

2. Journal  dc  Physiolofjie,"  1821,  T.  i.,  p.  3. 

3  Milne  Kdwards,  Phy.siologie,  Tome  iv.,  p.  310. 


IXFLUEXCE  OF  IXSPIBATIOX.  333 

contraction,  can  be  experimentally  determined  by  placing  a  vein  in 
commnnication  with  a  mercm'ial  manometer,  and  observing  the  va- 
riations in  the  height  of  the  mercury  due  to  muscular  contraction, 
whether  produced  naturally  or  by  movements  of  the  animal,  or  in- 
duced by  stimuli.  In  the  experiments  of  Magendie  ^  and  Bernard  - 
the  mercury  rose  50  mm.  (2  in.)  above  the  normal  venous  pressure 
after  a  general  muscular  contraction.  However  important  muscu- 
lar action  may  be  in  promoting  the  flow  of  venous  blood,  that  it  is 
not  indispensable  is  shown  by  the  fact  that  the  blood  flows  through 
the  veins  in  parts  that  are  paralyzed.  When  we  come  to  study  the 
mechanism  of  respiration  it  will  be  seen  that  the  thoracic  walls  alter- 
nately expand  and  contract  synchronously  with  the  fall  and  rise  of 
the  diaphragm  in  the  production  of  the  inspiratory  and  expiratory 
movements.  It  will  become  apparent,  then,  that  the  rarefaction  of 
the  air  within  the  thorax  during  its  dilatation,  which  causes  the  en- 
trance of  the  external  air  into  the  trachea  and  the  lungs  in  inspira- 
tion, must  exercise  a  similar  suction  influence  upon  the  blood  flow- 
ing in  the  large  and  extensible  veins  emptying  into  the  heart.  This 
action  of  the  thoracic  walls  ^^•ill  have,  however,  little  or  no  influ- 
ence upon  the  blood  of  the  aorta,  its  walls  being  too  resisting  to 
give  to  any  extent.  The  suction  force  thus  exerted  by  the  thorax 
during  inspiration  upon  the  venous  blood  flowing  toward  the  heart 
extends  also,  to  a  certain  extent,  to  the  veins  situated  outside  of 
the  thorax.  The  fact  already  alluded  to,  of  the  walls  of  the  supe- 
rior vena  cava,  jugular,  subclavian,  etc.,  adhering  to  the  surrounding 
tissues  bv  aponeurotic  layers,  and  so  being  kept  open,  evidently  favors 
the  flow  of  the  blood  through  these  veins  toward  the  heart  during  in- 
spiration. AVere  it  not  for  such  a  disposition  the  veins  would  entirely 
collapse  through  atmospheric  pressure.  The  hepatic  veins  also  ad- 
here to  such  an  extent  to  the  tissue  of  the  liver  that  when  divided 
they  remain  open,  and  the  inferior  vena  cava,  in  which  these  veins 
terminate,  is  further  surrounded  by  fibrous  expansions,  which  fix  it 
to  the  margin  of  the  diaphragm  through  which  it  passes  on  its  way 
to  the  heart.  The  anatomical  relations  of  the  parts  are  such,  there- 
fore, as  to  favor  the  flow  of  the  venous  blood  from  the  liver  toward 
the  heart  during  the  contraction  and  consequent  fall  of  the  dia- 
phragm incidental  to  inspiration.  That  such  a  suction  force  is 
really  exerted  upon  the  venous  blood  during  inspiration  by  the  tho- 
rax is  seen  whenever  a  violent  inspiratory  effort  is  make.  At  such 
times  the  veins  at  the  lower  part  of  the  neck  are  seen  to  empty 
themselves  completely.  The  experiment  of  Barry,  already  de- 
scribed, illustrates  the  power  of  this  suction  force,  the  fluid  being 
sucked  up  into  the  glass  tube  introduced  into  the  jugular  vein  with 
each  inspiration.  Barry,  however,  exaggerated  the  influence  of 
this  suction  force.  That  it  does  not  ordinarily  extend  much  be- 
yond the  thorax  can  be  proved  by  introducing  the  glass  into  the 

^Op.  cit.,  Tome  iii.,  p.  162. 

^Lecons  sur  la  Phys.  et  Path,  du  Systeme  Yeneux,  Tome  i.,  p.  285.     Paris,  1858. 


334  CIRCULATION  OF  THE  BLOOD. 

anterior  end  of  the  jugular  vein,  when  little  or  no  variation  will  be 
observed  in  the  level  of  the  liquid  with  the  inspiratory  eifort. 

Death  from  the  entrance  of  air  into  the  veins  is  due  to  the  suc- 
tion force  exerted  by  the  thorax  during  inspiration.  The  consider- 
ation of  such  cases  belongs  to  pathology,  but  it  may  be  mentioned 
here  incidentally  that  the  cause  of  death  is  due  to  the  blood  becom- 
ing frothy  or  spumous  when  mixed  with  air,  and  in  that  condition 
will  not  circulate  through  the  pulmonary  capillaries,  hence  the  left 
side  of  the  heart  is  found  on  post-mortem  examination  emj^ty. 

It  might  naturally  be  supposed  that,  as  inspiration  favors  the 
flow  of  the  venous  blood  toward  the  heart,  the  expiration  would 
oppose  it.  Were  expiration  due  solely  to  the  contraction  of  the 
thoracic  walls,  such  would  be,  at  least  to  a  certain  extent,  the  case, 
but,  as  we  shall  see,  the  air  is  expelled  during  expiration  from  the 
lungs  to  a  great  extent  through  the  elasticity  of  the  organs  them- 
selves, and,  as  Milne  EdAvards  ^  suggests,  this  action  of  the  lungs, 
so  far  from  compressing  the  veins  near  the  heart,  tends  to  dilate 
them.  A  part  of  the  pressure  due  to  contraction  of  the  thoracic 
walls  that  would  otherwise  compress  the  veins,  is,  therefore,  neutral- 
ized by  the  elasticity  of  the  lungs.  It  can  be  shown  experimentally 
by  the  manometer,  as  the  above  consideration  would  lead  us  to  ex- 
pect, that  the  effect  due  to  inspiration  upon  the  flow  of  the  venous 
blood  far  exceeds  that  of  expiration.  The  valves,  further,  while 
offering  no  obstacle  to  the  flow  of  the  blood  during  inspiration,  pre- 
vent, to  any  extent,  regurgitation  during  expiration.  Thus,  if  the 
manometer  be  placed  in  the  internal  jugular  vein  above  the  valves, 
the  effect  of  inspiration  is  the  same  as  when  placed  below  them,  but 
in  the  first  case  the  reflux  during  expiration  amounts  to  nothing. 
If  expiration  be  violent,  however,  then  the  reflux  may  be  consider- 
able ;  thus  the  veins  of  the  neck  during  singing  or  prolonged  speech 
are  seen  to  swell  up,  and  when  any  effort  is  made  in  which  the  glot- 
tis is  closed.  The  dilatation  of  the  thorax  has  but  little  effect  upon 
the  blood  flowing  in  the  great  veins  of  the  abdomen  on  account  of 
the  flaccidity  of  their  walls,  but  the  diaphragm  falling  during  in- 
spiration compresses  the  viscera,  and  they  in  turn  pressing  upon  the 
vena  cava  and  its  branches,  force  the  blood  toward  the  heart,  re- 
gurgitation toward  the  extremities  being  prevented  through  the 
closing  of  the  valves.  With  the  rise  of  the  diaphragm  the  pressure 
upon  the  vena  cava  will  be  relieved,  and  the  blood  will  rapidly  flow 
into  it  again  from  the  extremities.  Should  the  expiration,  however, 
be  labored  or  violent,  and  the  abdominal  walls  contract,  then  the 
pressure  exerted  upon  the  viscera  would  be  an  obstacle  to  the  flow 
of  the  venous  blood  from  the  extremities.  In  order  to  appreciate 
the  influences  of  respiration  upon  the  flow  of  the  venous  blood,  as 
seen  from  what  has  just  been  said,  we  must  carefully  consider  the 
conditions  of  the  inspiration  and  expiration,  as  the  same  cause  may, 
under  different  circumstances,  produce  exactly  the  opposite  effect. 
'Op.  cit.,  Tome  iv.,  p.  419. 


BAPIDITY  OF  CIRCULATION.  335 

On  the  whole,  respiration  favors  the  flow  of  the  venous  blood  from 
the  periphery  to  the  heart,  and,  as  we  shall  see  hereafter,  the  flow 
of  the  arterial  blood  from  the  heart  to  the  periphery. 

The  contractility  with  M'hich  the  veins  are  endowed  assists  some- 
what in  the  lower  animals  the  flow  of  the  blood.  This  influence  is 
limited  in  man,  however,  to  the  large  veins  near  the  heart,  and  is 
even  there  ven'  slight.  Gravity,  while  favoring  the  flow  of  the 
venous  blood  from  parts  above  the  heart,  opposes  that  from  below. 
AVhile  muscular  action,  respiration,  contractility,  gravity,  etc.,  no 
doubt  at  times  favor  the  flow  of  the  venous  blood  toward  the  heart, 
it  must  not  be  forgotten  that  all  these  conditions  are  only  supple- 
mentary to  the  force  of  the  heart,  this  being  suflicient  to  force  the 
blood  throughout  the  entire  vascular  system. 

We  have  seen  that  the  velocity  of  the  blood  varies  considerably 
in  the  different  parts  of  the  vascular  system,  being  greatest  in  the 
large  arteries,  least  in  the  capillaries,  and  intermediate  between 
these  extremes  in  the  veins,  so  far  as  can  be  estimated. 

There  remains  now  to  be  determined  as  far  as  possible,  the  general 
rapiditv  of  the  circulation  ;  that  is,  the  period  necessary  to  complete 
the  entire  circuit,  or  the  time  that  elapses  during  which  a  particle  of 
blood  passing  out  of  the  left  ventricle  traverses  the  arterial  capil- 
lary and  venous  systems,  returning  by  the  right  side  of  the  heart 
and  lungs  to  the  point  from  which  it  started. 

The  general  rapidity  of  the  circulation  can  be  easily  and  satisfac- 
torily determined  experimentally  in  a  living  animal  in  the  follow- 
ing manner,  as  was  first  done  by  Hcring  •}  A  harmless  substance, 
and  easily  recognized,  is  injected  into  the  jugular  vein,  and  blood  is 
drawn  as  quickly  as  possible,  and  at  intervals,  from  the  correspond- 
ing vein  of  the  opposite  side  of  the  head,  the  time  being  carefully 
noted  when  the  substance  injected  can  be  detected.  Suppose,  for 
example,  that  a  solution  of  ferrocyanide  of  potassium  be  injected 
into  the  jugular  vein  of  a  rabbit,  the  salt  can  be  recognized  in  the 
blood  of  the  opposite  vein  in  about  seven  seconds.  In  this  experi- 
ment the  blood  carrying  the  salt  passes  to  the  right  side  of  the 
heart,  then  through  the  lungs  to  the  left  side,  from  there  into  the 
aorta,  and  traversing  the  capillaries  of  the  head  and  face  returns 
back  by  the  jugular  vein  on  the  opposite  side.  If  the  substance  be 
injected  into  the  femoral  vein  the  period  elapsing  is  slightly  longer, 
the  vessels  throuo-h  which  the  blood  flows  beincr  somewhat  lonofer. 
This  is  more  evident,  however,  in  a  large  animal  like  a  horse,  than 
in  a  small  one  like  a  rabbit.  Ferrocyanide  of  potassium  is  not 
only  used  in  this  experiment  on  account  of  it  being  harmless,  but 
from  the  readiness  with  which  its  presence  can  be  determined  in  the 
blood.  Vierordt  -  improved  somewhat  Hering's  method  by  collect- 
ing the  blood  as  it  flowed  at  small  intervals  in  little  vessels  that 

^Zeitschrift  fiir  Phvsiologie  Treviranus,  1829,  Band  iii.,  p.  85.  Archiv  f.  phy- 
siol.  Heilkunde,  1853,' Band  xii.,  s.  112  ;  1832,  Band  v.,  s.  58. 

^Die  Erscheinungen  und  Gesetze  der  Stfomgeschwindigkeiten  des  Blutes,  etc.. 
s.  65. 


336  CIRCULATION  OF  THE  BLOOD. 

were  fixed  to  a  disk  which  revolved  at  a  fixed  rate,  the  time  being 
determined  a  little  more  accurately.  The  results  of  the  experi- 
ments of  both  these  observers,  however,  agree  essentially.  Accord- 
ing to  Hering,  the  rapidity  of  the  circulation  in  an  animal  is  in- 
versely as  its  size,  and  directly  as  the  rapidity  of  the  action  of  its 
heart.  Thus,  while  in  the  rabbit  we  have  seen  that  the  circulation 
from  jugular  to  jugular  is  accomplished  in  6.9  seconds,  in  the 
goat,  dog,  and  horse,  12.8,  15.2,  and  27.3  seconds  are  required 
respectively. 

If  it  be  assumed  that  at  each  ventricular  systole  180  grammes 
(6.4  ounces)  of  blood  are  ejected  into  the  aorta  and  that  the  heart 
beats  72  times  per  minute,  it  follows  that  during  that  time  13  kilo- 
grammes (28  pounds)  of  blood  will  pass  through  the  heart.  If, 
however,  the  blood  in  the  body  amounted,  for  example,  to  only 
about  7.2  kilogrammes  (16  pounds),  it  is  obvious  that  less  than  one 
minute  (about  32  seconds)  would  be  required  for  all  the  blood  to 
pass  through  the  heart  (13  :  60  : :  7  :.»  =  32.3),  an  estimate  which 
agrees  closely  with  that  determined  by  experiment  in  the  horse. 
The  only  objection  to  this  manner  of  determining  the  time  required 
for  the  whole  mass  of  the  blood  to  pass  through  the  heart  is  the 
uncertainty  as  regards  the  exact  amount  of  blood  in  the  body,  and 
of  the  quantity  expelled  with  each  ventricular  systole.  From  the 
nature  of  the  case  these  data  must  be  variable ;  the  estimate  will 
be  true,  however,  within  limits. 

In  confirmation  of  what  has  just  been  said  in  reference  to  the 
rapidity  of  the  general  circulation,  etc.,  it  may  be  mentioned  that 
the  time  elapsing  between  the  introduction  of  a  jioison  into  the 
blood  and  its  characteristic  eifects  is  about  the  same  as  that  observ^ed 
in  the  experiment  of  Hering. 

Resume  of  the  History  of  the  Discovery  of  the  Circulation 
of  the  Blood. 

The  discovery  of  the  circulation  cannot  be  attributed  to  the  work 
of  any  one  man,  })ut  to  that  of  many,  extending  over  a  period  of 
more  than  two  thousand  years.  Harvey,  with  whose  name  the 
discovery  of  the  circulation  is  invariably  associated,  and  justly  so, 
must,  however,  share  the  honor  with  those  who  preceded  as  well  as 
with  those  who  followed  him,  for,  on  the  one  hand,  the  pulmonary 
circulation  was  discovered  by  Servetus  and  Colombo  before  Harvey 
was  born,  and,  on  the  other,  the  capillary  circulation  was  not  dis- 
covered by  Malpighi  until  after  Harvey  died.  To  the  apprehen- 
sion of  the  author '  at  least  the  discovery  of  the  circulation  is 
marked  by  six  well-defined  epoch-making  periods,  viz.  : 

1.  The  structure  and  functions  of  the  valves  of  the  heart. 
Erasistratus,  B.  C.  304.' 

>H.  C.  Cliapman,  Historv  of  the  Discovery  of  the  Circuhition  of  tlie  Blood. 
Phila.,  1884,  p.  ^A. 

'^  Claudii  Galeni,  Opera  Omnia,  Venetiis,  1556. 


DISCOVERY  OF  CIRCULATION  OF  THE  BLOOD.  337 

2.  The  arteries  carry  blood  during  life,  not  air.  Galen,  A.  D. 
165.^ 

3.  The  pulmonary  circulation.     Servetus,   1553." 

4.  The  systemic  circulation.     Cffisalpinus,   1593.^ 

5.  The  pulmonary  and  systemic  circulations.     Harvey,  1628.^ 

6.  The  capillaries.     Malpighi,  1G61.^ 

While  it  is  true  that  Harvey  did  not  demonstrate  the  circulation 
of  the  blood,  never  having  seen  the  capillaries,  he  saw  the  blood 
circulating  in  the  mind's  eye  for  he  argued  that  more  blood  passes 
through  the  heart  in  a  given  time  than  can  be  accounted  for  by  the 
quantity  of  the  blood  in  the  vessels  ;  hence  the  blood  must  pass  and 
repass  through  the  heart,  and  in  estimating  the  amount  of  blood 
flowing  from  the  left  ventricle  into  the  aorta  during  a  short  period 
of  time  even,  the  same  blood  must  necessarily  be  counted  over  and 
over  again. 

Again,  after  noticing  the  pulsating  heart  in  the  snake  as  it  ap- 
peared after  the  animal  had  been  opened,  Harvey  calls  attention  to 
the  fact  that  if  the  vena  cava  be  compressed  it  gradually  empties 
itself  between  the  point  of  compression  and  the  heart ;  whereas,  if 
the  aorta  be  compressed,  it  becomes  distended  between  the  heart 
and  the  point  of  compression,  showing  conclusively  that  the  blood 
in  the  vena  cava  flows  from  the  periphery  towards  the  heart, 
whereas  the  blood  flows  in  the  aorta  from  the  heart  towards  the 
periphery.  If  the  great  classic  of  Harvey  contained  nothing  more 
than  the  arguments  just  advanced,  they  alone  would  have  sufficed 
to  have  established  the  doctrine  of  the  circulation,  even  though 
Harvey  was  obliged  to  assume,  to  complete  his  theory,  that  the 
blood  passed  from  the  arteries  to  the  veins  by  anastomosis  of  ves- 
sels or  by  porosities  of  the  flesh  and  solid  parts  that  are  pervious 
to  the  blood  *"  the  capillaries  not  having  been  then  discovered. 

'  Galenus,  Ebenda,  cap.  6. 

2  Christianismi  Eestitutio,  MDLIII. 

''De  Plantis  Libri,  Florentine,  1583,  Lib.  1,  Cap.  II.,  Qusestionum  Medicaram, 
Venetiis,  lo93,  Lib.  II. 

^Exercitatio  anatomica  de  motu  cordis  et  sanguinis  in  animalibus,  Francofurti, 
MDCXXVIII.     Prelectiones  Anatomife  Universalis,  London,  1880. 

^  Opera  Omnia,  Lug  Bat,  1687. 

^  "Aut  anastomosin  vasorum  esse,  aut  porositates,   carnis  &  partium  solidarum, 
pervias  sanguini  esse."     Harvey,  Exercitatio,  Cap.  xi.,  p.  51. 
22 


CHAPTER    XX. 

RESPIRATION. 

We  have  seen  that  all  vital  activity  is  accompanied  by  waste,  that 
mental,  mnscnlar,  and  secretory  action,  and  the  production  of  ani- 
mal heat,  involve  the  development  of  carbon  dioxide,  urea,  etc. 
Sncli  principles  produced  through  the  decomposition  of  the  food  and 
tissues,  if  retained  in  the  system  soon  cause  death,  hence  the  neces- 
sity of  their  being  eliminated  ;  excreted.  As  the  degree  of  vital 
activity  is  conditioned  by  that  of  the  cell,  of  fermentation,  oxida- 
tion, etc.,  and  as  it  is  through  respiration  that  oxygen  is  absorbed, 
and  carbon  dioxide  exhaled,  it  is  evident  that  this  function  is  both 
absorbing  and  excretory  in  character,  and  must  constitute  a  most 
important  part  of  nutrition.  As  might  be  expected,  therefore,  the 
absorbing  of  oxvgcn  and  elimination  of  carbon  dioxide  are  not 
necessarily  limited  to  any  part  of  the  body,  but  may  go  on  in  every 
part  of  it.  Further,  while  the  carbon  dioxide  excreted  is,  to  a  con- 
siderable extent,  due  to  the  combination  of  the  oxygen  absorbed 
with  the  carbon  of  the  body,  there  is  no  reason  to  suppose  that  the 
carbon  dioxide  excreted  at  any  one  moment  is  produced  through  the 
combustion  of  the  oxygen  supplied  by  the  air  inspired  at  that 
moment.  On  the  contrary,  the  oxygen  may  have  been  locked  up 
in  the  tissues,  and  supplied,  not  from  the  lungs,  but  from  a  diifer- 
ent  part  of  the  economy  altogether.  In  fact,  an  animal  will  exhale 
carbon  dioxide  in  an  atmosphere  of  hydrogen.  Under  such  circum- 
stances, the  oxygen  of  the  carbon  dioxide  must  have  been  absorbed 
at  some  previous  period. 

In  the  widest  sense  of  the  term  respiration  may  then  be  consid- 
ered as  the  process  by  means  of  whicli  oxygen  is  absorbed  by  the 
system,  and  carbon  dioxide  is  excreted,  whatever  may  be  the  source 
of  the  latter.  It  is  often  said  that,  while  animals  inhale,  plants  ex- 
hale oxygen,  and  that  animal  and  vegetable  life  stand,  therefore,  in 
a  complementary  relation  to  each  other.  In  one  sense  this  is  true, 
since  green  plants  under  the  influence  of  solar  light  decompose  car- 
bon dioxide  and  water,  giving  up  the  oxygen  and  appropriating  the 
carbon,  elaborating  the  latter  into  starch,  fat,  cellulose,  etc.  Ani- 
mals, on  the  other  hand,  through  the  absorption  of  oxygen,  burn 
the  carbon  of  their  food  produced  by  plants,  and  exliale  carbon  diox- 
ide. This  antithesis  between  plant  and  animal  life  exists,  however, 
only  so  long  as  the  plant  is  regarded  as  the  means  by  which  inorganic 
matter  is  combined  in  a  form  suitable  as  nutriment  for  the  animal. 
When,  however,  the  remaining  phenomena  of  plant  life  are  con- 
sidered, such  as  the  germination  of  the  seed,  the  expansion  of  the 


STRUCTURE  OF  RESPIRATORY  ORGANS. 


339 


leaf,  the  butlding  and  flowering,  the  movement  of  the  sap,  it  will  be 
found  that  all  such  depend  uj^on  the  absorption  of  oxygen,  and 
cease  when  the  plant  is  deprived  of  it.  Respiration,  therefore,  is 
as  important  a  function  in  plant  as  in  animal  life. 

The  phenomenon  of  respiration  or  breathing  in  animals  is  usu- 
ally associated  with  the  presence  of  specialized  organs,  like  lungs, 
gills,  etc.  Such  structures  are,  however,  not  indispensable  for  the 
performance  of  this  function,  since  the  muscle  of  a  frog,  when  sep- 
arated from  the  animal  and  drained  of  its  blood,  will  absorb  oxy- 
gen and  excrete  carbon  dioxide  as  long  as  the  muscle  retains  its 
irritability.  There  are,  indeed,  two  kinds  of  respiration,  an  in- 
ternal one,  taking  place  in  all  parts  of  the  body,  the  tissues  giving 
up  to  the  blood  the  carbon  dioxide  generated  in  them,  and  absorb- 
ing oxygen  from  it,  and  an  external  one,  the  blood  giving  up  to  the 
atmosphere  through  the  lungs  or  skin  its  carbon  dioxide  and  re- 
ceiving oxygen.  It  is  the  latter  form,  or  external  kind  of  respira- 
tion, ordinarily  known  as  breathing,  that  we  propose  considering 
more  particularly  at  present. 

A  respiratory  organ  consists  essentially  of  a  membrane  separat- 
ing tissue  or  blood,  containing  carbon  dioxide,  on  the  one  hand, 
from  the  atmosphere,  or  some  other  medium  containing  oxygen, 
on  the  other ;  the  membrane  being  of  such  a  character  as  to  permit 
of  osmosis. 

It  may  be  mentioned  in  this  connection  that  a  convenient  method 
of  illustrating  the  osmosis  of  carbon  dioxide  and  oxygen  through 
a  membrane  is  to  immerse  a  pig's  bladder 
filled  with  venous  blood  in  a  bell-jar  of 
oxygen,  the  carbon  dioxide  readily  pass- 
ing through  the  membrane  into  the  oxy- 
gen, and  the  latter  in  the  reverse  direction 
into  the  venous  blood. 

Whether  the  animal  be  aquatic  or  ter- 
restrial, simple  or  complex,  the  respira- 
tory organs  are  only  modifications  of  this 
simple  membranous  type  of  structure,  and 
this  will  be  found  to  be  true,  as  they  ap- 
pear in  the  form  of  skin,  gills,  tracheie, 
or  lungs.  Thus,  in  many  of  the  lower 
forms  of  life,  as  in  the  hydrozoa  and  ac- 
tinozoa,  of  which  the  jelly  fish  (Fig.  164) 
and  anemone  are  familiar  examples,  sim- 
ply formed  animals,  in  which  the  diifcr- 
eutiation  of  the  functions,  or  the  division 
of  labor  is  not  carried  to  any  great  extent,  respiration  is  effected  by 
the  general  cutaneous  surface,  the  skin  readily  permitting  an  ex- 
change between  the  oxygen  dissolved  in  the  sea-water  and  carbon 
dioxide  developed  within  their  bodies. 

In  many  animals  such  as  the  Mollusca  (Fig.  165),  fishes,  perenni- 


FiG.  KU. 


^-^i^^t^, 


Jellv  fish. 


340 


EESPIEATION. 


branchiate  batrachia  (Fig.  16G),  the  respiratory  organs  assume  the 
form  of  gills,  delicate  membranons-like  structures,  whose  thin 
walls  readily  permit  of  an  osmosis  between  the  oxygen  of  the  sur- 
roundinof  water  and  the  carbon  dioxide  of  the  blood. 


Fig.  165 


Fig. 


Head  and  gills  of  mcnobrauchus. 


Another  form  of  respiration  is  the  tracheal.  This  is  seen  in 
insects,  centipedes,  etc.,  and  consists  of  innumerable  delicate  mem- 
branous branching  tubes  or  tracheae,  ramifying  throughout  the 
entire  body  of  the  animal,  and  which,  opening  externally  by  lateral 
apertures,  the  spiracles  or  stigmata,  permit  the  entrance  of  the  air. 
Finally  in  batrachia,  reptiles,  birds,  and  mammals,  including  man, 
respiration  is  effected  by  the  skin  and  lungs.  The  action  of  the 
skin  as  a  respiratory  surface  Avill  be  considered  with  its  other  func- 
tions, and  before  describing  the  lungs  in  man,  let  us  consider  a 
more  simple  type  of  lung — that  of  the  frog,  for  example. 

The  lungs  of  the  frog  (Fig.  167)  consist  of  two  vascular  bladder- 
like sacs,  communicating  directly  by  short  bronchi,  or  rather  bron- 
chial openings,  with  the  larynx.  On  opening  the  lung  the  inner 
surface  (Fig.  168)  will  be  seen  to  be  more  or  less  honeycombed, 
and  the  alveoli  subdivided  into  still  smaller  spaces,  or  cells.  These 
cells  all  communicate  with  the  central  pulmonary  cavity,  and  are 
lined  with  a  capillary  network  intermediate  between  the  arterioles 
running  along  the  attached  borders  of  the  septa  and  the  venules 
along  the  free  borders.  It  is  evident  that  a  far  greater  extent  of 
vascular  surface  is  exposed  to  the  air,  by  this  segmented  or  honey- 
combed disposition  of  the  inner  surface,  than  if  the  latter  was 
smooth.  If  the  lungs  of  the  frog  be  now  compared  with  those  of 
a  lizard  or  turtle,  the  only  noticeable  difference  is  that  this  segmen- 
tation of  the  lung  is  more  marked,  while  in  birds  and  mammals  it 
is  carried  to  such  an  extent  that  each  lung  consists  essentially  of 
an  immense  number  of  these  honeycombed  sacs  subdivided  into 
cells,  the  extent  of  the  vascular  space  exposed  to  the  air  being, 
therefore,  enormously  increased.  The  respiratory  organs  in  man, 
in  the  widest  sense  of  the  term,  include  the  nares,  mouth,  pharynx, 
larynx,  trachea,  lungs,  thorax,  and  appro])riate  muscles.  That  the 
nares,  not  the  mouth,  constitute  the  natural  entrance  for  the  air  to 
the  lungs  is  shown  by  the  foct  that  in  certain  mammals  breathing 


ACTION  OF  NARES. 


341 


is  accomplished  through  the  nares  alone.  Thus  in  the  cetacea,  of 
which  the  whale,  dolphin,  porpoise,  etc.,  are  examples,  the  soft  pal- 
ate is  very  much  developed  and  so  disposed  to  embrace  the  glottis 
and  maintain  the  cavity  of  the  larynx  in  communication  with  the 
posterior  nares,  a  free  passageway,  however,  being  left  on  either 
side  for  the  food.  Such  a  disposition  of  the  parts  makes  it  possi- 
ble for  the  elephant  to  use  its  nose  or  trunk,  pharynx  and  larynx 
as  a  siphon  to  suck  up  its  drinks  and  transfer  the  same  to  the 
mouth,  at  the  moment  that  the  latter  is  open  the  posterior  nares 
communicating  with  the  glottis  only.  In  the  horse,  camel,  etc., 
the  soft  palate  is  also  well  developed,  and  surrounds  the  large  epi- 


FiG.  167. 


Fig.  168. 


Luug  of  frog,  shon'-iug  its  internal  sur 
face.    (Dalton.  ) 

glottis  to  such  an  extent  as 
to    cut    off    completely    all 

Respiratory  organs  of  a  frog,  as  scon  on  their  interior  COmmUuicatioU  bctWCen  the 
surface,  a.  Hyoiaeau  apparatus  h.  Cartilaginous  riug  mOUth  and  the  pliarVUX,  ex- 
at  the  root  of  the  lungs,     c.  Pulmonary  sacs,  covered  '■  '     n     i 

with  vascular  ramitications.     (Dalton.)  CCpt  at  the  momCUt  01    deg- 

lutition. Indeed,  in  the 
horse,  if  the  facial  nerves  which  supply  the  muscles  of  the  external 
nares  be  divided,  the  animal  dies  from  asphyxia. 

In  describing  the  structure  of  the  hippopotamus,  the  author  called 
attention  ^  to  the  fact  that  when  the  animal  passes  under  the  water, 
the  larynx  is  so  elevated  within  the  pharynx  that  a  continuous 
passage  is  offered  to  the  air  from  the  external  nares  to  the  lungs, 
enabling  the  animal  to  breathe  when  almost  entirelv  submerged. 
A  similar  elevation  of  the  larynx  is  seen  in  the  young  kangaroo, 
and  to  a  certain  extent,  also,  in  the  human  foetus  and  infant.  The 
ill  effects  often  experienced  in  breathing  through  the  mouth  in  a 
cold,  dry  atmosphere  further  prove  that  the  natural  entrance  to  the 
respiratory  tract  is  the  nose,  since  the  air  as  it  passes  over  the 
partly  ciliated  moist  and  very  vascular  and  warm  mucous  mem- 
brane lining  the  nasal  cavities  absorbs  water,  and  is  elevated  to  the 
temperature  of  the  body  before  entering  the  lungs.  The  action  of 
the  nares  in  ordinary  breathing  is  n-ot  very  apparent,  but  when  the 
iH.  C.  Chapman,  Proc.  Aoad.  Nat.  Sciences,  p.  130.     Philadelphia,  ISSl. 


342 


RESPIRATION. 


breathing  becomes  labored,  then  it  is  very  evident.  The  air  having 
passed  the  nose  and  the  pharynx,  enters  the  larynx,  a  triangnlar- 
like  structure  surmounting  the  trachea  and  consisting  of  sufficiently 


Fig.  169. 


Fig.  170. 


Human  larynx,  viewed  from  above  in  its  ordi- 
nary post-mortem  condition.  5.  Vocal  mem- 
branes. 1.  Thyroid  cartilage.  4.  Arytenoid 
cartilages.     0.  Opening  of  the  glottis. 


The  same,  with  the  glottis  opened  by  separa- 
tion of  the  vocal  cords.  5.  Vocal  membranes. 
1.  Thyroid  cartilage.  4.  Arytenoid  cartilages. 
0.  Opening  of  the  glottis.     ( L).iLTOX. ) 


rigid  cartilages  to  resist  atmospheric  pressure  united  by  ligaments 
and  movable  through  muscles.  The  detailed  structure  of  the  larynx 
we  will  defer  till  our  account  of  the  voice,  considering   at  present 

only  such  of  its  parts  as  influence  respira- 
FiG.  171.  tion.      The  larynx  is  lined  with  mucous 

membrane,  continuous  with  that  of  the 
pharynx ;  the  epithelium,  hoAvever,  ex- 
cept that  covering  the  vocal  cords,  is  of 
the  ciliated,  columnar  variety,  the  move- 
ment of  the  cilia  being  from  below,  up- 
ward. If  the  larynx  be  viewed  from 
above  (Figs.  169,  170),  or  in  section 
(Fig.  171),  it  will  be  observed  that  it  is 
divided  into  an  upper  and  lower  com- 
partment by  the  rima  glottidis  (0),  or 
the  aperture  of  the  glottis,  a  triangular- 
like  orifice,  the  sides  and  base  of  which 
are  formed  by  the  true  vocal  cords  (Fig. 
171)  (5,  6)  and  arytenoid  cartilages  (4). 
The  vocal  cords,  or,  more  properly,  the 
vocal  membranes,  consist  of  elastic  tissue 
covered  Avith  very  thin  mucous  mem- 
brane, and  extending  from  the  thyroid 
cartilages  (Fig.  171,  1  and  2)  anteri- 
orly, to  the  cricoid  (3),  and  base  of  the 
arytenoid  cartilages  (4)  posteriorly.  The  up])er  edges  of  the  vocal 
membrane  extending  from  the  reentering  angle  of  the  thyroid  carti- 


View  of  the  vocal  membrane.  1. 
Left  half  of  the  thyroid  cartilage.  2. 
Right  lialf  turned  forward  and 
partly  cut  away.  3.  Cricoid  carti- 
lage. 4.  .'Vrytenoid  cartilages,  o. 
Right  half  of  the  vocal  membrane, 
'(i.  Upper  l)order  of  the  left  half.  7. 
Arytenoid  muscle.  The  upper  bor- 
ders of  the  V(jcal  membrane,  e.\- 
tended  between  the  arytenoid  car- 
tilages and  tlie  thyroi<l,  constitute 
the  so-called  "true  vocal  cords." 
(LEioy.) 


RESPIRATORY  ACTION  OF  GLOTTIS. 


343 


lage  tojthe  hn^e  of  the  arvteuoitl  are  somewhat  thickened,  and  are 
usually  and  incorrectly  described  as  separate  organs,  the  "  vocal 
cords."  The  upper  or  false  vocal  cords,  so-called  because  they 
have  uo  influence  in  the  production  of  voice,  are  the  thickened 
upper  edges  of  the  ventricle  or  sac-like  pouches  extending  outward 
and  upward  from  the  larynx  between  the  vocal  cords,  and  lined 
with  the  mucous  membrane  of  the  same.  The  glottis  or  triangular 
orifice  between  the  vocal  membranes  and  arytenoid  cartilages  is  the 
passage  through  which  the  air  from  the  nose  and  pharynx  enters 
the  trachea  and  lungs,  and  during  life  is  alternately  dilated  and 
contracted  synchronously  with  the  movements  of  the  chest.     During 

Fig.  172. 


;n5i^^-? 


Humau  larynx,  trachea,  bronchi,  and  lungs  ;  showing  the  ramification  of  the  bronchi,    and  the 
division  of  the  lungs  into  lobules.    (Daltox.) 


inspiration  the  glottis  (Fig.  170)  opens,  admitting  the  air  freely  to 
the  trachea,  while  in  expiration  as  the  air  is  expelled  upward  from 
below  the  vocal  membranes  collapse.  These  movements  constitute 
the  respiratory  movements  of  the  glottis  and  are  increased  or  dimin- 
ished in  intensity  in  proportion  to  those  of  the  chest.  AVe  shall  see 
that  while  expiration  is  usually  a  passive  process,  inspiration  is  an 
active  one,  and  its  tendency  is  to  draw  the  vocal  membranes 
together.  This  is  provided  against,  however,  through  the  action  of 
the  posterior  crico-arytcnoid  muscles,  which  arise  from  the  posterior 
surface  of  the  cricoid  cartilage,  converge  upward  and  outward,  and 


344 


BESPIRATION. 


Fig.  173. 


are  inserted  into  the  base  of  the  arytenoid  cartilages.  In  contract- 
ing, these  muscles,  therefore,  dilate  at  the  moment  of  inspiration  the 
glottis.  During  expiration,  however,  these  muscles  are  relaxed, 
the  vocal  membranes  through  their  elasticity,  and  through  the  con- 
traction of  the  lateral  crico-arytenoid  muscles  are  approximated,  and 
the  expired  air  separates  them  as  it  passes  upward  from  the  trachea. 
The  importance  of  the  epiglottis  covering  the  larynx  during  deglu- 
tition, and  thereby  preventing  foreign  bodies,  especially  of  a  liquid 
nature,  from  passing  into  the  larynx  having  been  already  noticed, 
it  w^ill  not  be  necessary  to  dwell  further  upon  the  function  of  this 
structure  in  its  relation  to  deglutition  and  respiration. 

The  inspired  air  having  passed  through  the  larynx  enters  the 
trachea  (Fig.  172,  T),  a  tube  from  10  to  12  cm.  long  (4  to  4.8  in.) 
and  21  mm.  {^-^  in.)  in  width,  beginning  at  the  lower  border  of  the 
cricoid  cartilage  above  and  terminating  as  the  two  bronchi  below. 
The  trachea  consists  of  16  to  20  cartilagi- 
nous rings,  or,  more  correctly,  arcs  the  pos- 
terior third  of  each  ring,  being  imperfect, 
deficient  in  cartilage,  the  intervening  space 
being  filled  up  with  loose  fibrous  tissue. 
The  cartilaginous  rings  are  connected  by  a 
strong  fibro-elastic  membrane,  which  so  ex- 
tends over  and  under  them  in  a  thinned 
condition  that  they  are,  as  it  were,  im- 
bedded within  it.  The  last  ring  of  the 
trachea  is  somewhat  modified  in  shape,  its 
lower  border  being  brought  to  a  median 
point  so  as  to  accommodate  itself  to  the 
bronchi.  The  function  of  the  cartilaginous 
rings  of  the  trachea  is  to  keep  the  latter 
open  under  varying  conditions  of  pressure. 
Within  the  fibrous  tissue  filling  up  the 
posterior  third  of  the  cartilaginous  rings 
are  found  unstriped  muscular  tissue,  the  fibers  of  which  are  dis- 
posed in  a  transverse,  and  to  a  certain  extent,  also,  in  a  longitu- 
dinal, direction.  The  action  of  these  muscular  fibers,  sometimes 
called  the  tracheal  muscle,  is  to  diminish  the  area  of  the  trachea 
by  approximating  the  cartilaginous  rings,  and  the  ends  of  each  ring, 
and  of  so  preventing  too  great  distention  when  the  pressure  within 
the  air  passages  becomes  very  great.  The  trachea  is  lined  with 
mucous  membrane,  its  epithelium  being  of  the  columnar  ciliated 
character.  Tlie  motion  of  the  cilia  being  from  below,  upward,  a 
current  is  produced  by  which  the  mucus  is  carried  upward  toward 
the  larynx. 

Although  the  cilia  are  microscopic,  varying  in  length  from  the 
•^-^-0  to  the  :j-l^  of  a  millimeter  (the  2-5V7r  ^^  ^he  -^-^-q^  of  an  inch 
in  length  ;  nevertheless,  through  tlieir  vibratory  motion  a  greater 
force  is  exerted  than  might  be  expected.     The  mechanical  effect 


Single  lobule  of  human  lung, 
o.  Ultimate  bronchial  tube,  b- 
Cavity  of  lobule,  c,  c,  c.  Pul- 
monary cells,  or  vesicles.  (Dal- 
TON. ) 


COMPOSITION  OF  NASAL  MUCUS. 


345 


Fig.   174. 


produced  by  the  motion  of  the  vibratile  cilia  can  be  shown  by 
means  of  the  instrument  known  as  that  of  Calliburccs.  This  consists 
(Fig.  174)  of  a  brass  stage  (H)  which  can  be  elevated  and  depressed 
on  a  vertical  axis  (K)  by  means  of 
the  screw  (^I),  whose  movement  is 
graduated.  The  brass  stage  sup- 
ports a  cork  (I),  upon  which  is  hori- 
zontally disposed  an  aluminium  rod 
(D),  terminating  in  an  index  (F). 
The  brass  stage,  axis,  and  disk,  etc., 
are  usually  covered  with  a  glass  cyl- 
inder, through  which  passes  a  safety 
tube  (S),  into  which  hot  water  is 
pourecl,  by  means  of  which  the  at- 
mosphere is  kept  moist  and  the  tem- 
perature maintained  at  28°  C  (82° 
F.).  The  mucous  membrane  of  the 
frog,  whose  cilia  are  to  be  examined, 
having  been  placed  upon  the  cork 
(I),  before  it  is  covered  with  the 
glass  jar,  is  then  brought  up  almost 
in  contact  with  the  aluminium  rod 
(D)  by  elevating  the  brass  stage  (H). 
When  so  adjusted,  if  the  mcml^rane 
be  kept  moist  and  warm,  the  alumin- 
ium rod  will  rotate  on  its  axis 
through  the  action  of  the  cilia,  the 
index  (F)  moving  around  the  gradu- 
ated circle  (G)  about  once  in  three 
minutes  for  an  hour  and  upwards.  As  the  aluminium  rod  with 
the  index  weighs  about  0.07  gramme  (1.08  grains),  it  is  evident 
that  considerable  mechanical  effect  is  produced  relatively  to  the 
small  size  of  the  organs  exerting:  the  force.  The  motion  of  the  cilia 
of  human  mucous  membrane  can  often  be  seen  upon  the  surface  of 
recently  extracted  nasal  polypi  when  the  latter  are  viewed  under 
the  microscope. 

The  composition  of  the  na.sal,  as  well  as  that  of  the  bronchial  and 
pulmonary  mucus,  is  shown  in  the  following  : 


Apparatus  of  CallibureCs. 


CoMPosiTiox  OF  Nasal  Mucus.' 


Water 

Mucosin  .... 

Sodium  lactate 
Organic  crystalline  principles 
Fatty  matters  and  cholesterin 
Sodium  and  potassium  chloride 
Phosphates     .... 
Sodium  sulphate  and  carbonate 


993.00 

53.30 

1.00 

2.00 

5.60 
3.50 
0.90 


'  Eohin,  Lefons  sur  les  humeurs,  p.  450.     Paris,  1867 


346  RESPIRA  TION. 

Composition  of  Bronchial  and  Pulmonary  Mucus.' 

Water 955.520 

Mucosiu 23.754 

Watery  extract 8.006 

Alcoholic  extract  .......  1.810 

Fat 2.887 

Sodium  chloride    .......  5.825 

"        sulphate 0.400 

"        carbonate 0.198 

"       phosphate 0.080 

Calcium  phosphate  with  traces  of  iron           .         .  0.974 

"         carbonate 0.291 

Silica  and  calcium  sulphate  .....  0.255 


1000.000 


The  trachea  terminates  inferiorly  in  the  bronchi  (Fig.  172,  B, 
B) ;  the  right  bronchus  differs  from  the  left  in  being  the  shorter, 
attaining,  usually,  a  length  of  2.5  cm.  (1  inch),  while  the  left  is  al- 
most twice  as  lono-.  The  sjeneral  structure  of  the  bronchi  corre- 
sponds  in  every  way  to  that  of  the  trachea ;  the  cartilaginous  rings 
are,  how^ever,  shorter,  and  narrower,  and  less  numerous,  the  right 
bronchus  consisting,  usually,  of  from  six  to  eight  rings,  the  left  of 
from  nine  to  twelve.  Each  bronchus  divides  and  subdivides  di- 
chotomously  into  the  bronchial  tubes  (Fig.  172).  The  latter  di- 
verging in  every  direction,  and  never  anastomosing,  gradually  be- 
come smaller  and  smaller,  and  more  delicate  in  structure,  and  when, 
finally,  they  are  reduced  to  about  the  diameter  of  the  -§■  of  a  mm. 
(yl^g-  of  an  inch),  they  terminate  in  a  primary  lobule  (Fig,  173). 
The  bronchial  tubes  differ  in  several  respects  from  the  bronchi,  of 
which  they  are  the  diverging  branches.  Thus,  in  the  larger  ones, 
the  cartilages  are  disposed  of  as  irregular-shaped  plates,  of  various 
sizes,  all  over  the  sides  of  the  tubes  instead  of  in  the  form  of  im- 
perfect rings ;  in  the  medium-sized  tubes  the  cartilages  become 
smaller  and  less  numerous,  while,  finally,  in  tubes  having  a  diam- 
eter of  less  than  J  of  a  mm.  (-^L  of  an  inch)  they  disappear  alto- 
gether. The  terminal  bronchial  tubes  then  consist  of  a  delicate 
fibro-elastic  external  membrane,  containing  circular  muscular  fibers 
and  a  very  thin  lining  of  mucous  membrane,  the  epithelium  of 
which  is,  however,  still  ciliated.  As  just  stated,  each  bronchial 
tube  finally  terminates  in  a  primary  lobule.  The  primary  lobule, 
with  a  diameter  usually  of  2  mm.  (J^  of  an  inch),  consists  of  a  sac, 
which  is  essentially  an  expansion  of  the  terminal  bronchial  tube, 
hence  its  name  of  infundibulum.  The  cavity  of  the  primary  lob- 
ule (Fig.  173,  h)  is  subdivided  by  thin  partitions,  projecting  from 
its  inner  surface  into  secondary  compartments,  the  alveoli,  or  the 
pulmonary  air  cells,  e,  c,  having  a  diameter  of  from  ^  to  ^  of  a 
mm.  (2-J-^  to  Yi  of  an  inch) ;  these,  while  separated  from  each  other 
by  the  partitions,  communicate  with  the  central  cavity  or  intercel- 
lular air  passages,  wliich,  in  turn  opens  into  the  terminal  bronchial 
'  Nasse,  Journal  of  piakt.  Chemie,  1843,  Band  xxix.,  s.  65. 


PRIMARY  LOBULES  OF  THE  LUNGS. 


347 


Fig.  175. 


tube,  tliroiic>;li  ^^llich  the  inspired  air  ultimately  passes  to  the  air 
cells.  The  air  cells,  amounting  to  725  millions  in  number/  and 
representing  an  area  of  nearly  two  hundred  square  meters  (2000 
feet),  are  polyhedral  sacs,  surrounded  by  anastomosing  elastic  fibers, 
and  consist  of  a  fibro-elastic  wall,  containing,  probably,  some  mus- 
cular fibers,  and  lined  with  a  tessellated  epithelium.  The  epithe- 
lium is  more  homogeneous  and  easily  demonstrated  in  the  foetus 
than  in  the  adult.  If  the  primary  lobule  of  the  human  lung  be 
now  compared  with  the  lung  of  the  frog,  it  will  be  seen  that  it  rep- 
resents the  entire  frog's  lung  in  miniature.  The  primary  lobules  of 
the  human  lung  unite  through  connective  tissue  into  larger  second- 
ary lobules,  and  the  latter  uniting,  constitute  a  lung.  The  polyhe- 
dral markings  upon  the  surface  of  a  lung  indicate  the  margins  of 
the  secondary  lobules,  while  careful  examination  will  disclose  also 
the  outlines  of  tlie  primary  lobules  composing  the  secondary  ones. 
Finally,  the  integration  of  the  primary 
lobules  into  the  secondary  ones,  and 
the  latter  into  lobes,  is  carried  still 
further  into  the  left  lung  than  in  the 
right,  the  former  consisting  of  two 
lobes,  the  latter  of  three.  While  tlie 
lungs  are  nourished  by  the  bronchi,  it 
is  by  means  of  the  pulmonary  arteries 
that  the  venous  blood  is  carried  to  them 
from  the  right  side  of  the  heart  and 
aerated.  The  pulmonary  artery  arising, 
as  we  have  seen,  from  the  right  ven- 
tricle of  the  heart,  soon  divides  into  a 
rijrht  and  left  l)ranch  for  either  luns:. 
Following  the  bronchus  and  bronchial 
tubes,  the  artery  divides  and  subdi- 
vides, the  branches  becoming  smaller  and  smaller  as  they  approach 
the  primary  lobules  (Fig.  17o),  until  finally  they  terminate  as 
the  pulmonary  capillaries.  The  terminal  arterial  capillaries  sur- 
round each  alveolus  or  air  cell  as  a  vascular  circle,  which  anasto- 
moses with  those  of  the  adjacent  alveoli.  From  these  vessels  arise 
a  capillary  network  (Fig.  175),  so  closely  set  that  the  meshes  are 
even  smaller  than  the  diameter  of  the  vessels  themselves,  the  latter 
having  usually  a  diameter  of  from  J^  to  2^^^-  of  a  mm.  (2  oV"o  ^^ 
5  oVo  ^^  ^"  inch).  This  network  supports  the  bottom  of  each  air 
ceil,  and  the  blood  that  it  carries  is  separated  from  the  air  of  the 
cells  only  by  its  wall  and  the  extremely  delicate  epithelial  lining  of 
it.  The  carbon  dioxide  of  the  venous  blood  conveyed  to  the  lungs 
by  the  pulmonary  artery  is  thus  separated  from  the  oxygen  of  the 
air  within  the  air  cells  brought  by  the  trachea  by  nothing  but  the 
wall  of  the  capillary  and  epithelium  of  the  air  cell.  The  rapidity 
with  which  the  osmosis  of  these  gases  takes  place  through  such  a 
1  Landois,  op.  cit.,  p.  190. 


Diagram  of  two  primary  lobules  of 
the  lungs,  magnified.  1.  Bronchial 
tube.  2.  A  pair  of  primary  lobules 
connected  with  tibro-elastic  tissue.  3. 
Intercellular  air  passages.  4.  Air 
cells.  5.  Branches  of  the  pulmonary 
artery  and  vein.     (Leidy.) 


348  RESPIRATION. 

delicate  septum  will,  therefore,  be  readily  imagined  ;  the  osmosis 
being  still  further  insured  through  the  great  vascularity  of  the 
parts,  the  respiratory  surface  being  thereby  continually  kept  moist, 
which  greatly  promotes  the  exchange  of  the  gases. 

The  full  influence  of  the  air  upon  the  blood  is  further  secured 
in  that  the  capillary  plexus  is  so  disposed  between  the  walls  of  two 
adjacent  air  cells  that  one  of  its  surfaces  is  exposed  to  each.  It 
has  been  estimated^  that  a  thin  layer  of  blood  of  150  square 
meters  (1500  feet)  is  exposed  in  the  lungs  to  the  air  of  the  air  cells, 
and  that  this  blood,  amounting  to  perhaps  2  liters  (3.4  pints),  is 
renewed  10,000  times  in  twenty-four  hours.  This  estimate  is  based 
upon  the  assumption  that  the  surface  of  the  capillaries  is  equal  to 
about  three-fourths  the  surface  of  the  air  cells.  That  this  is  not  an 
exaggeration  may  be  inferred  from  the  fact  of  an  injected  lung 
appearing  to  consist  of  nothing  but  capillaries.  From  the  capillary 
network  surrounding  the  air  cells  the  pulmonary  veins  arise,  which, 
uniting  wdth  each  other,  gradually  form  four  larger  trunks,  which 

finally  terminate  in  the  left  auricle  of 
^^^'-  ^'^-  the  heart  and  convey  to  it  the  aerated 

oxygenated  blood  to  be  distributed,  as 
we  have  seen,  by  the  arterial  system  to 
all  parts  of  the  body. 

Having  described  the  pulmonary  air 
cells  and  blood  vessels,  the  passage  by 
osmosis  of  the  carbon  dioxide  from  the 
blood  into  the  air  cells  and  of  the  oxy- 
gen from  the  air  cells  into  the  blood, 
let  us  now  consider  the  means  by  wliich 
^,.  ...       f  ,      ,  the  air  is  drawn   into  the    lunffs  and 

Diagrammatic  view  of  i)leiiral  sacs.  o 

expelled  from  them. 

Tlie  heart  and  lungs  are  suspended  by  the  great  blood  vessels  in 
the  thoracic  cavity.  The  thorax  consists  of  the  sternum  ante- 
riorly, the  dorsal  vertebra  posteriorly,  and  the  ribs  laterally.  It  is 
covered  in  above  by  the  cervical  muscles  and  fascia,  below  by  the 
diaphragm,  and  laterally,  etc.,  by  the  intercostal  muscles.  The 
thoracic  cavity  is  therefore  air-tight.  If  the  lungs  be  examined 
in  Situ,  it  will  be  found  that  the  surface  of  each  lung  is  covered  with 
a  serous  membrane  continuous  with  that  lining  the  inner  surface  of 
the  thorax  or  tlie  pleura.  To  understand  the  relations  of  the  pleurse 
to  the  lungs  and  walls  of  the  thorax,  let  us  first  conceive  the  pleura 
as  consisting  of  two  bladders  (Fig.  176),  and  so  placed  within  an 
empty  thorax  that  the  outer  wall  (c)  of  each  bladder  will  adhere 
to  the  inner  surface  of  the  wall  of  the  thorax,  the  inner  walls  (r?) 
of  each  bladder  remaining  free. 

Suppose  now  that  the  heart  and  lungs  be  inserted  between  the 
inner  free  walls  of  the  two  bladders,  and  that  each  of  the  latter  be 
made  to  adhere  to  the  surface  of  the  lung  with  which  it  is  in  con- 
1  Kuss,  Physiologic,  1873,  p.  338. 


THE  PLEURAL  SACS. 


349 


Diagrammatic  view 
interi)Osed. 


)f  pleural  sacs  with  heart  and  luugs 


tact.  Such  a  disposition  being  made  (Fig.  177)  the  bladders  will 
then  represent  the  two  pleurae,  the  inner  walls  {d  d)  the  visceral 
layer,  the  outer  wall  (c  c)  the  parietal  layers,  and  the  space  between 
the  layers  the  pleural  cavities,  the  spaces  between  the  bladders  or 
the  pleura  constituting  the  mediastinal  spaces,  the  narrow  septum 
formed  through  the  union  of  the  two  pleurae  the  mediastinum.  In 
health  the  opposed  sur- 
faces of  the  visceral  and 
parietal  layers  of  the 
pleura  are  always  in  con- 
tact, there  being  only  fluid 
enough  between  them  to 
insure  their  gliding 
smoothly  over  each  other. 
Practically,  therefore,  in 
normal  respiration  there  is 
no  pleural  cavity.  This 
must  necessarily  be  so, 
since  the  thorax  being  an 
air-tight  cage,  as  it  dilates 
through  the  action  of  the 
inspiratory  muscles  and 
recedes  from  the  lungs,  the 
air  within  the  latter  will  expand  and  push  the  lungs  after  the  re- 
ceding thorax  and  so  keep  the  visceral  layer  of  the  pleura  in  contact 
with  the  parietal  one.  The  air  within  the  lungs  becoming  rarefied 
at  the  same  time  through  expansion,  the  external  denser  air  will  pass 
through  the  trachea  into  the  lungs  until  the  pressure  of  the  air  within 
the  latter  is  the  same  as  that  of  the  atmosphere.  It  will  be  observed 
that  while  it  is  the  force  of  the  inspiratory  muscles  that  dilates  the 
chest,  it  is  the  pressure  of  the  air  that  expands  the  lungs,  and,  fur- 
ther, that  inasmuch  as  the  lungs  are  elastic  and  therefore  otfer  a  re- 
sistance to  their  expansion,  the  air  must  overcome  this  resistance,  and 
hence  the  pressure  exerted  by  the  air  within  the  lungs  upon  the  heart 
and  blood  vessels,  etc.,  outside  of  them  must  be  less  than  that  of  the 
external  atmosphere.  Thus,  suppose,  for  example,  that  the  pres- 
sure exerted  by  the  atmosphere  as  measured  by  the  barometer  be 
760  mm.  of  mercury,  and  that  at  the  end  of  a  quiet  inspiration  the 
pressure  exerted  by  the  elastic  tissue  of  the  lung  amounts  to  9  mm. 
of  mercury,  then  the  pressure  of  the  air  within  the  lungs,  that  is, 
the  intra-pulmonary  pressure  as  exerted  upon  the  blood  vessels 
outside  of  the  lungs  would  amount  to  751  mm.  of  mercury,  the 
latter,  or  the  intra-thoracic  pressure,  as  it  is  called,  being  equal  to 
the  difference  between  the  intra-])ulmonary  and  elastic  pressures 
(760  —  9  =  751).  It  should  be  mentioned,  however,  that  as  the 
elastic  tension  exerted  by  the  lungs  is  proportional  to  their  dis- 
tention, that  is  to  the  depth  of  the  inspiration,  the  intra-thoracic 
pressure  maybe  much  less  than  in  the  example  just  given,  amount- 


350  RESPIRATION. 

ing  to  only  720  mm.  of  mercury  ckiring  forced  inspiration,  the 
elastic  tension  then  being  as  much  as  40  mm.  of  mercury  (760  — 
40  =  720).  On  the  other  hand  as  the  thorax  contracts,  and  its 
capacity  diminishes,  the  air  within  the  lungs,  exerting  now  a  greater 
pressure  than  the  air  without,  will  pass  out  of  the  lungs,  through 
the  trachcffi  by  which  it  had  just  entered  the  lungs,  of  course  col- 
lapsing, their  elasticity  now  aiding  the  expulsion  of  the  air  to  the 
same  extent  as  it  formerly  opposed  its  entrance. 

After  what  has  just  been  said  it  is  obvious  that  the  intra-pulmo- 
nary  j^ressure  or  the  pressure  excited  by  the  air  within  the  lungs  is, 
during  inspiration,  negative,  that  is,  less  than  that  of  the  atmos- 
phere, since  the  external  air  then  passes  into  the  lungs,  whereas  dur- 
ing expiration  it  is  positive,  or  greater  than  that  of  the  atmosphere 
since  the  air  then  passes  out  of  the  lungs.  On  the  other  hand  the 
intra-thoracic  pressure,  or  the  pressure  of  the  air  within  the  lungs,  on 
the  blood  vessels,  etc.,  outside  the  latter  will  be  negative,  both  during 
inspiration  and  expiration,  since  as  long  as  there  is  any  air  in  the  lungs 
the  pressure  exerted  by  it  on  the  outside  of  the  latter  will  be  more 
or  less  neutralized  by  the  pressure  exerted  by  the  elastic  pulmo- 
nary tissue.  If,  however,  expiration  be  forced,  as  in  obstruction  of 
the  respiratory  passages  by  violent  coughing,  for  example,  the  air  in 
the  lungs  luay  be  so  compressed  as  to  exert  a  pressure  upon  the 
blood  vessels  outside  the  lungs  as  suffices  not  only  to  neutralize  the 
elastic  tension  of  the  pulmonary  tissue,  thus  rendering  the  pressure 
equal  to  that  of  the  atmosphere,  but  even  to  elevate  the  mercury 
80  mm.  higher  and  of  so  making  the  intra-thoracic  pressure  posi- 
tive, or  higher  than  that  of  the  atmosphere.  As  a  still  further 
proof  that  the  lung  is  pushed  out  by  the  air  within  it  and  not 
pulled  out  by  the  receding  chest  wall  it  may  be  mentioned  that  if 
a  hole  be  made  in  the  chest  the  lungs  will  collapse,  however  forcible 
the  inspiratory  movements  of  the  chest  may  be,  since  there  is  noth- 
ing to  oppose  their  elastic  tension,  the  atmospheric  pressure  being 
exerted  equally  on  both  the  inner  and  outer  surfaces  of  the  lungs. 

The  action  of  the  thorax  and  the  lungs  in  respiration  was  long 
ago  compared  by  Boyle  ^  to  a  bellows  without  a  valve,  but  with  a 
bladder  within.  According  to  Boyle,  who  appears  to  be  the  first  to 
have  comprehended  how  respiration  is  accomplished,  the  air  is 
drawn  into  the  lungs  as  the  thorax  expands  just  as  the  air  was 
drawn  into  the  bladder  as  the  bellows  dilates  and  expelled  from  the 
lungs  as  the  thorax  contracts  as  the  air  is  expelled  from  the  bladder 
as  the  bellows  contracts. 

The  dilatation  of  the  thoracic  cavity  and  the  taking  in  of 
the  air  is  known  as  inspiration,  the  contraction  of  the  thoracic  cav- 
ity and  the  giving  out  of  the  air  expiration,  the  two  acts  constitut- 
ing respiration. 

Let  us  consider  now  a  little  more  in  detail  tlie  means  by  which 
this  alternate  dilatation  and  contraction  of  the  thoracic  cavity  caus- 
ing respiration  is  eifected. 

'Works,  Vol.  i.,  London,  1744,  p.  G4. 


CHAPTER   XXI. 


EESPIEATION.— (Con/m»ef^) 

MUSCLES    OF   RESPIRATION. 

Reflection  iipou  the  origin  and  insertion  of  the  various  mus- 
cles acting  upon  the  thorax  makes  it  evident  that  some  of  these 
muscles  in  contracting  will  expand  the  chest,  causing  inspiration, 
while  the  relaxation  of  these  muscles,  together  with  the  elasticity  of 
the  lungs  and  the  action  of  certain  other  muscles,  will  contract  it, 
causing  expiration.  The  muscles  involved  in  the  production  of 
respiration  will  then  natiu'ally  divide  themselves  into  two  groups, 
those  of  inspiration  and  those  of  expiration.  To  the  study  of  these 
let  us  now  turn. 

Inspiration 

Of  all  the  inspiratory  muscles  the  diaphragm  is  the  most  impor- 
tant, since  the  capacity  of  the  chest  is  enlarged  to  a  greater  extent 
through  its  contraction  than  by  that  of  any  other  muscle.  Indeed, 
in  the  male  sex  at  least,  as 

we  shall  see,  gentle  breath-  Fig.  ITS. 

ing  is  accomplished  almost 
entirely  by  the  action  of  the 
diaphragm.  The  diaphragm 
being  attached  (Fig.  178), 
to  the  ensiform  cartilage  of 
the  sternum,  to  the  carti- 
lages of  the  six  or  seven 
lower  ribs,  and  often,  also, 
to  their  osseous  portions  to 
the  arcuate  ligaments  and 
the  bodies  of  the  first,  second 
and  third  lumbar  vertebra?, 
to  the  invertebral  cartilages 
of  the  right  side,  and  to  the 
bodies  of  the  first  and  second 
lumbar  vertebrae,  etc.,  of  the 
left  (the  crura?)  covers  in 
therefore  the  lower  circum- 
ference of  the  thorax.  From 
this  origin  the  diaphragm 
passes  upward  into  the  cav- 
ity of  the  thorax  as  a  vaulted  arch  or  dome  (Fig.  179,  B),  the  cen- 
tral tendon  being  the  common  point  of  insertion  of  the  muscular 
fibers  wdiicli  are  of  the  voluntary  character.     The  diaphragm  pre- 


Interior  view  of  the  diaphragm.  1,  2,  .3.  The  three 
lobes  of  the  central  tendon,  surrounded  by  tlie  fleshy- 
fasciculi  derived  from  the  inferior  margin  of  the  thorax, 
the  crura,  4,  .5,  and  the  arcuate  ligaments,  6,  7.  8.  Aortic 
orifice.  9.  QSsophageal  oritice.  10.  Quadrate  foramen. 
11.  Psoas  muscle.    12.  Quadrate  lumbar  muscle. 


352 


BESPIRATION. 


sents  several  openings  through  which  pass  the  oesophagus,  aorta, 
vena  cava,  etc.,  and  is  supplied  by  the  phrenic  nerve.  During  the 
state  of  repose,  as  we  have  just  seen,  the  diaphragm  presents  the 
form  of  a  dome  or  of  a  vaulted,  arched,  or  curved  surface.  If  the 
diaphragm,  however,  be  observed    during  contraction,  as  can    be 

readily    done    by    opening 
Fig.  179.  largely  the  abdominal  cav- 

ity of  a  completely  insen- 
sible living  mammal,  a  cat, 
dog,  or  rabbit,  for  example, 
it  will  then  be  seen  that 
through  the  contraction  of 
its  muscular  fibers  the 
curved  surface  of  the  dia- 
phragm assumes  more  the 
form  of  a  plane  (Fig.  179, 
A),  and  that  the  floor  of 
the  thorax  descends,  the 
cardiac  part  more  particu- 
larly from  5  to  40  mm., 
according  to  the  depth  of 
the  inspiration.  The  effect 
of  the  descent  of  the  dia- 
phragm is,  therefore,  to  en- 
large in  a  vertical  direction 
the  capacity  of  the  thorax, 

Diagrammatic  sections  of  the  body  in  inspiration  and     and  tO  rarefy  thc  air  within 
expiration.     A.  Inspiration.     B.  Expiration.     Tr.  Tra-    •,  rpi  ,  1       •      1      • 

chea.     St.  Sternum.      I).  Diaphragm.     Ah.  Abdominal     it.        1X16  CXtemal    air   DCing 

rHuxLEY."  ''"'"^'"^  """^'"^^  ''""''''"'  *"'  stationary  air.     ^j^^^^  dcnSCr  tliau  that  withiu 

the  lungs  rushes  into  the 
latter  and  proportionally  distends  them  in  consequence.  The  dia- 
phragm through  its  contraction  acts  then  as  an  inspiratory  muscle ; 
it  need  hardly  be  added,  however,  that  it  is  not  the  diaphragm, 
but  the  air,  that  actually  distends  the  lungs.  The  author  is  in 
the  habit  of  illustrating  the  action  of  the  diaphragm  in  respira- 
tion by  the  simple  apparatus  represented  in  Fig.  180.  This  con- 
sists of  a  bell-jar  («),  the  walls  of  which  correspond  to  the  thorax, 
and  in  which  are  suspended  the  lungs  {LL),  the  trachea  (2)  pass- 
ing through  the  air-tight  fitting  cork.  The  bottom  of  the  jar  is 
closed  in  air-tight,  with  India  rubber  (5)  corresponding  to  the  dia- 
phragm. It  is  needless  to  say  that  there  is  no  such  amount  of 
space  as  (r?)  corresponding  to  the  pleural  cavity  in  the  human  being 
in  a  state  of  health.  Such  being  the  disposition  of  the  parts,  by 
pulling  down  the  India  rubber  (5)  the  air  within  the  jar  will  be- 
come rarefied  as  indicated  by  the  rise  of  the  mercury  in  the  ma- 
nometer, the  lungs  LL  will  ox])and,  and  the  external  air  will  pass 
into  the  latter  until  the  pressure  is  tlie  same  as  that  of  the  atmos- 
phere.    With  the  elevation  of  the  India  rubber  the  condition  of 


THE  DIAPHEAGM. 


353 


Diagrammatic  view  of  apparatus  to  show  the  action 
of  the  diaphragm. 


the  pressure  of  the  air  ^vithin  and  witliout  the  jar  being  reversed, 
the  air  will  pass  out  of  the  lungs,  the  latter  collapsing.  As  the 
diaphragm  descends  it  pushes  downward  and  forward  the  abdomi- 
nal viscera,  and  as  the  anterior  and  lateral  walls  of  the  abdomen 
are  extensible,  they  give  way  to  the  pressure  so  exerted  and  are 
protruded.  With  each  inspiration,  therefore,  the  descent  of  the 
diaphragm  in  man  becomes  perfectly  evident  through  the  movement 
of  the  abdomen.  The  action  of  the  diaphragm  in  producing  in- 
spiration may  be  readily  imi- 
tated in  man  and  mammal  Fig.  180. 
just  dead,  by  opening  the 
abdomen  and  pulling  the 
central  tendon  downward. 
The  external  air  will  rush 
into  the  lungs,  and  often 
■\^-ith  a  distinctly  audible 
sound.  While  the  vertical 
diameter  of  the  chest  is  en- 
larged throuo;h  the  descent 
of  the  diaphragm,  neverthe- 
less, through  the  attachment 
of  the  latter  to  the  sternum 
and    false    ribs,    during   its 

contraction  through  the  pulling  of  the  sternum  and  the  upper  false 
ribs  downward  and  inward,  and  the  lower  ribs  upward  and  in- 
ward toward  the  vertebral  column,  there  would  be  a  tendency  to 
diminish,  to  some  extent,  the  capacity  of  the  thorax.  This  effect 
is,  however,  counteracted  by  the  ribs  being  elevated  at  the  same 
time  as  the  diaphragm  descends,  and  through  the  action  of  cer- 
tain muscles,  to  be  described  later.  The  elevation  of  the  ribs  is 
such  a  constant  accompaniment  of  the  descent  of  the  diaphragm 
that  in  general  terms  it  may  be  stated  that  inspiration  is  effected  by 
the  descent  of  the  one,  and  the  ascent  of  the  other,  and  this  is  true, 
even  though  the  breathing  appear  entirely  diaphragmatic. 

The  ribs  (Fig.  181)  pass  from  their  articulations  with  the  dorsal 
vertebrae  downward  and  forward ;  they  are  somewhat  twisted  in 
shape  and  are  twelve  in  number.  The  upper  seven  or  true  ribs  are 
articulated  -^rith  the  sternum  ;  of  the  remaining  five  or  false  ribs,  the 
eighth,  ninth,  and  tenth  are  joined  to  the  seventh  rib,  the  last  two 
ribs,  viz.,  the  eleventh  and  twelfth,  are  unattached  anteriorly,  and 
are  hence  known  as  floating  ribs.  As  the  ribs  are  elevated  they 
recede  from  each  other,  the  intercostal  spaces,  with  the  exception  of 
possibly  the  first  two,  being  widened.  At  the  same  time  they  are 
rotated  outward,  assuming  a  more  horizontal  position,  and  in  tend- 
ing to  straighten  themselves  become  less  curved.  Through  their 
attachment  to  the  sternum  the  lower  portion  of  the  latter  is  thrown 
forward,  the  flexibility  of  this  part  of  the  thorax  being  mainly  due 
to  the  sternal  attachment  of  the  ribs  beino;  cartilao-inous  and  not 


23 


354 


RESPIRATION. 


osseous.  The  effect  of  this  change  in  the  form,  position,  and  direc- 
tion of  the  ribs  and  sternum  is  to  enlarge  the  capacity  of  the  chest 
in  every  direction,  vertically  through  the  separation  of  the  ribs, 
laterally  through  their  rotation  outward  and  straightening,  antero- 
posteriorly,  through  the  movement  forward  of  the  sternum. 

As  the  external  air  passes  then  into  the  expanding  lungs,  it  is 
evident  that  inspiration  is  produced  through  the  elevation  of  the 
ribs  as  well  as  through  the  descent  of  the  diaphragm.  The  extent 
of  the  increase  of  the  capacity  of  the  chest  through  the  elevation 
of  the  ribs  is  greatly  influenced  by  the  length,  degree  of  curvature, 
character  of  the  angles  of  the  ribs,  etc.  Thus  from  the  ribs  being 
directed  obliquely  downward  and  forward  when  elevated,  and  as- 
suming a  more  horizontal  posi- 
FiG.  181.  tion  their  external  ends  recede 

from  the  posterior  wall  of  the 
thorax  and  increase  proportion- 
ally its  antero-posterior  diam- 
eter. As  the  ribs  are  elevated 
they  remain  nearly  parallel  to 
each  other  ;  it  follows,  therefore, 
that  the  inspiratory  effect  pro- 
duced by  this  movement  of  the 
ribs  will  be  proportional  to  the 
length,  or,  more  accurately 
speaking,  to  the  length  of  the 
chord  of  the  arc  represented  by 
the  curve  of  the  rib.  This 
length,  however,  varies  consid- 
erably, increasing  rapidly  from 
the  first  to  the  fifth  rib,  attain- 
ing its  maximum  at  the  eighth 
rib,  diminishing  then  progres- 
sively from  the  ninth  to  the 
twelfth.  Other  things  being 
equal,  it  follows,  then,  that  the 
increase  in  the  antero-posterior 
diameter  of  the  chest  is  greater  at  the  level  of  the  seventh  to  the 
ninth  ribs  than  at  the  upper  or  lower  part  of  the  thorax.  It  is 
for  this  reason  that  during  inspiration  the  inferior  portion  of  the 
sternum  moves  so  much  more  forward  than  the  upper  portion.  The 
transverse  diameter  of  the  chest,  on  the  other  hand,  is  greatly  in- 
fluenced by  the  amount  of  the  curvature  of  the  ribs,  and  this  varies 
considerably.  Thus  the  curvature  increases  from  the  first  to  the 
third  ribs,  the  maximum  amount  being  about  that  of  the  sixth ; 
there  is  but  little  difference,  however,  as  regards  the  curvature  of 
the  ribs  included  between  the  sixth  and  ninth.  The  amount  of  the 
curvature  can  be  measured  by  the  versed  sine  of  the  arc  of  the 
circle  represented  by  the  rib,  or,  what  is  the  same  thing,  the  dis- 


Front  view  of  the  thorax.  1,  2,  3.  The  three 
pieces  of  the  sternum.  4,  5.  The  dorsal  vertebrae. 
6.  The  first  true  rib.  7.  Its  head.  8.  Neck.  9. 
Tubercle.  10.  The  seveuth  true  rib.  11.  Costal 
cartilages.  12.  The  Hoatiug  ribs.  13.  Groove  for 
the  intercostal  blood  vessels. 


ACTION  OF  THE  BIBS. 


355 


tance  from  the  middle  line  of  the  thorax  to  the  most  prominent 
part  of  it  laterally.  The  angle  made  by  the  osseons  part  of  the 
ribs  with  their  sternal  or  costal  ones,  and  the  length  of  their  car- 


FiG.   182. 


Dorsal  regiim. 
Expiration.  lu.spiration. 


Fig.  183. 


Anterior  region  of  the  thorax. 
Inspiration.  Expiration. 


Fig.  184. 


Fig.  185. 


Expiration. 


Inspiration. 


tilaginons  portions  increase  from  the  fonrth  to  the  seventh.     Con- 
sequently, it  is  in  this  part  of  the  thorax  that  the  increase  of  capacity 


356  RESPIEA  TION. 

due  to  the  elasticity  and  flexibility  of  the  cartilage  is  greatest.  The 
different  extent  to  which  the  capacity  of  the  thorax  is  enlarged  in 
its  various  diameters  during  inspiration,  the  influence  due  to  the 
variation  in  the  length,  curvature  of  the  ribs,  etc.,  are  shown  by 
the  diagrams  (Figs.  182,  183,  184,  185)  illustrating  the  admirable 
and  exhaustive  "svork  of  Sibson.^  Let  us  consider  now  the  muscles 
which  elevate  the  ribs,  and  so,  together  with  the  action  of  the  dia- 
phragm, cause  inspiration. 

Muscles  of  Eespiratiox. 

Inspiration.  Expiration. 

Ordinary. 

Diaphragm       .....     Internal  intercostals, 

osseous  portion. 
External  interco.stals. 

Internal  intercostals,  sternal  portion.   Triangularis  sterni. 
Scaleui     ......     Infra  costales. 

Levatores  costarum. 

Auxiliary. 
Serratus  posticus  superior         .         .     Oblique. 
Accessorius       .....     Transversal  is. 

Sterno-cleido-mastoid       .         .         .     Sacro  Lumbalis. 

Levator  anguli  scapulte. 

Trapezius,  superior  portion. 

Serratus  magnus. 

Pectorales  major,  inferior  portion. 

Pectorales  minor. 

These  muscles  are  usually  described  as  consisting  of  two  sets, 
ordinary  or  extraordinary,  or  auxiliary,  according  as  the  breathing 
due  to  their  action  is  easy  or  forced.  There  is,  however,  no  such 
sharp  line  of  demarcation  observable,  it  being  impossible  to  say  just 
where  ordinary  easy  breathing  ends,  and  forced  breathing  begins, 
great  difference  being  observed  in  this  respect  within  the  limits  of 
health,  according  to  individual  peculiarities.  There  are  certain 
muscles,  however,  such  as  the  external  intercostals,  scaleni,  etc., 
w^iich  intervene  in  easy  inspiration  ;  these  we  will  consider  first, 
and  afterward  those  coming  into  play  when  the  breathing  is  ex- 
aggerated. That  the  external  intercostal  muscles  (Fig.  186,  2)  are 
inspiratory  in  function  one  would  infer  from  their  attachments,  and 
the  direction  of  their  fibers.  Passing  from  rib  to  rib  from  above 
downward,  and  from  behind  forward,  in  contracting  these  muscles, 
will  approximate  and  elevate  the  ribs.  Experiment  justifies  this 
view  of  the  inspiratory  function  of  the  external  intercostal  muscles, 
since,  if  they  be  expo.sed  in  a  living  animal  Avith  each  insi^iration, 
they  will  be  seen  in  contracting  to  elevate  the  ribs.  Inasmuch, 
however,  as  the  general  direction  of  the  sternal  portion  of  the  inter- 
nal intercostals  is  also  from  above  doAvnward,  and  rather  forward 
than  l)ackward,  through  the  change  in  the  curve  of  the  rib,  analogy 
would  lead  us  to  suppose  tliat  their  action  is  the  same  as  that  of  the 
'Phil.  Trans.,  1846,  p.  501. 


INSPIRA TORY  MUSCLES. 


60  i 


external  intorcostals,  and  that  they  must,  therefore,  be  also  regarded 
as  inspiratory  in  function.  This  view  is  confirmed  by  the  observa- 
tions of  Berard/  made  upon  a  man  in  whom  the  pectoral  muscle 
was  so  atrophied  as  to  permit  of  an  experimental  investigation  of 
the  function  of  the  partly  exposed  sternal  portion  of  the  internal 
intercostal  muscle.  When  the  sternal  part  of  the  muscle  was  stimu- 
lated, the  cartilage  of  the  second  rib  was  elevated,  and  with  it  the 
anterior  extremity  of  the  corresponding  osseous  rib. 

The  scaleni  passing  obliquely  downward  from  their  origin,  the 
transverse  processes  of  the  lower  six  cervical  vertebne,  to  their 
insertion,  the  first  and  second 

ribs,    in    acting    from    their  Fig.  186. 

orisfin  during;  contraction  will 
elevate  these  ribs,  and  indi- 
rectly the  whole  thorax.  To 
prove  that  the  scaleni  do  act 
in  this  way  it  is  only  neces- 
sary to  sc£ueeze  between  the 
fingers  the  part  of  the  neck 
including  these  muscles  to 
feel  them  contract  Avith  each 
inspiration.  The  movement 
then  experienced,  the  so- 
called  respiratory  pulse  of 
Magendie,-  becomes  very 
evident  when  the  superior 
part  of  the  chest  is  much  di- 
lated. The  action  of  the 
scaleni  is  not  only  to  elevate 
the  ribs,  but  to  fix  the  first 
rib  as  an  origin  from  which 
the  intercostal  muscles  that 
elevate  the  ribs  can  act.  Ordinarily  inspiration  is  also  effected 
by  the  levatores  costariun  (Fig.  186)  as  these  muscles,  arising  from 
the  transverse  processes  of  the  twelve  dorsal  vertebrae,  and  in- 
serted fan-like  into  the  upper  edges  of  the  ribs  between  the  tu- 
bercles and  the  angles  in  contracting,  elevate  the  ribs.  The  action 
of  the  muscles,  which  we  have  just  considered,  usually  suffices 
to  produce  easy  inspiration.  When  breathing,  however,  becomes 
difficult,  labored,  or  very  difficult,  then  inspiration  is  aided  through 
the  contraction  of  several  muscles,  the  serratus  posticus  superior, 
accessorius,  sterno-cleido-mastoid,  levator  anguli  scapulae,  superior 
portion  of  the  trapezius,  serratus  magnus,  and  the  pectoral  muscles. 
It  is  not  necessary  to  dwell  upon  the  anatomical  disposition  of 
these  muscles  to  prove  their  importance  in  labored  inspiration. 
It  is  evident  that  the  serratus  posticus  superior  passing  trom  the 

^  Physiologic,  Tome  iii.,  p.  269. 

^Precis  elementaire  de  physiologie,  2(1  ed.,  Tome  ii.,  p.  323. 


View  of  several  of  the  middle  dorsal  vertebra  and 
ribs,  to  show  the  intercostal  muscles  (A,  B).  J^.  A. 
P'rom  the  side.  B.  From  behind.  1, 1.  The  levatores 
costarum  muscles,  short  and  long.  2.  The  external 
intercostal  muscles.  3.  The  internal  intercostal 
layer  shown,  in  the  lower  of  the  two  spaces  repre- 
sented, by  the  removal  of  the  external  layer,  as  seen 
in  A  in  the  upper  space,  in  front  of  the  external  layer. 
The  deficiency  of  the  internal  layer  toward  the  ver- 
tebral column  is  shown  in  B.     (After  Cloc^uet.  ) 


358  RESPIRATION. 

vertebral  column  to  be  inserted  into  the  second,  third,  fourth,  and 
fifth  ribs,  will,  in  contracting,  elevate  the  ribs,  that  the  accessorius, 
extending  from  the  last  cervical  vertebrae  to  the  angle  of  the  ribs, 
will  produce  the  same  effect.  The  sterno-cleido-mastoid  acts  upon 
the  clavicle  and  sternum,  and  the  levator  anguli  scapulse,  trapezius, 
and  serratus  magnus,  through  the  scapula.  Finally,  the  upper  ex- 
tremities being  fixed,  the  pectoral  muscles,  reversing  their  action, 
will  elevate  the  ribs,  their  force  under  such  circumstances  acting 
upon  the  thorax  instead  of  from  it.  The  serrati  postici  inferiores 
and  quadrate  lumborum  muscles  are  regarded  by  some  physiologists 
as  aiding  the  muscles  just  mentioned  in  deep  inspiration  ;  according 
to  others,  these  muscles  are  expiratory  in  character. 

Expiration. 

Expiration  is  essentially  a  passive  process,  consisting  in  the  re- 
turn of  the  thorax  to  the  condition  in  which  it  was  before  inspira- 
tion. The  ascent  of  the  diaphragm,  and  the  descent  of  the  ribs  in 
diminishing  the  capacity  of  the  thorax,  cause  the  expulsion  of  the 
air,  or  expiration.  The  relaxation  of  the  inspiratory  muscles  is, 
however,  accompanied  by  the  contraction  of  certain  muscles  which 
together  with  the  elasticity  of  the  lungs  aids  in  expelling  the  air 
from  the  chest.  Inasmuch  as  the  fibers  of  the  osseous  portion  of 
the  internal  intercostal  muscles  (Fig.  186)  pass  from  rib  to  rib  in 
exactly  the  opposite  direction  as  those  of  the  internal  intercostal — 
that  is,  from  above  downward,  but  backward — we  would  naturally 
conclude  that  in  contracting  they  would  depress  the  ribs  instead  of 
elevating  them,  that  their  function  is  expiratory  instead  of  inspira- 
tory. Experiment  proves  that  this  view  is  correct,  since,  if  the 
osseous  portion  of  the  internal  intercostal  muscles  be  exposed  in 
a  living  animal  by  dissecting  off  the  external  ones,  they  will  be 
found  to  contract  during  expiration.  This  antagonism  in  the  ac- 
tion of  the  internal  and  external  intercostal  muscles  may  be  illus- 
trated by  a  simple  mechanical  arrangement  known  as  Hamberger's 
apparatus,  though  it  was  really  invented  by  Bernouilli.  This  con- 
sists (Fig.  187,  A)  of  two  bars  (a  and  h),  which  are  attached  on 
the  one  hand  to  a  long  vertical  rod  (c)  firmly  supported,  and,  on 
the  other  hand,  to  a  short  one  {d).  The  two  bars,  tlie  long  and  the 
short  vertical  rods,  represent  respectively  the  spinal  column,  two 
ribs,  and  a  portion  of  the  sternum.  The  two  bars  («  and  6)  are 
maintained  in  the  horizontal  position  by  two  elastic  bands  {w  z  and 
X  y),  which  are  so  attached  that  as  they  pass  from  bar  to  bar  they 
cross  each  other  at  nearly  right  angles.  The  elastic  band  {x  y) 
passing  from  above,  downward  and  forward,  represents  the  external 
intercostal  muscle,  the  band  [w  z)  passing  from  above  doAvnward, 
but  backward,  the  osseous  portion  of  the  internal  intercostal  mus- 
cle. If  the  band  {w  z)  be  removed  (Fig.  187,  B),  there  being 
nothing  to  oppose  the  elasticity  of  the  band  x  y,  or  the  external 
intercostal  muscle,  the  bars  or  ribs  will  be  elevated.     If  the  band 


EXPIRATORY  MUSCLES. 


359 


w  z  be  now  replaced,  and  the  band  x  y  removed  (Fig.  187,  C), 
then  the  bars  of  the  ribs  will  be  depressed,  there  being  nothing  to 
oppose  the  elasticity  of  the  band  w  z.  While  the  action  of  the  ex- 
ternal and  internal  intercostal  muscles  in  respiration,  as  we  have 
described  them,  appears  to  be  capable  of  demonstration  in  the  liv- 
ing animal  and  imitated  by  mechanical  contrivances,  nevertheless, 
it  must  be  admitted  that  the  action  of  these  muscles  has  given  rise 


Fig.  187 


Diagram  of  models  illustrating  the  actiou  of  the  external  and  internal  intercostal  muscles. 
B.  Inspiratory  elevation.     C.  Expiratory  depression.     (Huxley.) 

to  more  discussion  than  that  of  all  the  other  muscles  in  the  body, 
and  that  the  most  diverse  opinions  have  been  offered,  and  are  still 
held  as  to  their  function.  Thus,  while  according  to  Borelli,  Haller, 
and  Cuvier,  both  the  external  and  internal  intercostal  muscles  are 
inspiratory,  just  the  opposite  opinion,  that  they  are  both  expiratory 
was  held  by  Vesalius,  Beau  and  Maissiat  Galen.  Bartholinus  con- 
sidered the  external  intercostals  to  be  expiratory,  the  internal  in- 
spiratory, while  Spigelius  and  Yesling  held  the  external  intercos- 
tals to  be  inspiratory,  the  internal  expiratory.  The  external  and 
internal  intercostals  were  regarded  at  once  inspiratory  and  expira- 
tory by  Mayow  and  Magendie,  while  according  to  Arantius  and 
Cruveilhier,  both  the  internal  and  external  intercostals  are  passive 
in  inspiration  and  expiration,  performing  simply  the  office  of  a  re- 
sisting wall  in  respiration. 

Whatever  view  may  be  held  as  to  the  function  of  the  internal 
intercostal  muscles  in  respiration,  there  can  be  no  doubt  that  the 
triangularis  sterni  and  infracostalis,  and  possibly,  as  already  men- 
tioned, the  serratus  posticus  inferior,  are  expiratory  muscles.  The 
triangularis  sterni  acting  from  its  origin,  the  ensiform  cartilage,  the 
lower  border  of  the  sternum,  and  the  lower  costal  cartilages,  in 
drawing  down  the  cartilages  of  the  second,  third,  fourth,  and  fifth 
ribs  must  diminish  the  capacity  of  the  chest.  The  infracostales 
produce  the  same  effect,  their  fibers  passing  from  the  inner  surface 
of  one  rib  to  the  inner  surface  of  the  first,  second,  and  third  below, 
their  action  being  from  below  upward.  The  muscles  that  we  have 
just  described  visually  suffice  in  tranquil  expiration  ;  in  difficult  or 


360  RESPIRATION. 

labored  expiration,  iu  the  acts  of  blowing,  phonation,  etc.,  the  mus- 
cles entering;  into  the  formation  of  the  abdominal  walls  also  conie 
into  play.  The  general  effect  of  these  muscles,  viz.,  the  external 
and  internal  oblique,  transversalis,  sacro-lumbalis,  etc.,  is  in  con- 
tracting to  push  up  the  abdominal  viscera  and  diaphragm  into  the 
thorax,  diminishing  its  capacity  in  the  vertical  diameter ;  these 
muscles,  however,  in  being  attached  to  the  ribs  or  costal  cartilages 
depress  at  the  same  time  the  ribs  and  consequently  diminish  the 
thorax  in  its  antero-posterior  and  transverse  diameters  also.  The 
effect  of  these  muscles  is,  therefore,  to  aid  powerfully  in  the  expul- 
sion of  the  air  from  the  chest  in  forced  expiration,  and  as  their 
action  and  that  of  the  diaphragm  is  more  or  less  voluntary,  and 
at  the  same  time  opposed  to  each  other,  the  intensity  and  dura- 
tion of  expiration  can,  to  a  great  extent,  be  regulated  arbitrarily. 
The  importance  of  this  relation  is  well  seen  in  singing,  in  performing 
upon  wind  instruments,  etc.,  the  skill  exhibited  depending  largely 
upon  the  nicety  with  which  the  contractions  of  these  muscles  can 
be  adjusted  to  each  other. 

We  have  already  seen  that  the  lungs  are  elastic,  and  were  it  not 
for  the  pressure  exerted  upon  the  inner  surface  of  the  lungs  by  the 
inspired  air  the  lungs  would  collapse  in  virtue  of  this  elasticity,  and 
a  considerable  space  in  consequence  would  be  left  between  the  lungs 
and  the  chest-wall.  The  natural  tendency  of  the  lungs  to  contract 
through  their  elasticity  is  well  seen  when  air  is  allowed  to  enter  the 
pleural  cavities.  Under  such  circumstances  as  already  mentioned 
the  atmospheric  pressure  being  exerted  equally  on  both  the  inner 
and  outer  surfaces  of  the  lungs,  there  is  nothing  to  oppose  their 
elasticity  and  the  lungs  therefore  collapse.  If  one  end  of  a  tube  be 
passed  into  the  trachea  of  an  animal  just  dead,  and  ligated,  and  the 
other  end  be  inserted  into  a  water  or  mercurial  manometer,  with  the 
entry  of  air  through  an  oj)ening  made  into  the  pleural  cavity  the 
lungs  will  collapse  iu  virtue  of  their  elasticity,  the  level  of  the  liquid 
in  the  proximal  end  of  the  manometer  will  be  observed  to  fall,  that 
of  the  distal  end  to  rise,  the  difference  in  the  level  of  the  two  indi- 
cating and  measuring  the  amount  of  elastic  force  exerted.  It  was 
in  this  way  that  Carson  ^  first  showed  that  the  elasticity  of  the  lungs 
in  the  calf,  sheep,  or  dog  would  support  a  column  of  water  twelve 
to  eighteen  inches  in  height,  and  in  the  rabbit  six  to  ten  inches, 
and  exert  a  pressure  in  man  amounting  to  about  half  a  pound  upon 
the  square  inch. 

Finally,  the  contractility  of  the  bronchi  and  elasticity  of  the 
thoracic  walls  themselves  contribute  iu  expelling  the  air  from  the 
chest.  It  is  usually  considered  that  in  inspiration  the  upper  ribs 
are  elevated  before  the  lower,  and  in  expiration  the  lower  ribs  are 
depressed  before  the  upper,  the  motion  being  wave-like  from  above 
downward  and  from  below  upward.  According,  however,  to  the 
observations  of  Ransome^  it  would  appear  that  the  reverse  ob- 
'Phil.  Trans.,  1820,  p.  29.  2.Stethometer,  1870,  p.  37. 


DIFFERENCE  OF  BREATHING  IN  SEXES. 


361 


tains,  the  lower  ribs  in  inspiration  being  elevated  first  and  the 
upper  ones  last,  and  that  in  expiration  it  is  the  upper  ribs  that  are 
depressed  first  and  the  lower  ones  last.  Even  if  such  is  the  case, 
it  is  not  inconsistent  with  the  view  that  the  upper  part  of  the  chest 
is  moved  first  in  inspiration,  the  lowest  last,  since  if  the  scaleni  act 
before  the  intercostal  muscles  the  upper  ribs  would  be  elevated  be- 
fore the  lower  by  the  action  of  the  scaleni,  even  if  the  lower  inter- 
costal muscles  contracted  before  the  upper.  It  is  possible  that  the 
difference  of  opinion  in  reference  to  the  order  in  which  the  ribs  are 
elevated  and  depressed  is  due  to  the  action  of  the  intercostal  muscles 
being;  considered  without  reference  to  the  simultaneous  action  of  the 
other  respiratory  muscles. 

While,  in  a  general  way,  it  can  be  said  that  inspiration  is  due  to  the 
descent  of  the  diaphragm  and  the  ascent  of  the  ribs,  and  expiration 
to  the  ascent  of  the  diaphragm  and  descent  of  the  ribs,  neverthe- 
less, there  is  a  noticeable  difference,  described  more  particularly  by 
Bean  and  Maissiat,^  as  to  the  relative  importance  of  the  parts  played 
by  the  diaphragm  and  the  ribs,  as  observed  in  the  breathing  of  the 
two  sexes.  Thus  while  in  the  male  sex  breathing  is  accomplished 
by  the  diaphragm  and  the  inferior  part  of  the  thorax,  or  the  portion 


Fig.  188. 


Fig.  189. 


The  changes  of  the  thoracic  and  abdominal 
walls  of  the  male  during  resijiratiou. 


The  same  in  the  female.     (Hutchinson.) 


below  the  sixth  rib,  in  the  female  sex  it  is  the  superior  part  of  the 
chest,  or  that  above  the  seventh  rib  (Figs.  188,  189),  which  takes 
an  active  part  in  respiration.  It  might  be  supposed  that  the  supe- 
rior costal  type  of  breathing  characteristic  of  the  female  is  due  to 

iArchive.s  generalcs  de  medecine,  1843,   3d  ser.,  t.  xv.,  p.  397  ;  4th  ser.,  1843, 
t.  i.,  p.  265  ;  t.  ii.,  p.  257  ;  t.  iii.,  p.  249. 


362  EESPIEA  TION. 

peculiarities  of  dress,  such  as  the  wearing  of  corsets,  the  squeezing 
of  the  Avaist,  etc.,  which  would  interfere  with  or  prevent  even 
the  lower  part  of  the  chest  expanding,^  That  this  is  not  the  only- 
cause,  however,  is  proved  by  the  fact  that  the  superior  costal 
t^^e  of  breathing  prevails  even  in  females  that  have  never  worn 
any  kind  of  clothing  whatever.  That  the  superior  costal  type  of 
breathing  is  of  advantage  to  the  female  is  obvious  when  one  con- 
siders the  extent  to  which  the  abdominal  viscera  and  diaphragm  are 
pushed  up,  as  is  the  case  during  pregnancy,  through  the  enlarge- 
ment of  the  uterus.  Under  such  circumstances,  if  the  breathing  of 
the  female  was  of  the  inferior  costal  type  and  diaphragmatic,  like 
that  of  the  male,  inspiration  would  be  difficult  and  labored.  It  is 
also  on  account  of  this  peculiarity  in  breathing  that  women  can 
tolerate  with  so  little  inconvenience  large  accumulations  of  fluid  in 
the  abdominal  cavity.  While  in  the  adult  the  diaphragmatic  in- 
ferior costal  type  of  respiration  of  the  male  as  contrasted  with  the 
superior  costal  type  of  the  female  is  perfectly  evident,  the  distinction 
in  young  children  is  not  noticeable.  Indeed,  children  under  about 
ten  years  of  age  breathe  almost  entirely  by  the  diaphragm.  It  is 
not,  as  a  general  rule,  until  near  puberty  that  the  distinction  in 
breathing  characteristic  of  the  adult  sexes  becomes  apparent. 
Boerhaave,'  however,  states  that  the  difiFerence  in  the  types  of 
breathing  in  the  sexes  in  some  cases  manifested  itself  as  early  as  the 
first  year. 

1 T.  J.  Mays,  The  Therapeutic  Gazette,  1887,  p.  297. 
2  Prselectiones  Academiae,  Gottingen,  1744,  p.  144. 


CHAPTER    XXII. 

'RESFIRATIOS.— (Continued.) 

RESPIRATORY  MOVEMENTS  AS  STUDIED  BY  THE  GRAPHIC 

METHOD. 

XoTWiTHSTAXDiXG  that  the  respiratory  movements  are  evident 
to  the  eye,  and  that  the  respiratory  organs  can  be  connected  with- 
out injury  with  apparatus  for  recording  their  movements,  it  must 
be  admitted  that  the  application  of  the  graphic  method  to  the  study 
of  respiration  does  not  give  as  satisfactory  results  as  is  the  case  in 
the  study  of  the  circulation.  Of  the  instruments  devised  for  the 
recording  of  the  respiratory  movements  graphically,  the  author  has 
found  the  pneumograph  and  stethometer  to  be  among  the  most  use- 
ful. The  pneumograph,  invented  by  Marey  ^  (Fig.  1 90),  consists  of 
an  elastic  plate  A,  which  is  applied  to  that  part  of  the  chest  whose 

Fig.  190. 


Pneumograph. 

movements  it  is  desired  to  study,  and  firmly  secured  there  by  tapes 
passing  around  the  neck  from  the  edge  of  the  plate  and  around  the 
chest  from  the  pillars  B  and  C,  projecting  from  the  plate.  To  the 
lower  end  of  the  pillar  B  is  attached  a  spring  (D),  the  free  end  of 
which  is  so  attached  that  it  presses  against  the  elastic  membrane 
covering  in  the  lower  surface  of  an  air-drum  (E),  the  latter  com- 
municating through  a  caoutchouc  tube  (F),  with  a  recording  tam- 
bour. With  the  bending  of  the  elastic  plate  A  through  the  expan- 
sion of  the  chest,  the  pillars  B  and  C  recede  from  each  other,  the 
spring  D  cea.sing  at  the  same  time  to  press  on  the  membrane  of  the 
air-drum  E.  The  air  within  the  drum  being  therefore  rarefied,  the 
air  from  the  recording  tamljour  is  drawn  into  it,  and  the  lever  at- 
tached to  the  tambour  is  depressed.  AVith  the  contraction  of  the 
chest  the  elastic  plate  straightens,  the  pillars  approach  each  other, 
the  spring  presses  against  the  elastic  membrane,  the  air  is  driven  out 
'  La  methode  Graphique,  p.  542. 


364 


RESPIRATION. 


of  the  drum  into  the  tambour,  and  the  lever  is  elevated.  The  de- 
pression of  lever  corresponds,  therefore,  to  inspiration,  the  elevation 
to  expiration.  By  placing  the  lever  of  the  recording  tambour  in 
contact  with  the  blackened  surface  of  the  cylinder  moving  by  clock- 


FiG.  191. 


L'pper  liue,  trace  of  cbronogiaph. 


Lower  line,  trace  of  respiratory  movemeuts.     Takeu  with 
pneumograph. 


Avork,  we  obtain  a  trace  like  that  of  Fig.  191,  representing  the 
breathing  of  a  man  set.  thirty  years.  In  this  trace  the  distance 
from  a  to  c  represents  one  respiration  ;  the  part  of  the  trace  from  a 
to  h,  due  to  the  descent  of  the  lever,  being  inspiratory  in  origin, 

that  of  ()  to  r-  due  to  the 
Fig.  192.  ascent  of  the  lever  expira- 

tory. It  will  be  observed 
that  the  inspiratory  move- 
ment, as  recorded  in  its 
trace,  a  to  h,  is  extremely 
abrupt,  becoming  more 
gradual  at  its  close,  and 
that  the  expiratory  move- 
ment (1)  to  e)  is  equally  ab- 
rupt at  the  beginning,  but 
that  the  gradual  movement 
at  the  termination  is  more 
marked  even  than  in  the 
case  of  the  inspiratory 
movement.  In  order  to 
determine  accurately  the 
number  of  respirations  in  a 
given  time,  the  length  of 
time  of  one  respiration,  the 
relative  duration  of  one  in- 
spiration and  expiration ; 
the  existence  of  pauses,  if 
any,  after  inspiration  and  expiration,  it  is  necessary  to  make  use  of 
some  chronographic  apparatus,  by  means  of  which  we  can  record 
graphically  the  time  elapsing  during  which  the  respiratory  move- 


>retronome. 


METRONOME.  365 

ments  are  being  studied.  For  this  purpose  we  make  use  of  the 
metronome  in  connection  with  an  electro-magnet.  The  metronome 
(Fig.  192)  is  the  same  as  that  used  by  musicians,  except  that  it  is  con- 
structed that,  with  each  beat  of  the  pendulum  a  spring  is  elevated  and 
depressed,  to  which  are  attached  two  needles,  dipping  into  mercury- 
cups.  This  is  accomplished  by  drawing  out  or  pushing  in  a  rod  to 
which  the  spring  carrying  the  needles  is  attached,  and  which,  by  so 
doing,  brings  the  spring  in  contact  with  the  periphery  of  either  one 
of  four  wheels  having  a  different  number  of  cogs.  The  number  of 
movements  of  the  spring  will  depend,  therefore,  upon  the  particular 
Avheel  with  whose  cogs  it  is  in  contact.  The  four  wheels  are  ro- 
tated by  the  axis  common  to  them,  and  a  fifth  one,  Avhose  motion  is 
due  to  an  axis,  moved  by  clockwork,  which  is  regulated  by  a  pen- 
dulum. With  the  elevation  of  the  spring  the  needles  are  raised 
out  of  the  mercury  in  the  cups,  and  with  its  depression  they  sink 
into  it  again.  As  the  needles  are  elevated  and  depressed  the  cur- 
rent, passing  from  the  battery  through  the  needles  and  mercury  to 
the  electro-magnet,  is  made  or  broken,  and  the  marker  connected 
with  the  latter  synchronously  depressed  and  elevated  in  the  manner 
already  described.  In  the  trace  obtained  by  applying  the  marker 
of  the  electro-magnet  to  the  blackened  surface  of  the  revolving  cyl- 
inder as  the  pendulum  beat  at  the  rate  of  sixty  seconds  to  the  min- 
ute, the  distance  between  two  vertical  lines  represents  one  second, 
and  as  one  respiration  was  performed  in  three  seconds  the  number 
of  respirations  was  twenty  per  minute,  the  breathing  being  more 
rapid  than  usual,  the  average  number  of  respirations  throughout  the 
day  being  from  fifteen  to  eighteen  per  minute.  It  will  be  observed 
from  a  comparison  of  the  traces  (Fig.  191)  that  the  duration  of  one 
respiration  was  three  seconds,  the  inspiratory  part  lasting  one 
second,  the  expiratory  two  seconds,  and  that  the  expiratory  lasted, 
therefore,  twice  as  long  as  the  inspiratory  effort ;  furtlier,  that  there 
was  no  appreciable  pause,  either  after  inspiration  or  expiration,  a 
gradual  slowing  up  of  the  movement  only  being  noticeable  after 
either.  Finally  the  little  undulations  of  the  trace  noticeable  at  the 
termination  of  expiration  are  cardiac  in  origin. 

The  object  of  the  stethometer  is  not  only  to  record  the  respira- 
tory movements  graphically,  but  to  determine  also  their  extent. 
The  instrument  consists  (Fig.  193)  of  two  parallel  bars,  the  lower 
ends  of  which  are  firmly  screwed  at  right  angles  into  a  crossbar  so 
as  to  form  a  rigid  frame.  Through  one  of  the  bars  passes  a  slen- 
der rod  (B'),  terminating  in  a  convex  ivory  knob  (B).  By  means 
of  a  screw  the  extent  to  which  the  rod  and  knob  are  pushed  within 
the  frame  can  be  varied  as  needed  and  firmly  fixed.  The  opposite 
bar  carries  a  spring  (I),  the  upper  part  of  which  carries  a  horizontal 
pin,  terminating  at  one  end  in  an  ivory  knob,  and  at  the  other  in  a 
brass  disk,  the  latter  being  in  contact  with  the  tambour  (A)  attached 
to  the  upper  part  of  the  bar.  The  two  ivory  knobs  not  only  face 
each  other,  Isut  lie  in  the  same  axis.     The  receiving  tambour  com- 


366 


BE8PIEATI0N. 


municates  by  means  of  the  tube  J  M'itli  the  recording  portion  of  the 
apparatus,  and  also  through  the  T-tube  with  an  India-rubber  ball,  the 
latter  being  used  to  fill  both  tambours  and  communicating  tube  (D). 

The  manner    of  adapting 
Fig.  193.  the  stethometer  to  the  chest 

\Adll  de})end  upon  the  part 
whose  movement  it  is  desired 
to  examine.  If,  for  example, 
we  wish  to  obtain  a  graphic 
representation  of  the  move- 
ments of  the  chest  in  a  trans- 
verse direction,  let  the  in- 
strument be  so  applied  that 
the  ivory  knobs  will  jjress 
upon  the  eighth  rib.  The 
knob  being  firmly  fixed,  with 
the  expansion  of  the  chest, 
the  rib  will  press  outwardly 
the  knob  of  the  receiving 
tambour,  the  air  will  be 
driven  out  of  it  into  the  re- 
cording one,  and  the  lever 
will  be  elevated ;  with  the 
contraction  of  the  chest  the 
air  will  return  from  the  re- 
cording to  the  receiving  tam- 
bour lever,  and  the  lever  will 
be  depressed.  With  the  steth- 
ometer, therefore,  inspiration 
corresponds  to  the  elevation 
of,  and  expiration  to  the  de- 
scent of  the  recording  lever,  just  the  opposite  to  what  happens,  as 
we  have  seen,  when  the  pneumograph  is  used.  To  obtain  a  trace 
representing  the  enlargement  of  the  chest  in  an  antero-posterior  di- 
rection, the  stethometer  can  be  applied  so  that  the  ivory  knobs  are 
in  contact  with  the  manubrium  sterni  and  the  third  dorsal  spine,  or 
the  eusiform  cartilage  and  the  tenth  dorsal  spine  respectively.  Fig. 
194  is  that  of  the  trace  obtained  by  the  stethometer  as  applied  to 
the  seventh  ribs  in  the  case  of  a  healthy  man,  set.  30  years,  and  is 
a  graphic  representation,  therefore,  of  the  respiratory  movements, 
in  so  far  as  they  depend  upon  the  enlargement  of  the  chest  in  a 
transverse  direction  in  that  particular  part  of  the  chest. 

It  is  not  necessary  to  dwell  upon  the  peculiarities  of  the  trace 
recorded  by  the  stethometer.  It  Avill  be  observed  that  the  part  of 
the  trace  from  a  to  h  corresponds  to  the  inspiration,  that  from  h  to 
c  to  expiration,  and  tliat  the  relative  duration  of  inspiration  to  ex- 
piration is  somewhat  different  from  that  observed  in  the  trace  ob- 
tained by  the  pneumograph,  the  number  of  respirations  being  in 


Recording  stethometer.  A.  Tympanum.  B.  Ivory 
knob.  B'.  Kod  which  carries  the  knob  opposed  to  B. 
C.  T-tube,  by  which  A  communicates,  ou  the  one 
hand,  with  the  recording  tympanum,  on  the  other 
with  an  eUistic  bag  (D).  The  purpose  of  the  bag  is 
to  enable  the  observer  to  vary  the  quantity  of  air  in 
the  cavity  of  the  tympanum  "at  will.  The  tube  lead- 
ing to  it  can  be  closed  by  a  clip.     (Sanderson.) 


THE  STETHOMETEB. 


367 


this  case  eighteen  to  the  minute.  On  an  average  the  ratio  of  in- 
spiration to  expiration  is  as  5  to  6.  In  order  to  determine  the  ex- 
tent of  the  enlargement  of  the  chest  by  the  stethometer,  the  in- 
strument must  be  graduated.  This  can  be  done  either  by  placing 
successively  between  the  ivory  buttons,  rods  differing  by  a  known 
length,  and  observing  the  diff'erent  levels  to  which  the  lever  is  ele- 
vated, according  to  the  rod  used,  the  vertical  distances  between  the 
horizontal  lines  made  by  the  lever  corresponding  to  a  definite  in- 
crease in  the  distance  between  the  ivory  knobs  of  the  particular  di- 
ameter of  the  chest  examined,  or  by  placing  directly  underneath  the 
ivory  knobs  a  graduated  rod,  carrying  a  vertical  slide,  which  can 
be  pushed  against  the  mova}:)le  knob,  and  noticing  the  different 
heights  to  which  the  recording  lever  is  elevated.     In  the  trace  rep- 

FiG.  194. 


upper  line  trace  of  respiratory  movements  taken  with  stethoineter. 

chronograph. 


Lower  line  trace  of 


resented  in  Fig.  194,  the  elevation  of  the  lever  through  the  space  a 
to  b  corresponds  to  an  increase  of  about  2  mm.  {-^^  of  an  inch)  in 
the  lateral  diameter  of  the  chest. 

AVhile  in  tranquil  breathing  the  increase  in  the  antero-posterior 
diameter  of  the  thorax  may  be  only  one  mm.  {-^-^  of  an  inch)  in 
forced  breathing,  according  to  Ransome,^  it  may  amount  to  as  much 
as  12  to  30  mm.  (i  to  1.2  inch). 

It  may  be  mentioned  that  the  movements  of  the  diaphragm  can 
be  studied  graj^hically  in  an  animal  by  inserting  through  the  ensi- 
form  cartilage  or  the  abdominal  walls  a  long  probe,  so  that  one  end 
will  be  in  contact  Avith  the  diaphragm  and  the  other  with  a  record- 
ing lever. 

In  describing  the  circulation  it  will  be  remembered  that  attention 
was  called  to  the  large  undulations  present  in  the  curve  of  blood 

'Sanderson,  Handbook  Phys.  Lab.,  p.  302. 


368  BESPIBA  TION. 

pressure,  and  which  at  that  time  were  simply  stated  as  being,  to  a 
certain  extent  at  least,  respiratory  in  origin.  In  order  to  study  the 
influence  of  the  respiration  upon  the  circulation,  it  is  essential  that 
a  comparison  should  be  made  between  the  curves  of  blood  pressure 
and  respiration  taken  simultaneously.  In  the  case  of  man  this  can 
be  done  by  applying  at  the  same  time  the  cardiograph  and  pneumo- 
graph and  comparing  the  traces  so  obtained,  or  in  an  animal  by  con- 
necting a  recording  tambour  with  its  trachea,  and  comparing  the 
respiratory  trace  so  obtained  with  that  of  the  pressure  of  the  blood 
in  its  carotid  artery,  taken  in  the  manner  already  described.  A 
comparison  of  the  traces  of  the  respiratory  movements  and  the  blood 
pressure  in  a  rabbit  (Fig.  195),  taken  by  the  latter  method,  shows 

Fig.  195. 


Traces  of  blood  pressure  and  respiratory  movements  of  rabbit  taken  simultaneously.     Lower 
trace  blood  jiressure.     Upper  trace  respiratory  movements. 

that  in  this  case  at  least  the  inspiration  is  almost,  if  not  absolutely, 
synchronous  with  the  rise  of  blood  pressure  and  expiration  with  the 
fall,  the  relation  between  the  two  naturally  suggesting  that  inspira- 
tion is  the  cause  of  the  one,  expiration  of  the  other.  Nevertheless, 
reflection  makes  it  clear  that  respiration  on  the  whole  favors  the 
circulation  of  the  blood  even  though  inspiration  promotes  it  to  a 
greater  extent  than  expiration.  Let  us  consider  in  detail  a  little 
why  this  must  be  the  case.  During  inspiration,  as  the  chest  ex- 
pands, the  air  within  the  lungs  becomes  rarefied  and  the  external 
air  passes  through  the  trachea  from  without  inward.  In  doing  this, 
however,  the  external  air  has  overcome  the  elasticity  of  the  lungs, 
the  pressure  exerted  by  the  air  within  the  lungs  upon  the  intratho- 
racic vessels  will  therefore  be  that  of  the  ordinary  atmospheric  pres- 
sure, less  the  pressure  due  to  the  elasticity  of  the  lungs.  Suppose, 
for  example,  that  the  pressure  exerted  by  the  elasticity  be  half  a 
pound  to  the  square  inch,  then  the  pressure  exerted  by  the  air 
within  the  lungs  upon  the  great  blood  vessels  or  the  intrathoracic 
pressure  will  be  only  fourteen  and  a-half  pounds,  that  of  the  atmos- 
phere being  fifteen  pounds.  The  effect  of  this  difference  of  the 
atmospheric  pressure  within  and  without  the  chest  during  inspira- 
tion is  tliat  a  greater  quantity  of  venous  blood  being  forced  through 
the  great  veins  toward  the  right  auricle  of  the  heart  and  thence 
through  the  lungs,  a  proportionately  greater  quantity  of  arterial 
blood  passes,  therefore,  through  the  left  ventricle  into  the  aorta,  the 
result  of  which  will  be  to  increase  the  blood  pressure.     The  flow  of 


CIRCULATION  AND  EESPIRATION. 


369 


the  venous  blood  from  the  periphery  to  the  heart  being:  promoted 
by  inspiration,  it  might  be  supposed  that  the  flow  of  the  arterial 
blood  in  the  reverse  direction  would  be  proportionally  retarded.  It 
must  be  remembered,  however,  that  the  pressure  exerted  by  the 
extrathoracic  air  upon  the  thin,  flaccid  Avails  of  the  veins  will  pro- 
duce a  greater  effect  than  upon  the  thick,  resisting  coats  of  the 
arteries,  and  that  the  pressure  of  the  external  air  so  exerted  is  not 
much  in  excess  of  the  resistance  that  the  heart  has  to  overcome  in 
driving  the  blood  from  the  ventricle  into  the  arterial  system  during 
its  systole.  During  expiration  the  conditions  being  the  reverse  of 
those  obtaining  during  inspiration  the  flow  of  blood  through  the 
arteries  is  favored,  since  apart  from  the  chest  being  compressed,  the 
pressure  exerted  by  the  intrapulmonary  air  upon  the  arteries  out- 
side the  lungs  becomes  greater  in  proportion  as  the  lungs  contract^ 
their  elastic  tension  diminishing  proportionally.  On  the  other 
hand,  the  flow  of  the  blood  through  the  veins  is  not  retarded  to  any 
great  extent  during  expiration  as  the  veins  are  somewhat  dilated  at 
the  moment  of  the  contraction  of  the  lungs,  while  regurgitation  is 
prevented  by  the  valves.  Respiration  on  the  whole,  therefore, 
favors  the  circulation,  since  inspiration  aids  the  flow  of  the  venous 
blood  without  offering  any  great  obstacle  to  the  arterial  flow,  while 
expiration  favors  the  flow  of  the  arterial  blood  without  retarding  to 
any  extent  the  venous  flow,  and  while  it  is  true  that  in  the  influence 
of  respiration  upon  the  circulation,  inspiration  is  more  important 
than  expiration,  nevertheless  the  difference  in  the  effect  of  the  two 


Fig.  190. 


/---ri 


Comparison  of  lilood  pressure  curve  with  curve  of  intrathoracic  ]ircssnre.  To  be  read  from  left 
to  riglit.  «  is  tlic  lil(i(j(l-prcssure  curve,  with  its  rcspiratiiry  iniiliilatiniis,  the  slower  heats  on  the 
descent  bein^  very  inarkeil.  6  is  the  curve  of  iutrathoracic  prc>Miic  olitaiued  by  connecting  one 
limb  of  a  manometer  with  the  pleural  cavity.  Inspiration  begins  at  /,  expiration  at  e.  The  intra- 
thoracic pressure  rises  very  rapidly  after  the  cessation  of  the  inspiratory  effort,  and  then  slowly 
falls  as  the  air  issues  from  the  chest ;  at  the  Ijeginning  of  the  inspiratory  efiort  the  fall  becomes 
more  rapid.     (Foster.) 

is  too  small  to  warrant  the  conclusion  that  the  large  rise  and  fall  in 
the  blood  pressure  are  entirely  caused  by  inspiration,  on  the  one 
hand,  and  expiration  on  the  other.  Further,  in  the  dog  and  in  the 
rabbit  also,  at  times,  there  is  no  absolute  synchronism  between  the 
vascular  and  respiratory  rhythms ;  in  the  dog,  for  example  (Fig. 
196),  the  rise  in  the  blood  pressure  lasting  not  only  to  the  end  of 
24 


370 


RESPIRATION. 


the  inspiration,  but  during  a  part  of  expiration,  and  the  fall  in 
blood  pressure  lasting  not  only  till  the  end  of  expiration,  but  during 
a  part  of  inspiration.  This  want  of  synchronism  between  the 
rhythms,  together  with  the  fact  that  the  large  undulations  character- 
istic of  blood  pressure  persist  even  after  all  respiratory  movements 
have  ceased,  proves  that  there  must  be  some  influence  other  than 
respiration  concerned  in  their  production.  Thus  if  an  animal,  a 
rabbit,  for  example,  be  curarized,  in  which  condition  the  respiratory 
nerves  cease  to  act  altogether,  the  heart  continues  to  beat,  artificial 
respiration  be  maintained  and  a  trace  of  the  blood  pressure  be  taken, 
a  curve  like  that  of  Fig.  197  will  be  obtained.  If  now  the  artificial 
respiration  be  discontinued  the  blood  pressure  rises,  and  the  char- 
acter of  the  curve  changes  ;  nevertheless,  a  rhythmical  rise  and 
fall  still  occur,  like  that  of  Fig.  197.  The  curve  so  obtained  is 
known  as  that  of  Traul)e,  from  having  been  first  described  by  that 
observer.     Inasmuch  as  respiration  has  entirely  ceased,  it  is  evident 

Fig.  197. 


l\  A  / 

/  l  !  I  i 
I  i'  \\ 


r-  A  A  A  ^  «  '"i  A  A  i\  '■'^■ 

mmmmmwm 

;     \\  \  \  \j  ill   V  «  v\/  i,  w     '  k  V)      i!  V  ^ 
i  M/  V  V  V  H  V 


f.        ;*'■    ?    'j 


Traube's  curves. 


X     ./' 


that  the  large  undulations  cannot  be  due  to  respiration.  The  only 
way  of  accounting  for  them  is  by  supposing  that  they  are  of  vaso- 
motorial  origin,  the  rhythmic  rise  and  fall  in  the  blood  pressure, 
through  the  rhythmic  constriction  of  the  arteries,  being  due  to  a 
rhythmic  stimulus  emanating  from  the  vasomotor  center  of  the 
medulla.  This  view  is  confirmed  by  the  following  facts  :  that  the 
phenomena  in  question  are  much  less  marked  if  the  spinal  cord  be 
divided  l)elow  the  medulla,  and  that  the  undulations  persist  even 
after  the  heart  itself  be  removed,  and  the  circulation  be  maintained 
artificially.     It  is  difficult  to  understand  why  the  vascular  rhythm, 


A B TIFICIAL  BESPIRA  TION. 


171 


due  to  the  vasomotor  center,  should  shuulate  and  be  superimposed 
upon  the  respiratory  rhythm  due  to  the  medullary  respiratory 
center,  unless  throug^h  conditions  in  the  evolution  of  the  animal  and 
which  we  are  not  familiar  with,  the  two  centers  in  the  medulla  have 
been  gradually  brought  to  act  synchronously.  It  will  be  seen, 
therefore,  that  while  the  rise  and  fall  in  the  blood  pressure  are  in- 
fluenced by  inspiration  and  expiration,  the  phenomenon  is  inde- 
pendent of  respiration,  or  probably  that  both  are  influenced  by  a 
common  cause. 

In  the  study  of  the  circulation  and  respiration  as  in  the  present 
case  it  is  often  necessary  to  maintain  artificial  respiration.  The 
form  of  apparatus  that  we  make  use  of  for  this  purpose  is  essen- 
tially a  mercurial  pump    (Fig.    198),   consisting  of  two   cast-iron 


Fig.  198. 


Mercurial  pump  for  artificial  respiration. 

cylinders  A,  B  (B  not  being  .seen  in  Fig.  198),  concentrically  dis- 
posed and  firmly  fixed  in  a  solid  frame  C.  The  space  between  the 
cylinders  contains  mercury,  through  which  the  bell-jar  E  covering 
the  internal  cylinder  B  is  elevated  or  depressed  by  the  vertical  mo- 
tion of  the  rod  F  connecting  it  with  the  wheel  G,  to  the  rotation 
of  which  the  motion  of  the  rod  is  due.  The  internal  cylinder  B 
opens  externally  through  the  two  brass  nozzles  H  and  I.  Each  of 
these   nozzles  is  provided  with  a  valve,  which,  however,  open  in 


372  BESPIBA  TION. 

opposite  directions — that  of  H  from   witliout  inward,  that   of  I 
from  within  outward.     As  the   bell-jar  is  elevated   the  air  jiasses 
through   H  into   the  internal  cylinder,  and  as 
Fig.  199.  it  descends  the  air  passes  out  of  it  through  I, 

and  thence  by  means  of  a  tube  terminating  in 
a  canula  to  the  trachea  of  the  animal  whose 
respiration  is  to  be  maintained.  The  rotation 
of  the  wheel  G,  to  which  the  action  of  the 
respiratory  pump  is  due,  is  eifected  by  a  Backus 
water  motor  (K)  to  which  the  wheel  is  con- 
eauuia.  nected  by  the  band  I.     The  Mater  supplying 

the  motor  is  conveyed  to  it  from  the  hydrant 
in  the  laluiratory  by  the  tube  M  and  away  from  it  to  the  waste- 
pipe  by  the  tube  X. 

The  canula  that  we  use  for  insertion  into  the  trachea  is  that  of 
Ludwig,  and  consists  of  a  tube  of  glass  (Fig.  199)  of  which  the 
end  a,  Avhen  /)i  sitd,  faces  the  lungs  and  through  Mhich  the  air  to 
be  inspired  passes,  the  expired  air  escaping  l)y  a  small  opening. 
In  ordinary  tranquil  respiration  no  sound  is  heard  unless  the  ear 
be  applied  directly  to  the  chest,  excepting  when  the  mouth  is 
closed  and  the  breathing  exclusively  nasal,  then  a  soft  murmur  ac- 
companies both  inspiration  and  expiration.  If  the  ear,  or  better, 
the  stethoscope,  be  successively  applied  over  the  trachea  and  the 
chest,  a  very  noticeable  difference  will  be  observed  in  the  character 
of  the  sound  heard,  as  the  air  passes  through  these  parts  both  in 
inspiration  and  expiration.  As  might  be  expected,  as  the  air  passes 
in  and  out  of  the  trachea,  the  character  of  the  sound  is  tubular.  In 
inspiration,  the  sound,  attaining  its  maximum  intensity  immediately, 
maintains  it  to  the  close  of  the  act,  when  it  rather  suddenly  ceases. 
Immediately,  or  after  a  very  brief  interval,  the  expiratory  sound 
follows,  attaining  soon  its  maximum  intensity,  but,  unlike  the  in- 
spiratory sound,  rather  dying  away  than  ceasing  abruptly.  As  the 
air  passes  into  the  small  bronchial  tubes  and  expands  the  pulmonary 
air  cells  it  gives  rise  to  a  sound  difficult  of  description,  and  which 
can  only  be  appreciated  by  being  heard.  It  is  usually  described 
as  being  of  a  breezy  or  vesicular  character,  and  is  less  intense  than 
the  tracheal  murmur.  The  sound  gradually  increases  in  intensity 
from  the  beginning  to  the  end  of  inspiration,  and  ceases  rather  ab- 
ruptly. The  inspiratory  murmur  is  followed  without  any  interval 
by  the  expiratory  one,  lower  in  pitch,  less  intense,  and  lasting  a 
shorter  time.  It  must  be  mentioned,  however,  that  the  expiratory 
murmur  is  frequently  absent.  Certain  modifications  of  the  respira- 
tory sounds  and  movements,  such  as  snoring,  coughing,  sneezing, 
sighing,  ya-s\Tiing,  laughing,  sobbing,  and  hiccoughing  need  only  a 
passing  notice,  since  they  are  simply  exaggerations  of  either  the 
inspiratory  or  expiratory  movements,  or  of  both.  Snoring,  a  sound 
too  familiar  to  need  description,  occurs  when  the  mouth  is  open, 
and  is  due  to  a  vibration  or  flajiping  of  the  velum  palati   between 


NUMBER  OF  RESPIRATIONS  PER  MINUTE.  3/3 

the  two  currents  of  air  from  the  mouth  and  nose  together  with  a 
vibration  of  the  air  itself.  Coughing  and  sneezing,  usually  invol- 
untary acts,  consist  in  a  deep  inspiration,  followed  by  a  convulsive 
expiration,  differing  only  in  degree,  the  air  in  the  first  instance  be- 
ing expelled  by  the  mouth,  in  the  second  by  both  mouth  and  nares. 
Sighing  and  yawning  are  due  to  the  same  cause — want  of  oxygen 
in  tlie  blood — and  differ  from  each  other  only  in  the  former  being 
voluntary,  the  latter  involuntary.  In  both  these  acts  a  prolonged 
and  deep  inspiration  is  followed  by  a  quick  and  usually  audible  ex- 
piration. Laughing  and  sobbing,  though  expressing  very  different 
emotions,  are  produced  very  much  in  the  same  way,  and  are  the 
result  of  short,  quick,  convulsive  movements  of  the  diaphragm, 
which  are  accompanied  by  the  action  of  the  facial  muscles  produc- 
ing those  changes  in  the  features  so  characteristic  of  joy  or  sorrow. 
Laughing  and  sobbing,  like  yawning,  are,  so  to  speak,  catching,  or 
contagious.  Hiccough  is  a  purely  inspiratory  act,  and  consists  in 
sudden  convulsive  involuntary  contractions  of  the  diaphragm,  the 
glottis  constricting  spasmodically  at  the  same  time  ;  the  well-known 
sound  is  due  to  the  air  striking  against  the  closed  glottis.  Hic- 
cough is  frequently  caused  by  partaking  too  rapidly  of  dry  food  or 
effervescing  and  alcoholic  drinks,  and  is  not  an  infrec|uent  symp- 
tom of  disease. 

It  is  obviously  of  importance  that  the  number  of  respirations  in 
a  given  time  be  determined  as  accurately  as  possible.  A  great  dif- 
ference of  opinion,  however,  has  prevailed,  in  this  respect,  among 
physiologists,  Haller,^  for  example,  giviug  twenty  respirations  a 
minute  as  the  normal  number  ;  Magendie,'  fifteen  ;  Milne  Ed- 
wards,'^ sixteen  to  twenty-two.  This  disagreement  in  the  result  of 
a  mere  matter  of  observation  is  due,  in  some  instances,  to  the  num- 
ber of  cases  examined  having  l)een  too  limited  to  warrant  a  general 
conclusion,  and,  in  others,  to  infiuences  modifying  the  number  of 
respirations  within  the  limit  of  health  not  having  been  taken  into 
consideration.  The  importance  of  examining  a  great  number  of 
cases  before  drawing  any  conclusion  as  to  the  ayerasc  number  of 
respirations  per  minute  is  well  shown  by  the  observations  of 
Hutchinson.*  Of  1887  cases,  in  561  the  number  of  respira- 
tions was  found  to  be  twenty  per  minute ;  in  239  cases,  sixteen 
per  minute  ;  in  79  cases,  nine  to  sixteen  per  minute.  Such  a  dif- 
ference in  the  number  of  respirations,  as  observed  in  these  three 
sets  of  cases,  and  also  of  the  remaining  ones  examined,  prove  that 
there  must  be  numerous  conditions  influencing  the  rapidity  of  the 
respiratory  movements  as  we  have  seen  is  the  case  with  the  pulse. 

Among  these  the  influence  of  age  is  very  important,  thus,  as 
shown  by  Quetelet,''  the  number  of  respirations  at  birth  are  more 

'  Elementa  Physioloo:i;i',  Tomus  iii.,  p.  2S9. 

^Precis  elementairc  de  Pliysiologie,  Tome  iii.,  p.  337. 

^Physiologic,  Tome  ii.,  p.  4S0. 

* Cyclopa?di:i  of  Aiiiit.  and  Phys.,  Vol.  iv.,  Part  2,  p.  1085. 

^Quetelet,  h^ur  I'liomnu',  etc.,  1835,  Tome  ii.,  p.  84. 


of  cases. 

Per  minute. 

Ko.  of  eases. 

79 

21     . 

129 

239 

22 

143 

105 

23     . 

42 

195 

24     . 

243 

74 

24  to  40     . 

78 

561 

374  RESPIRATION. 

Number  of  Eespirations  per  Minute. 

Per  minute. 

9  to  16  . 

16  .  .  . 

17  .  .  . 

18  .  .  . 

19  .  .  . 

20  .  .  . 

In  a  total  of  these  1887  cases  the  majority  breathed  16  to  24  ;  one- 
third  20  respirations  per  minute. 

than  double  the  number  at  twenty  years  of  age,  and  from  this  age 
upward  the  number  of  respirations  diminishes.  It  is  evident,  there- 
fore, that  the  number  of  respirations  per  minute,  as  deduced  from 
the  examination  of  a  number  of  individuals,  will  depend,  cceteris 
paribus,  upon  their  age  ;  and  we  should  expect  to  find  young  per- 
sons breathing  more  rapidly  than  old  ones.  It  w'ill  be  readily  un- 
derstood, therefore,  why  561    persons,  on  an  average,  should  be 


Respirations  at  Different 

Ages. 

minute. 

Age. 

44 

At  birth. 

26 

5  years. 

20 

15  to  20  vears. 

19 

20  to  25^    " 

16 

30                 " 

18 

30  to  50       " 

found  to  breathe  twenty  times  per  minute,  and  239  persons  only 
sixteen,  if  the  first  set  of  persons  examined  are,  on  an  average, 
younger  than  the  second  set. 

In  speaking  of  the  various  conditions  that  modify  the  number  of 
cardiac  beats  in  a  given  time,  the  influence  of  size  was  noticed,  it 
being  mentioned  that  the  number  of  cardiac  beats  in  a  given  time 
was  more  numerous  in  the  young  and  small  child,  and  young  and 
small  animal,  than  in  the  adult  man  or  large  animal.  Xow,  the 
same  relation  that  we  have  just  pointed  out  as  existing  between 
youth  and  the  number  of  respirations  in  man,  will  also  be  found 
to  prevail  if  large  animals  are  compared  with  small  ones,  or  if 
the  same  animal  be  compared  at  different  ages.  Thus,  accord- 
ing to  Milne  Edwards,^  Mobile  the  number  of  inspirations  in  the 
whale  is  only  about  four  or  five  in  the  minute,  and  in  the  rhi- 
noceros, hippopotamus,  giraffe,  and  horse  ten  to  the  minute,  the 
number  of  respirations  are  thirty-five  or  more  in  the  same  period 
of  time  in  the  rabbit  and  guinea-pig,  while,  according  to  Colin,^ 
the  number  of  respirations  being  thirteen  to  sixteen  in  the  sheep, 
will  be  sixteen  to  seventeen  in  the  lamb ;  in  the  cow,  fifteen  to 
eighteen  ;  in  the  calf,  eighteen  to  twenty  ;  in  an  adult  dog,  fifteen  to 
eighteen  ;  in  the  young  dog,  eighteen  to  twenty.  The  cause  of  this 
difference  iu  the  number  of  respirations,  according  to  the  age  and 
^Physiologic,  Tome  ii.,  p.  486.  ^  p],yg}yiQgjg  (;;;Qjjjpjjj.^ig   Tome  il.,  p.  152. 


WOBK  PERFORMED  DURING  RESPIRATION.  375 

size  of  the  animal  \<,  no  doubt,  clue,  as  in  the  case  of  the  numl^er  of 
cardiac  beats,  to  tlie  same  cause,  that  of  the  vital  processes  gener- 
ally beinir  more  active  in  small  animals  than  in  laroe  ones. 

Sex  seems  to  influence  but  little  the  number  of  respirations,  no 
appreciable  diiference  being  observed  in  boys  or  girls ;  young  men, 
however,  breathe  a  little  more  rapidly  than  young  Avomen  of  the 
same  age.  Everyday  experience  teaches  us  to  what  an  extent  res- 
piration may  be  accelerated  by  nervous  excitement  and  exercise. 
The  influence  of  muscular  exertion  is  not  limited  simply  to  active 
exercise,  the  mere  change  from  the  recumbent  to  the  sitting  posi- 
tion, or  of  standing  up,  will  increase  the  respiratory  movements. 
Thus,  Dr.  Guy  states  that  lying  down  the  number  of  his  inspira- 
tions was  13  per  minute,  while  sitting  19,  and  when  standing  up  22. 
As  might  be  expected,  during  sleep,  the  number  of  respirations  is 
diminished,  according  to  Quetelet,^  the  diminution  being  about  1  in 
4,  or  25  per  cent.  It  will  be  seen,  from  what  has  just  been  said, 
that  the  number  of  respirations  must  vary  very  much  wathin  the 
limits  of  health  ;  and  that,  therefore,  only  an  approximately  aver- 
age number  can  be  ascertained.  Of  1887  cases  examined  by  Hutch- 
inson,^ 1731  breathed  from  16  to  24  times,  and  nearly  one-third  of 
them  20  times  a  minute.  The  average  number  of  respirations  we 
have  found  to  be  from  18  to  20  times  a  minute,  and  we  may  add 
here,  incidentally,  that  during  each  respiration  there  are  about  four 
heart  beats. 

Mechanical  "Work  Performed  During  Respiration. 

It  will  be  remembered  that  in  describing  the  circulation,  it  was  es- 
timated that  the  mechanical  work  performed  by  the  heart  amounted, 
in  twenty-four  hours,  to  75,000  kilogrammeters  (240  foot  tons). 
AVe  shall  see  hereafter  in  the  investigation  of  the  source  of  the 
energy  of  the  body,  that  it  is  equally  important  to  determine,  as  far 
as  possible,  the  mechanical  work  performed  by  the  respiratory  mus- 
cles. This  may  be  estimated,  at  least  approximately,  in  the  same 
way  as  in  the  case  of  the  heart  by  multiplying  the  weight  raised 
l)y  the  respiratory  muscles  l)y  the  height.  It  has  already  been 
mentioned  that  owing  to  the  elasticity  of  the  lungs  offering  a  re- 
sistance to  the  inspired  air  distending  them,  the  pressure  exerted 
by  the  latter  against  the  inner  surface  of  the  thorax  will  be  less 
than  that  exerted  by  the  external  air  upon  the  outer  surface  of  the 
thorax.  It  is  evident,  therefore,  that  at  each  inspiration,  the  chest 
lifts  so  much  of  the  weight  of  the  external  atmosphere  as  is  not 
neutralized  by  a  corresponding  part  of  the  internal  one,  the  weight 
raised  being  directly  proportional  to  the  elastic  tension  of  the  lungs 
that  is  to  the  depth  of  the  inspiration.  Let  us  suppose  that  the 
downward  pressure  of  the  atmosphere  upon  the  outer  surface  of 
the  thorax  is  15  pounds  upon  the  square  inch  and  the  upward  pres- 
sure of  the  internal  air  upon  the  inner  surface  14.8  pounds,  or  0.2 
»0p.  cit.,  p.  8-<.  Hjp.  cit.,  p.  1085. 


376  RESPIBA  TION. 

pound  less,  tlie  elastic  tension  of  the  lungs  amounting  to  that  in  easy 
breathing,  and  that  the  chest  with  an  area  of  300  square  inches  is 
elevated  0.04  of  an  inch,  the  Avork  done  during  each  inspiration  will 
be  0.2  foot  pounds,'  and  on  the  supposition  that  the  respirations  are 
on  the  average  15  per  minute,  to  nearly  2  foot  tons  -  per  day.  The 
work  done  by  the  diaphragm,  if  calculated  in  the  same  way,  will 
amount  to  about  2.8  foot  tons  per  day ;  that  is  if  it  be  supposed 
that  its  area  is  52  square  inches,  and  that  in  addition  to  lifting  0.2 
pounds  of  air  through  0.2  in.  it  overcomes  about  an  equal  amount 
of  abdominal  pressure.  Inasmuch,  however,  as  during  inspiration 
the  elasticity  of  the  thoracic  walls  is  overcome  by  the  inspiratory 
muscles,  the  work  done  in  this  respect  would  amount,  if  we  assume 
the  former  to  be  equal  to  that  of  the  elasticity  of  the  lungs  to  an 
additional  2  foot  tons  per  day.' 

Neglecting  the  weight  of  the  sternum  and  ribs  14  oz.  lifted  during 
sleep  or  when  the  body  is  in  the  recumbent  position,  the  total  work 
done  by  the  inspiratory  muscles  would  amount  to  nearly  7  foot  tons 
(2177  kilogramme ters)  per  day  and  in  deep  breathing  to  more  than 
twice  as  much.  The  above  estimate  of  the  w'ork  done  is,  of 
course,  only  an  approximate  one  to  be  regarded  as  what  may  be 
done  by  the  inspiratory  muscles  rather  than  what  is  done.  Inas- 
much as  we  have  seen  that  expiration  in  easy  breathing  is  a  passive 
process,  a  return  to  the  condition  of  equilibrium,  no  work  is  done 
by  the  expiratory  muscles.  If,  however,  expiration  becomes  forced, 
then  the  work  done  may  amount  to  nearly  as  much  as  that  in 
inspiration. 

Breathing   Capacity. 

On  account  of  the  importance  of  ventilation,  of  estimating  the 
amount  of  oxygen  absorbed,  and  carbon  dioxide  exhaled,  of  de- 
termining the  amount  of  heat  produced  in  the  body,  etc.,  it  is  nec- 
essary that  the  amount  of  air  inspired  and  expired  during  respira- 
tion should  be  actually  measured.  For  this  purpose  we  make  use 
of  the  spirometer.  The  instrument  described  by  Hutchinson,*  con- 
sists (Fig.  200)  essentially  of  a  cylindrical  vessel  (A),  containing 
water,  out  of  which  a  receiver  (B)  can  be  elevated  by  breathing 
into  it  through  a  tube  (C),  the  height  to  which  the  receiver  is  ele- 
vated and  depressed,  as  shown  by  the  scale  D,  indicating  the  vol- 
ume of  the  air  expired.  In  using  the  spirometer,  it  should  be 
placed  upon  a  firm,  level  table,  about  three  feet  from  the  ground. 
The  water  tap  A¥  then  having  been  turned  off,  and  the  air  tap 
T  opened,  clear,  cold  Avater  is  poured  through  the  spout  of  the  cy- 
lindrical vessel  A,  until  it  is  full,  any  excess  of  water  running  off 
by  the  tap  in  communication  with  the  air  tube.     The  counterpoising 

•0.2  X  0.04  X  300  =  2. 4  inch  pounds  =  0.2  foot  pounds  =  0.027  kilogiammetei-s. 

4820 
2  0.2  X  15  X  60  X  24  =  ,^.^,-  =  2  foot  tons  =  871  kilogramraeters. 

^It  mast  be  admitted,  however,  that  tlie  ehisticity  of  tlie  tlioraeie  walls  lias  not 
been  detennined.  *  ()\u  cit.,  p.  Kk;;). 


SPIROMETER. 


377 


Fig.  200. 


Aveiglits  being  then  .■suspended  within  tlie  framework  ]M,  and  over 
the  pnlleys,  and  the  air  tap  closed,  the  instrument  is  ready  for  an 
ob.servation.  The  person  wliose  breathing  capacity  is  to  be  deter- 
mined standing  erect  with  head  thrown  backward,  and  loosely 
attired,  applies  by  the  mouth- 
piece the  flexible  tube  C  to  his 
mouth  and  expires  into  the 
spirometer.  The  air  from  his 
lungs  passes  thence  into  the 
tube  E,  elevating  the  receiver 
B,  the  volume  of  air  expired, 
expressed  in  cubic  inches,  be- 
ing shown  by  the  number  of 
the  scale  to  which  the  index 
connected  with  the  receiver 
has  been  elevated.  On  the 
other  hand,  by  inhaling 
through  the  tube  C,  the  re- 
ceiver B  will  descend,  the 
amount  of  air  inspired  being 
indicated  by  the  scale  now 
read,  however,  in  the  reverse 
direction.  The  volume  of  air 
must,  however,  be  corrected 
for  temperature,  for  the  tem- 
perature of  the  air  will  be  at 
once  reduced  to  the  tempera- 
ture of  the  water  in  the  spi- 
rometer, to  which  it  has  passed, 
and  which  is  warm  or  cold  ac- 
cording to  the  season.  Practi- 
cally the  change  in  the  bulk  of  the  air  will  amount  to  about  ^i^  for 
every  degree  Fahr.,  and  the  difference  should  be  added  or  subtracted 
as  the  temperature  of  the  room  in  which  is  the  spirometer  is  below  or 
above  G0°.  Suppo.se,  for  example,  295  cu.  in.  be  breathed  into  the 
spirometer,  the  temperature  of  the  room  being  55°,  then  2.9  cu.  in. 
should  be  added  to  the  295  cu.  in.,  since  -^^^  equals  ^^-^  of  295, 
equals  2.95  cu.  in. ;  on  the  other  hand,  if  the  air  be  at  a  temperature 
of  70°,  then  5.9  cu.  in.  should  be  subtracted  from  the  295,  since  Jjj^^ 
equals  -gL.  of  295,  equals  5.9  cu.  in.  The  U-shaped  tube  acts  as  a 
gauge,  since,  as  long  as  the  colored  fluid  that  is  put  into  it  remains  at 
the  same  level  in  its  two  limbs,  the  density  of  the  air  -svithin  and 
without  the  receiver  is  the  same,  which  is  necessarily  an  indispen- 
sable condition  in  the  working;  of  the  instrument.  In  order  to 
expel  the  air  from  the  receiver,  and  return  it  to  its  original  posi- 
tion, the  plug  M  is  removed  Avith  one  hand,  while  the  receiver 
is  depressed  with  the  other.  The  experiments  having  been  con- 
cluded, and  it  is  desired  to  empty  the  water  out  of  the  spirometer, 


Hutchinson's  spirometer. 


378  BESPIRA  TION. 

it  is  only  necessary  to  open  the  water-tap.  If  a  healthy  adult 
breathe  easily  into  the  spirometer  in  the  manner  indicated,  it  will  be 
found  that  usually  about  30  cu.  in.  (489  c.  c.)  pass  into  the  instrument 
with  each  expiration.  If  now  the  air  be  expelled,  and  tlie  receiver 
returned  to  its  original  position,  and  the  air-tap  be  opened,  fresh 
air  will  pass  freely  into  the  receiver,  and,  the  pressure  of  the  air 
within  and  without  being  the  same,  the  receiver  will  be  elevated  by 
the  counterpoisiug  weights.  Suppose  a  hundred  cubic  inches  of  air 
have  been  passed  in  this  way  into  the  receiver,  and  now  a  gentle 
inspiratory  effort  is  made,  the  receiver  will  descend,  and  it  will  be 
found  that  its  index  has  fallen  to  the  number  70  on  the  scale^ 
shoM'ing  that  30  cu.  in.  of  air  have  been  inspired.  By  experiment- 
ing in  this  way  upon  a  number  of  persons,  it  will  be  found  that, 
(uteris  paribus,  on  the  average,  that  in  easy,  tranquil  breathing 
about  30  cu.  in.  of  air  are  taken  into  the  lungs  with  each  inspira- 
tion, and  about  30  cu.  in.  are  given  out  with  each  expiration.  In 
reality  the  expired  air  is  about  Jfr  *o  -^-^  less  in  volume  than  the 
inspired  air.  This  is  due,  as  we  shall  see,  to  the  fact  of  the  car- 
bon dioxide  excreted  being  a  little  less  in  amount  than  the  oxy- 
gen absorbed.  The  30  cu.  in.  of  air  inspired  and  expired  during 
each  respiration  are  usually  known  as  tlie  tidal  or  ordinary  breath- 
ing air.  If  now  a  forcible  expiration  be  made,  not  only  will  30 
cu.  in.  of  air  pass  into  the  spirometer,  as  in  easy  breathing,  but  as 
much  as  100  additional  cu.  in.  This  extra  quantity,  so  to  speak, 
of  expired  air  is  not  usually  changed  in  respiration,  but  only  when 
the  necessity  is  felt  of  more  completely  renovating  the  air  in  the 
lungs,  and  is  called,  therefore,  the  reserve  or  supplemental  air,  and 
amounts  to  about  100  cu.  in.  (1630  c.  c).  In  prolonged  expiratory 
efforts,  such  as  sneezing  and  blowing,  this  reserve  air  is  more  or 
less  expelled.  As  the  reserve  air  is  vitiated  through  continually 
receiving  water  and  carbon  dioxide  from  the  blood  of  the  lungs, 
pearl-divers  and  others  who  are  in  the  habit  of  temporarily  arrest- 
ing their  respiration,  instinctively  first  get  rid  of  their  reserve  air 
by  forcibly  expiring  several  times,  and  then  fill  their  lungs  with 
fresh  air.  If  the  chest  be  now  enlarged  by  a  forcible  inspiration 
instead  of  an  expiration,  the  spirometer  having  been  suitably  ar- 
ranged, as  much  as  110  cu.  in.  can  be  withdrawn  from  the  instru- 
ment over  and  above  the  30  cu.  in.  due  to  an  ordinary  inspiration. 
This  constitutes  what  is  known  as  the  complemental  air,  and  usually 
amounts  to  100  cu.  in.  (1G30  c.  c).  It  is  drawn  upon  whenever  an 
effort  is  made  that  demands  a  temporary  arrest  of  respiration,  in 
blowing,  yawning,  sneezing,  etc.,  to  a  certain  extent  in  sleep,  when 
the  breathing  is  deep,  at  the  moment  immediately  preceding  some 
muscular  effort,  etc.  The  complemental  air  can  also  be  indirectly 
estimated  l)y  deductiug  the  sum  of  tlie  tidal  and  reserve  airs  (30  cu. 
in.  plus  100  cu.  in.)  from  the  volume  of  the  extreme  breathing  air,  or 
that  which  can  be  expelled  from  the  lungs  by  the  most  forcible  ex- 
piration after  the  most  profound  inspiration,  and  which,  we  shall 


BREATHING  CAPACITY.  379 

see  in  a  moment,  amounts  to  2.'>0  cu.  in.  ;  thus  280  en.  in.  less 
l.')0  cu.  in.  equals  100  eu.  in.  The  capacity  of  the  lungs,  and  the 
fact  that  after  death  they  always  contain  air,  make  it  evident  that 
the  air  is  never  entirely  expelled,  even  by  the  most  powerful  expi- 
ration. A  certain  quantity  of  air,  therefore,  always  remains  in  the 
lungs.  It  is  known  as  the  residual  air,  and  may  be  approximately 
considered  as  amounting  to  1  (330  c.  c.  (100  cu.  in.).  The  amount  of 
residual  air  cannot  be  determined  directly  since  the  volume  of  air 
within  the  lungs  after  an  ordinary  expiration  consists  of  the  sum 
of  the  reserve  and  residual  airs.  If  this,  however,  can  be  deter- 
mined, the  deduction  from  it  of  the  reserve  air  will  give  the  resid- 
ual air.  It  is  well  known  that  hydrogen  gas  when  inspired  is  not 
absorbed  by  the  blood,  and  that  gases  will  diffuse  into  each  other 
until  the  mixture  becomes  uniform.  Such  being  the  case,  let  us 
suppose  that  1000  c.  c.  of  hydrogen  be  inspired  and  that  100  c.  c. 
of  the  mixture  is  shown  by  analysis  to  contain  23.5  parts  of  hy- 
drogen, the  whole  mixture  will  then  be  4459  c.  c.  (23.5  :  100  : : 
1000  :  X  =  4455),^  deducting  1000  c.  c.  as  expired,  the  remainder 
3255  c.  c.  will  be  the  sum  of  the  reserve  and  residual  volumes  from 
which  bv  sulitraetinff  the  reserve  volume  1630  c.  c.  we  obtain  the 
residual  volume  1625  c.  c.  (99.6  cubic  inches). 

Assuming  the  mean  capacity  of  the  chest  to  amount  to  312  cu. 
in.,  and  allowing  100  cu.  in.  for  the  heart  and  great  blood  vessels, 
and  100  cu.  in.  for  the  pareuchymatic  structure  of  the  lungs, 
there  would  remain  little  more  than  100  cu.  in.  for  the  residual 
air,  wdiicli  is  the  estimate  given  by  Hutchinson. 

While  the  method  just  described  gives  a  sufficiently  accurate  de- 
termination of  the  respiratory  capacity,  more  exact  results  are  ob- 
tained when  the  tube  of  the  spirometer  communicates  with  a  mask 
closely  fitting  to  the  face  of  the  person  experimented  upon.  The 
mask  is  jjrovided  with  two  openings  furnished  with  valves  working 
in  opposite  directions.  Through  one  of  the  openings  the  expired 
air  is  expelled,  while  through  the  other  the  air  to  be  inspired  passes 
from  the  spirometer.  A  more  simple  and  equally  eifective  apparatus 
consists  of  two  ivory  tubes  which  are  inserted  tightly  into  the  nos- 
trils and  which  connect  -with  a  common  tube,  dividing  into  two 
branches  ;  one  of  these  communicates  with  the  spirometer  and  trans- 
mits the  air  to  be  breathed,  the  other  allows  the  expired  air  to  es- 
cape. Each  of  the  branches  is  provided  with  a  valve  which  opens 
in  opposite  directions.  According,  therefore,  to  wdiich  of  the  ivory 
tubes  is  inserted  into  the  nose  the  air  can  be  either  inspired  from  or 
expired  into  the  spirometer. 

We  have  incidentally  alluded,  a  moment  since,  to  the  extreme 
breathing  capacity  ;  by  this  is  meant  the  volume  of  air  which  can 
be  expelled  from  the  lungs  by  the  most  forcible  expiration,  after 
the  most  profound  inspiration,  or  the  volume  that  can  be  inspired 
by  the  most  forcible  inspiration  after  the  most  profound  expiration. 
'X.  Grehant,  Journal  de  FAnatoraie,  1864,  p.  523. 


'380  RESPIRATION. 

It  Avas  called  by  Hutcliinson  ^  the  vital  capacity,  as  sig:nifyiiig  the 
capacity  or  volume  of  air  Avhich  can  only  be  displaced  by  living 
movements,  and  was  determined  by  this  observer  to  amount  in  a 
man  of  medium  height  (5  feet  8  inches)  to  ."3749  c.  e.  (230  cubic 
inches),  being  equal  to  the  sum  of  the  tidal  reserve  and  comple- 
mental  airs. 

The  experiments  upon  which  this  conclusion  was  based  were 
made  by  means  of  the  spirometer,  upon  nearly  5000  ])ersons. 
Hutchinson  also  showed  that  the  vital  capacity  is  influenced  by 
various  conditions.  Thus,  it  was  ascertained  that,  for  every  inch  of 
height  between  five  and  six  feet,  the  extreme  breathing  capacity 
is  increased  eight  cubic  inches.  Tlie  position  of  the  body  affects 
the  vital  capacity.  Thus,  in  one  individual  while  standing  erect, 
it  was  260  cubic  inches,  and  when  recumbent  it  Avas  2.")(),  a  diifer- 
euce  of  30  cubic  inches.  The  vital  capacity  is  influenced,  without 
doubt,  by  weight,  but,  as  the  weight  usually  increases  with  the 
height,  it  is  difficult  to  separate  the  effect  of  one  from  that  of  the 
other.  Age  has  also  an  influence,  the  vital  capacity  increasing  up 
to  the  thirtieth  year  of  life,  and  then  diminishing  to  the  sixtieth. 
The  vital  capacity  is  also  affected  by  the  sex,  being  greater,  as 
shown  by  Herbst,^  in  the  male  than  in  the  female.  As  might  be 
anticipated,  any  diseased  condition  affecting  the  mobility  of  the 
tliorax  or  the  dilatability  of  the  lungs,  will  modify,  more  or  less 
profoundly,  the  extreme  breathing  capacity,  hence  the  importance 
of  the  latter  as  a  test  of  health  or  disease.  Inasmuch  as  the  ex- 
treme breathing  air  is  made  up  of  the  tidal  reserve  and  complemen- 
tal  airs,  the  latter  will  be  affected  by  the  same  conditions  as  the 
former.  As  the  effects,  however,  are  less  marked  than  where  the 
whole  volume  of  air  is  considered,  it  will  be  necessary  to  call  further 
attention  to  them.  When  it  is  remembered  that,  with  each  inspira- 
tion, only  about  twenty  cubic  inches  of  air  are  introduced,  sufficient 
to  fill  the  trachea  and  large  bronchial  tubes,  it  is  evident  that  there 
must  be  some  subsidiary  force  acting  in  addition  to  the  ordinary 
respiratory  movements  of  the  chest  by  which  the  fresh  air  is  brought 
to  the  air  cells  and  the  vitiated  air  expelled.  The  interchange  be- 
tween the  fresh  air  in  the  upper  part  of  the  lungs  and  the  vitiated 
air  in  the  lower  part,  is  undoulitedly  due  to  the  diffusion  of  the  air 
containing  oxygen  and  carbon  dioxide,  and  which  goes  on,  accord- 
ing to  the  law  established  by  Graham,''  that  the  diffusil)ility  of 
gases  is  inversely  proj)ortional  to  the  square  root  of  their  densities 
— that  is,  that  the  diffusion  of  oxygen  is  to  the  diffusion  of  carbon 
dioxide  as  the  square  root  of  the  density  of  carbon  dioxide,  or 
\/1.529  =  1.237,  is  to  tlie  square  root  of  the  density  of  oxygen,  or 
x/lTuTSG  =  l.OoM,  or  1.237  :  1.0514  : :  95  :  81.  According  to 
this  la\v,  then,  the  lighter  gas,  the  air,  with  its  oxygen,  will  de- 
scend more  rai)idly  than  the  carbon  dioxide,  the  heavier  gas,  will 

iQp.  cit,  p.  lot;:.         ^  Meckel's  Archiv  f.  Ansit.  n.  Phys.,  p.  3,  s.  103,  1828. 
'Trans,  of  Royal  Sec  Kdinh.,  Vol.  xii.,  p.  573,  1834. 


THE  ^EROTOXOMETEB. 


381 


Fig.  201. 


ascend,  91  parts  of  oxygen  replacing  SI  parts  of  carbon  dioxide. 
As  this  difliision  is  continnally  going  on  between  these  gases,  tlie 
air  in  the  pulmonary  air  cells,  where  the  exchange  betw'een  the 
oxygen  and  carbon  dioxide  takes  place,  has  a  tolerably  uniform 
composition,  and  the  aeration  of  the  blood  is  far  less  intermittent  in 
its  character  than  the  respiratory  movements  of  the  thorax.  The 
passage  of  the  oxygen  from  the  air  of  the  pulmonary  air  cells  into 
the  blood  of  the  pulmonary  capillaries,  and  of  carbon  dioxide  in  the 
reverse  direction  from  the  blood  into  the  air,  is  due  to  the  fact  of 
the  tension  of  the  oxygen  of  the  air  being  higher  than  that  of  the 
blood,  and  of  the  tension  of  the  carbon  dioxide  of  the  blood  be- 
ing higher  than  that  of  the  air.  Necessarily,  therefore,  the  oxy- 
gen of  the  air  -within  the  lungs  will 
pass  through  the  wall  of  the  air  cell 
and  capillary  into  the  blood,  thence 
into  the  red  corpuscles,  combining,  as 
we  have  seen,  with  the  haemoglobin  of 
these  bodies,  while  the  carbon  dioxide 
will  pass  in  the  reverse  direction  from 
the  blood  through  the  wall  of  the  capil- 
lary and  wall  of  the  air  cell  into  the 
lungs,  and  thence  out  of  the  body.  It 
is  possible  that  the  pulmonary  epithe- 
lium in  acting  as  a  secretory  surface 
may  also  exercise  some  influence  in 
promoting  the  absorption  of  oxygen 
and  elimination  of  carbon  dioxide.  On 
the  other  hand,  the  oxygen  of  the  ar- 
terial blood  leaving  the  haemoglobin 
will  readily  diifuse  through  the  capil- 
lary into  the  tissues,  the  tension  of  the 
oxygen  in  the  latter  being  so  low  as 
to  amount,  practically,  to  nothing,  the 
oxygen  combining  in  some  stable  form 
as  rapidly  as  absorbed.  While,  o\A'ing 
to  the  continual  production  of  carbon 
dioxide  in  some  unknown  way  in  the 
tissues  out  of  the  oxygen  al)sorbcd,  the 
tension  of  the  carbon  dioxide  of  the 
tissues  being  always  higher  than  that 
of  the  blood  circulating  in  their  midst, 
the  carbon  dioxide  will  consequently 
dilFuse  in  the  opposite  direction  to  that 
of  the  oxygen,  viz.,  from  the  tissues  through  the  wall  of  the  capillary 
into  the  blood  now  become  venous  through  deoxidation  of  most  of 
its  haemoglobin.  The  tension  of  the  gases  in  the  blood  is  determined 
by  means  of  the  a?rotonometer.  This  (Fig.  201)  consists  of  a  long 
glass  tube  A,  communicating  above  by  means  of  the  stopcocks  B  C 


^Erotonometer. 


382  RESPIRATION. 

with  a  tube  (i)),  bringing  the  blood,  the  tension  of  whose  gases  is  to 
be  determined,  and  with  one  [E)  leading  to  the  eudiometer  for  the 
determination  of  the  gases,  and  below  with  a  bell-jar  (  (t),  standing 
over  mercury  and  with  the  reservoir  of  mercury  //.  The  glass  tube 
is  first  entirely  filled  with  mercury  so  as  to  exclude  the  air,  by  elevat- 
ing the  reservoir  H,  and  is  then  surrounded  by  hot  water  so  as  to 
maintain  the  temperature  of  the  blood  examined  at  that  of  the  animal 
from  which  it  was  drawn.  The  glass  tube  ^i  is  then  filled  through 
the  depression  of  the  mercurial  reservoir  with  a  mixture  consisting  of 
known  quantities  of  nitrogen,  oxygen,  and  carbon  dioxide.  The 
blood  being  allowed  to  flow  from  the  artery  or  vein  of  the  animal  for 
a  moment  out  of  the  tube  i),  so  as  to  exclude  the  air,  is  then  diverted 
into  the  gas  mixture  in  A.  As  the  blood  flows  down  through  the 
tube  into  the  mercury,  the  latter  is  driven  up  into  the  bell-jar  G,  while 
the  tension  of  its  oxygen  and  carbon  dioxide  are  increased  or  dimin- 
ished according  to  the  corresponding  tension  of  the  oxygen  and 
carbon  dioxide  of  the  gas  mixture,  as  finally  determined  by  the  an- 
alysis of  the  gases  in  the  eudiometer  E,  into  which  the  gases  are 
driven  by  the  elevation  of  the  mercurial  reservoir.  The  general  re- 
sults as  to  the  tension  of  the  oxygen  and  carbon  dioxide  in  the  blood 
as  obtained  with  the  sero tonometer  by  Pfliiger,^  Wolf  berg,-  Strass- 
burg,^  Nussbaum,^  are  as  follows  :  The  tension  of  oxygen  in  arte- 
rial blood  (one  atmosphere  =  760  mm.  of  mercury)  is  equal  to  29.6 
mm.  of  mercury,  corresponding  to  3.9  per  cent,  of  atmosphere 
(760  :  29.6  ::  100  :  .r  =  3.9),  that  of  carbon  dioxide  being  equal  to 
21.2  mm.,  corresponding  in  amount  to  2.8  per  cent,  of  atmosphere. 
The  tension  of  oxygen  in  venous  blood  is  22.04  mm.  of  mercury, 
corresponding  to  2.9  per  cent,  of  atmosphere,  that  of  carbon  dioxide 
being  equal  to  41  mm.  or  5.4  per  cent,  of  atmosphere.  Such  being 
the  tension  of  the  gases  of  the  blood,  it  is  obvious  that  since  the 
tension  of  the  oxygen  in  the  tissues  (tension,  O.OO)  oiFers  no  resis- 
tance to  that  of  the  oxygen  of  the  arterial  blood  (tension,  29.6)  and 
as  the  tension  of  the  carbon  dioxide  of  the  arterial  blood  (tension, 
21.2)  is  less  than  that  of  the  tissues  (tension,  o8,  possibly),  that 
the  oxygen  of  the  arterial  blood  will  pass  through  the  wall  of  the 
capillary  into  the  tissues  and  the  carbon  dioxide  formed  in  the  lat- 
ter into  the  blood  as  follows  : 

Relative  Tension  of  Oxygen  and  Carbon  Dioxide  in  Arterial 
Blood  and  Tissues. 

Oxygen.  CaiOmn  dioxide. 

Tension  in  arterial  blood  .         .     29.6  mm.  Hg       21.2 

Wall  of  capillary      ....    —  f f^  — 

Tension  in  tissues     ....       0.0  58.2 

On   the  other  hand,  it   has   been   shown,   by  catheterizing  the 
kings,^  that  although  the  tension  of  the  carbon  dioxide _of  the  at- 

'  Pfluger's  Arcliiv,  Bd.  vi.,  s.  43.  ^Baid.,  Band  iv.,  s.  465. 

"Ibid.,  Band  vi.,  s.  65.        *lbid.,  Band  vii.,  s.  296.        ^ Pfluger's  Archiv,  loc.  cit. 


TENSION  OF  OXYGEN  AND  CARBON  DIOXIDE.         -SSo 

mosphere  amounts  to  only  0.30  mm.  of  mercury  (0.04  per  cent,  of 
an  atmosphere),  tliat  of  the  air  of  the  alveoli,  or  ceils,  may  be  as 
much  as  29.1  mm.  (3.84  per  cent,  of  an  atmosphere),  and  that  wliile 
the  tension  of  the  oxygen  of  the  atmosphere  is  158.15  mm.  (20.8 
per  cent,  of  an  atmosphere),  that  of  the  alveolar  air  may  be  reduced 
to  138  mm.  (18.2  per  cent,  of  an  atmosphere).  If  it  be  admitted 
that  the  relative  tensions  of  the  gases  are  such,  then  the  tension  of 
the  carbon  dioxide  of  the  venous  blood  (tension  41)  being  greater 
than  that  of  the  alveolar  air  (tension  29.1)  and  the  tension  of  the 
oxygen  of  the  alveolar  air  (tension  138)  being  greater  than  that  of 
the  venous  blood  (tension  22),  tlie  carbon  dioxide  of  the  venous 
blood  will  pass  through  the  wall  of  the  lung  into  the  alveolar  air, 
and  the  oxygen  of  the  latter  into  the  venous  blood,  as  follows  : 

Relative  Tension  of  Oxygen  and  Carbon  Dioxide  in  Atmos- 
phere, Air  of  Alveoli  and  Venous  Blood  of  Lungs. 

Oxygen.  Carbon  dioxide. 

Tension  in  atmo-sphere  .         .     158.15  mm.  0.30 

Tension  in  air  of  alveoli       .         .     138.00  29.10 

Wall  of  lung         ....      —  I 1  — 

Tension  in  venous  blood       .         .       22.04  41.04 

The  amount  of  the  gases  and  the  condition  in  which  they  exist 
in  the  blood  have  alreadv  been  considered. 


CHAPTEK    XXIII. 


RESPIRATION.—  (Continued. ) 

ABSORPTION   OF   OXYGEN.— EXHALATION   OF   CARBON 

DIOXIDE. 

Having  seen  that  the  essence  of  respiration  consists  in  the  ab- 
sorption of  oxygen,  and  giving  up  of  carbon  dioxide,  and  the 
manner  in  which  the  air  containing  these  gases  is  respired,  it  re- 
mains for  us  now  to  determine  as  far  as  possible  the  amount  of 
oxygen  absorbed  and  carbon  dioxide  exhaled  in  a  given  time.  This 
is  one  of  the  most  imjiortant  problems  in  experimental  physiology, 
since,  as  we  shall  see,  the  amount  of  heat  and  energy  liberated  in 
the  body  will  depend  upon  the  amount  of  oxygen  absorbed,  and 
carbon  dioxide  and  Avater  exhaled.  The  amount  of  oxygen  ab- 
sorbed from,  and  carbon  dioxide  exhaled  into,  a  given  quantity  of 
air  can  be  determined  among  other  means  by  the  Valentin  and 
Brunner  apparatus. 

Fig.  202. 


This  consists  (Fig.  202)  of  a  Woulff's  bottle  A  having  a  capacity 
of  nearly  a  liter  (61  cu.  in.).  One  of  the  openings  communicates 
with  the  moutli-picce  B,  into  which  the  person  expires,  the  air  first 
passing  through  pumice-stone  and  sulphuric  acid  C  so  as  to  dry  it. 


ABSORPTION  OF  OXYGEN. 


385 


The  middle  opening  communicates  with  the  set  of  tubes  G  H  I  K. 
H  and  I  contain  phosphorus  and  baryta  for  the  absorption  of  the 
oxygen  and  carbon  dioxide  of  the  expired  air,  G  and  K  pumice- 
stone,  etc.,  that  of  G  for  the  absorption  of  the  watery  vapors  that 
may  have  escaped,  the  pumice-stone,  etc.,  in  C  Iv  for  retaining  that 
taken  up  by  the  dry  air  passing  through  the  baryta  solution,  and 
which,  if  lost,  would  cause  an  error  in  the  estimate  of  the  carbon 
dioxide  exhaled,  the  tubes  being  weighed  before  and  after  the  ex- 
periment. Through  the  middle  opening  of  the  Woulff 's  bottle  a 
funnel  (D)  provided  with  a  stopcock  is  introduced,  the  opening 
being  then  hermetically  closed.  The  funnel  is  filled  "w-ith  a  known 
quantity  of  mercury.  The  manner  of  using  the  apparatus  is  as 
follows  :  having  breathed  for  say  fifteen  minutes  through  the  mouth- 
piece until  the  air  of  the  WouliF's  bottle  has  been  entirely  dis- 
placed by  the  expired  air,  the  mouth- 
piece is  entirely  closed,  any  external 
air  being  further  prevented  from  pass- 
ing into  the  AVoulif 's  bottle  bv  the 
mercury  in  E  acting  as  a  valve,  the 
air-tightness  of  the  apparatus  being 
assured  by  the  rise  of  the  mercury  in 
the  tube  F,  through  the  contraction 
of  the  expired  air  in  A,  consequent 
upon  its  cooling  and  the  closure  of  the 
tube  funnel.  The  stopcock  of  the 
funnel  being  then  turned,  the  mercury 
passes  into  the  Woullf 's  bottle,  dis- 
placing a  known  quantity  of  expired 
air,  the  latter  passing  into  the  set  of 
tubes  G  H  I  K,  pre\aously  adjusted 
to  the  middle  opening.  The  weight 
of  the  tubes  H  and  I  having  been 
previously  determined,  their  increase 
in  w^eight  ^dll  give,  respectively,  the 
amount  of  oxygen  and  carbon  dioxide 
al)sorl)ed.  Deducting  now  the  amount 
of  oxygen  so  obtained  from  the  ex- 
pired air  from  that  contained  in  an 
equal  quantity  of  ordinary  inspired 
air,  the  remainder  will  be  the  amount 
of  oxygen  retained  in  the  inspiration  of  such  a  quantity  of  air ;  on 
the  other  hand,  deducting  the  trace  of  carbon  dioxide  usually 
present  in  the  atmosphere  from  that  obtained  from  the  expired  air, 
and  the  remainder  will  be  the  amount  of  carbon  dioxide  exhaled 
into  such  a  quantity  of  expired  air. 

A  much  more  expeditious  method  of  analysis,  however,  is  that 
of  Hempel.'       This  consists  in  passing  expired   air  into  a  gradu- 

^  Neue  Methoden  fiir  Analyse  der  Gase,  von  Dr.  W.  Hempel,  Braunschweig,  1880. 
25 


Hempel  apparatus. 


386  RESPIRATION. 

ated  burette  (Fig.  203  B)  filled  with  mercury,  the  latter  flowing 
out  of  the  burette  as  the  mercurial  reservoir  A  with  which  the 
burette  communicates  is  lowered  by  means  of  the  wheel  work  C 
attached  to  the  solid  v^'ooden  frame  fastened  to  the  table.  The 
sample  of  gas  so  obtained  reduced  to  standard  temperature  and 
pressure  is  then  driven  out  of  the  burette  B  by  elevating  the  mer- 
curial reservoir  into  a  Hempel  pipette  F  containing  a  concentrated 
solution  of  soda  and  after  remaining  there  long  enough  for  the  ab- 
sorption of  any  carbon  dioxide  present  is  driven  back  into  the 
graduated  burette  by  lowering  the  mercurial  reservoir,  the  diminu- 
tion in  volume,  the  latter  reduced  to  standard  temperature  and 
pressure,  representing  the  carbon  dioxide  absorbed.  The  pipette 
for  the  absorption  of  the  carbon  dioxide  being  removed,  the  bu- 
rette is  connected  with  one  containing  pyrogallic  acid  into  which  the 
sample  of  gas  just  freed  of  its  carbon  dioxide  is  driven  by  elevat- 
ins:  the  reservoir  and  in  which  it  is  allowed  to  remain  until  the 
oxygen  present  is  absorbed.  The  sample  of  gas  being  then  driven 
back  into  the  graduated  burette  by  lowering  the  reservoir  the 
diminution  in  volume,  reduced  to  standard  temperature  and  pres- 
sure, represents  the  volume  of  oxygen  absorbed. 

The  ordinary  atmospheric  air  consists  in  100  parts  of  a  mechan- 
ical mixture  rather  than  a  chemical  combination,  of  oxygen  20.81, 
nitrogen  7  9.15,^  and  carbon  dioxide  0.04  parts.  If,  however,  100 
volumes  of  expired  air  be  analyzed  by  either  of  the  two  methods 
just  mentioned  it  will  be  found  that  it  consists  of  a  mixture  of 
oxygen  16.033,  nitrogen  79.587,  carbon  dioxide  4.38  parts.  It 
will  be  observed,  therefore,  that  the  air  in  being  inspired  loses 
about  4.77  parts  oxygen  and  gains  about  4.34  parts  of  carbon 
dioxide,  the  nitrogen  remaining  practically  unchanged  in  amount. 
In  other  words,  of  a  given  volume  of  air  breathed  about  5  per  cent., 
or  J-g^,  will  represent  the  oxygen  absorbed  and  nearly  the  amount 
of  carbon  dioxide  expired,  the  oxygen  absorbed  not  being  exactly 
replaced  by  the  carbon  dioxide  expired,  since,  as  we  shall  see  pres- 
ently of  the  oxygen  absorbed,  part  only  is  expired  as  carbon  dioxide. 
Let  us  turn  now  to  the  consideration  of  the  amount  of  the  oxygen 
absorbed  and  carbon  dioxide  expired  in  twenty-four  hours  and  the 
conditions  influencing  the  same.  If  it  be  admitted  that  during  easy 
breathing  about  500  c.  c.  (30  cubic  iuclies)  of  air  is  inspired  and 
expired  at  each  respiration,  and  that  the  number  of  respirations 
throughout  the  day  are,  on  the  average,  15  per  minute,  the  air 
breathed  in  24  hours  will  be  10,800  liters  (381  cubic  feet)  and  the 
oxygen  absorbed  will  amount  to  515.16  liters  (18  cubic  feet),  or 
738  grammes,  and  the  carbon  dioxide  to  468.72  liters  (16.6  cubic 
feet),  or  926  grammes,  as  shown  in  the  following : 

'  Including  argon,  2  per  cent. 


AMOUNT  OF  AIR  INSPIRED.  387 

Air  Inspired  in  24  Hours,  etc. 

500  c.  c.  of  air  inspired  at  each  respiration. 
15  respii-ations  per  minute. 

7.5  liters  per  minute. 
60 
450         "       "    hour. 
24 

10,800         "        "    day. 

10,800  :  100  :  :  x  :  4.77 

X  =  515.16  liters  of  oxygen  absorbed. 

1  liter  of  oxygen  weighs  at  standard  pressure  and  temperature  1.4298 
grammes. 

515.16  liters  weigh  738  grammes. 

10,800  :  100  :  :  a;  :  4.34 

X  =  468.72  liters  of  carbon  dioxide  expired. 

1  liter  of  carbon  dioxide  weighs  1.966  grammes. 

468.72  liters  weigh  926  grammes. 

It  might  naturally  be  asked,  even  if  oxygen  is  absorbed  and  car- 
bon dioxide  expired  in  the  amounts  just  stated  for  a  short  period  of 
time,  does  it  follow  that  the  total  amount  of  the  gases  interchanged  in 
the  twenty-four  hours  will  be  the  same  as  that  obtained  by  the  method 
just  given  ?  That  such  is  the  case,  however,  has  been  proved  by 
experiments  like  those  of  Pettenkofer,^  made  with  the  celebrated 
respiration  apparatus  in  Munich,  large  enough  to  hold  a  man,  and 
in  which  the  observations  extended  over  a  period  of  twenty-four 
hours.  As  might  be  expected  from  the  nature  of  the  case,  the  de- 
termination of  the  amount  of  oxygen  absorbed  and  carbon  dioxide 
expired  by  a  human  being  in  a  given  time  must  be  of  an  approxi- 
mate character.  AYith  animals,  however,  it  is  different,  and  espe- 
cially in  the  case  of  small  ones,  in  which  the  conditions  are  very 
favorable,  the  determination  of  the  oxygen  absorbed,  as  well  as  the 
carbon  dioxide  expired,  can  be  most  accurately  determined.  The 
most  perfect  form  of  apparatus  as  yet  devised  for  this  purpose  is  that 
of  Regnault  and  Reiset."  It  consists  essentially  of  a  receiver  filled 
with  air  enclosing  the  animal  to  be  experimented  upon,  and  which 
communicates  on  the  one  hand  with  a  reservoir  supplying  oxygen  as 
fast  as  it  is  consumed  during  respiration,  and  on  the  other  with  an 
apparatus  for  the  absorption  of  the  carbon  dioxide  exhaled.  The 
detailed  disposition  of  the  apparatus  will  be  understood  from  Fig. 
204.  Within  the  tubulated  bell-jar  A,  immersed  in  the  cylinder  of 
water  B,  is  placed  a  little  animal,  a  dog,  for  example,  the  subject  of 
the  experiment.  The  animal  having  been  introduced  from  below, 
and  the  opening  hermetically  closed,  the  large  pipettes  G  G,  filled 
with  a  solution  of  potash  or  soda  of  known  strength  and  quantity, 
and  communicating  with  each  other  by  a  caoutchouc  tube,  absorb 
the  COj  exhaled  into  the  air  of  the  jar  A,  the  air  being  drawn 
alternately  into  the  pipettes  G  G  through  their  elevation  and  depres- 

1  Pettenkofer,  Ann.  Chem.  Pharm.  Suppl.,  B.  ii.,  1862,  s.  1. 

^Amiales  de  Chimie  et  de  Physique,  3"°^  ser.,  Tome  xxvi.,  1849,  p.  441. 


388 


RESPIRATION. 


sion  by  some  mechanical  arraDgement.  According  as  oxygen  is  ab- 
sorbed by  the  animal,  the  gas  pressure  falls  in  A,  and  consequently 
the  oxygen  of  the  balloon  N,  luider  the  pressure  of  the  calcium 
chloride  solution  in  P,  flows  through  J/,  replacing  that  lost  in  A. 
The  object  of  the  gas  pipette  ((  is  to  enable  the  observer  to  draw  a 
small  sample  of  gas  out  of  the  chamber  for  analysis.  The  temper- 
ature and  pressure  of  the  gas  within  the  chamber,  and  the  amount 
of  oxygen  in  the  chamber  at  the  beginning  and  the  end  of  the  ex- 
periment, as  well  as  that  delivered  to  the  chamber  being  known. 


Fig.  204. 


Regnault  and  Eciset  respiration  apparatus. 

the  amount  of  oxygen  absorbed  by  the  animal  can  be  determined, 
the  carbon  dioxide  expired  being  equal  to  the  difference  in  the 
weight  of  the  soda  pipettes  before  aud  after  the  experiment.^  The 
advantage  of  this  apparatus  is  that  the  animal  suffers  no  inconven- 
ience from  even  a  prolonged  confinement  within  the  chamber,  and 
that  the  oxygen  is  furnished  as  needed,  aud  the  carbon  dioxide  re- 
moved as  rapidly  as  produced.  The  amount  of  oxygen  absorbed 
and  carbon  dioxide  expired,  etc.,  by  a  small  monkey  during  a  period 
of  five  hours,  as  determined  by  means  of  the  Regnault  and  Reiset 
apparatus,  is  given  in  the  accompanying  Table  : 

1  For  a  detailed  description  of  the  apparatus  and  the  results  obtained  by  it  the 
reader  is  referred  to  Kcsearches  upon  Kespiration,  by  H.  C.  (.'hapman  and  A.  P. 
Erubaker,  Proc.  Acad.  Nat.  Sciences,  liS!)l,  p.  13. 


ABSORPTION  OF  OXYGEN.  389 

OxYGENi    Absorbed  and   Carbox  Dioxide  'Exhaled,    etc.,    by    a 
Monkey  (Cebus  Capucinus).' 

Grammes. 

Weight  of  oxygen  consumed  .....  13.47 

Weight  of  carbon  dioxide  produced         .         .         .  16.389 

Weight  of  oxygen  contained  in  tlie  carbon  dioxide.  11.919 
Ratio  between  the  weight  of  the  oxygen  contained 
in  the  carbon  dioxide  produced,  and  the  weight 
of  the  oxygen  consumed       .....       0.884 

Weight  of  oxygen  consumed  per  hour     .         .         .       2.694 
Weight  of  oxygen   consumed    per  liour  per  kilo- 
gramme of  animal        ......       1.347 

Weight  of  carbon  dioxide  produced  per  hour  .  .       3.277 

Weight  of  carbon  dioxide  produced  per  hour  per 

kilogramme  of  animal .  .....       1.638 

The  determination  of  the  amount  of  carbon  dioxide  expired  in  a 
given  time  is  as  important  as  that  of  the  oxygen  absorbed  since  the 
carbon  dioxide  containing  part  of  the  oxygen  absorbed  by  the  sys- 
tem during  some  previous  period  affords  the  means,  therefore,  of 
indirectly  estimating  the  same.  In  making  use  of  the  indirect 
method  of  determining  the  amount  of  oxygen  absorbed  by  an  animal 
the  water  exhaled  is  usually  estimated  simultaneously  with  that  of 
the  carbon  dioxide  expired.  One  of  the  most  accurate  forms  of 
apparatus  for  this  purpose  is  that  devised  by  Voit '  and  which  is  a 
modified  form  of  the  large  respiration  apparatus  of  Pettenkofer  al- 
ready referred  to.  The  small  respiration  apparatus  of  Voit  (Fig. 
205)  consists  of  a  chamber  H  in  which  the  subject  of  the  experi- 
ment, a  large  dog,  for  example,  is  placed ;  ^  of  a  large  drum,  and 
pumps  worked  by  a  water-wheel  for  the  production  of  a  constant 
draught  of  fresh  air  through  the  apparatus  ;  of  bottles  and  tubes 
containing  appropriate  materials  for  the  absorption  of  the  "svater  and 
carbon  dioxide  of  the  air  surrounding  the  chamber,  as  well  as  that 
from  within  it ;  and  of  meters  for  registering  the  total  amount  of 
air  that  has  passed  through  the  chamber,  of  the  fractional  part  of  the 
same  analyzed,  and  of  the  air  surrounding  the  chamber  analyzed  for 
comparison. 

The  chamber  H  in  which  the  animal  is  placed  consists  of  a  zinc 
framework  in  which  solid  glass  plates  are  imbedded,  a  part  of  Avhich 
at  the  front  of  the  chamber  is  movable  and  acts  as  a  door.  The 
other  two  openings  present,  are  for  the  entrance  and  exit  of  the  air 
ventilating  the  chamber.  The  air  entering  by  the  opening  a,  seen 
through  the  large  chamber  M,  passes  by  the  pipe  to  the  bottom  of 
the  chamber,  and  having  traversed  the  latter,  leaves  it  at  its  upper 
portion  by  the  pipe  b  and  passes  thence  by  the  pipe  d  (disconnected 
with  H  in  Fig.  205)  into  the  large  gas  meter  18  (Fig.  200),  whence 
having  been  measured,  it  is  expelled.  The  constant  current  of  air 
so   passing  is  drawn  out  of  the  tubes  d  b   and  chamber  H  by  the 

'  Chapman  and  Brnbaker,  op.  cit.,  p.  44. 

^  Zeitschrift  fiir  Biologie,  1875,  s.  532. 

3  In  that  case  the  tube  (Fig.  205)  is  connected  with  the  tubeb  of  the  small  cham- 
ber H;  when  the  subject  of  the  experiment  is  a  man,  however,  it  is  then  connected 
with  the  tube  b  of  the  larger  chamber  M. 


390 


RESPIRATION. 


rotation  of  the  drum  of  the  gas  meter  B,  whose  axis  is  in  connec- 
tion with  that  of  the  overshot  water-wheel  G,  through  the  teeth  of 
the  cog-wheel  on  the  axis  of  the  gas  meter  interlocking  with  those 
of  the  cog-wheel  on  the  axis  of  the  water-wheel.     The  water-wheel 


o 
fi 


is  kept  uniformly  rotating  through  the  flow  of  water  from  tlic  pipe  f 
connected  with  a  small  reservoir,  tlie  latter  communicating  in 
turn  with  that  supplying  the  building,  the  water  emptied  by  the 
buckets  of  the  water-wheel  passing  into  a  trough  is  carried  away 
by  the  waste  pipe  K.     Inasmuch  however,  as  with  the  water-wheel 


VOIT'S  RESPIRATION  APPARATUS. 


391 


rotating  only  once  a  minute  and  the  experiment  lasting  but  six 
hours  over  10,000  liters  of  air  pass  through  the  chamber  it_  is 
obvious  that  the  analysis  of  such  a  large  volume  of  air  would  in- 
volve a  great  expenditure  of  time  and  labor.  This  is  avoided  by 
divertinjj  part  of  the  air,  which  issues  from  the  chamber,  by  means 


of  mercurial  pumps,  from  the  tube  d  into  the  tube  .7,  terminating 
in  the  two  branches  /"  and  J'  and  of  determining  the  amount  of 
carbon  dioxide  and  water  in  two  samples  of  air.  The  air  from  J' 
passes  through  the  valve  v'  as  the  pump  is  elevated  by  the  crank 
connected  with  the  axis  of  the  water-wheel  and  returns  through 
the  valve  lo'  as  the  pmup  is  depressed,  thence  into  the  short  bottles 


392  BESPIEA  TION. 

e  e  containing  pumice-stone  and  sulphuric  acid  for  the  absorption  of 
the  water,  and  through  the  large  bottles  g  containing  water  and 
pumice-stone  for  resaturation,  then  through  the  tubes  1 1,  containing 
a  solution  of  baryta,  for  the  absorption  of  the  carbon  dioxide, 
finally  escaping  by  the  meter,  where  it  is  measured.  The  air  in  J" 
after  having  passed  through  a  similar  set  of  valves,  tubes,  etc., 
escapes  by  a  second  meter  where  it  is  measured.  By  this  arrange- 
ment, two  samples  of  air  are  therefore  analyzed,  the  mean  of  which 
represents  the  amount  of  carbon  dioxide  and  water  in  a.  given 
volume  of  air. 

As  the  external  air  passing  into  the  chamber  contains  carbon 
dioxide  and  water  as  well  as  the  internal  air,  the  amount  of  the 
same  must  be  determined.  This  is  done  in  exactly  the  same  way 
as  in  the  case  of  the  internal  air,  the  external  air  being  drawn  into 
a  tube  by  two  pumps  and  passed  through  a  double  set  of  bottles, 
tubes,  and  meters  similar  to  those  described.  The  amounts  of 
carbon  dioxide  and  water  in  a  given  volume  of  air  surrounding 
the  chamber,  having  been  determined,  this  is  deducted  from  the 
carbon  dioxide  and  water  in  an  equal  volume  of  air  that  has  passed 
simultaneously  through  the  chamber,  the  difference  giving  the 
amount  of  carbon  dioxide  and  water  expired  by  the  animal  into  a 
given  volume  of  air. 

It  remains  for  us  now  to  describe  a  little  more  in  detail  than  we 
have  done  the  manner  in  which  the  water  and  carbon  dioxide 
are  determined  by  means  of  the  absorbing  apparatus.  The  deter- 
mination of  the  amount  of  Mater  is  very  simple.  The  bottles  (e,  e, 
Fig.  206)  through  which  the  air  from  within  and  without  the 
chamber  passes  contain,  as  already  stated,  pumice-stone  and  sul- 
phuric acid,  which  has  a  great  avidity  for  water.  These  being 
weighed  in  scales,  before  and  after  the  experiment,  the  difference 
wall  give  the  amount  of  water  in  the  air  from  Avithin  and  without 
the  chamber ;  the  latter  amount,  as  we  have  already  mentioned, 
must  be  then  deducted  from  the  former,  in  order  to  get  the  amount 
of  water  exhaled  by  the  animal.  Water  having  been  absorbed  as  the 
air  passes  through  tlic  bottles  the  dried  air  is  resaturated  as  it  passes 
the  bottles  (/,  the  saturated  pumice-stone  Avithin  them  giving  up  the 
water  it  contains.  Were  not  the  air  so  resaturated  it  would  take 
up  water  from  the  solution  of  baryta  through  Avhich  the  air  next 
passes,  and  this  must  be  avoided,  as  the  solution  of  baryta  is  used 
for  the  absorption  of  carbon  dioxide. 

The  amount  of  carbon  dioxide  absorbed  is  determined  by  neu- 
tralizing the  baryta  solution  by  oxalic  acid  before  and  after  the  ex- 
periment, the  browning  of  turmeric  paper  being  used  as  an  indication 
of  the  point  of  neutralization.  The  method  will  be  made  clear  by 
the  following  example.  Suppose,  before  an  experiment  with  the 
respiration  apparatus,  it  was  ascertained  by  the  means  just  described 
that  exactly  72.4  c.  cm.  of  oxalic  acid  neutralized  25  c.  cm.  of  the 
standard  baryta  solution,  it  will  be  found  that  at  the  end  of  the 
experiment  it  requires  only  61.8  c.  cm.  of  oxalic  acid,  or  10.6  c.  cm. 


VOIT'S  RESPIRATION  APPARATUS.  393 

less,  to  neutralize  25  c.  cm.  of  the  baryta  solution,  drawn  out  of  the 
tubes  by  means  of  a  pipette.  As  the  carbon  dioxide  passes  through 
the  latter  during  the  experiment  it  combines  with  part  of  the  baryta, 
and  there  is,  therefore,  less  baryta  to  combine  with  the  oxalic  acid 
after  the  experiment  than  there  was  before.  Now,  as  for  each 
milligramme  of  carbon  dioxide  that  coml:»ines  with  the  baryta  dur- 
ing the  experiment  there  will  be  1  c.  cm.  less  of  oxalic  acid  required 
for  neutralization  after  experiment,  it  follows  that  10.0  milligrammes 
of  carbon  dioxide  must  have  been  absorbed  by  the  25  c,  cm.  of  the 
baryta  solution,  since  it  requires  10.6  c.  cm.  less  of  oxalic  acid  for 
neutralization  after  the  experiment  than  before.  In  other  words, 
the  baryta  before  the  experiment  combined  with  72.4  c.  cm.  of 
oxalic  acid,  after  the  experiment  with  61.8  c.  cm.,  because  during 
the  experiment  it  combined  with  10.6  milligrammes  of  carbon 
dioxide,  which  arc  volumetrically  equal  to  10.6  c,  cm.  of  oxalic 
acid.  Let  us  suppose,  for  example,  that  by  the  method  just  de- 
scribed the  amount  of  carbon  dioxide  and  water  expired  by  an 
animal  into  a  given  volume  of  air  has  been  determined,  then  the 
total  amount  of  carbon  dioxide  and  water  expired  by  tlie  animal  at 
the  end  of  the  experiment  would  be  obtained  by  multiplying  the 
amount  of  carbon  dioxide  and  Mater  in  the  given  volume  of  air  by 
the  ratio  of  the  latter  to  the  volume  of  air  that  has  passed  through 
the  large  and  the  two  small  meters  (internal  air)  and  that  still  re- 
mains in  the  chamber  H  and  the  tube  6  d  J,  and  adding  up  the  re- 
spective quotients. 

Kesults  of  Experiment  upon  a  Cat,    Obtained   with  the   Voit 

Kespiration  Apparatus.     Duration  of  Experiment, 

Six  Hours. 

Calculation  for  Carbon  Dioxide  and   Water. 


Carbon  dio.xide. 

Water. 

In  1000  liters  of  inner  air 
In  1000  liters  of  outer  air 

.      1.8085  grammes. 
.     0.5815          " 

12.457  grammes. 
11.445 

Difference    . 

.      1.2270          " 

1.012         " 

In  11600.5  liters  of  large  meter 
In  66.55  liters  chamber  and  tube 
In  121.02  3d  and  4th  meters  . 

.   14.23             " 

.      0.11 

.     0.15             " 

11.74 

0.07            " 
0.12            " 

Total   .... 

.   14.46             " 

11.93           " 

Calculation  foi 

f  Oxygen  Absorbed. 

Before  experiment. 

Weightof  animal  3001.3  grms.     \ 
Ingesta  .         .         0.0      " 

After  exper 

height  of  animal     . 

urine 

-r,       .       feces 
Egesta  <        , 
°            water 

carbon  dio 
Total      . 

•iment. 

.  2987. 80  grms, 
0.0       " 
0.0       " 

.       11.93     " 
xide       14.46     " 

Total         .   3001.3      " 

.  3014.19     " 
3001.30     " 

The  quantity  of  oxygen  absorbed  < 

equals  the  difference 

,  viz.:     12.89      " 

Weight  of  oxygen  in  carbon  dioxide  expired 

l^-^l  =  0.81 

Weight  of  oxygen  absorbed  12.89 


394  RESPIRATION. 

By  substituting  for  the  chamber  (iJ)  containing  the  animal  one 
large  enough  to  hold  a  human  being  (Fig.  211,  M)  the  carbon 
dioxide  expired  by  a  man  in  twenty-four  hours  has  been  found  to 
amount,  upon  a  mixed  diet,  to  930  grammes  (32.08  ounces),  and 
which  contains  253.6  grammes  (8.9  ounces)  of  carbon.  The  water 
exhaled  by  a  man  in  the  same  period  of  time  cannot,  however,  be 
accurately  determined  by  this  apparatus,  so  much  of  it  being  pre- 
cipitated in  the  chamber,  and  is  estimated,  as  Ave  shall  see  presently, 
by  another  method.  The  estimate  of  the  amount  of  carbon  dioxide 
expired  by  a  man  in  twenty-four  hours  just  given  does  not  differ 
essentially  from  that  of  Andral  and  Gavarret^  (921  grammes), 
though  greater  than  that  of  Edward  Smith"  (7(30  grammes).  The 
experiments  of  these  observers  were  made  with  the  object  of  de- 
termining only  the  carbon  dioxide  exhaled,  and  the  apparatus  con- 
sisted in  both  instances  of  a  mask  closely  fitting  the  face,  having 
two  openings  provided  with  valves  for  the  entrance  and  exit  of  the 
air,  the  carbon  dioxide  exhaled  in  the  experiments  of  Andral  and 
Gavarret  being  determined  by  means  of  a  solution  of  potash  con- 
tained in  U  tubes,  and  in  those  of  Smith  by  a  solution  of  potash 
arranged  in  numerous  layers.  The  mechanical  details  of  the  appa- 
ratus made  use  of  by  these  observers,  as  well  as  by  their  predeces- 
sors, Lavoisier  and  Seguin,  Prout,  Davy,  Dumas,  Allen  and  Pepys, 
Scharliug,  and  others,  not  being  as  perfect  as  those  of  the  Petten- 
kofer-Voit  respiration  apparatus,  just  described,  it  would  be  super- 
fluous to  dwell  further  upon  them.  In  this  connection,  however,  it  is 
proper  that  some  allusion  at  least  be  made  to  the  indirect  method  of 
determining  the  amount  of  carbon  dioxide  exhaled  in  a  given  time, 
so  successfully  applied  in  the  case  of  large  animals  by  Boussingault,^ 
This  method  consists  of  so  reo-ulatino;  the  diet  of  the  animal  ex- 
perimented  upon,  a  horse  or  cow,  for  example,  that  there  is  no  loss  of 
weight  during  the  experiment,  and  of  weighing  everything  introduced 
as  food,  solid  and  liquid,  and  all  discharged  as  urine  or  feces.  Know- 
ing the  quantity  of  carbon  entering  the  body  in  the  food,  and  leaving 
it  in  the  urine  and  feces,  the  diiFerence  between  the  carbon  of  the 
latter  and  the  former  (that  of  the  food  being  in  excess)  will  be  the 
amount  of  carbon  leaving  the  body  by  the  lungs  and  skin.  As 
regards  the  carbon  excreted  by  the  skin,  it  can,  for  such  approxi- 
mate determinations,  be  neglected,  since,  as  we  shall  see,  when  the 
skin  is  considered  as  a  respiratory  surface,  the  carbon  dioxide  ex- 
haled does  not  amount  to  more  than  between  -Jjj  and  -^^-^  of  the  total 
amount  excreted. 

The  amounts  of  oxygen  absorbed  and  carbon  dioxide  expired  in 
twenty-four  hours,  while  on  the  average  about  what  we  have  stated, 
are,  nevertheless,  affected  by  numerous  conditions.  Among  the 
most  important  of  these  are  the  rapidity  of  the  respiratory  move- 

^  Ann.  de  Chiraie  et  de  Physique,  3me  serie,  Tome  viii.,  p.  129. 

2 Phil.  Trans.,  Vol.  149,  1860,  p.  681. 

='Mem.  de  Chimie  agricole  et  de  Physiologie,  pp.  1-12.     Paris,  1854. 


EXHALATION  OF  CARBON  DIOXIDE. 


395 


ments,  sex,  age,  food,  digestion,  exercise,  fatigue,  sleep,  season,  tem- 
perature, period  of  the  day,  moisture,  atmospheric  pressure,  nervous 
system,  species,  body  weight  and  body  surface  of  animal.  Let  us 
consider  the  influences  exerted  by  the  above  somewhat  in  detail. 
The  osmosis  of  the  oxygen  of  the  air  and  the  carbon  dioxide  of  the 
blood  within  the  pulmonary  capillaries  not  being  a  sudden  action, 
but  a  continuous  one,  the  amount  of  the  gases  so  interchanged  will 
naturally  depend  on  the  length  of  time  during  which  the  air  re- 
mains in  contact  with  the  respiratory  surface ;  thus,  Vierordt,^  in 
the  experiments  performed  upon  his  own  person,  found  that,  when 
he  breathed  as  slowly  as  possible,  6  per  cent,  of  CO^  was  exhaled  in 
each  expiration,  but  that  when  he  breathed  as  rapidly  as  possible 
only  3  per  cent,  as  shown  in  the  following  Table  : 


Per  cent,  of  COj  in  expired  air. 
5.9 
4.3 
3.5 
3.1 
2.9 
2.8 


No.  of  expirations  per  minute. 

6 
12 
24 

48 

96 

150 


It  does  not  follow,  however,  that  because  the  per  cent,  of  carbon 
dioxide  contained  in  each  expiration  is  greater  during  slow  than  in 
rapid  breathing  that  more  carbon  dioxide  is  expired  in  a  given  period 
in  the  former  case  than  the  latter.  On  the  contrary,  the  reverse 
obtains,  since  the  small  per  cent,  of  carbon  dioxide  that  each  ex- 
piration contains  during  rapid  breathing  is  more  than  compensated 
for  by  the  greater  number  of  expirations.  Thus,  suppose,  for  ex- 
ample, that  250  c.  cm.  of  air  are  expired  six  times  in  a  minute, 
then,  as  each  100  c.  cm.  contain  5.9  c.  cm.  of  carbon  dioxide  : 
5.9  X  2.5  X  6,  or  88.50  c.  cm.,  will  be  the  amount  of  carbon  di- 
oxide expired  in  the  given  time.  On  the  other  hand,  if  the  same 
quantity  of  air  be  expired  twelve  times  in  a  minute,  each  expiration 
will  contain  only  4.3  per  cent,  of  carbon  dioxide,  and  yet  129  c. 
cm.  of  carbon  dioxide  will  be  expired  in  the  given  time,  since 
4.3  X  2.5  X  12  equals  129.  According  to  the  same  authority  if 
an  expiration  be  divided  into  two  equal  parts,  the  first  part  will 
contiiin,  on  an  average,  3.72  per  cent,  of  carbon  dioxide,  the  second 
5.44  per  cent.,  the  air  exhaled  during  the  first  period  of  the  expira- 
tion containing  less  carbon  dioxide  than  that  exhaled  during  the 
second  period.  The  amount  of  carbon  dioxide  exhaled  by  an  in- 
dividual depends  also  upon  the  sex.  Thus,  it  has  been  shown  by 
Andral  and  Gavarret  ^  that  one  more  gramme  of  carbon  (correspond- 
ing to  1.85  liters  of  carbon  dioxide)  was  exhaled  per  hour  by  the 
male  than  by  the  female.  Indeed,  the  difference  amounted  in  some 
instances  to  even  as  much  as  7  liters.     The  difference  in  the  weight 


'  Physiologie  des  Athmens,  p.  102.     Karlsruhe,  1845. 
2  Op.  cit. 


396  BESPIBA  TION. 

of  the  body  was  not  taken  into  consideration  in  the  observations  of 
Andral  and  Gavarret.  Scharliug,'  however,  found  that  more  car- 
bon dioxide  was  exhaled  by  the  male  than  the  female,  even  when 
this  was  estimated  with  reference  to  the  body  weight.  Apart  from 
the  greater  muscular  activity  of  the  male,  as  compared  with  the 
female,  being  sufficient  to  account  for  the  difference  in  the  amount 
of  carbon  dioxide  exhaled  by  the  sexes,  other  conditions  peculiar 
to  the  female  exert  an  influence  in  this  respect  that  must  not  be 
overlooked.  Thus  it  was  shown  by  the  experiments  of  Andral  and 
Gavarret,"  that  as  long  as  the  menses  succeeded  each  other  regularly, 
the  average  amount  of  carbon  dioxide  exhaled  remained  about  the 
same,  being  on  the  average  11.7  liters  per  hour,  with  their  cessation 
the  amount  increased  to  about  15  liters,  while  from  60  to  82  years 
of  age  it  diminished  from  13  to  11  liters.  Temporary  cessation 
of  the  menses  whether  due  to  pregnancy  or  other  causes,  is  also 
accompanied  by  an  increase  of  the  amount  of  carbon  dioxide 
exhaled. 

As  is  well  known,  during  the  first  few  hours  and  days  after  birth, 
the  infant  making  little  or  no  movement,  sleeping  most  of  the  time, 
generates  but  little  heat,  and  must,  therefore,  be  carefully  guarded 
against  changes  in  the  external  temperature.  At  this  early  period 
of  life  the  amount  of  ojygen  absorbed  and  carbon  dioxide  exhaled 
must  be  very  small.  With  the  thorough  estal)lishment  of  respira- 
tion, this  amount  is  increased,  and  from  the  fact  of  the  number  of 
respirations  being  greater  in  early  than  in  later  life,  it  is  probable 
that  the  amount  of  carbon  dioxide  exhaled,  considered  with  reference 
to  the  bodv  weight  is  greater  in  the  infant  than  in  the  adult.  The 
necessary  data  essential  for  such  a  comparison  are,  however,  too  insuf- 
ficient to  admit  of  more  than  the  general  statement  just  made.  From 
the  observations  of  Andral  and  Gavarret  ^  based  upon  the  exami- 
nation of  numerous  individuals  between  the  ages  of  12  and  102 
years,  we  learn  that  from  the  age  of  12  to  32,  there  is  an  absolute 
increase  in  the  amount  of  carbon  dioxide  exhaled,  from  32  to  00 
years  old  a  slight  diminution,  and  from  60  to  102 'years,  a  very 
considerable  one. 

Males.  Carbon  dioxide  exhaled  jjer  hour. 

12  to  16  years  of  age.  15  liters  (915  cubic  inches). 

17   "  19       "        "  20       " 

25  "  32       "        "  22       " 

32   "  60       "        "  20      " 

63  "  82        "        "  15.3   " 

102  "        "  11       " 

Wlien  these  observations  are  supplemented  by  those  of  Schar- 
ling,*  we  also  learn  that  the  amount  of  carbon  dioxide  exhaled  in 
youth,  relative  to  tlie  weight  of  the  body,  is  greater  than  that  in 
the  adult,  l)eing  in  the  case  of  a  boy,  for  example,  twice  as  much 

'Ann.  de  Chimie,  Tome  viii.,  1843,  p.  486.  ^  (^p    p\^ 

"Op.  cit.  *0p.  cit.,  p.  129. 


ABSOBPTIOX  OF  OXYGEX.  397 

as  in  a  man.  The  results  of  Scharling's  experiments  might  be  in- 
ferred from  those  of  Andral  and  Gavarret,  since  the  absolute  in- 
crease in  the  amount  of  carbon  dioxide  exhaled  between  the  period 
of  childhood  and  adult  life  is  small,  as  compared  with  the  increase 
in  the  weight  of  the  body  within  the  same  period. 

According  to  Pettenkofer/  more  oxygen  is  absorbed  up(jn  a  ni- 
trogenous than  upon  a  non-nitrogenous  diet,  and  more  upon  a  non- 
nitrogenous  one  than  upon  a  mixed  one,  the  interchange  of  oxygen 
and  carbon  dioxide  being,  as  might  be  expected,  least  during  fasting, 
as  was  shown  by  the  following  residts  obtained  by  the  above  ob- 
servers. 

Fasting.  Mixed  diet.      Xon-nitrogenous      Nitrogenous 

diet.  diet. 

Oxvgen       .         743  grms,       709  grms.       808  grms.      850  grms. 
Carbon  dioxide  695     '•  912     '•  839      '•        1003      '■' 

It  will  be  observed  that  it  is  only  in  the  ease  where  no  food  was 
taken  that  the  oxygen  absorbed  is  greater  than  that  of  the  carbon 
dioxide  expired. 

As  regards  the  influence  of  the  food  upon  the  exhalation  of  car- 
bon dioxide,  the  extended  series  of  experiments  performed  by  Dr, 
Edward  Smith  -  upon  himself  and  friends,  are  very  conclusive. 
Food,  with  reference  to  the  exhalation  of  carbon  dioxide,  can  be 
divided,  according  to  Dr.  Smith,  into  two  classes,  respiratory  exci- 
tants, which  increase  the  exhalation  of  carbon  dioxide,  and  non- 
exciters,  which  diminish  it.  The  excito-respiratory  foods  include 
the  nitrogenous  articles  of  diet,  milk,  sugar,  rum,  beer,  stout,  the 
cereals,  and  |X)tato ;  the  non-exciters,  starch,  fat,  certain  alcoholic 
compounds,  the  volatile  element  of  wines  and  spirits,  and  coft'ee 
leaves.  The  most  powerful  respiratory  excitants  are  tea  and  sugar, 
coffee,  rum,  milk,  cocoa,  ales,  and  chicory  come  next,  then  casein 
and  o^luten,  and  lastlv  gelatin  and  albimiin.  The  effect  of  takins: 
respiratory  excitants  is  soon  experienced  by  the  system,  the  maxi- 
mum effect  being  usually  attained  within  an  hour ;  their  action  is 
of  a  temporary  character,  and  the  effect  is  not  proportional  to  the 
quantity  taken.  Certain  respiratory  excitants,  like  tea  and  coffee, 
cause  an  exhalation  of  carbon  in  excess  of  that  supplied  by  these 
foods,  while  others,  like  sugar,  cause  an  evolution  less  in  amount 
than  that  supplied.  In  this  connection  it  may  l^e  mentioned  that 
the  soothing  influence  experienced  by  persons  suffering  from  de- 
pression of  spirits  by  drinking  tea  is  probably  due  to  the  exhalation 
of  carbon  dioxide  being  increased,  an  excess  of  carbon  dioxide  in 
the  system  giving  rise  to  such  feelings.  According  to  Dr.  Smith, 
brandy,  whiskey,  and  gin,  the  volatile  elements  of  alcohol,  gin, 
rum,  sherry,  and  port  ^^-ine,  when  inhaled  diminished  the  quantity 
of  carbon  dioxide  inhaled,  while  rum  and  malt  liquors,  on  the  con- 

'Sitzungber.  d.  Konigl.  baver  Acad.  d.  WLssen.,  1867,  s.  255. 
2 Ph.  Trans.,  Vol.  14lt,  1860,  p.  715. 


398  RESPIRATION. 

trary,  increased  the  exhalation.  While  the  effect  of  pure  alcohol, 
according  to  Prout,  Horn,  and  Vierordt,^  is  to  diminish  the  exha- 
lation of  carbon  dioxide,  just  the  opposite  effect  is  attributed  to  it  by 
Hervier  and  St.  Leger  and  Smith.  The  difference  in  the  result  of 
the  effect  of  alcohol  upon  the  exhalation  of  carbon  dioxide  observed 
by  these  experimenters  may  be  due  to  the  proportion  of  carbon  di- 
oxide in  the  expired  air  being  only  considered,  and  not  the  absolute 
quantity  exhaled,  as  was  the  case  in  the  experiments  of  Prout,  or 
to  the  alcohol  being  administered  with  or  without  food,  or  even  to 
individual  peculiarities. 

It  was  observed  by  Lavoisier  and  Seguin'  as  long  ago  as  the  end 
of  the  last  century  that  the  absorption  of  oxygen  was  increased  by 
digestion,  lowering  of  temperature,  and  the  performance  of  work — 
and  such  has  been  shown  to  be  the  case  by  the  investigation  of 
modern  observers,  even  though  the  amounts  of  oxygen  obtained 
by  Lavoisier  differ  both  relatively  and  absolutely  from  those  of  the 
latter.  It  must  always  be  a  source  of  regret  that  Lavoisier  did  not 
describe  the  apparatus  in  which  he  placed  Seguin,  and  by  means  of 
which  he  obtained  the  results  just  given,  the  genius  of  Lavoisier 
being  as  conspicuously  manifested  in  the  disposition  of  experimen- 
tal detail,  as  in  the  establishment  of  grand  generalizations.  In  all 
probability  the  apparatus  used  was  essentially  the  same  as  in  the 
case  of  the  experiments  performed  upon  the  guinea-pig  with  the 
same  object,  that  of  determining  the  amount  of  oxygen  absorbed  and 
carbon  dioxide  exhaled  in  a  given  time,  consisting  in  that  instance 
of  a  bell-jar  standing  over  a  pneumatic  trough,  wdthin  Avhich  the 
animal  was  introduced  and  supported,  after  being  passed  up 
through  the  water  of  the  trough,  the  oxygen  being  introduced  as 
needed,  in  known  quantities,  and  the  carbon  dioxide  exhaled  ab- 
sorbed by  alkali. 

Recent  researches*  have  shown  that  from  7  to  34  per  cent,  more 
oxygen  is  absorbed  and  from  7  to  31  per  cent,  more  carbon  dioxide 
expired  during  digestion  than  when  fasting.  This  increase  in  the 
gaseous  interchange  during  digestion  appears  to  be  due  not  only  to 
the  oxidation  of  the  products  of  digestion  and  to  the  chemical  pro- 
cesses incidental  to  the  latter,  but  more  especially  to  the  activity  of 
the  muscular  walls  of  the  alimentary  canal.* 

The  reverse  effect,  or  the  diminution  in  the  exhalation  of  carbon 
dioxide  in  the  absence  of  digestive  activity  through  the  depriving 
one's  self,  or  an  animal,  of  food,  was  also  shown  by  Yierordt  in 
his  own  person,  by  Spallanzani  in  the  case  of  snails  and  silk  worms, 
Marchand  in  frogs,  and  Bidder  and  Schmidt  on  cats.^ 

That  muscular  exertion  increases  the  absorption  of  oxygen  and 
expiration  of  carbon  dioxide,  has  also  been  proved  by  a  number  of 

1  Milne  Edwards,  Physiologie,  Tome  ii.,  p.  536. 

2  Mem.  del'  Acad,  des  Sciences,  1789,  p.  .575. 
»Loewv,  Pfliiger  s  Arcliiv,  Band  43,  1888,  s.  515. 
*Zuntzn.  Mering,  Ebenda,  Band  32,  1883,  s.  173. 
^  Milne  Edwards,  op.  cit.,  p.  538. 


ABSORPTION  OF  OXYGEN.  399 

observers.  Thus,  according  to  Yierordt/  during  moderate  exer- 
cise the  carbon  dioxide  exhaled  was  increased  in  amount  19  c.  c. 
(1.197  cubic  inches)  per  minute,  while  Dr.  Smith  ^  found  that  in 
walking  at  the  rate  of  three  miles  an  hour,  the  exhalation  of  carbon 
dioxide  in  one  hour  was  equal  to  that  exhaled  during  two  and  three- 
quarter  hours  of  repose  with,  and  three  and  one-half  hours  of  re- 
pose without  food,  and  that  the  amount  of  carbon  dioxide  expired 
during  one  hour's  work  on  a  tread-wheel  was  equal  to  four  and  one- 
half  hours  of  rest  with  and  six  hours  without  food.  According  to 
Pettenkofer,^  while  a  man  absorbed  during  rest  867  grammes  of 
oxygen  and  expired  930  grammes  of  carbon  dioxide,  he  absorbs 
during  the  performance  of  moderate  work,  1006  grammes  of  oxygen 
and  expires  1134  grammes  of  carbon  dioxide.  Hirn^  states,  how- 
ever, as  the  result  of  experiments  made  upon  several  men  that  four 
times  as  much  oxygen  is  absorbed  during  work  as  during  rest. 

The  oxygen  absorbed  and  carbon  dioxide  exhaled  is  also  very 
much  increased  by  involuntary  excitement  such  as  shivering  for 
example,  or  to  a  greater  extent  even  by  voluntary  effort.''  It 
should  be  mentioned  when  muscular  exertion  is  so  excessive  as 
to  produce  fatigue  and  exhaustion  that  the  gaseous  interchange  is 
diminished  and  the  same  holds  true  of  severe  mental,  as  well  as  of 
bodily  work. 

It  has  been  shown  by  Speck  '^  that  the  maximum  increase  of 
oxygen  and  carbon  dioxide  is  attained  before  that  of  exertion  ;  that 
according  to  the  position  of  the  body,  the  increase  for  the  same 
amount  of  work  varies,  that  for  a  given  amount  of  work  the  respira- 
tory activity  is  greatest  during  the  first  part  of  the  period  of  its 
performance ;  that  the  greater  the  increase  of  carbon  dioxide  ex- 
pired, the  less  is  the  increase  proportionally  of  oxygen  absorbed,  so 
that  the  carbon  dioxide  expired  may  contain  more  oxygen  than  is 
absorbed ;  that  the  quantity  of  air  breathed  is  so  intimately  related 
to  the  carbon  dioxide  expired  that  the  latter  may  be  regarded  as  a 
measure  of  respiratory  activity. 

A  natural  inference  from  what  has  just  been  stated  would  be 
that  during  sleep  the  oxygen  absorbed  and  carbon  dioxide  expired 
would  be  diminished,  and  such  has  been  shown  experimentally  to  be 
the  case."  According  to  Smith  -  the  amount  of  carbon  dioxide  expired 
during  the  night  as  compared  with  that  expired  during  the  day  was 
in  the  ratio  of  1  to  1.8.  In  hibernating  animals  like  the  marmot, 
for  example,  the  amount  of  gaseous  interchange  is  so  small  that  lit- 
tle or  no  difference  can  be  detected  in  the  composition  of  the  air  in 

'  C'vclopiedia  of  Anat.  and  Pliys.,  Vol.  iv.,  p.  348. 

2  Op.  cit.,  p.  713.  3Lo(._  cit. 

*  Exposition  analytique  et  experimentale  de  la  theorie  mecanique  de  la  Chaleur, 
3d  ed.,  Tome  i.,  p.  35. 

^Marcet,  A  Contribution  to  the  History  of  the  Respiration  of  ^lan.  London, 
1897,  p.  43. 

•■Deutsches  Archiv  f.  klin.  Medecin,  Band  45,  1889,  s.  4()1. 

'Milne  Edwards,  op.  cit.,  Tome  ii.,  p.  528.  ^Qp,  ^it.,  p.  693. 


400  RESPIRA  TION. 

which  the  animal  has  remained  for  three  hours  when  in  this  torpid 
state.  Indeed,  according  to  Kegnault  and  Reiset/  only  one-thir- 
tieth of  the  usual  amount  of  oxygen  is  absorbed  by  the  animal  when 
in  this  condition. 

The  experiments  of  Vierordt  -  show  that  with  slight  diminution 
in  the  external  temperature  the  amount  of  carbon  dioxide  exhaled 
by  man  is  increased  about  one-sixth.  Thus  the  external  tempera- 
ture being  between  3  and  15  degrees  C.  (37.4°  and  59°  F.),  the 
absolute  amount  of  carbon  dioxide  exhaled  per  minute  was  299.33 
c.  cm.  (about  18  inches),  while  with  the  external  temperature  be- 
tween 16  and  24  degrees  the  amount  exhaled  was  only  257.81  c.  cm. 
(15  inches).  The  result  of  Vierordt's  experiments  might  have  been 
anticipated,  since  a  fall  in  the  external  temperature  necessitates  a 
greater  production  of  heat,  the  high  temperature  of  the  body  being 
maintained,  and  this  implies  a  greater  absorption  of  oxygen  and 
consequently  a  greater  exhalation  of  carbon  dioxide.  AVhen  we 
come  to  study  the  production  of  animal  heat  we  shall  see  that  one 
of  the  most  striking  contrasts  between  mammals  and  birds,  as  com- 
pared with  remaining  animals,  is  the  power  the  former  possess  of 
generating  heat  to  replace  that  lost  through  a  fall  in  the  external 
temperature.  On  the  same  principle  as  that  just  mentioned  w^e 
should  expect  to  find  also  that  more  carbon  dioxide  is  exhaled  iu 
winter  than  in  summer,  there  being  a  greater  demand  for  the  pro- 
duction of  heat  in  the  former  case  than  in  the  latter.  This  has 
been  shown  to  be  the  case  more  particularly  by  the  researches  of 
Dr.  Edward  Smith. '^  Thus  the  maximum  amount  of  carbon  dioxide 
is  exhaled  in  January,  February,  and  March,  the  minimum  amount 
in  July,  August,  and  part  of  September  ;  June  and  July  being 
months  of  gradual  diminution,  October,  November,  and  December 
of  gradual  increase.  It  should  be  mentioned  in  this  connection, 
however,  that  animals,  and  probably  also  man,  cannot  at  once  adapt 
themselves  as  regards  their  respiration  to  sudden  changes  in  tem- 
perature. Thus  it  was  shown  many  years  ago  by  W.  Milne  Ed- 
wards ^  that  birds,  for  example,  in  w^inter  would  still  consume  the 
same  amount  of  oxygen  and  exhale  the  same  amount  of  carbon 
dioxide  as  usual,  though  the  external  temperature  w'as  artificially 
raised  to  that  of  summer  heat.  The  inverse  ratio  existing  between 
the  temperature  of  the  environment  and  the  amount  of  carbon 
dioxide  expired,  just  referred  to,  does  not,  however,  always  obtain, 
since  Page  and  others^  have  shown  that  w4iile  the  expiration  of 
carbon  dioxide  diminishes  with  a  rise  of  temperature  from  4.4°  C. 
(39.9°  F.)  to  14.3°  C.  (57.7°  F.),  with  the  attainment  of  the  latter 
temperature  the  expiration  increases.  The  effect  of  variations  in 
the  temperature  of  tlie  body  upon  respiratory  activity  differs,  how- 
ever, from  that  of  changes  in  the  temperature  of  the  environment, 

'Op.  fit.,  p.  411.  2 Op.  fit.,  p.  551.  3()p.  cit.,  p.  703. 

*  De  r  InlliK'iicc  (k's  Ajjcns  Phvsiques  sur  la  Vie.     Paris,  1824,  p.  200. 
5  Journal  of  Physiology,  Vol.' 2,  1S80,  p.  228. 


JXFLUEXCE  OF  PSESSUJiE.  401 

respiratorv  activity  being  increased  l\v  a  rise  and  diminished  by 
a  fall  in  the  bodily  temperature.  Thus  it  has  been  shown  by 
Colosanti  ^  that  while  g'uinea-pigs  absorb  per  kilogramme  per  hour 
948.17  c.  c.  of  oxygen,  the  temperature  being  37.1°  C.  (98.7°  F.), 
they  absorb  as  much  as  1242.6  c.  c,  the  temperature  being  39.7°  C. 
(103.4°  F.),  and  the  same  results  have  been  obtained  by  experi- 
ments- made  upon  man  during  the  condition  of  fever.  It  is  well 
known  also  that  the  absorption  of  oxygen  and  the  expiration  of 
carbon  dioxide  undergo  diurnal  variations,  the  gaseous  interchange 
rising  after  and  falling  before  meals,  the  minimum  being  reached  at 
night,  the  latter  effect  being  partly  due  to  the  fact  that  more  carbon 
dioxide  is  expired  during  sunlight  than  in  darkness. 

It  is  well  known  that  the  expiration  of  carbon  dioxide  is  greater 
in  a  moist  than  in  a  dry  atmosphere.  Thus,  according  to  Leh- 
mann,^  rabbits  exhaled  in  a  moist  air  the  temperature  being 
38°C.  (100°  F.)  352  c.  c.  (22  cu.  in.)  of  carbon  dioxide,  while  in 
a  dry  air  at  the  same  temperature  they  expired  only  240  c.  c. 
(15  cu,  in.). 

It  has  been  shown  among  others  by  Paul  Bert  ^  that  any  increase 
or  diminution  in  barometric  pressure  acts  upon  living  beings  in  in- 
creasing or  diminishing  the  tension  of  the  oxygen  in  the  air  they 
breathe,  and  the  blood  that  circulates  through  their  tissues,  and 
that  any  increase  or  diminution  in  atmospheric  pressure  is  unfavor- 
able to  living  beings  accommodated  as  they  now  are,  to  the  present 
tension  of  atmospheric  oxygen.  Indeed,  according  to  this  observer, 
all  life  perishes  in  air  sufficiently  compressed.  With  a  pressure 
simply  of  several  atmospheres  symptoms  of  narcotic  poisoning  set 
in  similar  to  those  experienced  in  breathing  an  atmosphere  contain- 
ing an  excess  of  carbon  dioxide,  and  due  probably  to  the  same  cause, 
namely,  an  excess  of  carbon  dioxide  in  the  blood.  With  still  higher 
pressure,  4  of  oxygen — that  is,  20  atmospheres,  and  upward — death 
takes  place  from  asphyxia,  accompanied  with  convulsions,  as  when 
caused  by  a  deficiency  of  oxygen.  Precisely  the  same  effect  is 
caused  by  the  gradual  diminution  of  atmospheric  pressure.  A 
sudden  diminution,  however,  causes  death,  probably  through  the 
liberation  of  gases  in  the  blood,  which  interfere  mechanically  with 
its  circulation. 

It  might  be  supposed  that  an  increase  or  diminution  in  the  den- 
sity of  the  air  inspired,  increasing  or  diminishing  the  amount  of 
oxygen  absorbed,  must  sooner  or  later  influence  the  amoimt  of  car- 
bon dioxide  exhaled.  That  such  is  the  case  is  shown  by  the  ex- 
periments performed  many  years  ago  by  Hervier  and  St.  Leger^  in 
which  it  was  proved  that  with  a  slight  augmentation  of  atmospheric 
pressure,  the   amount   of    carbon   dioxide   exhaled   Avas  increased. 

iPfliiger's  Archiv,  Band  14,  1877,  s.  125. 

^Fubini  and  Benedicenti.  MoleschoU  Untei-sucli. ,  Baud  14,  1892,  s.  623. 
3  Physiological  ('lieinistrv,  1885,  vol.  ii..  p.  144. 
*La  Pression  Barometrique,  1878,  p.  115.S. 
^Gazette  des  hopitaux,  3me  serie,  1849,  Tome  i.,  p.  374. 
26 


402  BESPIBA  TION. 

When  the  pressure,  however,  exceeds  twenty  atmospheres  the  pro- 
duction of  carbon  dioxide  is  diminislied  correspondingly  to  the 
diminished  oxidation,  and  with  still  higher  pressure  it  is  entirely 
arrested,  oxidation,  according  to  Bert,'  as  we  have  seen,  ceasing 
then  altogether.  With  a  diminution  of  atmospheric  pressure  the 
amount  of  carbon  dioxide  produced  is  also  diminished. 

The  oxygen  absorbed  and  carbon  dioxide  expired  is  necessarily 
influenced  by  the  integrity  of  the  nervous  system  since  the  nutritive 
processes  in  the  tissues,  as  we  shall  see  hereafter,  are  governed  by 
the  former. 

Thus  division  of  the  motor  nerve  supplying  a  muscle  reduces  the 
consumption  of  oxygen  22  per  cent.,  and  the  production  of  carbon 
dioxide  30  per  cent.,  while  sectiou  of  the  spinal  cord  diminishes  the 
absorption  by  the  tissues  of  oxygen  4  per  cent.,  and  the  expiration 
of  carbon  dioxide  20  per  cent.,  destruction  of  the  cord  causing  the 
gaseous  exchange  to  fall  to  a  minimum."  In  this  connection  it  may 
be  mentioned  that  the  respiratory  activity  is  much  greater  in  hot- 
blooded  than  in  cold-blooded  animals,  and  that  among  the  former 
the  respiratory  activity  of  birds  is  higher  than  that  of  mammals. 
Of  the  same  species,  cxeteris  paribus,  the  respiratory  activity  is 
greater  in  small  than  in  large  animals,  the  greater  consumjjtion  of 
oxygen  and  production  of  carbon  dioxide  being  due  to  the  fact  that 
the  body  surface  is  greater  in  relation  to  the  body  weight  in  the 
former,  which  entails  therefore  proportionally  a  greater  loss  of  heat. 

Having  considered  the  amounts  of  oxygen  absorbed  and  carbon 
dioxide  expired,  and  the  various  conditions  affecting  the  same,  let 
us  study  now  the  ratio  in  which  these  gases  are  interchanged.  As 
the  volume  of  carbon  dioxide  produced  through  the  combining  of 
carbon  with  oxygen  is  equal  to  the  volume  of  oxygen  entering  into 
its  formation,  it  follows  if  all  the  oxygen  absorbed  in  inspiration 
combines  with  carbon  to  form  carbon  dioxide,  the  volume  of  the 
carbon  dioxide  expired  ought  to  be  equal  to  that  of  the  oxygen 
inspired.  We  have  just  seen,  however,  that  the  inspired  air  loses 
while  in  the  lungs  4,78  vols,  per  cent,  of  oxygen,  M'hereas  it  gains 
only  4.34  vols,  per  cent,  of  carbon  dioxide.  The  ratio  of  the 
weight  of  oxygen  contained  in  the  carbon  dioxide  expired  to  the 
weight  of  the  oxygen  simultaneously  absorbed  was  called  by 
Pfliiger'^  the  "respiratory  quotient"  and  on  the  above  supposi- 
tion the  air  respired  being  estimated  in  liters  woidd  be  equal  to 


Grammes.  Liters. 

Oxygen  6.205  _  4. 34 
Oxygen  6.834  ~"  4.W 


0.907 


It  will  be  observed  that  the  respiratory  quotient  0.90  is  not  the 
ratio  of  the  weight  of  the  oxygen  absorbed  to  the  weight  of  the  car- 
bon dioxide  expired,  but  to  the  weight  of  the  oxygen  in  that  car- 

'Op.  c'it.,  p.  ]1.")2.  2Q„i„q„auf|^  Corapt.  rend.  Soc.  Biol.,  1884,  p.  342. 

aPHiiger's  Archiv,  Band  14,  1877,  s.  472. 


RESPIRATORY  QUOTIENT.  403 

bon  dioxide/  Since  the  latter  occupies,  however,  the  same  volume 
as  that  of  the  carbon  dioxide  expired,  the  respiratory  quotient  is 

CO 

often  expressed    by    the    formula  ~~   which    in    the    above  case 

4.34 
becomes    j-^q  =0.907.     Inasnuich  as  of  the  oxygen  absorbed  part 

only  is  expired  in  the  carbon  dioxide,  it  is  evident  that  part  leaves  the 
body  in  some  other  form  than  that  of  carbon  dioxide,  and  which  ex- 
plains the  fact  that  the  volume  of  the  expired  air  is  slightly  less  than 
that  of  the  inspired  air.  In  speaking  of  the  composition  of  the  car- 
bohydrates, it  will  be  remembered  that  attention  was  called  to  the 
fact  of  the  hydrogen  present  being  in  the  proportion  to  form  mth 
the  oxygen  water.  Suppose  now  that  starch,  a  carbohydrate,  be 
oxidized,  the  result  would  be  the  formation  of  carbon  dioxide  and 
the  setting  free  of  the  water,  the  reaction  being  as  follows  : 

C  AoO.  +  O,,  =  6(C0  J  +  5(H,p) 

In  an  animal  fed  exclusively  upon  starch  the  respiratory  (quotient 

will  be,  therefore,  unitv,  ~—^-  =  1,  the  volume  of  carbon  dioxide 

6(0,) 

expired  being  equal  to  that  of  oxygen  absorbed,  all  of  the  latter 
combining  with  carbon.  If,  however,  the  same  animal  be  fed  upon 
a  fat  in  which  the  hydrogen  is  in  excess,  more  than  sufficient  to  form 
water  with  the  oxygen  present,  the  absorption  of  oxygen  and  the 
oxidation  of  the  fat  would  result  in  the  formation  of  carbon  diox- 
ide and  the  setting  free  of  the  water,  as  in  the  first  case ;  but  as 
part  of  the  oxygen  absorbed  would  also  combine  with  that  part  of 
the  hydrogen  in  excess  to  form  water,  necessarily  some  of  the  oxy- 
gen absorbed  would  not  reappear  as  carbon  dioxide  in  the  expired 
air,  but  as  water.  The  reaction  would  be  as  follows,  supposing 
olein  to  be  the  fat  used  : 

C..H,,  +  SCH^OJ  +  0,„„  =  57(CO  J  +  2{Ilfi;)  +  46(H^O) 

The    respiratory  quotient  on  a  diet  of  fat  would  be,  therefore, 
57(00^)^0  71, 
80(0,)  -' 

If  the  animal  is  fed  uj)on  meat,  the  respiratory  quotient  is  found 
to  vary  from  0.75  to  0.81  (according  to  the  thoroughness  with 
which  the  meat  is  digested),  since  after  the  urea  was  separated  from 
the  albumin  the  remainder  of  the  meat  would  contain  an  excess  of 
hydrogen,  as  in  the  case  of  fat,  hence  part  of  the  oxygen  absorbed 
in  respiration  would  not  reappear  as  carbon  dioxide  but  as  water, 
part  of  the  oxygen  combining  with  the  carbon  to  form  carbon 
dioxide  and  part  combining  with  the  hydrogen  to  form  water. 

These  theoretical  considerations^  are  fully  confirmed  by  the  ex- 
periments of  Eegnault  and  Reiset  in  which  it  was  shown  that  in 

1  See  p.  389.  2  Qp.  eit. 


404  RESPIRATION. 

animals  fed  upon  starch  the  diiference  between  the  weight  of  the 
oxygen  absorbed  and  that  expired  in  the  carbon  dioxide  was  far 
less  than  in  the  case  of  animals  fed  upon  fat  or  meat.  On  the 
other  hand,  in  certain  kinds  of  vegetable  food,  fruits,  etc.,  the  oxy- 
gen present  being  in  excess  more  than  sufficient  to  form  ^vith  the 
hydrogen,  water,  it  is  to  be  expected  that  more  oxygen  will  be  ex- 
pired in  the  carbon  dioxide  than  absorbed  in  inspiration  as  shown, 
for  example,  in  the  oxidation  of  tartaric  acid 

C^H^O,  -r  O3  =  4(C0  J  -  3H^0 

The  respiratory  quotient  on  such  a  diet  would  be,  therefore,  more 
than  unity 

8(0)vols.       ^   _ 

The  respiratory  quotient  being  the  ratio  of  the  oxygen  absorbed  to 
the  carbon  dioxide  expired  must  be  affected  by  the  same  conditions 
that  we  have  seen  influence  the  gaseous  interchanges  and  will  vary 
according  as  the  diet  is  a  starvation  one,  mixed  or  limited  to  one 
particular  kind  of  food.  Thus,  the  respiratory  quotient  upon  a 
starvation  diet  is  equal  to  0.68,  upon  a  non-nitrogenous  one  0.75, 
upon  a  nitrogenous  one  0.90,  upon  a  mixed  one  0.94,  no  work 
being  done  and  the  oxygen  absorbed  and  carl)on  dioxide  expired, 
being  such  as  given  on  page  440.  Admitting  that  the  part  of  the 
oxygen  which  is  absorbed  in  inspiration  and  does  not  reappear  in 
the  carbon  dioxide  expired,  combines  with  hydrogen  to  form  water 
within  the  economy,  the  quantity  so  formed  and  exhaled  is  small 
as  compared  with  the  Avater  taken  in  as  such.  Suppose  that  the 
hydrogen  available  for  combustion  is  about  13  grammes  (200 
grains),  the  water  formed  would  amount  to  only  117  grammes 
(1805  grains), 

H.O  H  1I„0  H 

18      :     2      :  :     117      :     13 

whereas,  the  water  exhaled  from  the  lungs  of  a  man  amounts  on 
the  average  in  twenty  hours  from  400  to  800  grammes^  (6172  to^ 
12344  grains). 

The  manner  in  which  the  water  exhaled  by  an  animal  is  deter- 
mined has  already  been  referred  to  in  the  descri])tion  of  the  respira- 
tion apparatus  made  use  of  for  that  purpose.  In  the  case  of  man,^ 
however,  the  water  exhaled  can  be  more  accurately  determined  by 
breathing  into  a  curved  tube,  terminating  in  Liebig's  bulb,  filled 
"svith  sulphuric  acid  and  pumice-stone  for  the  absorption  of  the 
water,  the  latter  being  estimated  Ijy  the  increase  in  weight. 

The  amount  of  water  exhaled  from  the  respiratory  tract  Mill  be 
influenced,  as  in  the  case  of  inert  bodies,  by  the  amount  of  water 
present  in  the  atmosphere,  the  temperature,  and  the  pressure. 
Hence,  the  dryness  of  tlie  throat  and  fauces  experienced  by  persons 

1  Valentin,  Lehrbuch  der  Physiologie,  Band  i.,  s.  527  ;  Bunge,  Lehrbuch,  1894, 
s.  272. 


TEMPERA  TUBE  OF  EXPIRED  AIR. 


405 


Fig. 


ascendino^  into  high  altitudes  through  the  loss  of  water  due  to  the 
diminished  pressure  and  great  cold.  The  extent  of  the  respiratory 
surface  ^y\\\  influence  also  the  amount  of  aqueous  vapor  exhaled. 
This  is  well  seen  in  the  diminution  of  the  exhalation  in  old  ag'e,  as 
shown  by  Barral/  the  pulmonary  cells  becoming  larger,  a  less  extent 
of  respiratory  surface  is  offered.  Finally,  the 
amount  of  water  exhaled  is  increased  by  the  quan- 
tity of  water  taken  in  as  drink,  etc.,  and  by  the 
frequency  of  the  respiration.  In  conclusion,  it 
should  be  remembered  that,  if  the  ordinary  con- 
ditions prevailing  be  reversed,  water  may  be  ab- 
sorbed by  the  respiratory  surface  instead  of  being- 
exhaled.  The  sudden  gain  in  weight  frequently 
observed  in  individuals  who  had  not  partaken  of 
solid  or  liquid  food,  often  referred  to  by  -writers  on 
physiology,"  is  due,  no  doubt,  to  absorption  by  the 
lungs  of  the  watery  vapor  of  the  atmosphere,  rather 
than  to  cutaneous  absorption,  as  sometimes  sup- 
posed. 

The  expired  air  differs  from  that  inspired,  not 
only  in  having  lost  oxygen  and  gained  carbon  di- 
oxide and  water,  but  in  being  warmer.  It  is  due 
to  this  fact  that  the  volume  of  the  expired  air  is 
about  one-ninth  greater  than  that  of  the  inspired 
air.  If,  however,  both  the  expired  and  inspired 
air  be  reduced  to  standard  temperature  then  the 
volume  of  the  expired  air  will  be  found  to  be  less, 
as  already  mentioned,  than  that  of  the  inspired  air. 
According  to  Grehant,'^  the  air  being  inspired  by 
the  nares  and  having  a  temperature  of  22°  C. 
(71.6°  F.),  that  exhaled  by  the  mouth  had  a  tem- 
perature of  35°  C  (95°  F.),  as  determined  by  a 
thermometer  (Fig.  207,  C)  placed  within  the  appa- 
ratus A,  through  which  the  air  was  expired,  and 
which  was  uninfluenced  by  the  external  tempera- 
ture. When  the  air  was,  however,  inspired  by  the 
mouth,  the  air  expired  had  a  temperature  of  only  93°.  The  result 
of  Grehant's  observations  differ  a  little  from  those  of  Valentin/ 
previously  made.  According  to  the  latter  observer,  the  external 
temperature  being  at  20°  C.  {(i^°  F.),  that  of  the  expired  air  was 
37.2°  C.  (90°  F.).  The  temperature  of  the  surrounding  atmos- 
phere has  an  important  influence,  however,  upon  that  of  the  expired 
air ;  thus,  according  to  Valentin,  in  winter  the  external  tempera- 
ture being  —  10°  C.  (14°  F.),  that  of  the  expired  air  was  only 
29°  C.  (85°  F.). 


Apparatus  for  de- 
termining tempera- 
ture of  expired  air. 


'  Ann.  de  Cliimie,  1S49,  3me  ser.,  Tome  xxv.,  p.  166. 

^Carpenter's  Physiology,  p.  4U-1. 

^Journal  tie  I'Anat.  et  de  la  Phys.,  Tome  i.,  1864,  p.  546. 


'  Op.  oil. 


533. 


406  RESPIRATION. 

Ammonia  is  undoubtedly  exhaled  from  the  lungs,  being  almost 
invariably  found  in  the  expired  air.  In  fact,  it  is  only  absent  at 
certain  periods  of  the  day,  or  during  cold  weather,  as  noticed  by 
Richardson,^  In  certain  conditions  of  the  system,  as  in  cases  of 
ureemic  poisoning,  the  amount  of  ammonia  in  the  expired  air  is  so 
great  as  to  become  very  perceptible  to  the  patient." 

Considerable  difference  of  opinion  has  prevailed  among  physiolo- 
gists as  to  whether  nitrogen  was  absorbed  or  exhaled  during  respi- 
ration. The  researches  of  Regnault,^  Boussingault,^  and  Barral,^ 
however,  that,  in  mammals  and  birds  at  least,  under  ordinary  cir- 
cumstances, a  small  quantity  of  nitrogen  is  exhaled  in  respiration, 
equal  to  about  one-fiftieth  by  weight  of  the  oxygen  absorbed. 
The  reverse,  however,  appears  to  be  the  case  with  fishes,  according 
to  Humboldt  and  Provencal,*'  nitrogen  being  absorbed  by  those 
animals.  According  to  recent  researches "  in  the  case  of  man  no 
appreciable  amount  of  nitrogen  is  either  absorbed  by  or  given  out 
from  the  blood  during  respiration.  In  speaking  of  nitrogen,  it 
may  be  incidentally  mentioned  that  its  mixture  with  oxygen  as  the 
air  we  breathe  is  obviously  of  advantage,  since,  on  account  of  its 
great  diffusibility,  the  air  vitiated  with  carbon  dioxide  is  readily  re- 
newed during  respiration.  A  small  quantity  of  organic  matter, 
the  nature  of  which  is  not  thoroughly  known,  but,  as  we  shall  see, 
is,  to  a  great  extent,  poisonous  in  character,  is  constantly  present  in 
the  expired  air.  The  presence  of  this  organic  matter  can  be  shown 
through  the  putrefaction  of  the  aqueous  products  of  the  expired  air 
when  condensed  in  a  cool  receiver,  or  through  the  putrefaction  of  a 
sponge  saturated  with  the  vapors  exhaled  by  the  lungs. 

Many  articles  of  food,  like  onions,  garlic,  alcohol,  sj)irits  of  tur- 
pentine, drugs  like  camphor,  musk,  asafoetida,  when  absorbed  by 
the  blood  and  vaporized  in  the  system,  are  exhaled  by  the  lungs, 
being  readily  recognized  by  their  odor  in  the  expired  air.  That 
poisonous  gases  are  also  exhaled  by  the  lungs  is  rendered  very 
probable  by  the  experiments  of  Bernard  -  and  Nysten,^  in  which 
sulphuretted  hydrogen  and  carbon  oxide,  so  fatal  when  inhaled, 
were  ejected  into  the  veins  without  bad  eflPect,  being  eliminated  by 
the  lungs  as  ra])idly  as  they  were  taken  u[)  by  the  venous  blood. 

Many  animals  in  which  the  respiration  is  of  a  feeble  character, 
such  as  slugs,  snails,  certain  kinds  of  fish,  frogs,  etc.,  continue  to 
live  in  air  from  which  the  oxygen  has  been  removed  to  a  consider- 
able amount.^"  Such,  however,  is  not  the  case  with  animals  whose 
respiration  is  very  active,  as  in  man.  Any  considerable  diminution 
in  the  amount  of  oxygen  in  the  surrounding  air  soon  causes  death. 

'Tlie  Cause  of  tlie  ('oagulation  of  the  Blood,  p.  360.     Ijondon,  1857. 

^Lehmann,   Pliys.  C'liein.,  Vol.  ii.,  p.  434.     Philadelpliia,  1855. 

^Op.  cit.,  p.  510.  MJhimie  Agricole,  pj).  l-'24.     Paris,  1854. 

5 Op.  cit.,  p.  P29.  6 Milne  Edwards,  Physiologic,  Tome  ii.,  p.  599. 

'Marcet,  op.  cit.,  p.  27.  ^ Substances  Toxiques,  p.  58.     Paris,  1857. 

^Recherches  de  Physiologie,  p.  81. 

^^Mihie  Edwards,  Physiologic,  Tome  ii.,  p.  020. 


I  EX  TIL  A  no  X.  407 

Just  as  a  lamp  jj^oes  out  when  the  air  feedino:  it  does  not  contain 
more  than  about  1 7  per  cent,  of  oxygen,  so  with  the  lamp  of  life 
its  flame  too  dying;  out,  respiration  soon  ceasing,  if  the  amount  of 
oxygen  usually  present  in  the  atmosphere  be  diminished  ])y  ab- 
sorption, or  through  dilution  with  some  indifferent  gas.  In  fact, 
air  which  has  been  breathed  by  man  once  should  not  be  breatlied 
again ;  such  air  having  lost  oxygen  and  gained  carbon,  if  breathed 
twice,  will  give  up  but  little  oxygen  to  his  economy.  Indeed,  as 
shown  by  Lavoisier,^  air,  having  lost  about  10  per  cent,  of  oxygen, 
becomes  absolutely  irrespirable.  Such  is  found  to  be  the  case  in 
certain  parts  of  mines  where  the  air  contains  only  that  amount  of 
oxygen.  It  is  well  known,  also,  that  birds  and  mammals  will  suf- 
focate in  an  atmosphere  in  Avhich  the  amount  of  oxygen  has  been 
diminished  to  that  extent.  Thus,  a  mouse  ^x\\\  die  in  six  minutes, 
if  confined  in  such  an  atmosphere,  and  a  sparrow  in  an  hour,  if  the 
oxygen  be  diminished  to  half  that  amount,  or  5  per  cent.  It  is 
not,  however,  the  want  of  oxygen  alone  that  causes  death  in  breath- 
ing bad  air,  but  the  simultaneous  increase  of  carbon  as  well. 
The  ill  effects  experienced  under  such  circumstances,  such  as  head- 
ache, the  sense  of  oppression,  and  even  stupor  appear  to  be  due  not 
to  the  carbon  dioxide  expired,  but  to  the  organic  matter  which  it 
contains  just  referred  to.  This  is  shown  by  the  fact  that  an  atmos- 
phere containing  1  per  cent,  of  pure  carbon  dioxide  exerts  no  de- 
leterious eflPeet  upon  the  economy,  Avhereas  an  atmosphere  contain- 
ing the  same  amount  of  carbon  dioxide  that  has  been  expired  is 
not  only  highly  injurious,  but  soon  becomes  unendurable."  As  the 
nature  and  amount  of  the  organic  matter  expired  to  which  the 
deleterious  effects  of  breathing  vitiated  air  is  due  are  unknown,  the 
carbon  dioxide  expired  is  taken  as  a  measure  of  the  same.  Expe- 
rience has  shown  that  air  fit  to  breathe  should  not  contain  more 
than  0.07  per  cent,  of  carbon  dioxide,  and  as  468  liters  of  carbon 
dioxide  are  expired  in  twenty-four  hours  it  is  obvious  that  the 
latter  must  be  exhaled  into  668304  liters  of  air  if  that  air  is  to 
contain  only  0.07  per  cent,  of  carbon  dioxide. 


xlit. 


That  is  to  say,  every  human  being  must  be  supplied  with  over  27,- 
846  liters  of  air  per  hour  in  order  that  the  CO.,  exhaled  into  it 
should  not  exceed  in  amount  0.07  per  cent. 

A  room  having  a  cubic  capacity  of  10  meters  (352  cubic  feet) 
would  contain  air  enough  to  supply  a  human  being  enclosed  within 
it  with  oxygen  for  twenty-four  hours,  but  to  prevent  vitiation  of  the 
air  the  room  would  have  to  have  a  cubic  capacity  of  674  meters 

'  Denxieme,  Memoire  sur  la  respiration  mem.  de  Clieniie,  T.  iv. ,  p.  22. 
2  Pettenkofer,  Med.  Times  and  Gazette,  1862,  p.  459. 


co„ 

Air.      CO. 

0.07  : 

100  :  :  1 

X 

=  1128  air. 

:  1428 

:  :  168  lit. 

X  = 

668301  lit.  ai 

408  BESPIRATION. 

(23,724  cubic  feet)  iu  order  that  at  the  end  of  the  twenty-four  hours 
the  carbon  dioxide  exhaled  into  the  air  M'ould  not  amount  to  more 
than  0.07  per  cent. 

In  breathing  in  the  open,  where  the  atmospheric  air  is  out  of  all 
proportion  to  that  expired  by  any  one  individual,  at  no  moment  is 
any  want  of  fresh  air  experienced.  In  our  dwellings  also,  if  prop- 
erly constructed,  a  due  supply  of  fresh  air  is  maintained  by  the 
opening  of  the  windows  and  doors,  and  the  entrance  of  the  outside 
air  through  the  cracks,  crevices,  etc.  In  churches,  theaters,  lec- 
ture-rooms, barracks,  prisons,  hospitals,  etc.,  however,  where  large 
numbers  of  people  are  congregated  together,  the  proper  supply  of 
fresh  air  should  never  be  left  to  chance.  Indeed,  this  is  now  so 
well  understood  that  in  the  ventilation  of  such  buildings  as  the 
Chamber  of  Deputies  and  many  of  the  hospitals  in  Paris,  in  the 
House  of  Commons  in  Loudon,  in  the  Philadelphia  Academy  of 
Music,  etc.,  the  air  is  continually  renewed  by  means  of  fans  worked 
by  engines,  etc.,  regard  being  paid  to  the  fact  that  the  air  supplied 
is  in  reference  not  only  to  the  amount  of  oxygen  to  be  inspired,  but 
also  to  the  carbon  dioxide,  organic  matter,  etc.,  exhaled  to  be  car- 
ried away,  care  being  taken  that  the  expired  air  does  not  mix  with 
that  to  be  inspired,  and  at  the  same  time  that  drafts  be  avoided,  the 
velocity  with  which  the  air  passes  through  the  chambers  not  being 
greater  than  from  two  to  three  feet  per  second. 

Internal  Respiration. 

It  has  already  been  mentioned  that  while  in  external  respiration 
the  oxygen  of  the  air  passes  into  the  blood  and  the  carbon  dioxide 
of  the  blood  into  the  air,  in  internal  respiration  the  oxygen  of  the 
blood  passes  into  the  tissues  and  the  carbon  dioxide  of  the  tissues 
into  the  blood.  The  distinction  between  external  and  internal  res- 
piration is,  however,  a  superficial  one,  since  the  blood  is  the  means 
by  which  the  oxygen  of  the  air  is  indirectly  carried  to  the  tissues, 
and  the  carbon  dioxide  produced  in  the  latter  conveyed  to  the  air. 
It  should  be  remembered,  however,  that  the  blood,  in  addition  to 
being  the  means  of  transportation  of  oxygen  and  carbon  dioxide  to 
and  fro,  as  a  tissue,  consumes  oxygen  and  produces  carbon  dioxide 
like  other  tissues.  Thus  it  is  well  known  that  when  readily  oxi- 
dizable  substances  are  introduced  into  the  blood  and  the  latter  is 
transfused  through  the  lungs  or  lung  tissues  more  oxygen  is  taken 
up  and  carbon  dioxide  given  off  than  by  normal  blood.  There  ap- 
pears to  be  but  little  doulit  that  under  ordinary  circumstances  the 
tissues  give  uj>  to  the  blood  similarly  substances  whose  complete 
metamorphosis  involves  the  consumption  of  oxygen  and  production 
of  carbon  dioxide.' 

The  relative  avidity  with  which  the  tissues  absorb  oxygen  is  shown 
according  to  (^uinquaud-  in  the  accompanying  table,  100  grammes 

'  Bohr  and  IlcnriqiU'Z,  Coniptcs  Heiidiis,  Tome  114,  181)2,  p.  14i)(). 
^  Comptes  Eendus  Soc.  Biologie,  Tome  ii.,  ISUO,  p.  28. 


ABSORPTIOX  OF  OXYGEN  BY  TISSUES.  409 

of  tissue  having  been  snl)niitted  in  each  instance  to  experiment  for 
a  period  of  three  liours  at  a  temperature  of  38°C.  (100°F.). 

Absorptiox  of  Oxygex  by  Tissues. 


Muscle  . 

23  c.  c. 

Spleen   . 

8 

Heart     . 

21     " 

Lungs     . 

7.2 

Brain 

12     " 

Adipose  tissue 

6 

Liver 

10    •' 

Bone 

•5 

Kidney  . 

10    •• 

Blood     . 

0.8 

Oxygen  in  being  absorbed  by  the  tissues  appears  to  enter  into  some 
form  of  molecuhir  combination  since  its  tension  in  the  hitter  amounts 
practically,  as  already  mentioned,  to  zero.  That  tlie  carbon  diox- 
ide is  formed  to  a  great  extent,  at  least,  in  the  tissues,  is  shown  by 
the  fact  that  the  amount  of  carbon  dioxide  in  the  fluids  of  the  cav- 
ities of  the  body  is  greater  than  that  in  the  l^lood,  as  shown  below, 
and  which  can  only  be  accounted  for  on  the  supposition  that  the 
■carbon  dioxide  of  tliese  fluids  passed  into  them  from  the  tissues, 

Texsiox  of  Caebox  Dioxide  ix  Fliids  of  Body.' 

Mm.  Hg  tension. 

Arterial  l)lood 21.28 

Peritoneal  cavitv      .......  58.50 

Acid  urine         . " 68.00 

Cavitv  of  intestine  .......  58.50 

Bile  (gall  bladder) 50.00 

Hydrocele  fluid 46.50 

Lymph  (thoracic  duct)      ......  34.00 

Tlie  carbon  dioxide  produced  in  the  tissues  does  not  appear  to  be 
<lue  in  all  instances  to  the  immediate  combination  of  the  oxygen  of 
the  blood  with  the  carbon  of  the  ti.ssues,  since  the  latter  will  ex- 
hale carbon  dioxide  in  the  absence  of  oxygen,  even  in  an  atmos- 
phere of  hydrogen  or  nitrogen,  carbon  dioxide  being  produced  in 
the  tissues  through  the  intra-molecular  splitting  of  more  or  less 
broken-down  substances,  as  well  as  by  direct  oxidation. 

In  concluding  the  subject  of  respiration  attention  may  be  ap- 
propriately called  to  the  modifications  of  the  normal  respiratory 
movements  or  eupnoea,  such  as  apnoea,  absence  of  breathing  ;  hy- 
perno^a  or  polypnea,  exaggerated  breathing ;  dyspnoea,  labored 
breathing ;  and  asphyxia  or  suffocation.  Difference  of  opinion 
still  prevails  among  physiologists  as  to  the  cause  of  apnoea.  Such 
facts  as  that  apnoea  can  be  produced  by  rapidly  repeated  res- 
pirations, that  it  is  more  marked  after  the  breathing  of  pure  oxy- 
gen, than  that  of  air,  and  least  marked  when  the  air  contains  but 
little  oxygen,  have  lead  to  the  conclusion  that  the  blood  is  saturated 
with  oxygen  in  apnoea  and  that  the  necessity  of  respiration  is  not 
therefore  felt  in  that  condition.  It  has  been  shown,  however,  on 
the  one  hand  -  that  apncea  can  be  produced  by  inflating  the  lungs 

'  Stra&?burg,  Pfliiger's  Acrhiv,  B.  vi..  s.  d"). 

2  Head,  .Jour,  of  JPhysiology,  \o\.  10,  1889,  p.  43. 


410  RESPIRATION. 

with  hydrogen  as  well  as  with  oxygen  or  air,  and  on  the  other,  that 
apnoea  cannot  be  prodnced  either  by  inflation  with  hydrogen,  oxy- 
gen, or  air,  after  diyision  of  the  pneumogastric  nerves.  The  con- 
clusion drawn  from  these  experiments  is  that  the  rapid  inflation  of 
the  lungs  in  exciting  the  terminal  pulmonary  filaments  of  the  pneu- 
mogastric nerye,  giye  rise  to  impressions,  which,  being  transmitted 
to  the  medulla,  inhibit  the  inspiratory  impulses  from  the  respiratory 
center.  Polypnoea  or  hypernoea,  in  which  the  respiration  is  exag- 
gerated, is  due  either  to  the  respiratory  center  being  excited,  directly 
by  the  temperature  of  the  blood  being  increased,  or  reflexly  through 
stimulation  of  the  cutaneous  neryes  by  external  lieat.  Dyspna?a,  or 
deep  labored  breathing,  maybe  due  to  either  a  deficiency  in  the  oxy- 
gen or  to  an  excess  in  the  carbon  dioxide  of  the  air  breathed. 
Dyspnoea,  as  caused  by  a  deficiency  of  oxygen,  is  observed  in  cases 
where  a  man  or  animal  is  enclosed  in  a  small  chamber,  or  where 
pure  nitrogen  or  liydrogen  is  breathed,  the  carbon  dioxide  being  ex- 
haled and  carried  off,  even  as  rapidly  as  produced.  Dyspnoea,  a& 
due  to  an  excess  of  carbon  dioxide,  is  produced  when  an  animal  is 
forced  to  breathe  an  atmosphere  containing  carbon  dioxide  to  an 
amount  of  10  volumes  per  cent.,  even  though  oxygen  be  present 
and  in  greater  quantity  than  found  in  normal  air.  Dyspnoea,  as 
caused  by  a  deficiency  in  oxygen,  differs  from  that  caused  by  an  ex- 
cess in  carbon  dioxide.  In  the  former  case  the  inspirations  are 
vigorous  and  frequent,  the  blood  pressure  rises  and  death,  which  is 
due  to  asphyxia,  is  preceded  by  convulsions ;  in  the  latter  case  the 
expirations  are  vigorous  and  slow,  and  death,  which  appears  to  be 
due  to  a  kind  of  narcotic  poisoning,  is  not  preceded  by  convulsions. 
In  cases  of  carbon  dioxide  poisoning  the  respiratory  center  appears 
to  be  excited,  not  only  directly,  but  reflexly,  through  stimulation  of 
the  sensory  fibers  of  the  larger  bronchi.'  That  form  of  dyspnoea, 
due  to  muscular  activity,  appears  to  be  caused  by  substances  whose 
nature  is  unknown,  which  are  produced  during  muscular  contrac- 
tion, and  passing  into  the  blood  excite  the  respiratory  center. 
Cardiac  dyspnoea  is  due  to  the  blood  being  insufficient  in  quantity, 
hemorrhagic  dyspnoea  to  the  blood  being  poor  in  quality  as  well. 

Asphyxia,  from  «,  primitive,  and  Cif'J^'.z,  the  pulse,  literally  a 
state  of  being  without  pulse,  the  condition  brouglit  about  when  the 
system  is  deprived  of  a  due  supply  of  air,  whether  suddenly  by  oc- 
clusion of  the  trachea,  as  in  strangulation,  or  by  slow  suffocation 
through  breathing  in  a  confined  space,  manifests  itself  first  by  the 
breathing,  both  inspiratory  and  expiratory,  becoming  more  frequent 
and  deeper.  This  exaggeration  of  the  breathing,  or  hypernoea,  is 
soon  succeeded  by  a  condition  of  difficult  breathing,  or  dyspnoea, 
the  respiratory  movements,  at  the  same  time,  having  become  almost 
entirely  expiratory  in  cliaracter,  every  muscle  being  brouglit  into 
play  that  can  contribute  in  any  way  to  tliis  eflect.  Sooner  or  later, 
the  muscles  of  the  whole  body  become  involved  in  the  convulsive 
^  Gado  Zagari,  Du  Bois  Eeymond's  Arcliiv  fiir  Physiologic,  1890,  s.  'iSS. 


ASPHYXIA.  411 

expiratory  movements  that  follo^v.  General  convulsions  then  set 
in,  which,  after  lasting  a  short  time,  are  followed  by  collapse.  At 
this  stage  the  pupil  is  insensible  to  light,  the  cornea  fails  to  respond 
to  touch,  breathing  has  become  almost  entirely  inspiratory,  and  oc- 
curs onlv  at  long  intervals.  Finally,  with  a  long  and  deep  gasp 
death  takes  place,  with  the  head  thrown  back,  nostrils  dilated, 
opened  mouth,  straightened  trunk,  and  extended  limbs.  That  the 
convulsions,  which  occur  as  dyspnoea  passes  into  asphyxia,  are  due 
to  the  stimulation  of  the  respiratory  center  of  the  medulla  oblon- 
gata bv  the  insufficiently  arterialized  blood  circulating  through  it,  is 
proved  from  the  fact  of  such  convulsions  being  absent  if  the  spinal 
cord  has  been  previously  divided  below  the  medulla,  but  being  pres- 
ent if  the  part  of  the  brain  lying  above  the  medulla  only  be  re- 
moved. That  these  convulsions  are,  in  fact,  due  to  influences  ema- 
nating from  the  medulla  is  still  further  shown  by  tlie  rise  in  blood 
pressure  that  occurs  during  the  development  of  asphyxia,  and  which 
is  due  to  the  constriction  of  the  arterioles  through  the  stimulation 
of  the  vasomotor  center  by  the  excessively  venous  blood,  and  by 
the  fact  that  if  the  supply  of  blood  to  the  brain  be  cut  off  by  liga- 
tion of  the  vessels,  convulsions,  similar  to  those  observed  in  as- 
phyxia, follow.  The  facts  just  mentioned  will  become  more  signifi- 
cant, however,  when  the  structure  of  the  medulla  and  its  influence 
upon  the  respiration  and  the  circulation  have  been  considered. 

Owing  to  the  constriction  of  the  vessels  at  the  peri})lierv  that  ob- 
tains in  asphyxia,  offering  an  obstacle  to  the  flow  of  the  blood  from 
the  heart,  while  the  increased  respiratory  movement  favors  the  flow 
toward  it,  the  heart  soon  becomes  distended,  and,  finally,  exhausted, 
though  continuing  to  beat  for  a  few  moments  after  respiration  has 
ceased.  During  the  latter  stage  of  asphyxia  the  blood  pressure, 
therefore,  not  only  falls,  but  the  heart  is  weakened — that  is,  unable 
to  empty  itself  of  its  contents.  Hence,  in  post-mortem  examina- 
tions of  cases  of  death  from  asphyxia,  if  made  before  rigor  mortis 
has  set  in,  all  the  cavities  of  the  heart  will  be  found  choked  with 
blood.  "With  the  setting  in  of  rigor  mortis,  however,  the  blood  is 
expelled  from  the  left  side  of  the  heart,  the  right  remaining  gorged 
with  venous  blood.  The  difference  of  opinion,  that  sometimes  pre- 
vails, as  to  whether  all  the  cavities  of  the  heart  are  filled  with  blood 
in  death  from  asphyxia,  may  be  due,  therefore,  to  the  length  of  time 
intervening  between  death  and  the  making  of  the  post-mortem  ex- 
amination, having  been  different  in  the  cases  investigated.  In  this 
connection  it  may  not  be  without  interest  to  mention  that  Harvey  ^ 
notices  that,  in  cases  of  death  from  ordinary  causes,  the  left  side  of 
the  heart  and  arteries  are  found  empty ;  whereas,  in  sudden  death, 
as  from  syncope  or  drowning,  the  arteries,  as  well  as  the  veins,  are 
found  full  of  blood.  The  duration  of  asphyxia  varies  very  much 
in  different  animals,  and  according  to  the  age  of  the  animal.  Thus, 
a  dog  Avill  be  asphyxiated  by  occlusion  of  the  trachea  in  four  or 
1  "Works,  p.  115.     London,  1847. 


41 2  BESPIRA  TION. 

five  minutes,  a  rabbit  in  three  or  four  minutes  ;  whereas,  as  shown 
long  ago  by  BuiFon,^  puppies  just  born  can  be  submerged  in  warm 
milk  for  half  an  hour  at  a  time,  several  times  in  succession,  and  yet 
recover  ;  while,  according  to  Legallois,"  newborn  rabbits  lost  con- 
sciousness only  after  having  been  kept  thirteen  minutes  under  water. 
Milne  EdAvards^  refers  to  cases,  interesting  from  a  medico-legal 
point  of  view,  where  infants  born  asphyxiated  were  revived  seven 
and  even  twenty-three  hours  afterward.  The  remarkable  power 
that  animals  just  born  exhibit  in  resisting  asphyxia  depends  prin- 
cipally upon  the  demand  for  oxygen  lieing  so  slight  at  this  time. 
In  fact,  at  this  early  period  of  existence  the  newborn  mammal  is 
essentially  a  cold-blooded  animal,  it  depending  for  its  heat  almost 
entirely  on  external  warmth,  the  blood  is  still  mixed  through  the 
foramen  ovale  being  open,  the  circulation  and  respiration  have  not 
assumed  the  important  role  that  they  play  in  the  adult,  little  or  no 
muscular  exercise  is  taken,  most  of  the  time  being  passed  in  sleep, 
hence  but  little  oxygen  is  required.  The  connection  between  the 
deficiency  in  the  circulation  and  the  want  of  aeration  just  referred 
to,  is  also  seen  in  cases  of  syncope  in  the  adult,  it  being  well  known 
that  a  person  in  that  condition  can  resist  for  some  time  the  eifects 
of  asphyxia,  the  amount  of  oxygen  consumed  by  the  tissue  being, 
of  course,  less  in  proportion  as  the  circulation  is  slowed,  the  oxygen 
inspired  will  last,  therefore,  longer  than  usual. 

^Natural  History,  Vol.  iii.,  p.  337.     London,  1797. 
'^(Euvras,  Tome  premier,  p.  58.     Paris,  1880. 
''Op.  cit.,  p.  559. 


CHAPTER  XXIV. 

ANIMAL  HEAT. 

One  of  the  most  striking  phenomena  in  the  life  of  man,  and 
in  that  of  the  hot-blooded  animals  generally  (mammals  and  birds), 
and  of  plants,  also,  to  a  certain  extent,  which  did  not  escape  tlie 
attention  of  the  ancients,  is  the  almost  constant  temperature  main- 
tained by  the  body,  notwithstanding  the  great  extremes  in  temper- 
ature to  which  it  may  be  subjected.  Thus,  whether  one  lives  in  a 
changeable  climate,  or  passes  from  the  genial  atmosphere  of  the 
temperate  regions  into  the  extreme  heat  of  the  tropics,  53.3°  C. 
(129°  F.),^  on  the  other  hand,  or  into  the  intense  cold  of  the  arc- 
tics, —  57.7°  C.  (  —  72°  F.)^  on  the  other,  the  temperature  of  the 
body  varies,  as  we  shall  see,  but  little.  If,  however,  the  so-called 
cold-blooded  animals,  frogs,  for  example,  be  observed  in  this  re- 
spect, a  most  notable  diiference  becomes  at  once  apparent,  their 
temperature  being,  according  to  the  circumstance,  higher  or  lower 
than  that  of  the  surrounding  water  or  air,  and  any  rise  or  fall  in 
it  depending  upon  that  of  the  latter.  Thus,  according  to  Landois,'^ 
the  temperature  of  the  water  in  whicli  the  frog  is  immersed  being 
successively  2.8°,  20.6°,  and  41  °C.,  that  of  the  stomach  of  the 
animal  will  be  respectively  5.8°,  20.7°,  38.0°C.,  while  if  the  ani- 
mal be  living  in  air  at  a  temperature  of  5.9°,  19.8°,  and  40.4°  C, 
that  of  the  stomach  will  be  at  18.6°,  15.6°,  31.7°  C.  Thus,  as 
Hunter  expressed  it,  warm-blooded  animals  liave  a  certain  perma- 
nent heat  in  all  atmospheres,  while  the  temperature  of  cold-blooded 
ones  is  variable  with  every  atmosphere,  hence  the  distinction  of 
homoiothermal  and  poikilothermal  animals  introduced  by  Bergman,* 
and  which  being  based  upon  the  relation  of  the  temperature  of  the 
body  to  that  of  the  surrounding  medium  is  a  better  one  than  that 
of  hot-  and  cold-blooded  animals,  and  which  we  have  just  inciden- 
tally alluded  to. 

Temperature  of  Animals,^ 

Name  of  animal.  Temperature.  Observer. 

Aves — 

Chicken,  111°  F.  (43.8°  C.)  Davy.^ 

Guinea  fowl,  110  " 

Thrush,  109  " 

Sparrow,  108  " 

Goose,  107  " 

Screech  owl,  106  " 

^.laraeson,  British  India,  Vol.  iii.,  p.  170.        ^Erarjan,  Siberia,  Vol.  ii.,  p.  369. 
sPhysiologie,  s.  393.     Wien,  1883.  '  ■•  Gottinger  Studien,  Abth.  i.,  s.  595. 

5  When  not  otherwise  mentioned  the  tempei-ature  of  the  vertebrates  was  taken  in 
the  rectum.  ^Eesearches,  Phys.  andAnat.,  p.  161.     London,  1839. 


414 


ANIMAL  HEAT. 


>«ame  of  animal. 

Mammalia — 
Hog, 
Manatee, 
Rabbit, 


Sheep, 

Goat, 

Rat, 

Squirrel, 

Cat, 

Panther, 

Dog, 

Monkey, 

Porpoise, 

Ox, 

Elephant, 

Horse, 

Meptilia — 

Green  snake. 
Tortoise, 
Iguana, 
Alligator, 

A  mphibia — 

Frog, 
Pisces — 

Trout, 

Eel, 

Articulata — 
Beetle, 
Cockroach, 

Mollusca — 
Oyster, 
Snail, 

Echinodermata — 
Star  fish. 
Sea  urchin, 
Sea  cucumber. 

Vermes — 
Leech, 

Cn'Jenterata — 
Anemone, 
Jelly  fish, 

J'onfera — 
Sponge, 


Temperature. 

105         (40.3°  C.) 
104  abdomen, 
104  to  100, 


104 

104 

102 

102 

102 

102 

102 

101 

100  liver. 

100 

99.5 

99.5 


87     oesophagus, 

82.5 

69 

64 


58 
51 


Observer. 

Davy. 

Martine.' 

Prevost  and  Du- 
mas, ^  de  la 
Roche.  3 

Davy. 


Jones. « 
Davy. 


77  surrounding  air  76°, 

75  "  "   74°, 


Temp,  same  as  sea,  82°, 
76.5  surrounding  air,  76.25^ 


6-10°  F.  above  temp,  of  sea  (66.3°)  A^alentin.^ 
5-10  "  "  "      (66.7  )       " 

6-10  "  "  "      (67.6  )       " 


"  "      of  air  (56.     )  Hunter. « 

Valentin, 


5-10 
7-10 


"         "      of  sea  (69.4  ) 
"  "  "      (72.5  ) 


Same  as  sea  (68.3°  F.) 


1  Essays,  Medical  and  Philos.,  1740,  p.  387. 

^Annales  de  ('him.  et  de  Phys.,  2e  serie,  Tome  xxiii.,  p.  64,  1823. 

3  Journal  de  Physique,  Ixxi.,  p.  298,  ISIO. 

*  Investigations,  Chem.  and  Physiol.,  Smith  Contrib.,  1856. 

^Repertorium  fiir  Anat.  nnd  Phys.,  Vierter  Band,  s.  859.     Bern,  1839. 

*"  Works,  ed.  by  Palmer,  Vol.  iv.,  p.  147.     London,  1885. 


WALFERDIX  METASTATIC  THERMOMETER. 


415 


As   the   temperature 
species,  and  accordino; 


differs  often  in  individuals  of  tl 
to  the  biological  conditions  in- 
fluencing the  animal  at  the  moment  of  observations,  and 
farther,  as  the  number  of  observations  are  compara- 
tively limited,  any  results,  such  as  offered  in  the  above 
resume  can  only  be  accepted  as  giving  approximately 
the  average  temperature  in  animals. 

Of  all  animals,  birds  have  the  highest  temperature, 
that  of  the  chicken,  for  example,  according  to  Davy  ^ 
being  as  high  as  43°  C.  (111°  F.),  a  slightly  higher 
temperature,  according  to  Pallas,'  even  being  found  in 
certain  small  birds.  Among  mammals  the  temperature 
of  the  rabbit  is  noteworthy,  amounting  to  40°  C. 
(105.8°  F.).  On  the  other  hand  the  temperature  of 
fishes,  with  some  exceptions,  is  not  usually  more  than 
0.5°  C.  (0.9°  F.)  higher  than  that  of  the  water  in  which 
they  life,  whilst  among  the  invertebrata,^  as  in  the  case 
of  mollusks,  star  fish,  jelly  fish,  anemone,  the  excess  of 
the  temperature  over  that  of  the  surrounding  medium 
may  be  even  less,  amounting  often  to  no  more  than 
0.2°  C.  As  an  exception  to  the  last  statement  and 
interesting  in  this  connection  may  be  mentioned  the 
considerable  amount  of  heat  developed  by  bees  and  ants 
when  swarming.  Although  a  great  number  of  observa- 
tions have  been  made,  some  difference  of  opinion  still 
prevails  as  to  what  constitutes  the  average  normal  tem- 
perature in  man.  This,  however,  is  readily  understood 
when,  as  we  shall  presently  see,  the  temperature  of  the 
body  not  only  varies  considerably  in  different  situations, 
but  according  to  numerous  circumstances  ;  among  others 
may  be  here  very  appropriately  mentioned  especially 
the  manner  in  which  the  thermometrical  observations 
should  be  made.  It  is  of  the  highest  importance,  not 
only  that  the  part  of  the  body  selected  for  taking  the 
temperature  should  be  mentioned,  but  that  the  ther- 
mometer used  in  making  the  observation  should  be  a 
standard  one. 

The  metastatic  thermometer  of  Walferdin  (Fig.  208) 
is  a  convenient  form  of  instrument  since  by  means  of  it 
a  variation  of  yi^-  of  a  degree.  Centigrade,  correspond- 
ing to  a  millimeter  in  length  of  the  mercury,  can  be 
accurately  determined.  The  instrument,  however  ex- 
cellent it  may  be  at  the  time  obtained,  should  neverthe- 
less be  constantly  tested. 

Further,  in  using  the  thermometer  it  should  be  so  ap- 

^ Researches,  Phjs.  and  Anat.,  p.  186.     London,  1839. 
^Gavarret,  De  la  Chaleur  Prouduite  par  les  Etres  Vivants,  p.  94. 
Paris,  1855. 

3  Milne  Edwards,  Physiologie,  Tome  neuvieme,  186.3,  p.  13. 


le   same 


Fig.   208. 


w 


\Vallerdiu's 
metastatic 
thermometer. 
(Laxdois.) 


416 


ANIMAL  HEAT. 


Fig.  209. 


plied  that  the  part  Avhose  temperature  is  to  be  determined  completely 
surrounds  the  bulb  of  the  instrument ;  hence,  of  all  parts  of  the  body, 
the  rectum  is  that  which  is  best  adapted  for  tliermometrical  obser- 
vations, the  instrument  being  inserted  to  a  depth  of  at  least  5  cm. 
(2  in.).  On  account,  however,  of  being  more  convenient,  the  axilla 
is  frequently  made  use  of  in  determining  the  temperature  of  the 
human  body.  It  must  be  remembered  in  that  case  then  that  the 
temperature  is  usually  ^^-g-  to  1  degree  lower  than  that  of  the  rec- 
tum. The  tongue  and  vagina  arc  also  frequently  made  use  of  in 
taking  the  temperature.  Apart  from  individual  idiosyncrasies  the 
diiference  of  opinion  that  prevailed  more  particularly  among  the 

older  physiologists  with  reference  to  the 
temperature  of  man  is  largely  due  to 
neglect  of  the  precautions  just  referred 
to.  If  from  the  nature  of  the  case,  on 
account  of  the  size  of  the  cavity  to  be 
examined,  etc.,  the  application  of  a 
thermometer  is  inadmissible,  thermo- 
electric needles  are  then  made  use  of  in 
determining  the  temperature.  Even 
greater  precautions  must  be  taken  than 
when  the  observation  is  made  in  the 
usual  way  on  account  of  the  delicacy  of 
the  apparatus,  as  slight  a  variation  as 
the  47PI7-Q-  of  a  degree  having  been  de- 
termined by  such.  Thermo-electric 
needles  (Fig,  209,  A  f,  f  A)  are  usually 
made  of  iron  and  German  silver,  each 
needle  consisting  of  iron  (f )  and  silver 
(A),  soldered  together  at  and  near  their 
points,  and  the  two  so  disposed  as  to 
constitute  together  an  element.  The 
iron  wires  being  in  the  middle,  and  the 
silver  ones  externally,  if  the  latter  are 
connected  with  each  other  through  a 
galvanometer  (M),  a  circuit  is  formed. 
The  deviation  of  the  needle  will  then 
indicate  the  temperature  of  the  part  examined  through  the  elec- 
tricity developed  by  the  contact  of  the  needles  Avith  the  heated 
surface.  The  wires  are,  of  course,  except  where  soldered  together, 
carefully  isolated,  and  where  held,  are  covered  with  silk  and  var- 
nish. When  the  difference  in  the  temperature  of  two  parts  of  the 
body  is  to  be  determined,  the  two  needles  are  imbedded  in  the 
parts,  and  the  intensity  of  the  current  measured  and  the  amount  of 
heat  determined,  the  relation  between  the  deviation  of  the  needle 
and  the  amount  of  heat  producing  it  having  been  previously  experi- 
mentally determined.  This  can  be  accomplished  by  immersing 
the    needles    with    delicate  thermometers    attached,   in    oil    baths 


Thermo-electric  needles.     (Landois.) 


TEMPER ATUEE  OF  THE  HUMAN  BODY.  417 

cliiFering  in  temperature,  for  example,  by  one  dei»:ree  C.  The 
deviation  of  the  galvanometer  needle  will  then  indicate  a  diifer- 
ence  in  temperature  of  one  degree  C  Suppose,  further,  that 
as  measured  by  the  scale,  the  deviation  of  the  galvanometer 
needle  amounts  to  150  mm.,  then  ^-^77  of  a  decree  C.  of 
temperature  is  indicated  by  a  deviation  of  1  mm.  of  the  needle. 
If  absolute  temperature  be  required,  then  one  needle  is  applied  to  a 
surface  maintained  at  a  known  temperature,  and  the  other  to  that 
whose  temperature  is  to  be  determined,  or  the  known  temperature 
can  be  gradually  reduced  until  there  is  no  deviation  of  the  needle. 
The  opposite  currents  being  then  equal  the  heat  producing  them 
must  be  equal — that  is,  the  unknown  heat  is  equal  to  the  known. 
It  was  by  means  of  such  a  thermo-electric  apparatus  that  Becquerel,^ 
and  Breschet  determined  the  temperature  of  the  biceps  muscle  under 
different  external  conditions,  to  be  referred  to  in  a  moment,  and 
Nobili  and  ^Melloni  -  proved  that  the  internal  temperature  of  insects 
was  slightly  higher  than  that  of  the  surrounding  atmosphere. 
Among  the  most  reliable  observations  that  have  been  made  with 
reference  to  determining  the  average  temperature  of  the  human  body 
may  be  mentioned  those  of  Hunter,'^  37.2°  C.  (98.9°  F.),  Daw,' 
37.3°  C.  (99.1°  F.),  AVunderliclV  37°  C.  (98.6°  F.),  Jurgensen,« 
37.2°  C.  The  mean  of  Jurgensen's  observations,  it  will  be  ob- 
served, is  the  same  as  that  of  Hunter,  a  confirmation  of  the  accuracy 
with  which  that  great  physiologist  investigated  the  subject  of  ani- 
mal heat  as  all  other  biological  phenomena.  The  results  of  Jurgen- 
sen's experiments  are  most  important,  both  on  account  of  their 
number  and  the  length  of  time  over  which  they  extended.  They 
consisted  in  reading  oif  at  intervals  of  five  minutes  tlie  indications 
of  a  thermometer  permanently  retained  in  the  rectum,  and  extended 
over  three  days.  The  mean  obtained  by  Jurgensen  was  37.2°  C. 
(98.9°  F.),  which  we  will  consider  as  being  the  average  normal 
temperature  of  the  human  bodv,  although  variations  l)ctween  37° 
and  38°  C.  (98.(3°  and  100.4° 'F.)  may  occur  within  the  limits  of 
health. 

Among  the  various  conditions  that  modify  the  normal  temperature 
may  be  mentioned,  in  addition  to  the  influence  of  the  part  of  the 
body  examined,  to  which  we  have  already  incidentally  alluded,  that 
exerted  l^y  age,  sex,  the  time  of  day,  food,  muscular  and  mental 
work,  external  temperature,  etc.  To  the  consideration  of  these  let 
us  now  turn. 

1  Ann.  des  Sciences  Xaturelles,  2d  sen,  1835,  t.  iii.,  p.  •2()9. 

2  Ann.  de  Chimie  et  de  Physique,  1S.>1,  t.  xlviii.,  p.   208. 

'^  Works  of  .John  Hunter,  ed.  bv  J.  F.  Palmer,  vol.  i.,  p.  289.  London,  1835. 
Phil.  Trans.,  1844,  p.  61. 

^Eesearches,  Phvs.  and  Anat.,  18.S9,  vol.  i.,  p.  162. 

5  Op.  cit.,  s.  92." 

^  Deutsche  Arch iv  klin.  Med.,  Band  iii.,  s.  166. 

27 


418  ANIMAL  HEAT. 

Age  and  Sex. 

According  to  Andral/  Biirensprung,-  and  others,  the  temperature 
before  birth,  as  well  as  immediately  afterward,  is  slightly  higher 
than  that  of  the  mother ;  but  as  the  newborn  child  possesses  but 
little  power  of  resisting  external  cold,  its  temperature  soon  falls, 
within  two  hours,  perhaps,  from  37.8°  to  35.2°  C.  (100.04°  to 
95.3°  F.).  Hence  the  importance  of  providing  for  the  infant  suf- 
ficient warmth  by  suitable  means,  and  to  the  neglect  of  which  the 
death  in  many  instances  is  undoubtedly  due.  Immediately  after 
birth  the  temperature  of  the  infant  taken  in  the  rectum  is  between 
37.5°  and  37.8°  C.  (99.5°  and  100.04°  F.),  falling  after  the  first 
bath  to  37°  C.  (98.6°  F.)  and  even  lower,  while  during  the  next  ten 
days  it  varies  between  37.25°  and  37.6°  C.  (98.9°  and  99.6°  F.), 
being  notably  increased  by  screaming,  etc.  During  the  period  in- 
tervening between  early  infancy  and  the  age  of  puberty  the  tem- 
perature falls  about  0.2°  C.  (3.6°  F.),  and  from  there  on  till  adult 
life  falls  about  0.2°  C.  still  more,  the  normal  temperature  or  37.2° 
C.  (98.9°  F.)  being  then  reached.  After  sixty  years  of  age  the 
temperature  begins  to  rise  again,  and  at  eighty  years  has  again 
reached  that  of  the  newborn  child.  This  rise  in  temperature  in  old 
age  is  probably  due  to  the  diminished  circulation  of  the  anaemic 
skin,  since  it  cannot  be  supposed  that  the  production  of  heat  has 
been  increased.  As  a  general  rule,  sex  has  no  appreciable  influ- 
ence upon  the  temperature  of  the  body.  According  to  Ogle,^  how- 
ever, the  temperature  of  the  female  appears  to  be  slightly  higher 
than  that  of  the  male. 

Diurnal  Variations. 

The  temperature  of  the  body,  like  the  frequency  of  the  pulse, 
respiration,  and  exhalation  of  carbon  dioxide,  exhibits  periodical 
variations.  From  the  numerous  observations  of  Davy,  Hallmann, 
Gierse,  Biirensprung,  Lichteufels,  Frohlich,  Damrosch,  Ogle,  Lieb- 
ermeister,  Jurgensen,^  it  appears  that  the  temperature  of  the  body 
increases  very  quickly  from  (5  A.  M.  to  11  A.  M.,  but  from  that  time 
forward  increases  more  slowly,  reaching  a  maximum  between  5  and 
6  P.  M.  About  7  in  the  evening  the  temperature  begins  to  fall, 
reaching  the  minimum  about  5  A.  M.,  tlie  diiference  being  in  24 
hours  usually  about  1°  C.  (1.8°  F.),  though  it  may  amount  to  as 
much  as  2°  C.  (3.6°  F.). 

Climate  seems  to  influence  the  time  of  day  at  which  the  maxi- 
mum and  minimum  temperatures  occur,  the  minimum  being  reached, 
according  to  Davy,  in  England  by  midnight,  but  in  the  tropics  not 
before  6  or  7  A.  m. 

iCompt.  Rend.,  T.  Ixx.,  p.  825. 

2V.  Biirensprung,  Arch.  f.  Anat.  u.  Phys.,  1851,  s.  138. 
3Kirke's  Physiology,  10th  ed.,  p.  255.     Phihi.,  1881. 

*Rosentlial,  die  Physiologic  der  thierischen  Warme  in  Ilcnuann,  op.  cit.,Vierter 
Band,  s.  322. 


VARIATIONS  IN  TEMPERATURE.  419 

Diurnal  Variation  in  Temperature/ 


A.  M. 


M. 


P.  M. 


our. 

Barensprung. 

i'avy. 

Ilallmann. 

Gierse. 

Jurgensen. 

5 

....  Cent 

36.7 

36.6 

6 

36.68 

36.7 

36.4 

7 

36.94* 

36.63 

36.98 

36.7* 

36.5* 

8 

37.16* 

36.80* 

37.08* 

36.8 

36.7 

9 

36.89 

36.9 

36.8 

10 

37.26 

37.36 

37.23 

37.0 

37.0 

11 

36.89 

37.2 

37.2 

12 

36.87 

37.3* 

37.3* 

1 

36.83 

37.13 

37.3 

37.3 

2 

37.05 

37.21 

37.50* 

37.4 

37.4 

3 

37.15* 

37.43 

37.4* 

37.3* 

4 

37.17 

37.5 

37.5 

5 

37.48 

37.05* 

37.31 

37.43 

37.5 

37.5 

6 

36.83 

37.29 

37.5 

37.6 

7 

37.43 

36.50* 

37.31* 

30.00 

37.5* 

37.6* 

8 

.... 

37.4 

37.7 

9 

37.02* 

37.4 

37.5 

10 

37.29 

37.3 

37.4 

11 

36.85 

36.72 

36.70 

36.81 

37.2 

37.1 

12 

.... 

.... 

37.1 

37.4 

1 

36.85 

36.44 

37.0 

36.9 

2 

.... 

36.9 

36.7 

3 

36.8 

36.7 

4 
Ast( 

Brisk  .signifies 

that  food 

was  taken. 

36.7 

36.7 

Supposing  with  Jurgensen,  tliat  the  day  temperature  begins  at 
6  A.  M.  with  ;36.4''  C,  and  ends  at  8  p.  m.  wdth  37.7°,  the^  dura- 
tion of  the  former  with  a  usually  mean  temperature  of  37. 3°,  ex- 
ceeds the  latter  with  a  mean  of  3G.9°  by  four  hours,  the  average 
temperature  for  tlie  whole  dav,  being,  as  already  mentioned,  about 
37.2°  C.  (98.9°  F.).  As  m^ight  be  expected,  ^Debczyn.ski  -  finds 
that  persistent  night  work  reve  rses  the  rhythm  of  the  variations 
of  temperature,  the  thermometer  standing  highest  in  the  morning 
(37.8°),  instead  of  in  the  evening  (35.3°). 

Food. 

As  in  the  long  run  the  heat,  as  we  shall  see,  is  due  to  the  com- 
bustion of  substances  taken  into  the  body  as  food,  it  follows  that 
the  production  of  heat  is  intimately  associated  with  that  of  nutri- 
tion. Inasmuch,  however,  as  it  is  not  until  the  last  stage  of  inani- 
tion in  the  starving  man  or  animal  that  the  temperature  notably 
falls,  it  having  been  previously  maintained  in  the  absence  of  food 
through  the  combustion  of  the  tissues,  it  is  not  to  be  expected  that  in 
health  the  mere  taking  of  food  will  influence  the  temperature  to  any 
great  extent,  since  the  fuel,  so  to  speak,  is  ordinarily  consumed  as 
rapidly  as  supplied,  and  when  deficient  is  made  up  at  the  expense  of 
the  tissues.  For  example,  very  hot  drinks  increase  the  temperature 
but  little.  Suppose,  for  example,  a  man  weighing  (JO  kilogrammes 
(132  pounds)  drinks  a  kilogramme  (2.2  pounds)  of  water  at  50°  C. 
'Landois,  op.  cit.,  s.  406.       ^  Yirchow  u.  Hirs?h,  Jahresber.,  1875,  Band  i.,  s.  248. 


420  AXniAL  HEAT. 

(122°  F.),  the  temperature  of  the  whole  body — supposing  it  to  be 
o7.2°  C.  (98.9°  F.)  aud  having  the  same  specific  heat  as  water — 
would  be  increased  only  about  0.2°  C.  (0.3°  F.).  It  must  be  re- 
membered in  this  instance,  as  in  many  others,  that  the  eiFect  of 
taking  a  hot  drink  is  not  so  simple  as  may  at  first  appear,  since  the 
circulation  being  increased  by  it  the  loss  of  heat  through  evapora- 
tion will  be  increased.  The  one  effect  neutralizing  to  a  certain  ex- 
tent the  other,  the  full  effect  of  the  drink  as  regards  elevation  of 
the  temperature  is  not  therefore  experienced.  Even  if  the  drinks 
contain  specific  substances,  such  as  tea,  coffee,  alcohol,  etc.,  the  tem- 
perature of  the  body  is  diminished  only  two-  or  three-tenths  of  a 
degree  C.  It  is  possible  that  the  loss  of  heat  experienced  in  the 
taking  of  alcohol  is  not  only  due  to  the  quickened  circulation,  but 
to  a  paralyzing  effect  exerted  upon  the  vasomotor  nerves  of  the 
skin,  whereby  a  greater  quantity  of  blood  l)eing  conveyed  to  the 
surface  than  usual,  more  heat  is  consequently  given  off  and  so  lost. 
On  the  other  hand,  while  the  effect  of  cold  drinks,  etc.,  is  to  dimin- 
ish the  temperature  of  the  body,  the  diminution  is  also  very  slight, 
amounting  usually  to  but  a  few  tenths  of  a  degree  C.  Thus,  ac- 
cording to  Lichteufels  and  Frolich,  AVinternitz,  and  others,^  drinks 
at  a  temperature  of  18°,  1(3.3°,  and  4.6°  C,  reduced  that  of  the 
body  in  the  first  two  instances  within  6  minutes  after  taking  them 
0.1°,  0.4°,  and  in  the  last  in  70  minutes  1.4°  C.  Further,  as  in 
the  digestion  of  solid  foods,  heat  is  required  to  assist  the  chemico- 
physical  changes,  it  might  be  expected  that  as  part  of  the  heat 
becomes  latent,  the  temperature  of  the  body  would  be  slightly  dim- 
inished temporarily  after  taking  the  food,  even  though  the  tempera- 
ture should  l)e  increased  later  through  further  oxidation.  That  such 
is  the  case  seems  to  he  shown  by  the  experiments  of  Vintschgau  and 
Dietl,"  made  upon  a  dog  with  gastric  fistula,  in  which  the  tempera- 
ture of  the  food  introduced,  and  which  differed  but  little  from  that 
of  the  body,  first  fell  and  then  rose.  From  what  has  just  been  said, 
however,  of  the  compensating  power  exercised  by  the  economy, 
whether  food  be  taken  or  withheld,  it  would  be  inferred  that  the 
influence  exerted  by  the  taking  of  food  upon  the  daily  variations 
must  be  very  slight,  if  any.  Indeed,  the  variations  in  temperature 
that  are  observed  after  meals,  as  a  matter  of  fact,  occur  whether 
food  be  taken  or  not.  The  most,  indeed,  that  can  be  said  is  that 
if  a  meal  be  taken  late  in  the  day  the  diminution  in  temperature, 
characteristic  of  that  period,  is  somewhat  put  off.  Indeed,  it  is  not 
until  shortly  before  death  caused  by  inanition  or  starvation,  for  the 
reasons  already  given,  that  the  temperature  is  notably  diminished. 

Muscular,   Mental,  and  Glandular  Action. 

We  shall  soon  see,  in  our  study  of  muscular  action,  that  at  the 
moment  of  muscular  contraction  a  considerable  amount  of  heat  is  set 

^  Rosenthal,  op.  cit. ,  s.  325. 

2Sitz.  d.  Weiner  Acad.  Math.-Xatur.  u.  CI.,  2  Abtli,  ix.,  s.  ()97,  1870. 


IXFLUEXCE  OF  MUSCULAR  EXERCISE.  421 

free — indeed,  probably  tlirce-foiirths  of  the  heat  developed  is  pro- 
duced in  the  muscles.  Thus,  according  to  Davv/  the  temperature  of 
the  room  being  66°  F.,  that  of  the  feet  60°,  under  the  tongue  98°, 
and  of  the  lu-ine  100°  ;  after  a  walk  in  the  open  air  at  40°  the  tem- 
perature of  the  feet  was  96.5°  and  the  urine  101°,  that  under  the 
tono-ne  being  unchanged.  Indeed,  daily  observation  as  well  as  special 
experiments  teaches  us  that  our  ^vhole  body  is  warmed  by  muscular 
exercise.  Further  consideration,  however,  will  show  that  the  body 
is  not  as  much  heated  as  one  would  be  led  to  expect  from  the 
amount  of  heat  developed  under  the  circumstances,  and  from  the 
rapiditv  with  which  the  temperature  of  the  body  foils  to  the  nor- 
mal with  the  cessation  of  the  exercise,  it  is  evident  that  as  fast  as 
the  heat  is  developed  it  is  as  rapidly  radiated  away  or  lost  as  some 
other  mode  of  energy.  The  influence  of  muscular  exercise  in  ele- 
vating the  temperature  of  the  body  is  also  well  seen  under  certain 
pathological  conditions  ;  the  temperature  in  tetanus,  for  example, 
rising,  according  to  Wunderlich,"  as  high  as  44.75°  C.  (111.2°  F.). 
It  should  be  mentioned,  however,  that  this  great  rise  in  temperature 
can  hardlv  he  attril)utcd  entirely  to  muscular  action,  since  in  all 
probabilitv,  at  the  same  time,  other  influences  come  into  play,  such 
as  the  action  of  the  vasomotor  nerves,  which  in  constricting  the 
vessels  of  the  skin  will  diminish  the  usual  loss  of  heat  due  to  radi- 
ation and  evaporation. 

Xervous-like  muscular  activity  is  also  accompanied  with  the  pro- 
duction of  heat.  Thus,  according  to  Davy,^  during  the  reading  of 
a  work,  in  England,  demanding  attention,  the  temperature  of  the 
bodv  was  increased  0.5°  F.  Mental  effort  iu  the  tropics  is  accom- 
panied by  a  still  greater  production  of  heat,  amounting,  in  some 
instances,  to  more  than  2°  F.,  as  in  the  giving  of  a  lecture,  for  ex- 
ample ;  in  the  latter  case  some  of  the  heat  was  probably  due  to  the 
muscular  action  involved.  Lombard*  has  also  determined,  by 
means  of  delicate  thermo-electric  apparatus,  local  increase  of  tem- 
perature in  the  head  resulting  from  mental  effort.  Schiff"''  has 
also  shown  that  the  action  of  the  nerves,  as  well  as  that  of  the 
brain,  is  accompanied  with  the  production  of  heat.  In  all  in- 
stances, however,  the  amount  of  heat  produced,  at  least  that  ap- 
pearing as  such,  is  a  small  part  of  the  heat  produced,  as  in  the  case 
of  muscle  being  converted,  as  we  shall  see  hereafter,  into  other 
modes  of  energy. 

Glandular  action  is  also  accompanied  by  the  production  of  heat 
due  to  the  chemical  activity  incidental  to  secretion.  Thus,  according 
to  Ludwig  and  Spiess  "^^  the  temperature  of  the  saliva  secreted  dur- 
ing stimulation  of  the  chorda  tympani  is  1  to  1.5°  C.  higher  than 
that  of  the  blood  of  the  carotid  artery  of  the  same  side.  AVe  have 
already  called  attention  to  the  fact  of  the  temperature  of  the  blood 

'Phil.  Trans.,  1844,  p.  63.         ^Qp.  cit.,  s.  400.        ^Pbil.  Trans.,  1845,  p.  443. 
*  Experimental  Eesearches  on  the  Regional  Temperature  of  the  Head.     London, 
1879.  3  Archiv  de  Pliy.  Normal  et  Path.,  1870,  pp.  5,  198,  323,  421. 

^Wien.  Sitzb.,  Band  xxv.,  1857. 


422  ANIMAL  HEAT. 

of  the  hepatic  vehi  being  higher  than  that  of  any  other  part  of  the 
body,  due,  in  part  at  least,  to  the  size  and  constant  activity  of  the 
liver. 

Surrounding  Temperature. 

Any  consideration  as  to  the  temperature  of  man  or  animal  would 
naturally  suggest  the  influence  exerted  by  that  of  the  surrounding 
atmosphere,  and  concerning  which  there  was,  at  one  time,  much 
diflFerence  of  opinion.  So  distinguished  a  teacher  as  Boerhaave,  for 
example,  advocated  ^  that  neither  man  nor  any  animal  that  breathes 
by  lungs  can  live  in  an  atmosphere  the  temperature  of  which  is  as 
high  as  that  of  their  own  bodies  and  cites  ^  in  support  of  this  view  the 
experiments  performed  at  his  request,  by  Fahrenheit  and  Provost, 
which  consisted  in  placing  a  sparrow,  a  cat,  and  a  dog  in  a  sugar- 
baker's  oven,  heated  to  146°  F.,  and  in  which  it  was  found  they 
soon  died.  Notwithstanding  the  result  of  these  experiments,  the 
great  Haller,  basing  his  opinion  upon  the  testimony  of  Lining 
Adarason,  and  other  travelers,  as  to  the  intense  heat  that  prevailed 
in  certain  parts  of  this  country,  South  Carolina,  Senegal,  and  else- 
where, hekP  in  opposition  to  the  view  entertained  by  Boerhaave 
that  man  could  not  only  live  in  an  atmosphere  16°,  but  even  28 °F., 
higher  than  that  of  the  blood.  About  this  time  important  obser- 
vations bearing  upon  this  question  were  made  by  Franklin  and 
Governor  Ellis.  In  a  letter  dated  London,  June  17,  1758,  in  re- 
ferring to  a  hot  Sunday  passed  in  Philadelphia,  in  June,  1750, 
Franklin  *  recalls  tliat,  during  the  day,  when  the  thermometer  was 
at  100°  F.,  in  the  shade,  his  body  never  grew  so  hot  as  the  air 
surrounding  it,  or  the  inanimate  bodies  immersed  in  the  same  air, 
and,  with  his  usual  acuteness,  accounts  for  the  body  being  kept 
cool  under  such  circumstances  by  continual  sweating,  and  by  the 
evaporation  of  that  sweat. 

Within  a  month  of  the  same  year — that  is,  in  July  17,  1758 — 
Governor  Ellis,  in  a  letter  to  his  brother  in  London,  called  atten- 
tion particularly  to  the  fact  that,  while  in  Georgia,  a  thermometer 
suspended  from  under  an  umbrella  which  he  carried  during  a  walk 
of  one  hundred  yards  registered  105°  F.,  the  temperature  of  his 
body  was  only  97°.  The  letter  of  Governor  Ellis  being  communi- 
cated to  the  Royal  Society  ^  was  thereby  at  once  insured  a  wide  cir- 
culation ;  that  of  Franklin,  though  •written  first,  was  not  made 
public,  however,  till  afterward."  Shortly  after  the  observation  of 
Ellis,  just  referred  to,  it  was  ascertained  l^y  Tillet,"  in  experiment- 
ing with  a  baker's  oven,  that  the  young  women  in  attendance  were 
accustomed  to  remain  in  it  for  a  few  minutes  even  when  at  a  tem- 

'  Pnplectioncs  Academicise,  Gottingen,  1740,  ^'ol.  ii.,  p.  211. 

^  Elcmonta  Chemiir,  Lipste,  1732,  Tomus  Primus,  p.  238. 

^Klementii  Phvsiologiii?,  p.  37.     Lausanne,  MDCCLX. 

*  Works,  Vol.  'iii.,  p.  301.     Phila.,  180<). 

5]'hil.  Trans.,  17o9,  Part  ii.,  Vol.  1.,  p.  755. 

^.Journal  de  Physique,  1773,  Tome  ii.,  p.  453. 

'Mem.  de  I'Aead.  des  Sciences,  1764,  Tome  Ixsxi.,  p.  188. 


SURROUNDING  TEMPERATURE.  423 

peratQve  of  126.6°  C.  (260°  F.).  In  one  instance  Tillet,  anxious 
for  the  safety  of  the  woman,  requested  her  to  come  out,  but  she  as- 
sured him  she  felt  no  inconvenience,  and  remained  in  the  oven  for 
ten  minutes,  the  latter  having  a  temperature  of  137.7°  C.  (280°  F.) ; 
indeed,  on  her  coming  out,  beyond  the  flushing  of*  the  face,  there 
was  nothing  especially  noticeable.  While  the  facts  just  referred  to 
excited  considerable  interest  at  the  time,  it  was  not  till  some  years 
later,  however,  that  any  further  experiments  were  performed  with 
the  object  of  ascertaining  the  effect  of  heated  air  upon  the  tempera- 
ture of  the  body.  In  1774,  the  subject,  however,  was  taken  up 
again  by  Fordyce,  who,  together  with  Blagden,  Solander,  Banks, 
and  others,  experimented  upon  themselves,  either  in  a  room  heated 
with  flues,  and  upon  the  floor  of  which  boiling  water  was  poured, 
or  in  rooms  heated  with  flues  only.  The  result  of  these  experi- 
ments, as  descril)ed  l)y  Blagden,^  may  be  summed  up  as  follows  : 

In  the  room  containing  vapor  Fordyce  was  able  to  bear  for  10 
minutes  a  temperature  of  43.3°  C.  (110°  F.),  20  minutes  48.8° 
C.  (120°  F.),  and  for  15  minutes  a  heat  gradually  increasing  from 
53.8°  to  54.4°  C.  (119°  to  130°  F.).  In  these  experiments,  it  is 
said,  that  the  temperature  under  the  tongue  and  of  the  urine  did 
not  rise  higher  than  37.7°  C.  (100°  F.),  In  the  room  heated  with 
flues  onlv,  and  containing  dry  air,  Fordyce,  together  with  Blagden 
and  Banks  in  the  room,  could  stand,  however,  a  higher  heat  than 
in  the  former  instance,  supporting  for  ten  minutes  a  temperature  of 
92.2°  C.  (198°  F.).  Shortly  after  these  experiments  it  was  ascer- 
tained by  Dobson,-  from  observations  made  in  the  sweating-room 
of  the  Liverpool  Hospital,  that  individuals  could  stand  for  periods 
between  10  and  20  minutes  a  temperature,  if  the  air  be  dry,  of  be- 
tween 94.4°  and  106.6°  C.  (202°  and  224°  F.).  Fordyce,  him- 
self, as  mentioned  in  a  subsequent  paper  by  Blagden,^  was  able  to 
endure  for  8  minutes  even  as  high  a  temperature  as  127°  C. 
(260°  F.),  the  uncomfortable  feeling  experienced  quickly  passing 
away  with  the  breaking  out  of  a  profuse  sweat.  The  immunity 
possessed  by  persons  habitually  exposed  from  time  to  time  to  a  dry 
atmosphere,  having  a  temperature  even  higher  than  that  to  which 
Fordyce,  Blagden,  etc.,  were  subjected,  is  undoubtedly  due,  in  a 
great  measure  at  least,  as  Franklin  supposed,  to  the  cold  produced 
through  the  evaporation  of  the  cutaneous  perspiration  and  pulmo- 
nary exhalation.  In  this  way  can  be  explained  how  the  workmen 
of  the  sculptor  Chantry  went  into  a  furnace  having  a  temperature 
of  171°  C.  (340°  F.),  and  Chabert,  the  fire  king,  into  one  at  be- 
tween 204°  and  315.5°  C.  (400°  and  600°  F.).  Indeed,  the 
salutary  effect,  under  such  circumstances,  of  keeping  the  tempera- 
ture down  by  evaporation  was  fully  recognized  by  Fordyce  and 
Blagden,*  and  proved  by  them  in  the  following  way  :  Two  similar 
earthen  vessels,  one  containing. water  only  and  the  other  an  equal 

iPliil.  Trans.,  Vol.  Ixv.,  1775,  Part  i..  p.  111.  ^ifj^.ni,  p.  4(13. 

3  Idem,  p.  484.  *0p.  cit.,  p.  491. 


424  ANIMAL  HEAT. 

quantity  of  water,  with  a  bit  of  wax,  were  put  upon  a  piece  of 
wood  in  the  heated  room.  In  an  hour  and  a  half  the  pure  water 
was  heated  to  60°  C.  (140°  F.),  while  that  containing  the  wax  had 
acquired  a  temperature  of  66°  C.  (152°  F.),  as  the  wax  in  melt- 
ing had  formed  a  film  upon  the  surface  of  the  water,  and  thereby 
had  prevented  evaporation.  Further,  it  was  observed  that  the 
pure  water  never  came  near  the  boiling  point,  but  if  a  small  quan- 
tity of  oil  was  dropped  into  it,  as  had  been  done  before  with  the 
wax,  finally  the  water  in  both  vessels  boiled  briskly.  The  effect  of 
sweating  in  keeping  down  the  bodily  temperature  is  daily  seen  in 
the  taking  of  Turkish  as  compared  with  Russian  baths,  an  equally 
high  temperature  being  much  better  borne  in  the  former,  on  account 
of  the  air  being  dry,  than  in  the  latter,  where  the  air  is  moist. 
The  profuse  perspiration  induced  through  hot  baths  has  long  been 
a  matter  of  comment ;  as  early  as  the  first  half  of  the  last  century 
Le  Monnier/  in  speaking  of  the  natural  hot  baths  at  Baregas,  with 
a  temperature  in  the  hottest  part  of  44.4°  C.  (112°  F.),  observes 
that  the  sweat  poured  down  from  his  face  after  remaining  in  it  8 
minutes,  and  that  after  that  time  he  was  obliged  to  leave  the  bath, 
with  reddened  and  swollen  skin,  and  greatly  increased  pulse  through 
violent  attacks  of  vertigo.  The  conclusion  draAvn  from  the  different 
experiments  of  Fahrenheit  and  Provost,  Tillot,  Fordyce,  and  Blag- 
den,  etc.,  that  we  have  just  described,  was  that  man  could  not  only 
exist  in  an  atmosphere  having  a  higher  temperature  than  that  of  his 
own  body,  but  that  the  latter  remained  unchanged,  even  when  that 
of  the  surrounding  atmosphere  was  greatly  increased,  notwithstand- 
ing that  in  an  experiment  with  a  dog  the  temperature  was  found  by 
Fordyce  to  increase.  It  would  appear,  however,  without  doubt, 
from  later  ol)servations,  that  with  an  increase  in  the  temperature  of 
the  surrounding  air  there  is  an  increase  in  that  of  the  body.  Thus, 
in  the  experiments  made  by  De  la  Roche  ^  and  Berger,  it  was  found 
that,  after  remaining  15  minutes  in  a  vapor  bath,  with  a  tempera- 
ture varying  between  37.5°  and  48.8°  C.  (99.5°  and  119.8°  F.), 
the  temperature  in  the  mouth  was  increased  3.1°  C  (5.5°  F.), 
while  in  dry  air,  but  at  a  temperature  of  80°  C^  (176°  F.),  the 
temperature  was  increased  about  5°  C.  (9°  F.).  According  to 
Davy  ^  also,  who  made  a  great  number  of  observations  in  different 
parts  of  the  world,  the  mean  temperature  of  the  body  in  the  tropics 
is  about  1°  F.  higher  than  in  England.  Such  a  variation  has  been 
held  by  Boileau,^  for  example,  as  abnormal,  and  as  an  indication  of 
a  slight  disturbance  in  the  system  due  to  change  of  climate,  and  to 
which  certain  delicate  persons  are  liable.  The  observations  of 
Eydoux  ■''  and  Souleyet,  made  during  the  voyage  of  the  "  Bonite," 
and   of  Brown-Sequard,*'    to    the  Isle  of   France,  though  less  in 

'Mem.  de  I'Acad.  des  Sciences,  1747,  Tomelxiv.,  p.  271. 

^Theses  de  I'ecole  de  medecine  de  Paris,  180G,  No.  11.     Journal  de  physique, 
1776,  Tome  vii.,  p.  57. 

3Philos.  Transact.,  IS-jO,  p.  437.  ^Lancet,  1878,  p.  413. 

^Comp.  Kend.,  1838,  Tome  vi.,  p.  45(5.        ^Journal  de  Physiology,  T.  ii.,  p.  554. 


SURROUNDING  TEMPERATURE.  425 

number  than  those  of  Davy,  so  far  as  they  go,  confirm  the  result 
obtained  by  that  reliable  observer.  Davy^  also  showed,  from  a 
number  of  observations,  that  the  mean  temperance  of  the  air  being 
15.5°  C.  (60°  F.),  that  of  the  body  was  36.7  C.  (98.28°  F.), 
whereas,  if  the  temperature  of  the  air  rose  to  26.6°  C.  (80°  F.), 
the  temperature  of  the  body  rose  to  37.5°  C.  (99.67°  F.). 

The  temperature  of  individual  portions  of  the  body  has  been 
shown  to  increase  with  that  of  the  surrounding  medium,  as  well  as 
that  of  the  whole  body.  In  an  experiment  of  Becquerel  and  Bres- 
chet,^  for  example,  where  the  biceps  muscle  was  surrounded  for  1 5 
minutes  by  water  at  a  temperature  of  42°  C.  (107.6°  F.),  the  tem- 
perature, as  determined  by  their  thermo-electric  apparatus  was  in- 
creased two-tenths  of  a  degree.  The  rise  in  temperature,  through 
increase  of  heat  in  the  surrounding  atmosphere,  can  be  well  shown 
in  animals.  Thus,  according  to  Rosenthal,^  the  temperatm'e  of  a 
rabbit  rose  from  the  normal,  38°  C.  (104.4°  F.)  to  45°  C.  (113°  F.), 
while  the  external  temperature  was  increased  from  32°  to  40°  C. 
(89.6°  to  104°  F.),  death  taking  place  at  the  latter  temperature. 
Essentially  the  same  result  was  obtained  in  the  experiments  of 
De  la  Roche  and  Berger  with  a  guinea-pig.  According  to  these  ob- 
servers, as  well  as  Rosenthal,  an  increase  in  the  temperature  of 
6°  to  7°  C.  (10.8°  to  12.6°  F.)  above  the  normal,  however  brought 
about,  is  fatal  to  all  animals.  It  would  appear  from  these  experi- 
ments as  well  as  the  earlier  ones  of  Provost  and  Fahrenheit,  that 
large  animals  bear  a  high  temperature  better  than  small  ones,  prob- 
ably Ijecause,  in  the  latter,  a  greater  quantity  of  heat  is  produced 
relatively  and  more  quickly.  Thus,  in  the  experiments  of  Fahren- 
heit, already  referred  to,  of  the  three  animals  placed  in  the  oven  the 
sparrow  died  in  8  minutes,  whereas  the  dog  and  the  cat  survived 
28  minutes.  According  to  De  la  Roche  and  Berger,  a  mouse  died 
in  32  minutes,  the  temperature  being  increased  from  57.5°  to 
63.7°  C.  (135°  to  146.6°  F.),  while  a  guinea-pig  survived  1  hour 
and  25  minutes,  the  temperature  rising  from  62  to  80°  C.  (143.6° 
to  176°  F.);  a  young  ass,  however,  though  weak  at  the  end  of  the 
experiment,  successfully  resisted  for  nearly  three  hours  a  tempera- 
ture increased  from  60°  to  75°  C.  (140°  to  167°  F.).  In  the  case 
of  man,  in  certain  pathological  conditions,  as  in  typhoid  and  typhus 
fever,  the  temperature  of  the  l)ody  may  rise  to  40.5°  and  41.1°  C. 
(105°  and  106°  F.),  and  yet  recovery  take  place.  The  highest 
temperature  yet  observed  in  man,  and  ending  in  recovery,  was  in  a 
case  of  injury  to  the  spine,  reported  by  Dr.  J.  Teale/  in  which  the 
thermometer  registered  50°  C.  (122°  F.).  The  elevation  in  tem- 
perature in  sunstroke,  40°  to  44.4°  C.  (104°  to  112°  F.),  is  also 
very  consideral)le ;  in  such  cases,  however,  the  high  temperature  is 
to  be  attributed,  in  part  at  least,  not  only  to  the  eifect  of  exposure 
to  the  sWs  heat,  but  also  to  the  exercise  taken  incidental  to  the 

1  Eesearclies,  Phvs.  and  Anat.,  p.  Klo.       ^Ann.  des  .Sciences  Xat.,  1838,  p.  271. 
"Op.  cit.,  s.  337.'  *  Lancet,  March  6,  1875. 


426  AXIMAL  HEAT. 

character  of  the  occupation  of  those  usually  attacked,  such  as  field 
and  street  laborers,  soldiers,  etc. 

Inasmuch,  as  we  have  seen,  through  the  free  action  of  the  skin, 
and  with  proper  precautions  taken  as  regards  exercise,  food,  cloth- 
ing, etc.,  man  can  live  in  an  atmosphere  the  temperature  of  which 
is  much  higher  than  that  of  his  body,  it  might  naturally  be  sup- 
posed that  through  similar  compensating  agencies  intense  cold  can  be 
equally  well  resisted,  if  not  better  than  intense  heat.  Such,  indeed, 
experience  proves  to  be  the  case,  the  temperature  of  the  body  of 
man,  even  when  exposed  to  the  intense  cold  of  the  Arctic  regions, 
is  almost  the  same  as  in  the  temperate  ones,  since  the  amount  of 
heat  generated  absolutely,  is  greater  on  account  of  the  quantity  and 
quality  of  food,  and  relatively  so,  from  the  fact  of  the  clothing,  etc., 
being  of  such  a  character  as  to  retain  the  heat  produced.  In  ani- 
mals the  latter  protective  effect  is  provided  for  Ijy  their  fur,  wool, 
feathers,  etc.,  as  the  case  may  be. 

A  glance  at  the  temperature  of  Arctic  animals,  as  given  below, 
will  show  how  little  the  temperature  of  the  body  in  such  animals 
differs  from  that  of  animals  in  temperate  regions,  though  the  differ- 
ence in  the  temperature  of  the  former,  as  compared  with  that  of 
the  surrounding  atmosphere,  mav  amount  to  as  much  as  76.7°  C. 
(170°  F.). 

Temperature  of  Arctic  Aximals.' 


Anim 

al. 

Temp. 

of  animal. 

Temp,  of 

air. 

Difference. 

Arctic  fox 

.     41.o°C 

.(106. 7°F.) 

—25.6° 

c. 

67.1°C. 

(( 

.     38.5 

—20  6 

59.1 

a 

.     37.8 

—19.4 

57.2 

1  ( 

.     38.5 

—29.4 

67.9 

i  i 

.     37.6 

—26.2 

63.8 

a 

.     36.6 

—23.3 

59.9 

i  i 

.     37.6 

—23.3 

60.9 

a 

.     40.3 

—20.3 

70.7 

White  hare 

.     38.3 

—29.4 

67.7 

Fox 

1  ( 

.     37.8 
.     41.1 

—26.2 
—35.6 

64.0 

76.7 

a 

.     39.4 

—32.8 

72.2 

a 

.     38.9 

—31.7 

70.6 

u 

.     38.3 

—35.6 

73.9 

Wolf 

.     40.5 

—32.8 

73.3 

On  account  of  water  Ijeing  a  better  conductor,  and  having  also  a 
greater  capacity  for  heat  than  air,  the  temperature  of  the  body  will 
fall  more  rapidly  if  exposed  to  cold  water  than  to  air  at  the  same 
temperature  ;  hence  the  great  effect  of  cold  baths  in  the  treatment 
of  fevers  so  much  in  vogue,  particularly  in  Germany,  in  late  years, 
and  th(;  great  benefit  derived  from  the  application  of  ice  in  the 
treatment  of  sunstroke.  While  man  and  animals  can  resist  the 
most  intense  Arctic  cold  by  the  agencies  just  referred  to,  neverthe- 
less a  far  less  degree  of  cold,  if  suddenly  and  directly  applied  to 

^Gavarret,  op.  cit.,  p.  101.     Parry's  Journal,  p.  130.     Philadelphia,  1821. 


PRODUCTION  OF  ANIMAL  HEAT.  427 

the  body,  will  soon  prove  fetal.  Thus,  according  to  Rosenthal,^ 
animals  die  if  the  temperature  of  their  bodies  be  reduced  to  24°  C. 
(75.2°  F.),  and  such  is  usually  the  case  in  man  also,  as  shown  by 
the  clinical  cases  referred  to  by  the  same  liigh  authority  ;  though,  as 
well  known,  the  temperature  in  cholera  may  fall  as  low  as  18.3°  C. 
(64.9°  F.).  There  are  some  other  conditions  in  addition  to  those 
already  mentioned  which  may  affect  the  temperature  of  the  body. 
Of  such  are  the  eff'ects  exerted  by  race,  country,  labor,  sea-sick- 
ness, and  barometrical  variations.  As  such  influences  are,  however, 
either  exceptional  or  temporary  in  their  character,  we  will  not  dwell 
fiirther  upon  them,  merely  mentioning  that,  according  to  the  late 
distinguished  Professor  Dunglison,"  the  temperature  of  the  uterus 
during  labor  may  rise  as  high  as  41.1°  C.  (106°  F.),  that  of  the 
vagina  at  the  same  time  being  40.5°  C.  (105°  F.). 

Production  of  Animal  Heat. 

Having  considered  the  temperature  of  the  body,  and  the  various 
modifying  conditions,  it  now  remains  to  account  for  the  production 
of  this  heat,  and  the  manner  in  which  the  latter  is  regulated.  Xot- 
mthstanding  that  a  certain  amount  of  heat  is  produced  through  the 
double  decompositions  and  hydrations  continually  taking  place  in 
the  economy,-^  there  can  be  no  doubt  that,  by  far  the  greatest 
amount  of  heat  produced  is  due,  as  Lavoisier  supposed,  to  the  slow 
combustion  continually  o-oino;  on  within  the  body  of  the  animal, 
caused  by  the  absorption  of  oxygen,  the  interchanging  of  which 
with  carbon  dioxide,  etc.,  we  ha  ye  seen,  constitutes  the  essence  of 
respiration. 

In  the  paper  on  the  calcination  of  metals,  brought  l)efore  the 
Academy  of  Sciences,  in  1775,  Lavoisier*  had  shown  that  in  the 
decomposition  of  mercuric  oxide  by  heat  the  principle  (oxygen)  so 
obtained  supported  both  combustion  and  respiration,  whereas,  when 
the  same  substance  was  reduced  by  carbon  the  principle  then 
obtained  (carbon  dioxide)  supported  neither.  These  fundamental 
facts  having  been  established,  two  years  later  Lavoisier'^  further 
showed  that  animals  absorb  oxygen  and  exhale  carbon  dioxide,  and 
during  the  same  year  formulated  a  view  on  combustion  in  general 
in  which  respiration  was  regarded  as  a  slow  process  of  combustion, 
oxygen  being  absorbed  and  carbon  dioxide  and  heat  given  off"  just  as 
in  the  burning  of  coal.  As  might  have  been  expected  from  the 
methods  of  investigation  so  characteristic  of  the  great  chemist  and 
physiologist,  Lavoisier  soon  instituted  a  series  of  experiments  with 
the  view  of  ascertaining  Avhether  the  amount  of  carbon  dioxide  ex- 
haled and  heat  produced  by  an  animal  in  a  given  time  was  such  as 
ought  to  be  expected  on  the  supposition  that  a  certain  amount  of 
carbon  had  been  burned  in  the  body  of  the  animal,  the  amount  of 

'Op.  cit.,  s.  133.  2 piiy^iology,  1856,  8th  ed.,  Vol.  i..  p.  6U2. 

^D'Arsonval,  C'omptes  Rendus,  Aout 'ioth,   1879. 

*Mem.  de  I'Acad.  des  Sciences,  1775,  p.  520.  ^gbenda,  1777,  p.  183. 


428  ANIMAL  HEAT. 

carbon  dioxide  given  off  and  heat  produced  ]>y  the  combustion  of  a 
similar  amount  of  carbon  outside  of  the  body  having  been  previously 
determined,  and  of  so  establishing  the  truth  of  his  theory  by  ex- 
perimental demonstration.  For  this  purpose,  in  conjunction  with 
Laplace,  he  invented  the  ice  calorimeter/  This  consisted  essentially 
of  three  chambers,  concentrically  disposed  ;  in  the  innermost  cham- 
ber was  placed  the  substance  mIiosc  lieat  was  to  be  determined,  in 
the  middle  one  ice,  the  melting  of  which  was  the  measure  of  the 
heat  produced,  it  having  been  previously  determined  how  much 
heat  is  required  to  melt  a  given  quantity  of  ice,  wliile  in  the  outer 
chaml)er  ice  was  also  placed  in  order  to  shield  that  in  the  middle 
chamber  from  the  external  temperature,  the  melted  ice  passing  out 
by  openings  in  the  two  outer  chambers  provided  with  stopcocks. 
Having  determined  by  their  experiments  the  amount  of  heat  that 
would  lie  produced  Ijy  the  burning  of  a  pound  of  carbon  Lavoisier 
and  Laplace  then  placed  a  guinea-pig  in  the  innermost  chamber  of 
their  ice  calorimeter,  so  modified  as  to  permit  of  the  free  passage  of 
a  current  of  air,  so  that  the  respiration  of  the  animal  should  not  be 
interfered  witli,  and  found  that  the  amount  of  carbon  burned  by  the 
guinea-pig  while  in  the  calorimeter  as  deduced  from  the  carbon 
dioxide  expired  was  only  sufficient  to  account  for  about  nine-tenths 
of  the  heat  produced  as  measured  by  the  ice  melted. 

This  fact,  together  with  another  one  observed  at  the  time,  namely, 
that  all  the  oxygen  absorbed  did  not  return  in  the  carlion  dioxide 
exhaled,  led  Lavoisier^  afterward  (1785)  to  the  conclusion  that  of 
the  oxygen  inspired  part  combined  with  hydrogen  to  form  water 
and  that  the  heat  developed  by  the  combustion  of  the  hydrogen,  if 
added  to  that  due  to  the  combustion  of  the  carbon,  would  account 
for  the  heat  produced  by  an  animal,  as  in  tlie  experiment  with  the 
guinea-pig,  just  described,  and  which  could  not  be  accounted  for  by 
the  combustion  of  the  carbon  alone.  The  final  conclusion  of  La- 
voisier as  to  the  nature  of  respiration  and  calorification,  leased  upon 
the  closest  reasoning,  observation,  and  experiments,  extending  over 
many  years,  is  best  expressed  in  his  own  words  :^  "  Respiration  is 
only  a  slow  combustion  of  carbon  and  hydrogen,  and  which  re- 
sembles in  every  respect  that  which  goes  on  in  a  lighted  lamp  or 
candle,  and,  from  this  point  of  view,  animals  which  respire  are  true 
combustiljles,  which  form  and  consume  themselves.  In  respiration, 
as  in  combustion,  it  is  the  atmospheric  air  which  furnishes  the  oxy- 
gen and  caloric,*  but,  as  in  respiration,  it  is  the  substance  itself  of 
the  animal ;  it  is  the  blood  which  furnishes  the  combustible.  If 
animals  do  not  repair  hal)itually  by  food  that  whicli  they  lose  in 

^  Mem.  de  1' Acad,  des  Sciences,  1780,  p.  3o5. 

2  Hist,  de  la  .Societe  Koyale  de  Medecine,  1787,  508. 

"Mem.  de  I'Acud.  des  Sciences,  1789,  p.  570. 

*  To  appreciate  this  passage  it  must  be  borne  in  mind  that  at  tlie  date  when  it  wa.s 
written  oxygen  was  supposed  to  be  composed  of  oxygen  united  with  caloric,  the 
principle  of  heat  or  fire,  and  that  during  the  formation  of  carlwn  dioxide  through 
the  combination  of  oxygen  with  carbon  the  caloric  was  set  free. 


THE  CALORIMETER.  429 

respiration,  the  oil  will  soon  give  out  in  the  lamp,  and  the  animal 
would  perish,  as  a  lamp  extinguishes  itself  through  want  of  feeding. 
The  proof  of  this  identity  of  eifects  between  respiration  and  com- 
bustion is  immediately  furnished  by  experiment.  In  fact,  the  air 
which  has  maintained  respiration  does  not  contain  any  longer,  at  its 
exit  from  the  lungs,  the  same  quantity  of  oxygen  ;  it  contains  not 
only  carbonic  acid  [carbon  dioxide] ,  but,  in  addition,  more  water 
than  it  contained  before  inspiration." 

And  now,  after  a  lapse  of  more  than  a  century,  the  only  essential 
criticism  that  can  be  made  upon  the  views  of  Lavoisier  as  to  the 
origin  of  animal  heat,  apart  from  the  hypothesis  of  caloric  implied, 
is  that  he  held  that  the  lungs  were  the  seat  of  the  combustion, 
whereas  it  is  known  that  combustion  goes  on  in  all  parts  of  the 
body.  But  even  while  holding  this  view  Lavoisier  showed  his 
profound  appreciation  of  the  nature  of  the  phenomena,  since  he 
distinctly  states,  in  one  of  his  communications,^  that  possibly  the 
carbon  dioxide  is  not  produced,  but  only  exchanged  with  oxygen  in 
the  lungs.  However  important  his  generalizations,  as  to  the  matter 
of  respiration  and  animal  lieat,  nevertheless,  dying  on  the  scaffold 
a  victim  to  the  fury  of  the  French  Revolution,  Lavoisier  left  his 
work  unfinished.  With  the  view  of  settling,  if  possil)le,  some  of 
the  questions  left  undetermined  by  their  great  chemist,  the  Paris 
Academy  offered,  in  1821,  a  prize  for  the  best  essay  on  the  origin 
of  animal  heat.  The  prize  being  aAvarded  to  Depretz,  his  essay  was 
shortly  afterward  published,^  that  of  the  unsuccessful  competitor, 
Dulong,'^  not,  however,  until  several  years  afterward — in  fact,  after 
the  death  of  its  author.  To  avoid  repetition,  we  will  consider  the 
calorimeters  made  use  of  by  these  experiments  and  the  results  ob- 
tained with  them  together. 

The  calorimeter  of  Dulong  and  Depretz  did  not  differ  in  prin- 
ciple essentially  from  the  water  calorimeter  previously  made  use  of, 
for  the  same  purpose,  by  Crawford.*  It  consisted  essentially,  like 
the  latter,  of  two  chambers,  an  inner  one,  in  ^vhich  the  animal 
within  a  willow  cage  was  placed,  and  an  outer  one,  containing  the 
distilled  water,  the  elevation  of  whose  temperature  was  taken  as 
the  measure  of  the  heat  produced  by  the  animal.  In  the  calorim- 
eter of  Crawford,  however,  while  the  air  of  the  inner  chamber 
was  gradually  diminished,  and  at  the  end  of  the  experiment  was 
transferred  to  an  eudiometer  for  analysis,  in  that  of  Dulong  and 
Depretz  the  air  in  the  inner  chamber  was  continually  renewed  by 
air  from  a  gasometer,  and  being  transmitted  from  the  inner  cham- 
ber through  a  spiral  tube  placed  within  the  water  of  the  outer 
chamber,  passed  thence  into  a  water  gasometer,  where  it  could  be 
measured  and  analyzed,  the  air,  in  the  meantime,  as  it  passed 
through  the  spiral  tube,  giving  off  the  heat  (communicated  by  the 

^Mem.  del' Acad,  des  Sciences,  177",  P-  191. 

'^Ann.  de  Chimie  et  de  Physique,  1824,  Tome  xxvi.,  p.  337. 

''Ibid.,  3ieme  serie,  1841,  Tome  i.,  p.  440. 

*  Experiments  and  Observations  on  Animal  Heat.     London,  17S8,  p.  315. 


430 


ANIMAL  HEAT. 


animal)  to  the  surrounding  water,  and  so  elevating  its  temperature. 
The  amount  of  heat  produced  by  the  animal,  as  determined  by  the 
elevation  of  the  temperature  of  the  water,  is  expressed  in  calories, 
or  heat  units,  a  heat  unit  being  the  amount  of  heat  necessary  to  ele- 
vate the  temperature  of  a  pound  of  distilled  water  one  degree  Cent, 
or  Fahr.,  according  to  the  thermometer  used,  or,  as  is  more  usually 
understood  at  the  present  day,  the  amount  of  heat  necessary  to  ele- 
vate the  temperature  of  one  kilo.  (2.2  lbs.)  one  degree  Cent.  The 
amount  of  heat  produced  by  the  animal  expressed  in  heat  units 
while  in  the  calorimeter  is  then  obtained  by  multiplying  the  weight 
of  the  water  by  the  number  of  degrees  by  which  the  temperature 
of  the  water  has  been  increased.  Suppose,  for  example,  that  the 
water  in  the  calorimeter  weighed  20  kilo.,  and  its  temperature  had 
been  elevated  as  shown  by  the  thermometers  two  degrees  Cent,, 
then  40  calories,  or  heat  units,  Avould  have  l^een  produced  during 


Fig.  210. 


Water  calorimeter  of  Dulong. 

the  experiment  by  the  animal,  the  latter  having  neither  gained  nor 
lost  heat,  since,  if  the  animal  gained  heat,  it  is  evident  that  all  of 
the  heat  produced  was  not  given  off*  to  the  water,  and  if  it  lost  heat 
the  latter  was  not  produced  during  the  experiment,  but  simply  ra- 
diated away  from  it,  as  would  have  been  the  case  with  any  heated 
l)ody.  In  the  first  case,  the  heat  retained  by  the  animal  must  be 
added  to  the  heat  as  determined  by  the  calorimeter ;  and,  in  the 
second  case,  the  heat  lost  by  the  animal  must  be  subtracted.  In 
making  calorimetrical  experiments,  therefore,  the  temperature  of 
the  animal  must  be  taken  at  the  bes^innine:  and  the  end  of  the  ex- 
periment.  It  must  be  also  remembered,  however,  that  the  materi- 
als entering  into  the  composition  of  the  calorimeter,  such  as  copper, 
iron,  brass,  etc.,  absorb  heat,  even  if  in  less  amount  than  the  water, 
and  this  heat  also  expressed  in  heat  units  must  be  added  to  that 
absorbed  l)y  the  water.  Tliis  can  be  readily  estimated,  the  weight 
of  the  materials  and  their  specific  heat,  or  capacity  for  heat,  being 


'  THE  CALOKIMETER.  431 

known,  the  capacity  for  heat  of  water  being  taken  as  unity.  Sup- 
pose, for  simplicity,  that  the  calorimeter  is  made  out  of  copper, 
and  that  it  weighs  10  kilo.  ;  now  the  specific  heat  of  copper  be- 
ing 0.09  that  of  water,  it  is  evident  that  if  the  10  kilo,  of  copper 
be  multiplied  by  0.09,  the  product  0.90,  or  the  water  equivalent, 
when  multiplied  by  the  two  degrees  Cent,  equals  1.8,  which  will 
be  the  amount  of  heat  expressed  in  heat  units  absorbed  by  the 
copper,  and  which  must  be  added  to  the  40  heat  units  already 
obtained ;  or,  what  is  the  same  thing,  if  the  water  equivalent  of 
the  copper  0.9,  be  added  to  the  20  kilo,  of  water,  and  the  re- 
sult 20.9  be  multiplied  by  2,  the  quotient  will  be  the  same  as 
before — that  is,  41.8  heat  units  produced  by  the  animal.  In  other 
words,  each  kilo,  of  copper,  having  0.09  the  capacity  of  heat  of 
a  kilo,  of  water,  10  kilo,  of  copper  may  be  regarded  as  equiva- 
lent to  0.9  kilo,  of  water,  which,  when  added  to  the  20  kilo,  of 
water  and  multiplied  by  2,  or  the  temperature  gained,  gives  41.8 
heat  units.  It  is  hardly  necessary  to  add,  after  what  has  just  been 
said,  that  of  the  other  metals  usually  entering  into  the  construction 
of  the  calorimeter  the  heat  absorbed  by  them,  as  well  as  that  re- 
tained or  given  oif  by  the  animal,  which,  as  we  have  seen,  must  be 
added  to  or  subtracted  from  the  41.8  heat  units,  for  example,  ac- 
cording as  the  animal  has  gained  or  lost  heat  during  the  experi- 
ment, is  determined  in  exactly  the  same  way  as  in  the  case  of  the 
copper.  As  regards  obtaining  the  water  equivalent  of  the  animal 
placed  in  the  calorimeter — that  is,  its  weight  multiplied  by  its 
specific  heat — a  difficulty  presents  itself,  since  the  specific  heat  of 
animals  has  not  been  absolutely  determined.  The  latter  is  usu- 
ally accepted  as  being  0.8,^  that  being  the  mean  specific  heat  of 
the  tissues  so  far  determined,  water  being  taken  as  unity.  In 
determiuino:  the  amomit  of  heat  o-iven  off  bv  an  animal  in  a 
calorimeter  there  is  another  consideration  which  must  not  be  over- 
looked, and  which  is  a  slight  source  of  error  even  in  the  best 
constructed  calorimeters.  That  is  the  slight  loss  of  heat  due  to  con- 
duction and  radiation  from  the  instrument,  and  which  cannot  be  en- 
tirely prevented.  The  loss  of  heat  from  this  cause,  however,  can 
be  reduced  to  a  very  small  amount  by  proper  precautions,  such  as 
surrounding  the  calorimeter  ^vith  down,  etc.,  as  was  done  by  Craw- 
ford, or  ])y  lowering  the  temperature  of  the  water  in  the  calorimeter 
some  degrees  below  that  of  the  surrouuthng  atmosphere,  the  sup- 
position being  that  the  heat  absorbed  from  the  surrounding  air  dur- 
ing the  first  half  of  the  experiment  would  be  radiated  back  again 
during  the  latter  half,  and  that  this  source  of  error  could,  therefore, 
be  neglected,  as  was  admitted  in  the  experiments  of  Dulong  and 
Depretz.  The  loss  of  heat  due  to  radiation,  etc.,  can  be  also  deter- 
mined experimentally,  and  can  be  then  taken  into  account  in  the 
final  calculation  ;  or,  by  self-regulating  gas-jets,  heat  can  be  sup- 

^  Liebermeister,    Handburli  der  Pathologie  u.    Tlierapie  des  Fiebers,   p.    147. 
Leipzig,  1875.     Kosenthal,  Archiv  f.  Anat.,  etc.,  1878,  p.  215. 


432  ANIMAL  HEAT. 

plied  to  restore  that  which  is  lost.  Further,  it  is  important  that 
the  heat  should  be  thoroughly  diffused  through  the  water  in  the 
calorimeter ;  this  can  be  accomplished  by  the  stirrers,  as  in  the  ap- 
paratus of  Dulong  and  Depretz,  or  by  any  other  suitable  mechanical 
arrangement.  The  great  improvement  in  the  experiments  of  Du- 
long and  Depretz,  however,  as  compared  with  those  of  their  prede- 
cessors, consisted  in  comparing  the  expired  air  with  the  inspired  air, 
and  determining  the  amount  of  heat  produced  and  carl)on  dioxide  ex- 
haled simultaneously ;  whereas,  in  the  experiments  of  both  Lavoisier 
and  Crawford,  this  was  done  with  the  same  animal,  but  at  diiferent 
times.  Notwithstanding  the  great  number  of  experiments  per- 
formed by  Dulong  and  Depretz,  and  the  general  acceptance  with 
which  their  views  were  received,  not  much  importance  can  be  at- 
tached to  them  at  the  present  day  on  account  of  the  following  rea- 
sons :  First.  That  the  temperature  of  the  animal  within  the  calorim- 
eter was  assumed  to  remain  unchanged  during  the  experiment, 
although  Lavoisier  had  distinctly  called  attention  to  the  improba- 
bility of  such  being  the  case.  Second.  Of  the  amount  of  carbon 
dioxide  exhaled  by  the  animal  being  underestimated,  part  of  it  be- 
ing absorbed  by  the  water  of  the  gasometer  into  which  it  passes. 
Third.  Of  the  amount  of  heat,  as  deduced  from  the  carbon  dioxide 
exhaled,  being  also  underestimated,  both  on  account  of  the  estimate 
of  Lavoisier  of  the  heat  produced  by  the  combustion  of  carbon  and 
hydrogen  obtained  with  an  ice  calorimeter,  being  accepted  as  the 
basis  of  comparison  with  the  heat  produced  l)y  an  animal  in  a  water 
calorimeter,  and  because  the  heat-producing  power  of  the  carbon 
and  hydrogen  burned  even,  as  determined  by  Lavoisier,  is  manifestly 
too  low  as  shown  by  the  later  and  accurate  experiments  of  Fabre 
and  Silberman  ;^  and  further,  that  no  account  was  taken  of  the  heat 
produced  by  the  burning  of  the  sulphur  and  phosphorus  in  the  ani- 
mal economy.  Fourth.  That  the  ratio  of  the  carbon  to  the  hydro- 
gen was  erroneously  estimated,  an  important  source  of  error,  since 
far  more  heat  is  produced  by  the  combustion  of  hydrogen  than  by 
an  equal  weight  of  carbon.  Fifth.  From  the  carbon  and  hydrogen, 
to  whose  combustion  is  the  heat  principally  due,  being  supposed  to 
exist  in  the  free  condition,  which  they  evidently  do  not. 

Later  investigators  have  endeavored  to  utilize  the  results  of  Du- 
long and  Depretz  in  considering  them  as  influenced  by  the  condi- 
tions just  referred  to,  but  as  the  attempts  have  been  far  from  satis- 
factory, it  is  not  necessary  to  dwell  upon  them. 

During  late  years  a  number  of  investigations  have  been  made 
calorimetrically,  with  the  olyect  of  determining  the  heat  produced 
by  an  animal  in  a  given  time.  Among  these  may  be  mentioned 
especially  those  of  Senator "  upon  dogs.  The  calorimeter  used  in 
these  experiments  was  essentially  the  same  as  that  of  Dulong's,  the 

^Ann.  de  Chimie  et  de  Physique,  3ieme  sen,  Tome  xxxiv.,  p.  357;  Tome 
xxxvi.,  p.  51  ;  Tome  xxxvii.,  p.  405. 

2  Archiv  f.  Anat.  u.  Phys.,  1872,  s.  1,   1874,  s.  18. 


THE  CALORIMETEE. 


433 


only  cliiFerence  l)eing  that  it  was  usually  filled  with  warm  water  in 
order  to  prevent  the  animal  losing  heat.  The  ventilation  of  the 
chamber  in  Avhich  the  animal  was  placed  was  maintained  l)y  aspira- 
tion, the  current  of  air,  before  entering  the  calorimeter,  being  freed 
from  its  carbon  dioxide  by  passing  it  through  potash,  and  the  carbon 
dioxide  exhaled  into  it  by  the  animal  being  determined  after  it  left 
it  by  Pettenkofer's  method.  In  the  final  estimation  of  the  heat 
produced  by  the  animal,  in  addition  to  that  taken  up  by  the  calori- 
meter, the  heat  absorbed  by  the  air  passing  through  the  instrimient 
was  also  considered.  Senator  found,  as  the  mean  of  his  experiments, 
that  a  dog  fed  daily  produced  16.5  calories  or  heat  units  per  hour, 
with  an  exhalation  during  the  same  time  of  4.4  grammes  of  carbon 
dioxide,  there  being  produced,  as  a  general  rule,  2.5  calories  for 
every  kilogramme  (2.2  pounds)  of  weight.  In  order  to  obtain  the 
amount  of  heat  produced  in  twenty-four  hours,  the  16.5  calories 
were  multiplied  l)y  24,  l)ut  as  it  is  uncertain  ^vhether  the  production 
of  heat  is  constant,  this  is  hardly  admissible.  The  general  conclu- 
sion to  be  drawn  from  the  experiments  of  Senator  is,  that  there  i& 
no  constant  relation  existing  between  the  production  of  heat  and 
the  exhalation  of  carl)on  dioxide,  and  while  during  digestion  the 
production  of  l)oth  is  increased,  in  starvation  both  are  diminished. 

Fig.  211. 


Calorimeter. 


The  calorimeter  (Fig.  211)  made  use  of  by  the  author  consists  of 
two  copper  cylinders  concentrically  disposed,  the  outer  space  a  or  the 
space  between  the  cylinders  being  closed  at  both  ends  with  copper, 
the  inner  space  6,  or  the  space  within  the  cylinder,  being  closed  at 
one  end  by  copper,  and  at  the  other  end  by  an  annular  door  consist- 

28 


434  ANIMAL  HEAT. 

ing  of  brass  and  glass,  and  which  can  be  hermetically  closed  by  the 
brass  clamps  and  rubl)er  facing  soldered  to  the  brass  rim  internally. 
The  outer  chamber  a  is  filled  with  distilled  water  by  means  of  a  funnel 
introduced  through  the  opening/,  and  when  full  contains  18.1  kilo. 
(40  lbs.)  of  water.  The  inner  chamber  h,  at  the  end  opposite  the 
door,  communicates  by  a  stopcock  (c/)  with  the  external  air,  and 
through  the  opening  h  in  its  roof  with  a  copper  spiral,  which,  after 
making  a  dozen  turns  around  the  inner  cylinder  within  the  water 
of  the  outer  chamber,  terminates  in  the  opening  k  of  the  latter.  By 
means  of  the  mercurial  pump  (already  described)  the  ventilation  of 
the  inner  chamber  can  be  thorougidy  maintained,  the  air  entering 
the  latter  through  the  opening  at  <l  and  passing  thence  l)y  the  open- 
ing h  into  the  spiral  /  and  out  by  the  opening  k  with  the  same  tem- 
perature at  which  it  entered,  the  heated  air  being  gradually  cooled 
as  it  passes  through  the  spiral,  the  heat  being  alisorbed  by  the  sur- 
rounding water.  If  it  is  desired  to  compare  the  expired  with  the 
inspired  air,  the  air  freed  from  its  water  and  carbon  by  Voit's 
method  is  made  to  pass  through  a  meter,  before  it  enters  the  cal- 
orimeter and  through  one  after  it  leaves  it,  being  previously  freed 
from  its  water  and  carbon  in  the  same  manner  as  was  the  inspired 
air.  Fittinir  in  the  floor  of  the  inner  chamber  of  the  calorimeter  is 
a  movable  copper  pan  with  a  sieve-like  cover  on  which  the  animal 
rests,  the  object  of  the  cover  being  that  the  urine  of  the  animal  can 
trickle  into  the  pan  and  insure  cleanliness.  Ventilation  having 
been  assured  by  the  action  of  the  pump  and  the  temperature  of  the 
water  in  the  outer  chamber  noted  by  introducing  a  thermometer 
into  the  opening  /  and  that  of  the  animal  taken,  the  latter,  having 
been  previously  weighed,  is  placed  within  the  chamber  on  the  tray 
and  the  door  securely  closed.  Suppose  the  experiment  has  lasted 
one  hour,  and  it  be  admitted  that  the  heat  lost  by  radiation  and 
conduction  from  the  calorimeter  be  replaced  by  that  furnished  by 
the  gas  jcts,^  the  flow  of  gas  being  regulated  by  the  valve  V,  wdiich 
with  the  heating  of  the  water  is  pressed  outward  (through  the  pres- 
sure of  the  column  of  water  in  the  tube  t,  replacing  the  thermometer) 
against  the  opening  transmitting  the  gas  and  thereby  diminishing 
its  flow,  and  which  with  the  cooling  of  the  water,  is  drawn  back 
again  from  the  opening,  thereby  increasing  it  again.  To  determine 
the  calories  or  lieat  units  produced  by  the  animal,  a  rabbit,  for  ex- 
ample, during  the  time  mentioned,  we  have  only  now  to  multiply 
the  number  of  degrees  by  which  the  temperature  of  the  water  has 
been  increased  by  its  weight,  to  which  has  been  added  the  water 
equivalent  of  the  copper,  brass,  glass,  rubber,  and  solder  entering 
into  the  construction  of  the  calorimeter,  and  adding  or  subtracting 
the  heat  gained  or  lost  by  the  animal  as  determined  immediately  at 
the  conclusion  of  the  experiment.  Suppose  that  the  temperature  of 
the  water  in  tlie  calorimeter  has  increased  0.5°  C,  the  temperature 

'By  enveloping?  tlie  ciiIdriniotcT  with  a  thick  jacket  of  wool  or  iVatliers  the  gas 
jets  can  be  dispensed  with. 


WATER  EQUIVALENT.  435 

at  the  beginning  of  the  experiment  being   15°  C.  (51)°  F.),  and  at 
the  end  15.5°  C.  (59.9°  F.),  and  the 


Water 

equivalent, 

copper 

= 

21  lbs, 

X  0.095 

=  1.995 

brass 

= 

23.25 

"lbs. 

X  0.093 

=  2.162 

iron 

= 

0.09 

X  0.11 

=  0.009 

glass 

= 

1.25 

X  0.19 

=  0.237 

rubber 

= 

0.6 

X 

=  0.0^ 

tin 

= 

0.5 

X  0.05 

=  0.025 

a 

lead 

= 

0.5 

X  0.03 

=  0.015 

u 

materials 

=  4.443 

Adding  the  water  equivalent  of  the  materials  used,  4.4  lbs.,  to 
the  weight  of  the  water,  40  lbs.,  making  44.4  lbs.,  or  20.1  kilo., 
and  multiplying  the  latter  by  0.5°  C,  the  number  of  degrees  gained 
by  the  water,  the  product,  10.05,  will  be  the  number  of  calories  or 
heat  units  produced  by  the  animal,  supposing  the  temperature  of 
the  latter  to  have  remained  unchanged.  Suppose  the  animal,  how- 
ever, lost  0.9°  C,  its  temperature  being  39.2°  C.  at  the  beginning 
of  the  experiment  and  38.3°  C.  at  the  end,  then  there  must  be  sub- 
tracted from  the  10.05  calories  2.16 — that  is,  the  product  of  the 
weight  of  the  rabbit,  6.6  lbs.,  or  3  kilo.,  by  its  .specific  heat,  0.8° 
by  0.9°  (3  X  0.8  x  0.9  =  2.16);  the  total  number  of  heat  units 
produced  by  the  rabbit  in  an  hour  would  then  be  7.8  calories.  If 
the  rabbit  gains  the  same  number  of  degrees,  then  the  2.16  calories 
must  be  added  to  instead  of  being  sul)tracted  from  the  10.05  heat 
units,  making  the  total  amount  of  heat  produced  12.21  heat  units. 

In  the  experiment  just  described  it  was  assumed  that  the  temper- 
ature and  aqueous  vapor  of  the  air  i.ssuing  from  the  calorimeter  was 
the  same  as  that  entering  it.  If,  however,  the  air,  as  it  passes 
through  the  calorimeter,  and  the  water  evaporated  from  the  lungs 
and  skin,  absorb  heat  the  amount  of  heat  so  expended  being  also 
produced  by  the  animal,  as  well  as  that  imparted  to  the  water  of 
the  calorimeter,  must  be  determined  and  added  to  the  latter.  The 
amount  of  heat  ab.sorbed  by  the  air  passing  through  the  calorime- 
ter is  readily  ol)tained  by  reducing  the  given  volume  of  air  to  that  of 
standard  pressure  and  temperature  and  multiplying  the  weight  of 
the  latter,  first  by  its  specific  heat,  0.26,  and  then  by  the  number  of 
degrees  by  M'hich  its  temperature  is  increased.  The  heat  expended 
by  the  animal  in  evaporating  the  water  from  its  lungs  and  skin  is 
estimated  by  determining  first  the  difference  in  the  amount  of  the 
water  of  the  air  passing  in  and  out  of  the  calorimeter,  and  multi- 
plying the  weight  of  the  excess  of  the  water  by  582,  that  being  the 
number  of  heat  units  expended  in  evaporating  1  kilogramme  of 
water. 

It  should  be  mentioned  in  this  connection  that  a  small  amount 
of  heat  is  carried  off  in  the  urine  and  feces  voided  by  the  animal 

^The  specific  heat  of  rubber  slip  not  having  being  determined,  the  heat  actually 
produced  wa.s  slightly  greater  than  that  given  in  text.  The  amount,  however,  would 
be  so  small  that  it  may  be  neglected. 


436  ANIMAL  HEAT. 

which  is  usually  ucglected  iu  calorimetrical  experiments.  We  shall 
sec  however,  that  in  estimating  the  total  amount  of  heat  produced 
by  the  animal  that  the  heat  so  dissipated  though  small  in  amount 
must  be  taken  into  consideration. 

Calorimetrical  investigations  have  been  made  also  upon  man  by 
Scharling/  Yogel,"  and  Hirn,^  but  with  rather  unsatisfactory  re- 
sults. The  apparatus  made  use  of  by  these  experimenters  was 
essentially  the  same,  consisting  of  a  chamber  in  which  the  man  was 
placed  and  which  was  kept  in  a  room  maintained  at  a  temperature 
as  constant  as  possible,  the  increase  in  the  temperature  of  the 
chamber,  together  with  the  heat  lost  through  cooling,  being  regarded 
as  produced  by  the  man  during  the  experiment.  Since  the  tem- 
perature of  the  chamber  after  being  somewhat  elevated  after  that 
remains  constant,  the  heat  as  produced  being  radiated  away,  accord- 
ing to  the  Newtonian  law  of  cooling,  the  amount  of  heat  produced 
will  be  equal  to  the  diiference  between  the  constant  temperature  and 
the  initial  temperature  multiplied  by  the  coefficient  of  cooling,  the 
latter  being  determined  experimentally.  In  the  experiments  of 
Scharling  and  Yogel  this  was  accomplished  by  placing  a  vessel  filled 
with  hot  water  in  the  chamber  and  comparing  the  loss  of  heat  of 
the  water  with  the  increase  of  the  temperature  of  the  chamber,  and 
in  those  of  Hirn  by  burning  hydrogen  and  comparing  the  actual 
result  with  that  obtained  by  calculation.  On  account  of  the  many 
sources  of  error  incidental  to  such  a  crude  method  of  experimenta- 
tion as  that  just  described,  an  approximate  value  only  can  be  at- 
tached to  the  results  so  obtained,  and  the  same  may  be  said  of  the 
estimates  of  the  amount  of  heat  produced  based  upon  the  rise  in 
the  temperature  of  the  water  of  a  bath  in  which  a  man  is  im- 
mersed,^ or  of  that  of  a  calorimeter  inclosing  only  a  part  of  a 
person,  a  limb,  for  example.'  Nevertheless,  it  should  be  mentioned 
that  the  estimates  of  these  observers  of  the  heat  produced  by  a  man 
in  twenty-four  hours  do  not  differ  as  much  as  might  be  supposed,, 
amounting,  according  to  Scharling,  Vogel,  Hirn,  Liebermann,  and 
Leyden,  to  316<S,  2400,  37'20,  3525,  and  2370  calorics  respectively^ 
allowance  being  made  for  the  size  and  weight  of  the  individual  ex- 
perimented upon. 

Since  the  heat  produced  by  an  animal  is  due  to  the  combustion 
of  its  food  it  might  be  supposed  that  it  Mould  be  only  necessary  to 
determine  the  amount  of  carbon,  hydrogen,  sulphur,  phosphorus, 
etc.,  that  it  contained,  and  the  products  of  their  combustion,  carbon 
dioxide,  water,  urea,  etc.,  obtained  from  the  excreta  in  order  to  de- 
termine the  amount  of  heat  produced.  It  must  be  borne  in  mind, 
however,   that   to  effect  the  combustion   of   the   food — that  is,  to 

'Journal  fiir  pract.  ("hemic,  xlviii.,  s.  485,  1849. 

2Archiv  d.  ver.  f.  Wiss.  lleilk.  Xeue  folge,  I'.and  i.,  s.  441,  180o. 

^Recherches  sur  I'tMiuivak'nt  nimmique  de  la  flialeur,  Colmar,  185S.  Exposi- 
tion analytiqiie  ct  experinK'ntalo  dc  la  tlieorie  nit'canicjiie  do  la  clialcur,  o<l  ed.,  T. 
i.,  p.  27.      Paris,  1S7-').  *  LiobeniU'ister,  op.  cit.,  p.  2;59. 

5  Leyden,  Deutsch.  Arehiv  f.   klin.  med.,  IHGU,  s.  273. 


HEAT  PRODUCING  POWER  OF  FOOD.  437 

transform  it  into  carbon  dioxide,  water,  etc.,  a  certain  amount  of 
heat,  or  an  equal  amount  of  energy  of  some  kind,  is  required,  since 
the  carbon,  hydrogen,  and  other  combustible  matters  do  not  exist 
in  the  food  in  the  free  gaseous  state,  but  in  a  state  of  molecuUir 
combination.  A  certain  unknown  amount  of  heat  would  have  to 
be  deducted  therefore  from  the  amount  estimated  if  based  upon  an 
analysis  of  the  food  and  the  excreta.  In  other  words,  the  heat 
producing  power  of  food,  or  any  fuel,  cannot  be  estimated  from  the 
amount  of  combustible  matters  it  may  contain,  since  the  heat  to  be 
expended  in  breaking  up  the  chemical  combinations  constituting 
these  matters,  and  of  setting  free  the  heat  previously  locked  up 
in  them  is  practically  unknown.  It  is  for  the  reasons  just  given, 
as  well  as  for  the  further  one  of  the  accepted  estimates  of  Dulong 
of  the  amount  of  heat  produced  by  the  combustion  of  a  given 
weight  of  carbon,  hydrogen  being  too  low,  that  the  calculation  of 
Helmholtz  ^  of  the  amount  of  heat  produced  by  a  man  weighing 
82  kilo,  in  twenty-four  hours,  viz.:  2731.2  calories,  can  only  be 
accepted  as  approximating  the  truth.  And  while  the  calculation  of 
Ludwig,"  of  a  daily  production  on  the  average  of  3191.i)  calories 
is  free  from  the  last  source  of  error  mentioned,  being  based  upon 
the  data  of  Barral  and  the  higher  estimates  of  Fabre  and  Silber- 
man  of  the  heat  value  of  the  carbon  and  hydrogen  burned,  never- 
theless, as  it  also  assumes  that  the  combustion  of  the  carlwn  and 
hydrogen  of  the  food  develops  as  much  heat  as  if  existing  in  the 
free  condition,  it  is  open  to  the  same  objection  as  the  calculation  of 
Helmholtz.  In  fact,  the  only  way  in  which  the  amount  of  heat 
produced  through  the  combustion  of  food  can  be  actually  deter- 
mined, is  by  l)urning  it  in  a  calorimeter,  as  was  done  by  Frankland,^ 
and  of  so  obtaining  its  heat  value  by  direct  experimentation.  The 
instrument  we  make  use  of  for  this  purpose,  the  same  as  that  of 
Frankland,  of  the  convenient  form  devised  by  Thompson,  consists 
of  a  copper  cylinder  with  a  capacity  of  120  e.  cm.,  open  l)elow,  and 
with  the  rim  perforated  with  small  openings,  but  closed  above, 
and  with  the  cavity  of  the  cylinder  prolonged  into  a  narrow  tube 
provided  with  a  stopcock  near  its  end,  and  of  a  smaller  cylinder  with 
a  capacity  of  15  c.  cm.,  open  above,  but  closed  below,  the  lower 
portion  of  the  cylinder  fitting  into  the  little  cup  of  the  stand,  the 
latter  being  provided  with  three  elastic  springs  which  securely  hold 
the  large  cylinder  when  the  latter  encloses  the  small  one.  Within 
the  small  cylinder  is  placed  the  substance  to  be  burned  ^nth  a  small 
fuse  attached  with  a  combustible  whose  heat  values  are  known. 
The  latter  being  lighted,  the  large  cylinder  is  immediately  placed 
over  the  small  one,  the  elastic  springs  holding  it  fast,  and  the  in- 
strument so  put  together  at  once  plunged  into  a  long,  narrow  vase 
containing  a  known  quantity  of  distilled  water  whose  temperature 

lEncyl.  Wr)rtc'rlnK'li  tier  ^Med.  AVissvn.,  Band  xxxv.,  s.  555.     Berlin,  1840. 
^Lehrljiu'h  der  Physiologie  dos  Menschen,  Zweiter  Auflage,  Zweite  Band,  s.  749. 
Leipzig,  18()1.  » Philos.  Mag.,  1866,  xxxii.,  p.  182. 


438  AXIMAL  HEAT. 

has  been  accurately  determiifecl  by  a  specially  constructed  thermom- 
eter graduated  into  tenths.  In  a  few  moments  fumes  ^yill  be  seen 
to  issue  from  the  holes  in  the  rim  of  the  outer  cylinder  into  the 
surrounding  water.  The  deflagration  being  ended,  and  the  stop- 
cock opened,  the  ^yater  will  rise  through  the  holes  into  the  cylinders. 
The  instrument  being  moyed  up  and  down,  the  heat  giyen  out  wdll 
soon  diffuse  itself  equally  throughout  the  water,  the  amount  of  heat 
produced  by  the  food  burned  lieing  determined  by  the  eleyation  of 
the  temperature  of  the  latter,  due  allowance  being  made  on  the  one 
hand  for  the  heat  absorbed  by  the  copper,  etc.,  and  on  the  other 
for  that  produced  by  the  burning  of  the  fuse  and  combustil)le  used. 
The  other  sources  of  error  incidental  to  the  workmg  of  the  appa- 
ratus are  so  slight  that  they  may  be,  according  to  Frankland^ 
neglected.  It  was  by  means  of  the  calorimeter  just  described  that 
Frankland  determined  by  actual  experiment  the  amount  of  heat 
developed  by  the  combustion  of  different  kinds  of  food. 

Heat  DEyELOPED  by  Burning  1  Gramme  (15.4  Gr.)  of  Different 
Articles  of  Food  Expressed  in  Heat  Units.' 

A  heat  unit  is  equal  to  the  amount  of  heat  necessary  to  raise  the  tem- 
perature of  1  kilo.  (2.2  lbs.)  of  distilled  water  1°  C.  (1.8°  F.). 

When  oxidized  outside  of  body.     When  oxidized  inside  of  body. 


Dry. 

Natural  condition. 

•      Dry. 

Natural  condition. 

Cod- liver  oil 

9.107 

9.107 

Fat  of  beef . 

9.069 

• 

9.069 

Butter 

• 

7.264 

7.264 

Guiness'  stout 

6.401 

1.076 

6.401 

1.076 

Arrowroot  . 

3.912 

3.912 

Lump  sugar 

3.348 

3.348 

Grape  sugar 

3.227 

• 

3.227 

Yelk  of  egg 

6.460 

3.423 

6.24 

3.30 

Hard  boiled  egg  . 

6.S21 

2.383 

6.05 

2.28 

Cheese 

6.114 

4.647 

5.74 

4.36 

Mackerel     . 

6.064 

1.789 

5.71 

1.61 

Lean  of  beef 

5.313 

1.567 

4.85 

1.42 

Milk    . 

5.093 

0.662 

5.07 

0.62 

White  of  egg 

4.896 

0.671 

4.21 

0.57 

Veal    . 

4.514 

1.314 

4.02 

1.11 

Ham  (boiled) 

4.343 

1.980 

3.68 

1.68 

Bread  (crumb) 

3.984 

2.231 

3.84 

1.45 

Flour  . 

3.936 

. 

3.84 

Rice  (ground) 

3.813 

. 

3.76 

Cabbage 

3.776 

0.434 

3.65 

0.42 

Potatoes 

3.752 

1.013 

3.69 

0.99 

It  will  be  seen,  however,  from  a  glance  at  the  above  resum6 
of  Frankland's  experiments,  that  the  fatty  and  carbohydrate 
foods  are  as  thoroughly  burned  in  tlic  body  as  out  of  it,  though 
more  slowly,  Avhereas  the  albuminous  substances  are  but  imper- 
fectly so.  This  is  as  might  have  been  expected,  since,  as  we 
have  already  mentioned,  except  in  certain  temporary  conditions  in 

'  Frankland,  op.  cit. 


FOOD  STUFFS  B VEXED  IX  THE  BODY.  439 

a  state  of  health,  fat  and  starcli  are  never  found  in  tlie  excreta, 
these  substances  passing  out  of  the  body  as  carbon  dioxide  and 
water,  being  as  thoroughly  oxidized  within  the  system  as  if  burned 
in  pure  oxygen  outside  of  it,  whereas,  as  Ave  shall  presently  see, 
uric  acid  and  urea  are  normal  constant  ingredients  of  the  excreta, 
these  suljstances  representing  so  much  unburned  proteid  which 
passes  out  of  the  system  in  this  form. 

Thus,  according  to  recent  researches,  while  1  gramme  of  muscle 
extracted  with  water  will  produce,  when  burned  out  of  the  body, 
5.778  calories,  the  same  amount  of  muscle  Mill  produce,  Avheu 
burned  in  the  body,  only  4.9o7  calories,  the  difference  of  0.841  of 
a  calorie  being  due  to  the  fact  that  one-third  of  the  proteid  passes 
out  of  the  economy  unburned  as  urea,  and  that  one-third  of  a 
gramme  of  urea  will  produce,  when  burned  outside  of  the  body, 
0.841  of  a  calorie.  In  estimating  the  amount  of  heat  produced 
by  the  burning  of  any  proteid  substance  within  the  body  one-third 
is  usually  deducted  as  representing  so  much  incombustible  material ; 
for,  although  in  all  probal)ility  proteid  is  converted  by  combustion 
into  carlwn  dioxide,  water,  and  ammonia,  as  the  latter  combines 
with  part  of  the  carl)on  dioxide  and  water  to  form  ammonium  car- 
bamate, the  antecedent  of  urea ;  of  the  heat  liberated  by  the  com- 
bustion one-third  is  locked  up  again  in  the  subsequent  synthesis. 

According  to  recent  experiments,  made  with  improved  form  of 
calorimeters,  the  diflFerent  food  stuffs  when  l)urned  in  the  body  will 
produce  as  follows  : 

Carbohydrates    ......     4.116  calories. 

Proteids 4.937         " 

Fats 9.312         '< 

Having  learned  the  amount  of  heat  developed  in  the  burning  of 
a  given  weight  of  carl)ohydrate,  proteid,  and  fat,  etc.,  out  of  the 
body,  it  still  remains,  knowing  ))y  analysis  how  much  of  such  sub- 
stances is  contained  in  the  food,  to  determine  from  the  carbon  diox- 
ide, water,  and  urea  in  the  excreta,  the  products  of  the  combustion 
of  such  substances,  the  amount  actually  burned  in  the  body,  and  of 
so  estimating,  by  means  of  the  above  data,  the  amount  of  heat  de- 
veloped within  the  body  on  a  normal  diet,  or  otherwise.  In  other 
words,  the  ingesta  or  the  food  must  be  compared  with  the  egesta  or 
the  excretions.  The  subject  of  the  observation  must  be  weighed  at 
the  beginning  and  the  end  of  the  experiment  to  learn  whether  the 
Aveight  has  remained  unchanged,  since,  if  the  individual  loses 
Aveight,  the  food  has  been  deticieut,  the  body  Avasting  to  supply  it ; 
and,  if  the  reverse  is  the  case,  the  food  has  been  in  excess,  the  body 
fattening.  Further,  the  experiment  should  extend  OA'cr  a  period  of 
twenty-four  hours,  and  longer,  when  possible,  in  order  to  aA^oid  the 
usual  source  of  errors  incidental  to  all  experiments  of  such  a  char- 
acter if  lasting  for  shorter  periods  of  time.  It  Avas  on  such  prin- 
ciples that  the  admirable   experiments  of  Ranke,  performed  upon 


440  AXniAL  HEAT. 

himself,  were  conducted,  and  it  may  be  mentioned,  incidentally,  in 
this  connection,  that  at  that  time  the  distinguished  physiologist  was 
tweutv-four  years  old,  six  feet  high,  weighed  one  hundred  and  fifty- 
four  pounds  (70  kilo.),  was  in  perfect  health,  and  that  the  appa- 
ratus made  use  of  Avas  the  Pettenkofer  respiration  apparatus  that 
Ave  have  already  referred  to.  The  results  obtained  by  Ranke  ^  are 
shoAvn  in  the  folloAving  table  : 

Heat  Produced  ix  24  Hours  by  the  Combustion  of  Food  withix 
THE  Body  as  Estimated  from  the  Egesta,  axd  Expressed  in 
Heat  Units. 

Nitrogenous  Diet. 
Ingesta.  N  C  Egesta.  N  C 

Meat,  1832  grammes.         62.29  229.36      Urea,        86.3  40.28     17.26 

1300   "  consumed,  44.19  162.75      Uric  acid,  1.9     0.65       0.70 
Fat  of  meat,  70   "  0.00     50.27 

Salts,  31    "  Salts,        26.6 

Water,        3371  e.  c.  Urine,  2073  c.  c. 

Fat  of  body,  75.14  grammes,     0.00     54.02      Feces.       99.0     3.26     14.88 

Water     ""71.00         "  Respiration,  231.20 

44.19  267.04  44.19  267.04 

Initial  weight     .....      72.927  kilogrammes. 
Terminal  weight         ....     72.781  " 

0.146  gramme. 
Heat  units  produced       ......     2779.5 

Starvation  Diet. 
Ingesta.  Egesta. 

Body  consumed.  Urea,  18.3    grammes. 

Albumin,      54.45  grammes.         Uric  acid,  0.24         " 

Fat,  195.94         "  Respiration,  180.00  cubic  meters. 

Heat  units  produced       ......     2012.8 

Non-nitrogenous  Diet. 

Ingesta.  Egesta. 

Starch,  300  grammes.      Urea,  17.1 

Sugar.'  100         "  Uric  acid,  0.54 

Fat,  150         "  Feces,  90.00 

Albumin  of  body,  51.55    "  Respiration,  200.00  cubic  meters. 

Heat  units  produced       ......     2059.5 

Mixed  Diet. 
Heat  units  produced  ......     2200 

It  will  be  observed  from  the  above  that  the  greatest  amount 
of  heat  was  produced  on  a  nitrogenous,  or  a  very  abundant 
meat  diet,  but  that  this  was  accomplished  at  the  expense  of  the 
body,  Ranke  lo.sing  148  grammes  in  weight,  his  body  supplying 
75.14  grammes  of  fat  in  addition  to  the  70  s-rammes  of  roast  meat 
and  71  grammes  of  Avater,  and  that  of  the  1<S."J2  grammes  of  meat 
eaten  only  l."]00  grammes  were  burned,  as  shown  by  the  amount  of 
urea  excreted.  It  folloAvs,  therefore,  that,  so  far  as  the  production 
of  heat  Avas  concerned,  the  same  result  might  IiaA'e  been  obtained 
'  Ranke,  Physiologie,  Dritte  Aufl.,  s.  196,  s.  566.     Leipzig,  1875. 


HEAT  PBODUCED   UPOX  A  MIXED  DIET.  441 

with  ').">2  less  grammes  of  meat,  but  with  71  more  grammes  of  fat. 
On  the  other  hand,  as  Rauke  mentions  in  speaking  of  the  heat 
produced  on  a  non-nitrogenous  diet,  of  the  150  grammes  of  fat 
eaten  only  68.5  grammes  could  have  been  burned,  81.5  grammes 
having  been  deposited  in  the  Ijody.  On  such  a  diet,  therefore, 
more  than  half  the  flit,  if  taken  with  the  view  of  producing  heat, 
would  be  superfluous. 

The  amount  of  heat  produced  upon  a  mixed  diet  such  as  that 
of  Rauke's,  as  determined  from  an  analysis  of  the  excreta,  is  some- 
what less  than  that  ol)tained  by  multiplying  the  ditferent  amounts 
of  food  stuffs  contained  in  such  a  diet  by  the  number  of  heat  units 
—  we  have  supposed  each  gramme  of  the  same  would  produce  when 
burned  in  the  body,  as  may  be  seen  from  the  following  calculation  : 

Carbohvdrates  240  grammes  X  4.116  =    OST.Si  calories. 
Proteids  100  "  X  4.937  =    493.70         " 

Fats  100         "  X  9.312  =    838.08         " 


Total  310  =  2319.62 

The  difference  amounting  to  about  one  hundred  calories  can  be 
to  a  great  extent  accounted  for,  however,  when  it  is  remembered 
that  Ilanke  assumed  that  one  gramme  of  proteid,  when  burned  in 
the  body,  would  jDroduce  4.2(33  instead  of  4.937  calories.  That 
the  two  methods  of  investigation  when  properly  applied  to  the 
same  animal  will  give  almost  identical  results  was  shown  by 
Rubner,^  l)y  an  experiment  made  with  a  dog  in  which  the  heat 
produced  by  the  animal  as  determined  directly  by  the  calorimeter 
differed  from  that  as  determined  indirectly  by  analysis  of  the 
excreta  by  less  than  0.5  per  cent.  While  the  heat  produced 
upon  a  mixed  diet  was  regarded  by  Ranke,"  Vierordt,'^  and 
Yoit,^  respectively,  as  amounting  to  2200,  2497,  and  3066  calories, 
according  to  the  more  recent  investigations  of  Danilewsky,-^ 
3210  calories  are  produced  upon  a  mixed  diet,  moderate  work  be- 
ing done  and  as  much  as  3780  calories,  the  work  being  of  a  very 
laborious  character.  Let  us  assume,  however,  with  Ranke  that  the 
heat  liberated  by  the  burning  of  the  food  amounts  to  only  2200 
calories,  that  is,  will  elevate  the  temperature  of  2200  kilo,  of  water 
1  °  C.  or  70  kilo.  31.4°  C.  (154  poimds  56.5°  F.).  Such  an  amount 
of  heat  if  applied  to  the  heating  of  a  hiunan  body  weighing  70 
kilo.  Moidd  elevate  the  temperature  34.1°  C.  (61.3° 'F.),  or  2.1"°  C. 
(4.8°  F.)  higher,  since  a  human  body  consisting  of  only  three-fifths 
water,  42  kilo.,  and  two-fifths  tissue,  28  kilo.,  and  the  latter  having 
a  specific  heat,  0.8  that  of  the  water,  the  2200  heat  units  would  he 
applied  to  heating  the  equivalent  of  64.4  kilo.  (146  pounds)  of 
water,  instead  of  70  kilo.   (154  pounds)  (28  x   0.8  =  22.4  water 

'  Zeitschrift  fiir  Biologie,  Band  30,  189:5,  s.  13ti. 

^Op.  cit.,  s.  207.  3  pl^,^.siologie^  VierteAufl.,  1S71,  s.  257. 

*  Hermann,  Handbuch,  Sechster  Band,  s.  52o. 

spfliiger's  Aixluv,  Band  30,  1883,  s.  190. 


442  .  ANIMAL  HEAT, 

2200 
equivalent,  22.4  +  42  =  64.4,  -_j^  =  34.1°).       In  other  words 

the  tissue  of  the  human  body,  from  this  point  of  view,  bears  the 
same  relation  to  its  water  as  the  brass,  copper,  etc.,  do  to  the  water 
of  the  calorimeter,  the  human  body,  in  foct,  serving  as  a  calorimeter 
for  the  determination  of  the  heat  produced  by  foods  when  l^urned 
within  the  body.  If,  however,  the  heat  produced  upon  a  mixed 
diet  will  elevate  the  temperature  of  a  human  being  weighing  70 
kilo.  34°  C.  in  24  hours,  then  at  the  end  of  that  time  the  temper- 
ature of  such  a  person  should  be  about  70°  C.  (126°  F.),  and  at 
the  end  of  4S  hours  104°  C.  (219°  F.),  instead  of  36°  C.  (98.9°  F.), 
the  normal  temperature  ;  as  a  matter  of  fact,  however,  we  have  seen 
that  the  temperature  of  the  human  body  varies  but  little. 

It  now  remains  for  us,  in  conclusion,  to  endeavor  to  account  for 
this  constant  temperature  somewhat  more  in  detail  than  we  have 
already  done,  and  that  leads  us  to  the  consideration  of  how  the  heat 
produced  is  expended. 

Expenditure  and  Regulation  of  the  Production  of  Heat. 

We  have  seen  that  there  are  produced  within  the  human  body  in 
twenty-four  hours  at  least  2300  calories,  or  heat  units  ;  that  is,  heat 
enough  to  raise  the  temperature  of  2300  kilo,  of  water  1°  C,  or 
23  kilo.  100°  C,  or  from  the  freezing  to  the  boiling  point.  It  is 
very  evident,  therefore,  that  were  such  a  production  of  heat  kept 
up,  and  the  heat  developed  not  dissipated,  but  retained  in  the  body, 
that  the  latter  in  the  course  of  two  days,  would  boil.  A  little  reflec- 
tion will  show,  however,  that,  in  addition  to  the  heat  given  off 
through  radiation  and  conduction,  if  the  temperature  of  the  body 
be  higher  than  that  of  its  surroundings,  that  a  certain  amount  of 
heat  leaves  the  body  in  a  latent  condition,  so  to  speak,  locked  up 
in  the  watery  vapor  exhaled  from  the  lungs  and  skin,  and  from  the 
fact  of  the  solid  and  liquid  food,  and  the  air  breathed  entering  the 
body  at  a  lower  temperature,  15°  C.  (99°  F.),  for  example,  than 
that  of  the  latter,  and  leaving  it  at  the  same  temperature,  37.1°  C. 
(98.9°  F.),  heat  must  also  be  absorbed,  and  that  there  must  be  a 
still  further  expenditure  of  heat  in  the  accomjilishiug  of  bodily  and 
mental  work,  since  there  can  be  no  doubt  tliat,  whatever  be  the  na- 
ture of  muscular  and  mental  energy,  the  latter  is  correlated  in  some 
way  with  heat,  the  disappearance  of  the  one  being  coincident  with 
the  appearance  of  the  other.  Now,  from  the  very  nature  of  the 
case,  the  relative  amounts  of  heat  expended  in  the  ways  mentioned 
must  vary  very  mucli,  according  to  the  character  of  the  climate,  of 
the  quantity  and  (piality  of  air  breathed,  of  food  taken,  of  the 
amount  of  muscular  and  mental  work  performed.  It  is  therefore 
impossible,  if  for  these  reasons  only,  to  indicate  exactly  what  be- 
comes of  the  heat  developed  in  the  body.  Further,  too  much 
importance  must  not  be  attached  to  any  tabular  resume    of  the 


EXPENDITURE  OF  HEAT.  443 

expenditure  of  heat,  since  the  data  upon  which  such  a  resume 
must  be  based  are,  to  a  certain  extent,  assumed.  It  is  only  of- 
fered as  illustrating  in  a  more  detailed  way  the  general  observa- 
tions regarding  the  expenditure  of  the  heat  just  made,  and  as  also 
showing  the  manner  in  which  a  table  could  be  drawn  up  if  all  the 
data  had  been  without  cavil  experimentally  determined.  It  should 
be  mentioned,  however,  that  this  criticism  applies  only  to  the  rel- 
ative amounts  of  expenditure  of  the  heat,  the  total  amount  of  heat 
leaving  the  body  being,  of  course,  that  produced  if  the  temperature 
of  the  body  remains  constant. 

A\"e  will  suppose  that  the  food  of  a  man  weighing  70  kilo.  (154 
pounds)  produces  in  twenty -four  hours  2300  calories,  or  heat  units  ; 
that  the  food  of  such  a  man,  including  the  air  breathed,  be  known  ; 
that  the  specific  heat  of  the  food  be  accepted  as  l^eing  0.8,  and 
that  of  the  air  0.2() ;  that  the  amount  of  watery  vapor  exhaled 
from  the  lungs  and  skin  has  been  determined  ;  that  it  be  admitted 
that  it  requires  582  heat  units  to  vaporize  1  kilo,  of  water  and  that 
the  muscular  work  performed  by  the  man  during  a  day  be  consid- 
ered as  amounting  to  112397  kilogrammeters,  that  is  to  say  the 
man  lifts  112397  kilo,  through  one  meter  (358  tons  through  one 
foot),  and  that  the  amount  of  heat  necessary  to  raise  the  tempera- 
ture of  one  kilo,  of  water  1°  C  or  a  heat  unit  if  applied  mechan- 
ically would  lift  423  kilo,  through  one  meter  (1.3  t(.)ns  through  one 
foot),  then  according  to  the  above  data  the  heat  produced  will  be 
expended  somewhat  as  follows  : 

Expenditure  of  Heat. 

1.5  kO.  (3.3  lbs.)  water        .         .         .     34.5  heat  units.     1.50  per  cent. 
1.5    "     solid  food,  raised  23°  C.  (73°F.)  27.6     "       "  1.20    "       " 

16.0    "     (35.2  lbs.)  air  inspired  .         .     95.6     "       "  4.15    "       " 


19.0  kil.  (41.8  lbs.)                                       157.7 

6.85 

0.4  kil.  (0.8  lbs.)  water  ev.  froni  lungs    232.8 

10.12 

0.6    "     (1.32 lbs.)     "      •'     "     skin       384.1 

16.70 

1.0  kil.  (2.2  lbs.)                                         616.9 

26.82 

Radiation  and  conduction            .          .   1272.6 

55.32 

External  or  muscular  work         .          .     252.8 

10.99 

2300.0     "       "      100.00    "       " 
Ratio  of  muscular  work  to  heat  1  to  9. 

It  will  be  observed,  that  of  the  2300  heat  units  produced  in 
twenty-four  hours,  about  7  per  cent,  are  expended  in  Avarming  the 
food,  including  the  water  and  air  breathed ;  20  per  cent,  in  evap- 
orating the  water  from  the  lungs  and  skin ;  55  per  cent,  in  radia- 
tion and  conduction  from  the  general  surface  of  the  body,  and  about 
11  per  cent.,  or  one-ninth,  of  the  whole  heat  produced  in  the  per- 
formance of  external  or  muscular  work.  Of  the  bo  per  cent,  of 
heat  that  we  have  supposed  is  radiated  or  conducted  away,  part 
must  be  regarded  as  that  heat  which  we  have  seen  is  expended  me- 
chanically in  jjerforming  the  internal  work  incidental  to  the  circu- 


444  ANIMAL  HEAT. 

lation  and  respiration,  bnt  which  in  being  transmuted  finally  into 
heat  aaain,  leaves  the  body  in  that  form  rather  than  as  mechanical 
energy.  AVhile  310  numerical  estimate  can  be  given,  as  yet,  of  the 
relation  existing  between  heat  and  nervous  energy,  there  can  be  no 
doubt,  however,  that  the  latter,  like  all  other  kinds  of  energy,  must 
be  developed  out  of  some  equivalent  form,  and  leaves  the  body  as 
such,  or  as  some  other  mode  of  motion.  That  nervous  energy  is 
developed  out  of  heat  appears  very  probable  from  the  experiments 
of  Lombard,  already  referred  to,  and  by  which  it  was  shown  that, 
while  all  mental  action  was  accompanied  with  the  production  of 
heat,  that  more  heat  disappeared  during  deep  thought  than  during 
reading  to  one's  self,  for  example,  of  emotional  poetry  ;  further,  it 
was  shown  by  the  same  experimenter  that  more  heat  disappeared 
than  when  the  reading  was  aloud — that  is,  had  a  muscular  expres- 
sion, part  of  the  heat  produced  in  the  latter  case  being  applied  to 
making  the  oral  or  muscular  eifort.  It  is  a  matter  of  daily  obser- 
vation that  silent  grief  is  deepest,  that  pent-up  emotion  finds  relief 
in  physical  action.  This  is  in  accordance  with  the  results  of  the 
experiments  just  mentioned,  since  the  heat  that  is  transformed  into 
emotions  or  ideas,  in  the  one  case,  becomes  muscular  action  in  the 
other,  and  just  in  proportion  as  there  is  more  of  the  one,  so  there 
is  less  of  tlie  other.  Hirn^  endeavored  to  determine,  experimen- 
tally, the  exact  quantity  of  heat  expended  in  the  performance  of 
mechanical  work  by  comparing  the  heat  produced  within  a  definite 
time  with  the  work  done,  the  latter  consisting  in  a  man  raising  his 
own  weight  through  a  given  height,  the  man  walking  upon  the  cir- 
cumference of  a  tread-wheel  rotating  in  the  opposite  direction  to 
himself.  According  to  Hirn,  a  man  weighing  75  kilo.,  during  an 
hour's  work  upon  the  tread-wheel  placed  within  the  calorimeter, 
produced  4.">0  heat  units,  whereas,  judging  from  the  amount  of  oxy- 
gen absorbed  and  carbon  dioxide  exhaled,  500  heat  units  were  pro- 
duced. What,  then,  became  of  the  70  extra  heat  units?  Accord- 
ing to  Hirn,  it  was  at  the  expense  of  this  amount  of  heat  that  the 
29,610  kilogrammeters  of  work  were  accomplished — that  is,  of 
raising;  75  kilo,  throug-h  nearlv  40(J  meters 

(423x70  =  2-='«^«  =  394). 

On  account,  however,  of  the  errors  incidental  to  the  construction 
of  the  apparatus,  and  of  the  amount  of  heat  produced  as  deter- 
mined from  the  oxygen  absorbed  being  estimated  as  too  high,  the 
results  of  Hirn,  as  just  given,  cannot  be  accepted ;  nevertheless, 
the  difference  between  the  amount  of  heat  that  appeared,  as  such, 
and  that  Av])i(.-li  ought  to  have  appeared,  can  only  be  accounted  for 
on  the  supposition  that  part  of  the  heat  produced  was  expended  in 
the  performance  of  mechanical  work,  and,  as  a  corollary,  it  follows 
that  less  heat  a]ipcars  during  a  muscular  contraction,  when  accom- 
'  Op.  cit.,  Tome  i.,  p.  35. 


REGULATION  OF  TEMPERATURE.  445 

panied  Avith  work,  than  when  without,  and  which  accords  with  daily 
experience. 

Having  considered  the  manner  in  which  animal  heat  is  produced 
and  expended,  it  remains  for  us  now  to  account,  so  far  as  is  possible, 
for  the  fact  tliat  the  temperature  of  a  hot-blood  animal  is  maintained 
nearly  constant,  notwithstanding  the  variations  in  that  of  its  sur- 
roundings. Among  the  conditions  regulating  the  production  of  ani- 
mal heat  may  be  mentioned  the  taking  of  solid  and  liquid  food,  the 
character  of  the  respiration  and  circulation,  the  action  of  the  skin, 
the  influence  of  bodily  size. 

While  the  amount  of  heat  produced  will  depend  on  the  quality 
and  quantity  of  the  food,  the  mere  taking  of  the  latter  in  the  form 
of  hot  or  cold  drinks,  for  example,  with  the  view  of  increasing  or 
diminishing  the  general  temperature  of  the  body,  as  is  so  commonly 
done,  will  have,  as  already  mentioned,  but  little  effect.  The  effect 
of  cold  drinks  in  lowering  the  general  temperature  of  the  body  must 
be  also  ecjually  slight  and  temporary.  On  the  other  hand  the  effect 
of  a  hot  drink,  as  we  have  seen,  may  be  exactly  opposite  to  what 
might  have  been  expected,  not  only  through  the  cooling  effect  due 
to  the  evaporation  as  in  the  drinking  of  hot  tea,  but  on  account  of 
the  specific  substance  of  which  the  hot  drink  consists.  Thus,  for  ex- 
ample, if  hot  spirits  be  taken,  while  at  first  a  sense  of  warmth  is 
experienced,  with  the  paralysis  of  the  vasomotor  nerves  by  the  al- 
cohol, a  greater  quantity  of  blood  flowing  to  the  skin  than  usual,  a 
proportionally  larger  quantity  of  heat  will  be  lost  from  the  general 
surface,  and  the  effect  of  the  hot  drink  will  be  in  the  long  run,  there- 
fore, to  lower  the  temperature  of  the  body  rather  than  to  raise  it. 
It  has  already  been  mentioned  that  about  4.1  per  cent,  of  the  heat 
produced  is  expended  in  warming  the  inspired  air,  and  it  might 
naturally  be  suj)posed  that  if  the  respiration  be  quickened  and  the 
amount  of  air  inspired  increased,  that  a  proportionally  greater 
quantity  of  heat  would  then  be  expended  in  warming  it.  Such 
Avould  appear  to  be  the  case,  dogs  and  other  animals  panting  when 
overheated,  since  they  sweat  only  in  those  parts  destitute  of  fur  or 
hair,  and  the  cooling  effect  of  the  perspiration  being  absent,  the  ex- 
cess of  heat  developed  is  carried  away  in  the  expired  air.  The  res- 
piration when  quick,  will  be  more  efficient,  therefore,  in  lowering  the 
general  temperature  of  the  body  than  when  slow.  Hence,  also,  the 
rapidity  of  the  breathing  in  heat  dyspnoea,  a  condition  due  to  the 
exposure  of  the  body  to  a  high  temperature.  Under  such  circum- 
stances a  considerable  amount  of  heat  is  carried  away  in  the  expired 
air,  and  the  temperature  of  the  body  is  thereby  prevented  from  rising 
as  high  as  it  would  be  without  such  compensatory  influence.  On 
account  of  so  much  heat  being:  g-iven  off  from  the  skin  amountino; 
through  radiation,  conduction,  and  evaporation,  to  nearly  eighty  per 
cent,  of  the  heat  produced,  any  change  in  the  condition  of  the  latter, 
as  regards  its  structure  or  the  amount  of  blood  circulating  through 
it,  etc.,  will  materially  influence  the  general  temperature  of  the  body. 


446  ANIMAL  HEAT. 

Were  the  temperature  of  the  skin  constant,  the  amount  of  heat  given 
oflF  or  taken  up  by  it  would  depend  simply  upon  that  of  the  sur- 
rounding atmosphere,  the  skin  losing  heat  if  the  temperature  of  the 
iiir  was  lowered,  and  gaining  heat  when  that  of  the  air  was  elevated. 
As  a  matter  of  fact,  however,  when  the  body  is  exposed  to  a  tem- 
perature cooler  than  its  own,  the  vessels  of  the  skin  contracting,  the 
general  surface  becomes  cooler,  the  difference  between  the  temper- 
ature of  the  body  and  the  surrounding  air  being  diminished,  the  loss 
of  heat  is  correspondingly  diminished  ;  on  the  other  hand,  when  the 
body  is  exposed  to  a  higher  temperature  than  its  own,  the  vessels  of 
the  skin  expanding,  the  general  surface  becomes  warmer,  and  a  cor- 
respondingly greater  amount  of  heat  is  lost. 

It  is  a  cause  frequently  of  surprise  to  most  persons  to  learn  that, 
no  matter  how  hot  or  cold  they  may  feel,  the  temperature  of  their 
body  nevertheless  remains  practically  the  same.  From  what  has 
just  been  said,  however,  as  regards  the  action  of  the  skin  in  regulat- 
ing the  temperature  of  the  body,  it  is  obvious  that  in  the  cooling 
of  the  body  through  the  evaporation  from  the  cutaneous  surface, 
when  exposed  to  a  higher  external  temperature,  the  greater  quan- 
tity of  hot  blood  then  circulating  through  the  cutaneous  vessels 
will,  in  impressing  the  sensory  nerves,  give  rise  to  a  general  sense 
of  warmth,  so  that  while  we  feel  warmer  our  body  is  actually  get- 
ting cooler  through  the  loss  of  heat  involved  in  the  evaporation. 
On  the  other  hand,  when,  through  the  exposure  to  extreme  cold,  the 
cutaneous  vessels  are  diminished  in  size,  the  smaller  quantity  of  hot 
blood  circidating  through  them  will  give  rise  to  a  sense  of  coolness, 
so  that  while  we  feel  cool  our  body  is  actually  becoming  warmer 
through  retention  of  the  heat  of  the  blood  within  it.  The  feeling 
Avarm  or  cold  depends,  then,  simply  upon  the  relative  amounts  of 
blood  circulating  in  the  skin. 

The  effect  of  the  successive  exposure  of  the  body  to  cold  and 
heat,  as  just  described,  is  well  seen  in  the  taking  of  cold  baths. 
While  in  the  bath,  the  vessels  of  the  skin  being  contracted,  the 
latter  is  pale  and  cold,  and  the  heat  is  retained,  on  emerging  from 
the  bath  the  vessels  being  dilated,  the  skin  is  red  and  warm,  and 
heat  is  then  given  oif  from  the  surface.  When  we  come  to  study 
the  structure  of  the  skin  somewhat  in  detail,  we  shall  see  that  its 
adipose  tissue,  being  a  bad  conductor,  prevents  any  great  amount 
of  heat  from  lacing  given  oif  from  the  inner  parts  of  the  body  to 
the  surface,  and  so  lost.'  This  effect  being  especially  well-marked 
in  those  cases  where  the  difference  in  temperature  on  both  sides  of 
the  skin  does  not  amount  to  more  than  about  9°  C.  (16°  F.),  the 
significance  of  tlie  good  effect  of  wearing  clothing  becomes  apparent, 
since  under  such  circumstances  the  body  of  a  man  is  surrounded  by 
a  layer  of  air  having  a  temperature  of  about  .'>0°  C.  (<S6°  F.),  the 
temperature  under  the  skin  being ^  8(5°  C.  (96.8°  F.),  the  difference 

Hvlui?,  Zeits.  fill-  Biologic,  x.,  s.  73. 

2Be«im'rel  and  Brescliet,  Ann.  des  Sciences  N;it.,  2ierae  ser.,  Tome  iii.,  p.  257  ; 
Tome  iv.,  p.  24:!. 


AMOrXT  OF  HEAT  PEODUCED.  -147 

amounting,  therefore,  to  only  0°  C.  (12.8°  F.).  Clothing  in  man 
plays  the  same  part  as  hair,  fur,  and  feathers  in  animals,  the  air 
inclosed  within  the  latter,  through  being  a  bad  conductor,  practically 
prevents  any  great  loss  of  heat  from  the  general  surface.  ]Man, 
however,  is  far  better  able  to  adapt  himself  to  changes  in  climate 
than  most  animals,  since  through  change  of  clothing,  food,  etc.,  and 
free  action  of  the  skin,  he  is  able  to  live  in  tropical  or  temperate 
recrions  as  well  as  in  arctic  ones. 

It  has  already  been  mentioned  that  through  the  evaporation  of 
the  water  from  the  skin  as  sweat  about  sixteen  per  cent,  of  the  heat 
produced  is  expended,  and  that  the  amount  of  water  evaporated  will 
depend,  among  other  conditions,  upon  the  amount  of  water  already 
existing  in  the  atmosphere.  It  is  very  evident,  therefore,  that  the 
temperature  that  a  person  can  endure  must  soon  reach  a  limit,  since 
if  the  temperature  of  the  surrounding  air  keeps  continually  rising, 
and  becomes  saturated  with  watery  vapor  and  is  unchanged,  the  body, 
notwithstanding  what  has  just  been  said  of  the  action  of  the  lungs, 
skin,  etc.,  will  become  as  hot  as  its  surroundings.  It  is  easier  to 
keep  out  cold — that  is,  to  keep  in  the  bodily  heat  by  proper  food, 
clothing,  and  active  exercise — than  to  keep  out  heat.  Travellers, 
when  properly  fed  and  clothed,  complain  less  of  the  cold  of  the 
arctic  regions  than  of  the  heat  of  the  tropics — indeed,  it  is  said  that 
while  crossing  the  Eed  Sea,  at  certain  seasons  of  the  year,  with  all 
precautions  taken,  foreigners  at  times  fear  they  will  lose  their  reason, 
the  heat  being  so  unendurable. 

An  important  condition  in  regulating  the  production  of  animal 
heat,  and  which  may  here  be  appropriately  considered,  is  the  influ- 
ence of  the  size  or  bulk  of  the  body  of  an  animal  as  compared  with 
its  surface  area ;  for  the  ratio  of  the  bulk  to  the  surface  area  being- 
proportional  to  the  size  of  the  animal,  and  the  heat  produced  being 
proportional  about  to  the  bulk,  and  the  heat  lost  to  the  surface  area, 
it  follows  that  of  two  animals  of  similar  shape  but  of  different  sizes, 
that,  other  things  being  equal,  the  larger  animal  of  the  two  will 
lose  relatively  the  least  heat.  Suppose,  for  example,  of  two  animals 
of  similar  shape,  that  one  be  ten  times  as  long  as  the  other,  then, 
while  the  loss  of  heat  in  the  larger  animal  will  be  as  its  surface  area 
10",  or  100  times  as  great  as  the  small  one,  the  heat  produced  by 
the  larger  animal  will  be  as  its  bulk  10^,  or  1000  times  as  great. 
It  follows,  therefore,  that  if  two  such  animals  have  the  same  tem- 
perature that  the  small  animal  either  retains  its  heat  much  better 
than  the  large  one  or  that  it  produces  heat  far  more  actively.  That 
the  latter  is  the  case  appears  from  the  fact  of  a  small  animal  taking 
more  food  relatively  than  a  large  one,  and  of  its  circulation  and 
respiration  being  absolutely  more  frequent.  Small  animals  are  also 
more  readily  affected  by  changes  in  the  external  temperature  than 
large  ones,  the  temperature  of  a  rabbit,  for  example,  under  such 
circumstances,  varying  more  than  that  of  a  dog,  that  of  a  young 
animal  more  than  that  of  an  old  one  of  the  same  kind,  as  that  of 


448  ANIMAL  HEAT. 

the  voung  child,  as  compared  with  that  of  the  adult.  Large  ani- 
mals, like  the  whale  or  hippopotamus,  live  either  habitually  or  tem- 
porarily in  the  water,  the  latter  being  a  better  conductor  of  heat 
than  air.  On  the  other  hand,  the  smallest  homoiothermal  animals 
live  in  the  tropics,  while  of  animals  of  the  same  kind  the  largest 
ones  live  in  temperate  or  cold  regions.  Of  course,  what  has  just 
been  said  with  reference  to  the  bulk  and  surface  area  in  the  pro- 
duction and  loss  of  heat  is  not  inconsistent  with  what  daily  obser- 
vation teaches  when  man  or  animal  changes  the  position  of  the  body, 
for  as  the  external  temperature  varies  if  the  body,  when  cold,  be 
contracted,  less  surface  being  then  exposed  less  heat  will  be  lost, 
whereas,  if,  when  overheated,  the  body  and  limbs  be  stretched  to 
the  utmost,  more  surface  being  exposed,  then  more  heat  will  be  lost. 

As  a  further  illustration  of  the  manner  in  which  the  production 
of  heat  is  regulated  in  reference  to  climate,  may  be  mentioned  the 
well-known  facts  already  alluded  to,  of  the  diet  of  the  inhabitants 
of  cold  countries  being  so  different  from  that  of  those  of  hot  ones, 
the  amount  of  food  consumed  by  the  former  not  only  being  greater, 
but  the  food  consisting  largely  of  fat  and  oil,  substances  eminently 
suitable  for  the  production  of  heat.  A  corresponding  diiference  in 
diet  is  also  made  use  of  by  the  inhal)itants  of  temperate  regions  in 
winter,  as  compared  with  summer,  and  with  the  same  effect  of  in- 
creasing the  production  of  heat  in  cold  and  of  diminishing  it  in 
hot  weather.  It  might  be  supposed  that  a  loss  of  heat,  in- 
ducing an  increased  production,  would  be  shown  from  the  amount 
of  oxygen  absorbed  and  carbon  exhaled,  and  notwithstanding  the 
numerous  difficulties  incidental  to  such  an  experimental  investiga- 
tion, it  may  be  said  that  the  general  result  obtained  by  Lavoisier, 
Crawford,  and  De  la  Roche,^  as  well  as  l)y  modern  experimenters, 
as  Rohring  and  Zuntz,"  Colasanti,^  Pfliiger,^  Prince  Theodore,^ 
Voit,"  etc.,  was,  as  a  rule,  that  the  consumption  of  oxygen  and  ex- 
halation of  carbon  dioxide  increased  with  a  fall  in  the  external  tem- 
perature and  diminished  with  a  rise  in  it,  though,  under  certain 
circumstances,  hot-blooded  animals  behaved  as  cold-blooded  ones — 
that  is,  the  absorption  of  oxygen  and  exhalation  of  carbon  dioxide 
increase  with  a  rise  in  the  external  temperature  and  diminish  with 
a  fall  in  it.  Within  certain  limits  at  least,  it  may  be  said  that, 
when  a  man  or  animal  is  exposed  to  cold,  the  production  of  heat  is 
increased,  as  shown  by  the  greater  amount  of  oxygen  absorbed  and 
carbon  dioxide  exhaled,  but  when  exposed  to  heat  the  reverse  is  the 
case  and  less  heat  is  jiroduced. 

While  we  have  seen  that  the  heat  produced  by  a  man  or  animal 
is  due  to  the  oxidation  of  the  food,  there  can  be  no  doubt  but  that 
the  regulation  (thcrmotaxis),  of  heat  production  (thermogenesis),  in 
relation   to  heat  dissipation  (thermolysis),  is   accomplished  by  the 

•Op.  cit.  2pfl(jg.ei-'s  Arcliiv,  1871,  iv.,  s.  57. 

»j:benda,  xiv.,  s.  9-2.  ■•Ebeiida,  1878,  xviii.,  s.  247. 

sZeitschrift  f.  Biol.,  1878,  xiv.,  s.  51.         6£benda,  .s.  57. 


AXniAL   HEAT.  449 

nervous  system.  AVhile  the  exact  manner  in  which  the  production 
and  dissipation  of  heat  is  influenced  by  the  ners'ous  system  is  as 
yet  but  imperfectly  understood,  recent  researches  render  it  highly 
probable  that  there  exist  what  may  be  called  thermogenic  centei-s 
situated  in  the  spinal  cord  and  brain  which  receive  impulses  trans- 
mitted to  them  by  afferent  nerves  from  the  periphery  and  emit 
reflexly  impulses  which  are  transmitted  in  a  reverse  direction  to 
muscles,  glands,  blood  vessels,  etc.  Indeed  it  is  only  by  assimiing 
the  existence  of  some  such  nervous  mechanism  ;  of  thermo-inhibi- 
tory  and  thermo-accelerator  centers,  that  we  can  explain  many  of 
the  phenomena  of  animal  heat  just  mentioned,  such  as  for  example, 
that  a  rise  or  fall  in  the  external  temperature  causes  a  diminution 
or  increase  in  heat  production  respectively. 

29 


CHAPTER   XXV. 

THE  KIDNEYS  AND  URINE. 

We  have  seen  that  duriuo;  dio-estion  the  food  is  transformed  into 
peptone,  glucose,  emulsified  fats,  etc.,  that  through  absorption  and 
the  circulation  the  latter  are  carried  to  the  tissues,  supplying  the 
cells  of  the  same  with  materials,  which,  either  in  being  assimi- 
lated serve  for  repair,  groAvth,  or  development,  or  in  being  de- 
stroyed are  a  source  of  energy  ;  that  the  destructive  metamorphosis 
going  on  in  the  body  caused  by  fermentation,  hydration,  oxidation, 
etc.,  incidental  to  life,  the  final  outcome  of  which,  at  least,  is  the 
production  of  carbon  dioxide,  water,  and  urea,  is  due,  to  a  far 
greater  extent,  to  the  destruction  of  the  food  by  the  cells  of  the 
tissues  than  to  the  destruction  of  the  tissues  themselves ;  that,  by 
means  of  the  lungs,  oxygen  is  introduced  into  the  system,  and  car- 
bon and  water  removed,  the  skin,  as  we  shall  see,  in  the  latter 
respect,  acting  also,  to  a  certain  extent,  in  the  same  way.  In  con- 
cluding our  account  of  nutrition,  it  remains  for  us  still  to  consider 
the  structure  of  the  kidneys,  and,  so  far  as  is  known,  the  manner 
in  which  the  urine  is  excreted  by  them  from  the  system.  It  will 
be  observed  that  we  speak  of  the  urine  as  being  excreted  by  the 
kidneys,  and  it  may  be  appropriately  mentioned  here  that,  while  it 
would  be  equally  correct  to  refer  to  the  secreting  as  w^ell  as  to  the 
excreting  of  the  urine,  the  word  secretion,  however,  is  usually 
made  use  of  in  referring  to  a  glandular  product  of  some  use,  such 
as  the  saliva,  gastric  juice,  etc.,  the  term  excretion  being  confined 
to  products  of  no  use,  to  be  gotten  rid  of,  such  as  the  urine.  In 
this  sense,  the  bile,  as  we  have  seen,  is  both  an  excretion  and  a 
secretion. 

A  kidney  may  be  regarded,  functionally,  as  consisting  essentially 
of  one  or  more  tubes,  opening  externally  at  one  end,  but  termina- 
ting internally  at  the  other  end  in  blind,  sac-like  capsules.  The 
tubes  and  their  capsules  are  lined  with  an  epithelium,  and  covered 
more  or  less  exteriorly  with  blood  vessels,  the  latter  su})plying  the 
tubes  with  blood,  from  which  are  excreted,  by  the  cells  of  their 
lining  epithelium,  the  urea,  water,  etc.,  constituting  the  urine  ; 
elaborated  and  transported  l)y  the  cells  into  the  interior,  or  lumen  of 
the  tul)es,  the  m'ine  passes  finally  tlience  out  of  the  ])ody.  Such  a 
disposition  as  that  just  described,  obtains  in  the  kidneys  of  the 
lower  vertebrates.  In  bdellostoma,  for  example,  one  of  the  cyclo- 
stomous  fishes,  the  kidney  consists  (Fig.  212,  A)  of  a  ureter  (a), 
from  which  are  given  oif,  at  right  angles,  short  uriniferous  tuljules 
(6,  b),  terminating   in    capsular-like   Malpighian  bodies   (c),  lined 


STRUCTURE  OF  THE  KIDNEY. 


451 


Fig.  212. 


Kidney  of  bdellostoma.     The  same  luaguified.    (Muller. 


with  an  epithelium,  and  supplied  externally  with  blood  vessels 
(Fig.  212,  B  d,  c).  The  kidneys  in  man,  smooth,  dark  red,  com- 
pressed, oval  bodies,  deeply  set  in  the  lumlxar  re_(i:ion,  opposite  the 
last  dorsal  and  two  or  three  upper  lumbar  vertebne,  present  such  a 
characteristic  form 
through  the  presence  of 
a  deep  notch  on  their 
inner  side  that  the  term 
reniform  or  kidney-form, 
derived  from  them,  is 
often  conveniently  made 
use  of  in  describing  vari- 
ous other  natural  objects. 
If  a  kidney  be  divided 
longitudinally  through  its 
breadth  (Fig.  213),  it  will 
be  observed  that  the  hilus 
or  notch  leads  into  a  cav- 
ity, the  sinus  of  the  kid- 
ney, which  is  filled  in  the 
natural  condition  with 
the  pelvis  (4),  or  expanded  upper  portion  of  the  ureter  (5),  and 
the  renal  vessels  (6,  7)  and  nerves.  Such  a  section  further  shows 
that  the  kidney  consists  apparently,  at  least,  of  two  distinct  sub- 
stances, an  internal  striated  portion,  the  medullary  substance  (2), 

and  an  external  ffranular-lookino; 
portion,  the  cortical  substance  (1). 
This  distinction  is,  however,  a 
purely  artificial  one,  being,  in  re- 
ality, due  to  tlie  urinifcrous  tubule 
(Fig.  214),  coursing,  in  its  begin- 
ning (8),  through  the  medullary  or 
interior  portion  in  a  straight  man- 
ner, Init  at  its  termination  (5),  in 
the  cortical  or  external  portion  in 
a  convoluted  one.  Theoretically, 
at  least,  if  the  uriniferous  tubules, 
of  which  the  kidney  largely  con- 
sists, could  be  unravelled  a  n  d 
straightened  out,  the  distinction  of 
medullary  and  cortical  substance 
would  then  cease  to  exist.  It  is, 
also,  very  apparent,  as  observable 
in  a  longitudinal  section  (Fig.  213), 
that  the  interior,  or  so-called  medul- 
lary, portion  of  the  kidney,  is  dis- 
posed in  from  ten  to  fifteen  conical  masses,  the  pyramids  of  Malpighi 
(2),  so  named  after  the  celebrated  anatomist  of  that  name,  the  bases 


Fir;.  213. 


1. 


Longitiuliual    section    of   a   kidney. 
Cortical  substance.    2.  Renal  pyramid. 
Renal  papilUe.    4.   Pelvis.    5.  "Ureter. 
Renal  artery.     7.  Renal  vein.     8.  Branches 
of  the  latter  vessels  in  the  sinus  of  the  kid- 
ney.    (Lkidy.) 


0. 


452 


THE  KIDNEYS  AND  URINE. 


of  which  are  imbedded  in  the  cortical  substance,  while  the  free  sum- 
mits, or  papillae  (3),  of  the  same  project  into  the  sinus  of  the  kid- 
ney. It  may  be  mentioned  in  this  connection  that  the  Malpighian 
pyramids,  together  with  the  cortical  substance  enveloping  each  of 
their   bases,  the  columnse,  or  septa  Bertini,'  correspond  to  the  dis- 


FiG.  214. 


Diagram  and  course  of  two  uriaiferous  tubules.     A.  Cortex.     P.  Poundary  zone.    r.  Papillary 
zone  of  the  medulla,    a,  a'.  Superficial  and  deep  layers  of  cortex,  free  from  glomeruli. 

tinct  lobules  of  wliich  the  human  kidney  consists  in  the  ftetal  state, 
and  while  becoming  indissolubly  blended  as  development  advances 
in  man,  remain  quite  distinct  throughout  life  in  many  of  the  mam- 
malia, as  in  the  otter  and  bear  among  the  carnivora,  and  in  the 

'Mem.  del' Acad,  des  Sciences,  1744,  p.  77, 


STRUCTURE  OF  THE  KIDNEY.  453 

cetacca — whales,  dolphins,  for  example.  If  now  the  apex  or  sum- 
mit of  one  of  the  Malpighian  pyramids,  or  papillae,  be  examined 
microscopicallv,  very  minute  orifices  (between  200  and  500)  will 
be  observed,  each  of  which  is  the  beginninu:  of  a  uriniferous  tubule 
(Fig.  214),  and  which  will  be  seen,  if  followed  in  longitudinal  sec- 
tion, to  pursue,  as  a  tube  of  Bellini,^  a  nearly  straight  course 
through  the  medullary  portion,  as  already  mentioned,  each  Bellinian 
tubule,  however,  soon  dividing  and  subdividing,  the  bundle  formed 
by  the  division  of  the  latter,  at  the  beginning  of  the  cortical  sub- 
stance, constituting  the  pyramids  of  Ferrein.-  The  uriniferous 
tubule  followed  thence  outwardly  toward  the  cortical  substance, 
then  turns  back  upon  itself  toward  the  medullary  portion,  and 
turning  once  more  toward  the  cortical  portion  as  the  ascending  and 
descending  loops  of  Henle '^  becomes  quite  convoluted,  constitut- 
ing the  cortical  tubules  of  Ferrein,*  terminating',  finally,  in  a  pouch- 
like dilatation,  the  capsule  of  Muller,'  the  latter,  as  we  shall  see, 
being  inflected  over  the  so-called  ^Nlalpighian  vascular  glomerulus, 
the  capsule  and  glomerulus  together  constituting  a  Malpighian  cor- 
puscle, as  first  described  by  Malpighi.'' 

The  uriniferous  tubules,  held  together  by  connective  tissue,  the 
stroma  about  50  mm.  (2  inches)  in  length,  and  with  a  diameter 
varying  between  the  1  and  ^V  o^  ^  millimeter  {-^-^-^  and  g^-g-  of 
an  inch),  the  Bellinian  tubules  being  the  largest,  consist  of  base- 
ment membrane  lined  with  epithelium  ;  the  latter,  however,  like 
the  diameter  of  the  tube,  differing  considerably  according  to  the 
part  examined,  being,  for  example,  distinct  and  columnar,  ^nth  a 
wide  lumen  in  the  straight,  or  Bellinian  tubules,  but  indistinct 
granular,  with  little  or  no  lumen  in  the  convoluted  tubules,  or 
tubules  of  Ferrein. 

The  kidneys  are  very  vascular,  the  arteries  being  large  vessels  in 
proportion  to  the  size  of  the  organs  which  they  supply.  The  renal 
artery  (Fig.  213,  6),  as  it  approaches  the  hilus  of  the  kidney,  sub- 
divides into  four  or  five  branches,  which,  entering  the  sinus,  pass 
thence  between  the  pjTamids  into  the  substance  of  the  kidney,  di- 
viding and  subdividing  as  they  ramify  through  the  cortical  sub- 
stance, each  branch  finally  terminating  in  an  afferent  vessel  (Fig. 
215,  1)  leading  to  a  Malpighian  glomerulus,  so  called  after  their  dis- 
coverer, Malpighi,  around  which,  as  already  mentioned,  as  first 
shown  by  Bowman,"  is  inflected  the  capsule  of  ]Muller,  or  the 
end  of  the  uriniferous  tubule.  Each  Malpighian  glomerulus 
(Fig.  215),  about  the  J  of  a  mm.  (-j-^-g-  of  an  inch)  in  diameter, 
including  the  investing  capsule,  consists  of  a  close-set,  spheroidal, 

1  Laurentii  Bellini,  Exercitatio  anatomica  de  structura  et  asu  renum,  pp.  64-72, 
Fig.  X.     Amstelodami,  1665. 

2  Mem.  de  I'Acad.  des  Sciences,  1749,  p.  284,  pi.  14  and  15. 

^  Abhand.  d.  K.  Ges.  d.  Wiss.  zu  Gottingen,  1862,  x.  *  Op.  cit. 

5  De  glandularum  secernentium  struclura  penitiore,  p.  101.     Lipsiis,  1830. 
5  Marcelli  Malpighi,  Philosophii  et  3Ied.  Bon  E.  Soc.  Reg.  Operum,  Tom.  sec. 
Londini,  1686.     De'Eenibus.  '  Phil.  Trans.,  1842,  p.  57. 


454 


THE  KIDNEYS  AND   URINE. 


Fig.  215. 


knot-like  net  of  capinarics,  from  which  emerge  an  efferent  vessel 
2,  which,  together  with  other  efferent  vessels,  forms  a  capillary  net- 
work {p)  along  and  between  the  uriniferous  tubules.  From  this 
network  the  renal  veins  (;■)  originate,  which,  converging,  form  the 
external  surface  of  the  kidney  toward  the  bases  of  the  pyramids, 
pass  through  the  sinus,  and,  becoming  confluent,  emerge  as  one 
trunk  (Fig,  213,  7)  from  the  hilus.  The  water,  urea,  etc.,  having 
been  excreted  by  the  epithelial  cells  lining  the  uriniferous  tubules 
from  the  blood  brought  to  them  by  the  renal  artery,  elaborated  as 
the  urine,  passes  down  through  the  uriniferous  tubules,  finally 
dribbling  out  of  tlieir  orifices  situated,  as  already  mentioned,  at  the 
apices  or  summits  of  the  Malpighian  pyramids 
(Fig.  213,  3),  one  or  more  of  the  latter  pro- 
jecting into  one  of  the  caliccs  or  infundibula, 
into  whicli  the  pelvis  or  upper  expanded  por- 
tion of  tlie  ureter  (4)  (within  the  sinus)  is 
subdivided,  a  further  passage-way  is  provided 
l)y  which  the  urine  is  conveyed  to  a  temporary 
reservoir — the  bladder — a  musculo-membra- 
nous  sac,  from  which  it  is  finally  eliminated 
during  micturition  from  the  body.  The  cali- 
ces,  pelvis  of  the  ureter,  and  the  ureter  proper 
consist  externally  of  a  fibrous  coat,  of  a  mid- 
dle unstriated  muscular  one,  and  internally 
of  a  lining  mucous  membrane.  The  fibrous 
layer  of  the  calices  at  the  base  of  the  pyra- 
mid becomes  continuous  with  that  investing 
the  sinus  of  the  kidney,  the  latter,  in  turn, 
being  a  continuation  of  its  external  fibrous 
capsule  ;  the  middle  muscular  layer,  thinning 
away  at  the  pelvis,  disappears  altogether  at 
the  base  of  the  pyramids,  while  the  mucous 
membrane  of  the  calyx  is  reflected  upon  the  pyramids,  becoming 
continuous  at  the  orifice  with  that  of  the  uriniferous  tubule.  It  is 
evident,  therefore,  that  leaving  out  of  consideration  the  anatomical 
details  just  described,  that  a  kidney,  physiologically,  may  be  re- 
garded as  consisting  essentially  of  one  or  more  uriniferous  tubules, 
supplied  with  blood,  a  uriniferous  tubule  consisting  of  basement 
membrane  separating  blood  on  the  one  side  from  a  secreting  cell  on 
the  other.  When  reduced,  therefore,  to  its  simjjlest  expression,  the 
structure  of  the  kidney  does  not  differ  in  any  way  from  that  of 
glands  in  general. 

Having  studied  the  structure  of  the  kidneys,  let  us  consider  now 
the  manner  in  which  the  urine  is  secreted.  That  the  latter  is  ex- 
creted but  not  elaborated  by  the  kidneys  to  any  extent  appears  not 
only  from  Avhat  has  been  learned  of  the  origin  of  its  constituents 
and  of  their  accumulation  after  ligation  of  the  renal  arteries,  ex- 
tirpation of  the  kidneys,  etc.,  but  from  the  fact,  also,  that  in  certain 


Diagram  showing  the  rela- 
tion of  the  Malpighian  body 
to  the  uriniferous  ducts  and 
l)lood  vessels,  a.  One  of  the 
interlobular  arteries.  1.  Ef- 
ferent artery  passing  into  the 
glomerulus,  m.  Capsule  of 
the  Malpighian  body.  /.  Uri- 
niferous tube.  2.  Efferent 
vessels  which  subdivide  in 
the  plexus  p,  surrounding  the 
tube,  and  finally  terminate  in 
the  branch  of  the  renal  vein, 
e.     f  Bowman.) 


EXCRETION  OF  URINE.  455 

cases  referred  to  by  Haller/  j^ysten/  Burdacb,^  and  Laycock/  in 
which  the  kidneys  were  either  congenitally  absent  or  not  acting, 
the  urine,  or  fluid  closely  resembling-  it  at  least,  was  vicariously 
excreted  by  the  skin,  pleura,  peritoneum,  mucous  membrane  of  the 
intestinal  canal,  salivary,  lachrymal,  and  mammary  glands,  ears, 
nose,  etc.  Such  being  the  case,  the  question  for  our  consideration 
is  the  determination  of  the  manner  in  which  the  diiferent  constitu- 
ents of  the  urine  arc  separated  by  the  renal  epithelium  from  the 
blood  supplying  the  kidney. 

We  have  just  seen  that  the  kidney  is  made  up  of  uriniferous 
tubules,  each  tubule  consisting  of  two  distinct  portions,  a  tubular 
part  and  a  capsular  part,  both  lined  with  epithelium  and  supplied 
with  blood  vessels.  The  blood  vessels  invaginated  by  the  capsular 
portion  being,  however,  disposed  in  a  capillary  knot  of  far  greater 
aggregate  capacity  than  the  branch  of  the  renal  artery  from  which 
it  originates,  and  of  the  single  exit  vessel  in  which  it  terminates, 
the  blood  must  be,  therefore,  retarded  as  it  flows  within  the  capsule, 
and  the  escape  of  its  water  much  favored  by  such  a  disposition. 
That  the  function  of  the  capsular  part  of  the  uriniferous  tubule,  as 
shown  by  Bowman,  is  to  filter,  drain  off  the  water  from  the  blood, 
the  urea,  etc.,  being  excreted  by  the  tubular  part  and  then  washed 
out,  so  to  speak,  by  the  water,  is  confirmed  by  what  is  seen  in  rep- 
tiles. Thus  in  the  boa,  uric  acid,  the  equivalent  of  the  urea  of 
mammals,  excreted  in  a  solid  state  is  only  found  in  the  tubular  por- 
tion of  the  uriniferous  tubule.  The  excretion  of  the  urine  will  then 
depend  essentially  upon  the  relation  of  the  pressure  of  the  blood  in 
the  renal  arteries,  120  to  140  mm.  mercury,  to  that  of  the  fluid 
within  the  tubules  and  ureter,  10  to  40  mm.,  the  amount  of  urinary 
materials  in  the  blood,  and  the  activity  of  the  renal  epithelium. 
The  influence  of  the  blood  pressure  is  shown  from  the  fact  that  the 
excretion  of  urine  is  diminished  with  the  lowering  of  the  pressure 
of  the  blood  whether  brought  about  generally  or  locally,  as,  for 
example,  by  division  of  the  spinal  cord  or  stimulation  of  the 
splanchnic  nerves ;  in  fact,  if  the  blood  pressure  falls  as  low  as 
40  mm.  of  mercury  the  excretion  of  the  urine  ceases.  On  the 
other  hand,  with  the  elevation  of  the  blood  pressure  as  induced  by 
stimulation  of  the  spinal  cord  or  by  division  of  the  splanchnic 
nerves  the  excretion  of  the  urine  is  increased.^  Experimental  in- 
vestigation has  shown,  however,  that  the  excretion  of  the  urine 
varies  not  only  with  the  pressure,  but  also  with  the  quantity  of 
blood  flowing  through  the  renal  glomeruli.  Thus,  for  example,  in 
experiments  made  with  excised  kidneys,  artificially  supplied  with 

1  Elementa  Physiologire,  Tomns  ii.,  p.  370. 

2  Reeherches  de  la  Phys.  et  de  Chimie,  p.  2G5. 

3  Pliysiologie  (Jourdain),  Tomns  vili.,  p.  2-18. 
*  Ediii.  Med.  and  Sui-o-.  .Journal,  18."5S. 

^The  influence  exerted  by  the  spinal  cord  and  splanchnic  nerves  upon  the  blood 
pressure  in  the  kidneys  will  be  better  appreciated  after  the  vasomotor  nerves  have 
been  described. 


456 


TEE  KIDNEYS  AND  URINE. 


blood,  the  amount  of  the  secretion  was  found  to  depend  more  upon 
the  rate  of  flow  than  upon  the  pressure/  It  can  be  readily  shown 
by  means  of  the  oncometer  and  oncograph  that  the  secretion  of  the 
urine  varies  with  the  quantity  of  the  blood  flowing  through  the 
kidney. 

The  oncometer  (Fig.  216)  is  a  metallic  capsule,  shaped  like  a 
kidney,  composed  of  two  halves  moving  on  a  hinge  (li),  by  which 
the  kidney  is  introduced,  the  renal  vessels  (a,  v,  u)  passing  out  by 

Fig.  217. 


Oncometer.  K.  Kidney  ;  the  thick  line  is 
the  metallic  capsule,  h.  Hinge.  I.  Tube 
for  filling  apparatus.  T.  Tube  to  connect 
■with  Tj.  a,  V,  ti.  Artery,  vein,  ureter.  (Stie- 
riNG,  after  Roy.) 


Oncograph.  C".  Chamber  filled  with  oil,  commu- 
nicating by  T,  with  T.  p.  Piston.  I.  Writing 
lever.     (Stirling,  after  Roy.) 


the  opposite  opening.  The  kidney  (K)  is  surrounded  mth  a  thin 
membrane,  and  the  space  (o)  between  the  latter  and  the  inner  sur- 
face of  the  capsule  filled  with  warm  oil  introduced  through  the 
tube  I,  which  can  be  closed  with  a  stopcock.  The  tube  T  being 
adapted  to  the  tube  T^  leading  into  the  metallic  chamber  C  of  the 
oncograph  (Fig.  217),  also  filled  with  oil,  any  increase  in  the  volume 
of  the  kidney  will  force  the  oil  from  the  space  o  into  the  chamber 
C,  and  the  piston  p  will  be  elevated,  and  with  it  the  recording  pen. 
On  the  other  hand,  any  diminution  in  the  volume  of  the  kidney 
through  stimulation  of  the  vaso-constrictor  nerves  will  cause  the  oil 
to  flow  from  C  into  o,  and  the  piston  and  with  it  the  recording 
pen  will  fall.  By  adapting  the  pen  to  the  cylinder  we  can  get  a 
trace  of  the  so-called  kidney  curve  (Fig.  218). 

Fig.  218. 


Trace  obtained  by  onci)gra])h. 

The  kidney  having  been  placed  within  the  oncometer  and  a  canula 
placed  into  the  ureter  so  as  to  measure  the  outflow  of  the  urine,  it  will 
be  observed  that  as  the  volume  of  the  kidney  contracts  through  stimu- 
lation of  the  vaso-constrictor  nerves,  the  excretion  of  the  urine  di- 

II.  Munk,  Yircliow's  Archiv,  Band  iii.,  1888,  s.  434. 


EXCRETION  OF  UEIXE.  457 

minishes,  whereas  when  the  volume  of  the  kidney  expands  through 
division  of  the  vaso-constrictor  nerves  the  excretion  of  the  urine  in- 
creases. That  the  renal  epithelium  exerts,  however,  an  excretory 
activity  independent  of  the  pressure  and  quantity  of  the  blood,  is 
shown  by  the  experiments  of  Heidenhaiu  ^  upon  animals  in  which, 
after  the  flow  of  uriue  had  ceased  through  section  of  the  spinal  cord 
below  the  medulla,  sodium  sulphoindigotate  being  injected  into  the 
veins  was  found,  after  death,  in  the  renal  epithelium  or  the  interior 
of  uriniferous  tubules  according  to  the  length  of  time  elapsing  be- 
tween the  injection  and  killing  of  the  auimals,  proving  that  the 
renal  epithelium  had  excreted  the  sulphoindigotate  from  the  blood. 
By  varying  the  quantity  of  the  salt  iujected  and  the  time  elapsing 
between  the  experiment  and  the  subsequent  examination,  Heiden- 
hain  was  able  to  follow  step  by  step  the  salt  as  it  passed  from  the 
blood  into  the  cells,  thence  through  the  latter  into  the  tubules  for 
some  little  distance.  There  being  no  fluid  passing  along  the  uri- 
niferous tubules  to  wash  away  the  sulphoindigotate,  the  latter  re- 
mained about  where  it  liad  been  excreted.  Not  a  trace  of  the  salt 
injected  could  be  found  in  the  epithelium  or  within  the  capsular 
portion  of  the  tubule,  the  cells  excreting  the  sodium  sulphoindigo- 
tate being  of  the  kind  described  by  Heidenhaiu  as  rod-shaped,  more 
especially  found  in  the  intercalary  portion  of  the  uriniferous 
tubule.  It  was  also  shown  by  these  experiments,  as  might  have 
been  expected,  that  there  was  a  limit  to  the  excreting  capacity  of 
the  renal  epithelium,  the  excretion  of  a  second  quantity  of  sul- 
phoindigotate injected  soon  after  the  first  being  very  imperfect.  It 
might  be  supposed  that  the  experiments  of  Heidenhaiu  with  sul- 
phoindigotate could  be  repeated  vaih.  urea,  uric  acid,  etc.,  ^nth  the 
^^ew  of  shoeing  that  these  substances  are  excreted  by  the  cells 
lining  the  tubular  and  not  by  those  lining  the  capsular  portion  of 
the  tubule.  Inasmuch,  however,  as  tlie  injection  of  urea,  etc.,  gives 
rise  to  a  copious  flow  of  urine,  even  after  section  of  the  spinal  cord 
below  the  medulla,  which  is  not  the  case  with  the  sulphoindigotate, 
the  urea  will  be  washed  along  the  tubules  as  fast  as  it  is  excreted, 
which  makes  it  impossible,  therefore,  to  say  by  what  part  of  the 
renal  epithelium  it  has  been  excreted.  It  is  well  known,  however, 
that  in  birds,  reptiles,  and  fishes,  branches  from  the  mesenteric, 
femoral  veins,  etc.,  pass  to  the  kidneys  (Fig.  219),  and  after  rami- 
fying through  the  latter  converge  and  finally  terminate  in  the  vena 
cava,  the  veins  being  known  collectively  as  the  renal  portal  system, 
or  the  system  of  Jacobson,-  after  their  discoverer.  The  blood  flows 
through  the  kidneys  in  these  animals,  therefore,  very  much  as  it 
does  through  the  liver  in  man.  Now  the  branches  of  this  renal 
portal  system,  together  with  the  eflerent  vessels  from  the  glomeruli, 
constitute  the  capillary  plexus  surrounding  the  tubular  portion  of 

1  Hermann,  Physiologie,  Funfter  Band,  Ereter  Theil,  s.  345. 
^  De  systemate  venoso  peculiar!  in  penultis  animalibus  observatio.     Copenhagen, 
1821. 


458 


THE  KIDNEYS  AND  URINE. 


Fig.  219. 


the  uriniferous  tubules,  the  glomeruli  themselves,  however,  being 
supplied  exclusively  by  branches  of  the  renal  artery.  It  is  obvious, 
therefore,  that  if  the  renal  artery  be  ligated  the  blood  will  be  en- 
tirely cut  off  from  the  glomerulus,  while  that  supplying  the  remain- 
ing portion  of  the  uriniferous  tubule  will  be  unaffected.  Such  being 
the  case,  it  follows  that  if  urea  still  appears  in  the  urine  after  liga- 
tion of  the  renal  arteries,  it  must  be  excreted  by  the  epithelium  of 
the  tubular  and  not  by  that  of  the  capsular  portion  of  the  uriniferous 
tubule.  These  theoretical  considerations  are  fully  borne  out  by  the 
experiments  of  Nussbaum,^  who  has  shown  that  while  sugar,  pep- 
tones, and  albumin  are  excreted  by  the  glomeruli,  these  substances 
not  appearing  in  the  urine  after  ligation  of  the  renal  arteries,  urea 
is  excreted  by  some  part  of  the  remaining 
portion  of  the  tubule,  urea,  when  injected  into 
the  blood,  g-iving  rise  to  a  flow  of  urine  even 
after  ligation  of  the  arteries. 

The  recent  experiments  of  Schroeder  ^  and 
of  Dreser^  made  with  sodium  chloride,  potas- 
sium nitrate,  caifein,  etc.,  prove  also  that  the 
increased  flow  of  blood  through  the  kidney 
after  the  taking  of  these  substances  is  due 
largely  to  some  specific  action  of  the  renal 
epithelium  and  more  especially  to  that  cover- 
ing the  glomeruli. 

The  urine,  like  the  l)ilc,  is  excreted  contin- 
uously, and  while  the  flow  may  be  increased 
or  diminished,  it  never  absolutely  ceases ,  in 
health  for  any  length  of  time.  The  urine 
trickling  through  the  mouth  of  the  uriniferous 
tubules  into  the  calices,  passes  thence  by  the 
ureters  into  the  bladder,  its  return  from  the 
latter  during  micturition  being  prevented  by  the  obliquely  disposed 
valvular-like  orifices  of  the  ureters. 

f-  »  The  bladder  is  a  musculo-membranous  sac,  the  muscular  fibers, 
chiefly  of  the  involuntary  character,  being  disposed  in  a  longitudi- 
nal and  circular  manner,  the  former  constituting  the  detrusor,  the 
latter  the  sphincter  vesicae,  by  the  contraction  of  which  the  urine  is 
either  expelled  or  retained  within  the  bladder.  Micturition  appears 
to  be  brought  about  essentially  as  follows  : 

During  the  intervals  in  which  the  urine  is  not  voided  the  sphinc- 
ter vesicae  is  in  a  state  of  tonic  contraction  ;  if,  however,  the  urine 
be  retained  for  some  time  the  contraction  of  the  sphincter  alone  is 
insuflicient  to  resist  the  outflow,  and  the  action  of  the  adjacent 
muscles  is  called  upon  to  assist  it.  The  disposition  to  urinate  after 
a  time  becoming  very   great  a   few   drops   of  urine  pass  into  the 

iPflu.'rei-'s  Archiv,  1877,  xvi.,  s.  139  ;  1878,  xvii.,  s.  580. 
^Arfliiv  fiir  exp.  Path.  u.  Pharm.,  Band  xxiv.,  1888,  s.  85. 
3Ebenda,  liandxxix.,  1892,  s.  303. 


c  !.  Vena  cava.  7?.  Kid- 
neys. ;■  r.  Vena  rcvehens. 
r(i.  Venaadvehens.  a.  Vena 
epigastrica.  h.  Vena  hypo- 
gastrica.  i.  Vena  ischiada. 
r.  Vesical  veins.    (Gagex- 

BAUR.) 


ACIDITY  OF  URINE.  459 

urethra,  the  impression  so  produced  then  calls  into  play  the  action 
of  the  detrusor  and  ejaculator  urinse,  the  sphincter  being  simultane- 
ously relaxed,  and  tlie  bladder  is  emptied.  Ordinarily  the  yoiding 
or  the  retaining  of  the  urine  is  a  yoluntary  act,  but  that  the  urine 
can  be  voided  at  regular  intervals  independent  of  the  will  is  shown 
by  the  regularity  with  which  the  action  is  performed  in  animals  in 
which  the  spinal  cord  has  been  divided,  and  in  human  beings  in 
which  it  has  been  injured.  The  mechanism  by  means  of  which  the 
muscnlar  contractions  are  Ijrought  about  in  response  to  stimuli,  the 
result  of  which  is  the  voiding  of  the  urine,  will  be  better  appreciated 
after  the  subject  of  reflex  action  has  been  considered. 

The  Urine. 

The  urine  is  a  clear,  amber-colored  fluid,  of  a  watery  consistence, 
containing  a  little  mucus,  saltish  in  taste,  with  a  characteristic 
though  not  disagreeable  odor,  acid  in  reaction,  and  with  a  specific 
gravity  varying  between  1.020  and  1.025.  The  color  of  the  urine 
appears  to  be  due  to  a  mixture  of  urobilin  or  its  mother  substance, 
urobilinogen,  and  of  seyeral  other  pigments  Ayhose  nature  is  as  yet 
but  imperfectly  understood.  The  coloring  matter  of  the  lunne  ap- 
pears to  be  identical  with  hydrobilirubin  (C.,.,H^^X^O.),  the  so-called 
urobilin  being  that  part  of  the  hydrobilirubin  derived  from  the 
bilirubin  of  the  bile  which  being  absorbed  passes  out  of  the  body  in 
the  urine  rather  than  in  the  feces.  The  varying  tints  often  observed 
in  the  urine  from  an  amber  color  to  red  are  probably  due  to  the 
oxidation  of  this  substance. 

Acidity  of  Urine. 

The  acidity  of  the  urine  is  not  due  to  free  acid,  as  can  be  shown 
by  there  being  no  precipitate  formed  on  the  addition  of  sodiimi 
hypophosphite,  but  to  the  presence  of  the  acid  sodium  phosphate 
(NaH^PO^),  the  latter  salt  being  probably  formed  by  the  reduction 
of  the  basic  sodimu  phosphate  (Xa.,HPO^)  of  the  blood,  by  abstrac- 
tion of  one  equivalent  of  its  sodiuin,  by  uric,  or  hippuric  acids, 
sodium  urate,  or  hippurate,  being  formed,  as  may  be  seen  from  the 
following  formula,  for  example  : 

Sodium  phosphate.  Uric  acid.  Acid  sodium  phosp.  Sodium  urate. 

2Na^HP0^       +       C^H^N^03      =      2NaH^PO^     +     Na^C^H^N^O^. 

The  acidity  of  the  urine,  due  to  acid  sodium  phosphate,  as 
measured  by  the  amount  of  a  standard  solution  of  caustic  soda 
necessary  to  neutralize  it,  is  equivalent  to  about  two  grammes  of 
oxalic  acid  in  twenty-four  hours,  supposing  the  urine  voided  in  that 
time  to  amount  to  1200  c.  cm.  The  solution  of  soda,  of  such  a 
strength  that  each  cubic  centimeter,  containing  0.0031  gramme  of 
soda,  exactly  neutralizes  0.0063  gramme  of  oxalic  acid,  is  added, 
drop  by  drop,  to  a  given   quantity  of  urine — say  100  c.  cm.,  until 


460 


THE  KIDNEYS  AND   IJEINE. 


Fig.  220. 


—  1000 


.__IOIO 


.1020 


1030 


.—1040 


litmus  paper  changes  violet  in  color,  /.  e.,  neither  to  red  nor  blue. 
The  number  of  cubic  centimeters  of  the  soda  solution,  as  read  off  on 
the  burette,  say  30,  when  multiplied  by  0.00()3  gramme,  will  give 
then  the  amount  of  acidity,  or  0.1890,  in  100  c.  cm.  of  urine,  as 
measured  in  grammes  of  oxalic  acid,  and,  consequently,  of  2.2 
grammes  in  1200  c.  cm. 

Specific  Gravity  of  the  Urine. — The  specific  gravity  of  the  urine, 
a  matter  of  great  importance  practically,  is  readily  determined  by 
the  urinometer  (Fig.  220),  the  stem  of  which  is  so 
graduated  that  when  immersed  in  water  the  level  of 
the  latter  stands  at  that  portion  of  the  stem  marked 
1000,  the  level  at  which  the  urine  stands,  as  read  off 
on  the  urinometer  when  the  latter  is  immersed  in 
the  urine  giving  the  specific  gravity  sought.  A  con- 
venient method  of  determining  the  solids  of  the  urine, 
approximately,  at  least,  is  by  means  of  what  is  gen- 
erally known  as  Trapp's,  or  C'hristison's,  formula, 
based  upon  the  fact,  as  empirically  shoM'n  by  that 
chemist,  of  the  specific  gravity  of  the  urine  bearing 
generally  a  close  relation  to  the  solid  matters  which 
it  contains  in  solution.  The  rule  is  as  follows : 
]Multiply  the  last  two  figures  of  a  given  specific 
gravity  expressed  in  four  figures — say  1.022,  by 
2.33;  the  result,  22  x  2.33  =  51.26  grammes,  will 
be  the  amount  of  solids  contained  in  1000  parts  of 
urine  having  a  specific  gravity  of  1.022,  and  if  the 
urine  passed  in  twenty-four  hours  amounts  to  1200 
c.  cm.,  then  the  solids  will  be  increased  proportion- 
ally, 1000  :  1200  : :  51.26  :  x  =  61 .51  grammes.  If 
the  specific  gravity  of  the  urine  be  below  1.018, 
greater  accuracy  will  be  obtained  by  multiplying  by 
2  instead  of  2.33.  On  the  supposition  that  1500 
c.  c.  of  urine  are  voided  in  the  twenty-four  hours, 
the  solids  are  usually  found  to  amount  to  60  grammes 
(926  grains)  or  40  grammes  of  solids  per  1000  c.  c. 
of  urine. 

The  daily  quantity  of  urine  excreted  amounts  in 
the  adult  man,  on  the  average,  according  to  Parkes,^ 
wlio  lias  compared  the  observations  of  many  ob- 
servers, to  about  1575  c.  c.  (fifty-two  and  a-half 
fluid  ounces).  As  little  as  1050  c.  c.  (thirty-five  ounces),  and  as 
much  as  2430  c.  c.  (eighty-one  ounces)  may,  however,  be  voided 
within  the  limits  of  health,  and  it  may  be  added  that  almost  every 
intervening  number  between  these  limits  has  been  given  as  the 
usual  average,  the  very  greatest  difference  prevailing  in  this  respect. 
Apart,  however,  from  personal  peculiarities,  the  amount  of  urine 
excreted  is  also  influenced  by  sex,  age,  and  season  of  the  year. 
^The  Composition  of  the  Urine,  p.  5.     London,  1860. 


DAILY  QUANTITY  OF  URINE.  461 

Thus,  less  (1200  c.  c.)  urine  is  excreted  by  women  than  men,  more 
by  children,  relatively  to  their  weight,  than  by  adults ;  more  in 
winter,  the  skin  being  then  less  active,  than  in  summer.  When  it 
is  considered  that  the  quantity  and  quality  of  the  urine,  as  we  shall 
see,  are  influenced  by  such  conditions  as  wakefulness,  sleep,  rest, 
exercise,  solid  and  liquid  food,  it  might  be  naturally  supposed  that 
considerable  differences  would  present  themselves  in  the  urine  passed 
at  different  times  during  the  day,  usually  five  or  six  times  within 
the  twenty-four  hours.  As  a  matter  of  fact,  diurnal  variations  do 
succeed  each  other  quite  regularly.  Thus,  the  urine  collected  dur- 
ing the  night  and  voided  early  in  the  morning  is  strongly  colored, 
distinctly  acid,  and  of  a  high  specific  gravity ;  toward  noon  it  be- 
comes paler,  less  dense  (1.003  to  1.008),  and  less  acid,  the  acidity 
even  disappearing  altogether ;  during  the  afternoon  and  evening 
the  color,  density,  and  acidity  increase,  while  by  night  it  has  become 
again  highly  colored,  markedly  acid,  and  with  a  specific  gravity  of 
1.028  or  even  1.030.  As  these  diurnal  variations  are,  however, 
increased  or  diminished  by  the  amounts  of  liquids  taken,  and  as  the 
acidity  of  the  urine  is  inversely  as  that  of  the  stomach,  and  may 
be  more  or  less  neutralized  by  fruits,  vegetables,  etc.,  the  lactates, 
malates,  and  tartrates  of  the  same  being  replaced  within  the  system 
by  carbonates,  and  reappearing  in  that  form  in  the  urine,  it  is  evi- 
dent that  if  the  acidity  and  specific  gravity  are  to  be  determined, 
one  sample  voided  will  not  suffice,  but  that  the  entire  quantity 
passed  in  twenty-four  hours  should  be  examined,  and  the  mean  re- 
sult taken.  It  is  worth  while  mentioning  that  with  reference  to  the 
liquids  absorbed  by  the  system  or  lost,  that  under  normal  conditions 
the  relation  of  the  specific  gravity  of  the  urine  to  that  of  the  liquids 
is  an  inverse  one.  Thus,  if  a  great  quantity  of  liquid  be  taken,  or 
the  perspiration  be  diminished,  the  amounts  of  solids  remaining  the 
same,  the  specific  gravity  of  the  urine  will  be  diminished,  whereas, 
if  drinks  be  abstained  from,  or  the  perspiration  be  increased,  the 
specific  gravity  will  be  increased.  If,  however,  notwithstanding 
that  a  great  quantity  of  liquid  be  absorbed,  the  specific  gravity  still 
remains  high,  or  with  a  diminution  in  the  liquid  the  specific  gravity 
remains  low,  there  would  be  reason  to  suspect  disease  through  the 
increase  or  diminution  respectively  in  the  solid  constituents  of  the 
urine,  and  such  would  also  be  the  case  if,  the  specific  gravity  re- 
maining constant,  the  quantity  of  urine  increased  or  diminished, 
and  vice  verm.  The  urine,  conveying  out  of  the  economy  many 
inorganic  and  organic  constituents,  is  a  highly  complex  fluid,  and, 
varying  much  as  regards  its  constituents,  it  is  difficult,  if  not  im- 
possible to  give  its  composition. 


462 


THE  KIDNEYS  AND  URINE. 


Composition  of  the  Urine  According  to  Parkes.' 


Constituents. 

By  an  average  man  of 

G6  kilo.    Per 

1  kilo  of  bod 

)'  weight. 

Water 

1500.000  gl 

ammes 

23.000  gr 

ammes 

Total  solids 

72.000 

1.100 

Urea 

33.180 

0.500 

Uric  acid 

0.555 

0.0084 

Hippuric  acid 

0.400 

0.0060 

Creatiuin 

0.910 

0.0140 

Pigmeut  and  other  substances       10.300 

0.1510 

Sulphuric  acid    . 

2.012 

0.0305 

Phosphoric  acid 

3.164 

0.0486 

Chlorine 

7.000  (8. 

12) 

grammes 

0.1260 

Ammonia 

0.770  grammes 

•  .  . 

Potassium 

2.500 

( i 

Sodium 

11.090 

t.  i 

Calcium 

0.260 

It 

Magnesium 

0.207 

L  i 

.  .  . 

Fig.  221. 


Urea. — Urea  (CON.,Hj),  the  most  important  constituent  of  the 
urine,  is  regarded  by  chemists,  as  already  mentioned,  as  being  car- 
bamide or  the  diamide  of  carbon  dioxide,  its  chemical  composition 

being  expressed  by  the  formula  CO  •!  xttj"-      Urea   is    a   colorless 

neutral  substance  very  soluble  in  water  and  boiling  alcohol  but  in- 
soluble in  ether,  and  crystallizing  in  four-sided  prisms  (Fig.  221). 

Urea  can  be  readily  obtained 
from  the  urine  in  the  following 
manner  :  Add,  say,  1.5  c.  c.  of 
pure  nitric  acid  to  3.5  c.  c.  of 
concentrated  urine  in  a  watch 
glass  and  set  aside  to  cool.  The 
nitrate  of  urea  then  formed  will 
be  precipitated  as  a  yellow 
crystalline  mass.  The  insoluble 
nitrate  caught  on  a  filter,  dried, 
and  dissolved  in  boiling  water, 
is  mixed  with  animal  charcoal 
to  remove  coloring  matters  and 
filtered  while  hot.  The  filtrate 
being  then  allowed  to  cool, 
colorless  crystals  of  nitrate  of 
urea  Avill  be  deposited.  The 
latter  being  dissolved  in  boil- 
ing water  and  barium  carbonate  added  as  long  as  effervescence 
takes  place,  l)arium  nitrate  and  urea  will  be  produced,  from  which 
after  evaporating  to  dryness  the  urea  can  Ix;  extracted  with  absolute 
alcohol.  On  evaporating  the  alcoholic  solution  of  urea  crystals  of 
pure  urea  are  obtained.  The  amount  of  urea  is  usually  deter- 
mined by  Davy's  method  which  is  based  upon  the  decomposition 
of  urea  into  water,    carl)on  dioxide,  and  nitrogen  by  an  alkaline 

'Op.  cit. 


Urea,  prepared  from  urine,  and  crystallized  by 
slow  evaporation.     (Lkiimann.) 


THE  UREAMETER. 


463 


Fig.  222. 


solution  of  sodium  hypobromite,  the  amount  of  urea  being  deter- 
mined from  the  nitrogen  set  free.  As  the  urine  contains,  how- 
ever, other  nitrogenous  constituents  than  urea,  such  as  urates  and 
creatinin,  which  will  also  be  decomposed  with  the  liberation  of 
nitrogen,  the  urates  must  be  removed  })y  acetate  of  lead  followed 
by  sodic  phosphate  and  the  creatinin  by  an  alcoholic  solution  of 
zinc  chloride,  otherwise  the  nitrogen  produced  would  represent  not 
only  that  derived  from  the  urea 
(90  per  cent.),  but  that  from  the 
remaining  nitrogenous  constit- 
uents (10  per  cent,  or  more). 
The  experimental  procedure  in 
making  use  of  Davy's  method 
for  the  determination  of  the 
urea  in  the  urine  is  as  follows  : 
A  given  quantity  of  a  solution 
of  sodium  hypobromite  freshly 
made  (100  gr.  of  caustic  soda 
in  250  c.  c.  of  water  to  which 
are  added  25  c.  c.  of  bromine) 
is  introduced  into  the  pyram- 
idal-shaped vessel  (Fig.  222), 
into  which  is  placed  a  test-tube 
containing,  say,  5  c.  c.  of  urine. 
The  pyramidal-shaped  vessel 
being  then  inclined,  the  urine 
will  mix  with  the  solution  of 
sodium  hypobromite,  and  the 
urea  will  decompose,  with  the  production  of  carbon  dioxide.  The 
latter  will  combine  with  the  soda  which  is  in  excess,  and  will  be 
retained  in  the  mixture,  while  the  nitrogen  set  free  will  pass  over 
into  the  graduated  burette  staudino-  in  mercurv  where  it  can  be  col- 
lected  and  measured.     The  reaction  is  as  follows  : 

CON^H^+  3(NaBrO)  +  2(NaOH)  =  3NaBr  +  Na^C03  +  SH^  + 

Let  us  suppose  that  the  nitrogen  obtained  from  the  decomposition 
of  the  urea  amounted,  when  corrected  for  temperatm'c  and  pressure, 
to  40  c.  c,  the  urea  in  5  c.  c.  of  urine  would  amount  to  0.108  of  a 
gramme,^  and  in  1500  c.  c.  of  urine,  to  32.4  grammes.  It  may  be 
mentioned  in  this  connection  that  the  total  amount  of  nitrocren  in 
the  urine  is  estimated  by  the  Kjeldahl  method."  This  consists  in 
heating  the  urine  (5  c.  c.)  with  an  excess  of  concentrated  or  fuming 
sulphuric  acid  (40  c.  c.)  until  all  the  nitrogen  has  been  converted 
into  ammonia  and  after  caustic  soda  has  been  added  in  excess  distill- 

'  1  gramme  of   urea  contains  0.46  of  a  gramme  =  372.5  c.  c.   of  nitrogen  or 
0.0027  of  a  gramme  of  urea  =  1  c.  c.  of  nitrogen  and  0.0027  X  40^0.108  gramme. 
2  Zeits.  fiir  Analyt.  Cheraie,  Band  22,  1883,  s.  366. 


Ureameter.     (Lakdois.) 


2N 


464  THE  KIDNEYS  AND  URINE. 

ing  the  ammonia  into  sulphuric  acid  i  —^  \  which  has  been  pre- 
viously titrated  with  soda   (  ^  )j  the  nitrogen  being  estimated  from 

the  amount  of  sulphuric  acid  that  combines  with  the  ammonia. 
Suppose,  for  example,  that  18,6  c.  c.  of  sulphuric  acid  have  com- 
bined with  ammonia  as  determined  by  titration,  then  as  1  c.  c.  of 
sulphuric  acid  corresponds  to  0.0028  of  a  gramme  of  nitrogen,^ 
the  latter  would  amount  in  5  c.  c.  of  urine  to  0.052  of  a  gramme 
(18.6  X  0.0028  =  0.052)  and  in  1500  c.  c.  of  urine  to  15.6 
grammes.  If  to  this  amount  of  nitrogen  there  be  added  the  0.94 
of  a  gramme  contained  in  the  feces  we  obtain  16.5  grammes  as  the 
total  nitrogen  eliminated  by  the  body  in  twenty-four  hours,  and 
w-hich,  when  multiplied  by  6.25^  gives  103.2  grammes  as  the 
amount  of  proteid  destroyed  in  the  same  period  of  time.  While 
the  urea  excreted  by  an  adult  amounts  upon  an  average  in  24  hours 
to  about  33  grammes  (509  grains)  it  should  be  mentioned  that  the 
quantity  excreted  varies  very  considerably  according  to  the  age, 
weight  of  the  body,  sex,  period  of  the  day,  season,  and  kind  of 
food.  Thus,  children  of  from  three  to  seven  years  of  age  with  a 
weight  of  only  one-fifth  that  of  an  adult  may  excrete  in  24  hours 
as  much  as  15.5  grammes  (240  grains).  As  might  be  expected, 
therefore,  the  amount  of  urea  excreted  continues  to  diminish  as  age 
advances.  It  would  appear  that  less  urea  is  excreted  by  the  female 
than  the  male  in  the  proportion,  perhaps,  of  about  half  a  grain 
less  in  the  female  for  each  pound  of  body  weight,  and  that  the 
amount  is  diminished  during  menstruation.  The  hour  of  the  day 
apparently  also  exerts  an  influence  upon  the  excretion  of  urea,  the 
greatest  amount  being  eliminated  after  breakfast  and  tea,  the  least 
during  the  night.  The  increase  or  decrease  observed  may  be,  how- 
ever, due,  to  a  certain  extent,  as  we  shall  see,  to  the  taking  of  or 
the  abstaining  from  food.  Like  the  urine,  more  urea  is  probably 
eliminated  in  cold  than  in  warm  weather. 

It  is  difficult,  if  not  impossible,  however,  to  give  exact  numerical 
estimates.  According  to  Dr.  E.  Smith,-^  the  daily  variations 
amounted  in  himself  in  a  year  to  from  14  to  45  grammes  (219  to 
700  grains). 

Of  the  conditions  influencing  the  production  of  urea,  none  is  so 
important  as  that  of  the  taking  of  food.  This  becomes  at  once  evi- 
dent when  the  amount  of  urea  excreted  upon  a  vegetable  or  mixed 
diet  is  compared  with  that  of  a  highly  animal  one.  Thus  while  the 
urea  excreted  by  Kanke,^  during  24  hours  on  a  vegetable  diet 
amounted  to  17  grammes  (264  grains)  and  on  a  mixed  one  to  between 
30  and  33  grammes  (463  to  617  grains)  on  a  highly  animal  diet  it 
was  increased  to  as  much  as  86  grammes  (1332  grains),  or  nearly 

iNeumeister,  op.  cit.,  s.  070.  ^Proteid  :  Nitrogen  ::  100  :  16. 

aProc.  of  RoyalSoc,  MavSO,  1861.  ^        .,        ^,        100       ^  „, 

^Physiologie/1872,  s.  190^  504.  ^  ^'ote^^  ""       -^   16^  "" 


PRODUCTION  OF  UEEA,  465 

three  times  as  much  as  Dormal.  From  such  facts  as  that  nearly  all 
of  the  nitrogen  of  the  food  consumed  passes  out  of  the  body  in  the 
form  of  urea  in  the  urine,  each  gramme  of  urea  implying  the  disin- 
tegration of  3  grammes  of  nitrogenous  matter,  or  about  15  grammes 
of  meat,  and  that  the  amount  of  urea  excreted  attains  its  maximum 
witliin  five  to  seven  hours  after  the  taking  of  food,  it  would  appear 
that  by  far  the  greatest  amount  of  the  urea  produced  must  be 
derived  directlv  from  the  disinteo-rati(m  of  the  nitroo:enous  food 
rather  than  of  the  tissues.  It  would  be  absurd  to  suppose  that  of 
the  five  pounds  of  meat  eaten  by  a  large  dog,  to  take  an  extreme 
instance,  the  nitrogenous  matter  of  the  same  should  be  first  trans- 
formed into  tissue,  then  decomposed  into  urea,  and  eliminated  by 
the  kidneys  within  the  short  space  of  24  hours. 

If  the  above  view  of  urea  being  derived  from  nitrogenous  food 
rather  than  nitrogenous  tissue  be  accepted,  it  is  readily  understood 
why  muscular  exertion  does  not  increase,  as  was  once  supposed,  the 
production  of  urea,  for  muscular  energy,  being  like  all  other  kinds 
of  so-called  vital  energy,  transformed  heat,  and  the  latter  being  de- 
veloped, if  not  exclusively,  at  least  to  a  greater  extent  out  of  fats 
and  carbohydrate  than  albuminous  food,  it  follows  that  muscular 
activity  will  be  measured  not  l^y  the  amount  of  urea  but  by  that  of 
the  carbon  dioxide  produced.  Such  theoretical  considerations  are 
fully  borne  out  by  experiments. 

Thus,  for  example,  in  the  ascent  of  the  Faulhorn  by  AVick  and 
Wislicenus^  involving  considerable  muscidar  exertion  so  far  from  the 
urea  being  increased  l)y  the  exercise,  it  was  actually  diminished, 
which  is  in  accordance  with  the  fact,  however,  that  no  albuminous 
food  had  been  taken  for  seventeen  hours  pre\'ious  to  the  ascent,  the 
diet  of  Fick  and  AVislicenus  consisting  of  cakes  made  out  of  fat, 
starch,  and  suo;ar.  Such  beino;  the  case  it  is  not  strange  that  the 
amount  of  urea  excreted  should  have  been  small,  it  being  derived 
from  the  nitrogenous  tissues  of  the  body,  the  latter  supplying  the 
nitrogenous  food  that  Avould  have  been  otherwise  present  had  the 
diet  been  a  mixed  one.  It  is  well  known  that,  even  in  starvation, 
more  urea  is  excreted  than  on  a  diet  consisting  of  sugar,  fat,  etc., 
since  the  latter  substances,  in  supplying  ready  materials  for  com- 
bustion, spare  the  tissues  of  the  body. 

That  there  is  an  enormous  amount  of  potiential  energy  locked  up 
latent,  so  to  speak,  in  sugars,  etc.,  is  made  evident  in  the  extreme 
weakness  and  emaciation  so  noticeable  in  diabetes,  since  the  sugar 
in  that  disease,  instead  of  being  burned,  and  constituting  as  nor- 
mally a  source  of  heat  and  energy,  passes  unoxidized  out  of  the 
body.  The  amount  of  energy  lost  to  the  system  under  such  cir- 
cumstances may  be  judged  of  when  it  is  remembered  that  in  ex- 
treme cases  of  diabetes  as  much  as  40  ounces  of  sugar  are  passed  in 
the  urine  in  twenty-four  hours,  and  that  if  the  16  ounces  of  carbon 
contained  in  such  an  amount  of  sugar  were  oxidized,  heat  enough 

1  London  Phil.  Magazine,  1866,  p.  485. 
30 


466  THE  KIDNEYS  AND  URINE. 

would  be  produced,  if  applied  media uically,  to  raise  20  millions  of 
pounds  1  foot  high,  or  carry  a  man  weighing  130  pounds  on  a  level 
66  miles.  The  system  being  deprived,  therefore,  in  this  disease  of 
such  a  source  of  force,  draws  upon  the  albuminous  tissues,  hence  the 
characteristic  emaciation  and  weakness. 

Essentiallv  the  same  result  was  obtained  by  Haughton,^  who 
found,  while  walking  five  miles  a  day,  that  the  urea  eliminated 
amounted  to  501.28  grains  ;  that  when  the  walk  was  increased  to 
20.74  miles  a  day,  and  kept  up  for  five  consecutive  days,  the  urea 
eliminated  amounted  to  only  501.16  grains,  or  actually  less. 
Parkes  -  found,  also,  that  in  the  case  of  two  soldiers,  who  walked  in 
two  davs  56  miles  on  a  non-nitrogenous  diet,  that  the  total  increase 
of  nitrogen  eliminated  amounted,  in  the  one  case,  to  only  about  3 
grains ;  and,  in  the  other,  1 5  grains  ;  corresponding  to  an  increase 
of  6.4  grains,  and  32.1  grains  of  urea,  respectively,  in  forty-eight 
hours.  The  case  of  Weston,  who  walked  over  300  miles  in  five 
consecutive  days,  cited  by  Flint'*  as  an  illustration  of  urea  being  in- 
creased by  muscular  exercise,  illustrates  really  only  what  we  have 
already  seen  to  be  the  case,  that  the  amoimt  of  urea  excreted  is 
greatly  increased  upon  a  highly  nitrogenous  diet,  and  that  heat,  the 
ultimate  source  of  muscular  force,  can  be  developed  through  the 
combustion  of  nitrogenous,  as  well  as  of  fatty  or  carl^ohydrate  foods, 
the  former  means  of  obtaining  the  necessary  heat  being,  however,  a 
far  more  expensive  way  than  the  latter,  and  entailing  greater  work 
upon  the  system.  It  is  true  that,  if  the  coal  gives  out,  the  steamer 
can  be  supplied  with  fuel  from  its  masts,  shrouds,  etc.,  and  other 
integral  parts  of  its  structure ;  one  does  not  resort,  however,  save 
in  dire  necessity,  to  such  a  source  of  fuel.  The  facts  of  the  case  of 
AVeston,  just  referred  to,  are  essentially  as  follows  :  Weston  walked 
in  five  consecutive  days  310  miles,  losing  in  weight  3  J  pounds. 
1173.80  grains  of  nitrogen  were  taken  into  the  system  in  the  food, 
and  1807.60  grains  were  eliminated  from  it  in  the  excreta,  leaving 
633.80  grains  of  nitrogen  to  be  accounted  for,  which  were  evidently 
derived  from  the  3  pounds  of  tissue  lost,  the  latter  containing 
633.80  grains  of  nitrogen  ;  the  remaining  quarter  of  a  pound,  lost 
in  weight,  probably  being  due  to  the  combustion  of  fiit  and  elimina- 
tion of  water.  Such  being  the  case,  and  Weston  having,  therefore, 
little,  if  any,  superfluous  fat  or  carbohydrate  matter  at  disposal  for 
the  production  of  heat  or  force,  it  would  appear,  from  the  large  quan- 
tity of  nitrogen  eliminated,  that  his  nitrogenous  tissues  were  largely 
drawn  upon  to  supply,  through  combustion,  the  heat  incidental  to  the 
production  of  such  a  muscular  effort.  The  3  pounds  of  muscular  tis- 
sue lost  by  Weston  during  the  walk,  supplied,  therefore,  the  body 
with  3  pounds  of  nitrogenous  food,  which,  in  being  consumed,  ac- 
counted for  the  elimination  of  633.80  grains  of  nitrogen,  corre- 
sponding to  1124  grains  of  urea,  just  as  if  he  had  eaten  3  pounds 

» British  Med.  Assoc,  1868.  2  Proc.  Eoyal  Soc,  1867,  No.  89,  94. 

3  New  York  Medical  Journal,  1871,  p.  687. 


PEODUCTIOX  OF  UREA.  467 

of  butcher's  meat,  instead  of  the  same  amount  of  his  own  body. 
That  this  conclusion  is  not  merely  a  theoretical  one  is  shown  by  the 
fact  of  Rubner/  weiirhing  72  kilo.,  being  able  to  consume  1.30 
kilo.  (2.8  pounds)  of  meat,  of  which  more  than  98  per  cent,  were 
perfectly  destroyed  in  the  system  with  the  production  of  the  corre- 
sponding amount  of  nitrogen.  It  has  also  been  shown  by  Voit " 
that  in  the  case  of  a  dog  working  on  a  tread-wheel  and  in  that  of 
man  doing  work  in  the  respiration  apparatus,  that  the  energy  ex- 
pended was  greater  than  that  derived  from  the  disintegration  of  ni- 
trogenous substances,  and  that  the  urea  excreted  was  within  certain 
limits,  at  least,  the  same  during  rest  and  the  performance  of  work. 
It  should  be  mentioned,  however,  that  some  difference  of  opinion 
still  prevails  among  physiologists  as  to  the  influence  exerted  by 
muscular  work  upon  the  excretion  of  nitrogen,  the  latter,  according 
to  Argutinsky^  for  example,  being  increased  by  muscular  work.  It 
appears,  however,  that  in  the  experiments  performed  by  this  ob- 
server, which  consisted  in  taking  long  walks,  climl)ing  mountains, 
the  diet  was  deficient  in  carbohydrates,  fats,  which,  necessitating 
the  disintegation  of  nitrogenous  material  that  would  not  have  been 
drawn  upon  had  the  diet  been  a  normal  one,  accounts  for  the  in- 
crease of  nitrogen  very  much,  as  in  the  case  of  \\'^eston  just  referred 
to. 

Not  only  has  it  been  held  that  muscular  activity  increases  the 
amount  of  urea,  but  mental  and  sexual  activity  as  well.  Even 
if  such  is  shown,  hereafter,  to  be  the  case,  apart  from  the  influence 
exerted  by  nitrogenous  food,  the  facts  are,  at  present,  too  few  to 
justify  giving  any  exact  numerical  estimate.  It  would  appear, 
from  what  has  just  been  said  w'ith  reference  to  the  production  of 
urea,  that,  to  a  large  extent  at  least,  it  is  derived  directly  from  the 
nitrogenous  principles  of  the  food  without  the  latter  becoming  first 
tissue. 

It  will  be  remembered  that,  in  considering  the  functions  of  the 
liver,*  many  facts  were  mentioned  in  favor  of  the  \aew  that  leucin, 
tyrosin,  etc.,  amide  products  of  pancreatic  digestion,  were  converted 
into  ammonium  carbonate  or  carl)amate,  and,  being  carried  to  the 
liver,  were  there  transformed  h\  a  process  of  dehydration  into  urea. 

Ammouium  carbonate.       Water.  Urea. 

(NHJ^C03   —   2Hp    =    COX^H^ 

Ammonium  carbamate.    Water.  Urea. 

CO>\H^   —   H^O    =    COX^H^ 

In  addition  to  the  facts  already  offered  in  favor  of  the  view  that 
urea  is  produced  in  the  liver,  and  somewhat  in  the  manner  just  de- 
scribed, it  may  be  also  mentioned  that  more  urea  is  found  in  the 
liver  than  in  any  gland  in  the  body,^  that  in  acute  yellow  atrophy 

'  Zeits.  fiir  Biolo.oie,  Band  xr.,  1879,  s.  122. 

2  Hermann,  Handbuch,  Band  vi.,  1  Theil,  1881,  ss.  189,  192. 

3Ptlugei-'s  Archiv,  Band  46,  1890,  s.  552. 

^Seejp.  150.  ^Centralblatt  med.  Wiss.,  1870,  s.  249. 


4(38  THE  KIDNEYS  AND  URINE. 

of  the  liver  the  urea  of  the  urine  is  replaced  by  leuciu  and  tyrosin, 
and  that  feeding  animals  with  leucin  increases  the  excretion  of  urea/ 
Admitting  that  by  far  the  greatest  quantity  of  urea  is  produced  in 
the  liver,  it  must  be  remembered  that  urea  is  not  only  found  in  the 
liver,  but  in  many  other  parts  of  the  system — in  the  chyle,  saliva, 
blood,  serous  fluids,  etc.,  and  that  in  starvation  in  the  absence  of 
all  food,  though  the  amount  of  urea  is  gradually  diminished,  it  is 
nevertheless  present,  even  to  the  last.  Of  course,  in  such  cases, 
one  part  of  the  body  being  nourished  at  the  expense  of  another, 
the  nitrogenous  tissues,  instead  of  food,  supply  the  materials  for 
the  development  of  urea.  That  such  is  the  case  is  shown  by  an 
experiment  of  Schondorif,"  who  observed  that  while  there  is  no 
increase  of  urea  in  the  blood  of  a  fasting  dog  irrigated  through  the 
limbs  of  a  well-fed  one,  there  is  a  very  decided  increase  of  urea  in 
the  blood  that  has  passed  through  the  limbs,  if  the  latter  be  irri- 
gated through  the  liver,  the  blood  taking  up  some  substance  from 
the  tissues  which  requires  the  action  of  the  liver  cells  to  be  con- 
verted into  urea. 

Urea  being  found  under  normal  circumstances  in  many  parts  of 
the  system,  and  being  derived  in  starvation  from  the  tissues,  it  is 
reasonable  to  suppose  that  part  of  the  urea  is  also  derived  from  the 
latter,  even  when  nitrogenous  food  is  taken,  and  since  leucin  and 
tyrosin  are  found  in  the  thyroid,  thymus,  parotid,  and  submaxillary 
glands,  kidney,  liver,  and  suprarenal  capsules,  as  well  as  in  the 
pancreas  and  spleen,  analogy  would  lead  us  to  suppose  that  they 
may  be  antecedents  of  the  urea  derived  from  tissue,  as  we  have 
supposed  them  to  be  of  the  urea  derived  from  food.  In  this  con- 
nection it  is  an  interesting  fact  that  M'hile  urea  is  not  found  in  the 
muscles,  spleen,  or  nervous  tissue,  creatin  (C^H^iN^O^)  enters  into 
the  composition  of  muscles  to  the  extent  of  two  per  cent.,  and  into 
that  of  the  spleen  and  probably  of  nervous  tissue  also.  Now,  since 
creatin,  throvigh  dehydration,  readily  becomes  creatinin  (C^H^NgO), 
and  the  latter  through  oxidation,  urea  (CON^H^),  it  is  quite  prob- 
able that  creatin  may  be  an  antecedent  of  urea  arising  out  of  the 
disintegration  of  the  muscular  tissues,  etc.,  but  converted  into  urea 
elsewhere.  It  should  be  mentioned,  however,  that  the  creatin,  or 
rather  creatinin,  normally  found  in  the  urine  is  not  derived  from 
the  muscular  tissue  of  the  body,  but  from  the  food,  since  it  varies 
in  quantity,  increasing  with  a  meat  diet,  but  not  with  exercise,  and 
is  absent  in  starvation.  On  the  supposition  that  urea,  whether 
derived  from  food  or  tissue,  is  not  elaborated  by  the  kidneys,  but 
simply  excreted  out  of  the  blood  brought  to  them,  we  might  expect 
to  find  that  the  blood  of  the  renal  artery  contained  more  urea  (0.03 
per  cent.)  than  that  of  the  renal  vein  (0.01  per  cent.),  but  also  with 
the  extirpation  of  the  kidneys,  or  the  ligation  of  the  ureters,  which 
has  practically  the  same  effect,  that  the  urea  Mould  accumulate  in 

'  Scliultzen  and  Nent-ki,  Zeit.  fiir  Biolofjie,  1872. 
^Pfliiger's  Archiv,  Band  54,  1893,  s.  420. 


URIC  ACID. 


469 


the  blood.  Such  indeed  has  Vjeen  found  experimentally  to  be  the 
case,  Yoit  ^  obtaining-  after  extirpation  of  the  kidneys  in  an  animal 
5.3  grammes  of  urea,  or  almost  the  same  amount  as  Avould  have 
been  normally  excreted  {p.S  grammes)  in  the  same  time.  It  may  be 
mentioned  that  the  toxic  effects  appearing  under  such  circumstances 
appear  to  be  due  not  so  much  to  the  accumulation  of  a  great 
quantity  of  urea  as  to  the  retention  within  the  system  of  other  un- 
defined proteid  substances. 

Uric  Acid. — Of  the  remaining  constituents  of  the  urine,  uric  acid 
(C5H^X^03)  is  the  most  important,  it  being  like  urea,  one  of  the  forms 
in  which  nitrogen  leaves  the  economy.  Indeed,  in  reptiles  and 
birds,  uric  acid  is  the  principal  form  in  which  nitrogen  is  eliminated. 
Uric  acid  existing  in  the  urine  in  the  form  of  urates,  usually  as  a 
brownish-yellowish,  powdery  substance  ;  ammonium  or  sodium 
urate  (Fig.  223)  may  be  readily  obtained  by  the  decomposition  of 
the  same.  Thus,  if  nitric  or  hydrochloric  acid  be  added  to  freshly 
filtered  urine  in  the  proportion  of  about  two  per  cent,  by  volume, 


Fig. 


Fig.  224. 


Sodium  urate  from  urinary  deposit. 


Uric  acid,  deposited  slowly  from  urine. 


and  the  mixture  be  allowed  to  remain  at  rest,  within  twenty-four 
hours  uric  acid  will  be  deposited  as  thin  crystals  on  the  sides  of  the 
vessel.  These  crystals  (Fig.  224)  are  usually  transparent,  yellow- 
ish, rhombic  plates,  with  the  angles  roimded  off,  and  are  frequently 
collected  together  in  rosette,  star-like  clusters  and  spheroidal  masses. 
The  crystalline  forms  of  uric  acid  are,  however,  very  variable, 
depending  upon  the  concentration  of  the  solution  from  which  they 
are  obtained,  the  rapidity  with  which  they  are  formed,  and  whether 
they  are  separated  out  spontaneously  or  by  the  addition  of  acids  to 
the  urine.  Uric  acid  when  freed  from  impurities  is  a  colorless, 
crystalline  powder,  tasteless  and  without  odor.     If   uric  acid  be 

1  Centralblatt  med.  "Wiss.,  1868,  p.  468. 


470  THE  KIDNEYS  AND  URINE. 

boiled  with  nitric  acid  it  dissolves  with  a  yellow  color,  and  with  an 
abundant  liberation  of  gas.  If  the  solution  be  now  evaporated  a 
brilliant  red  stain  is  left,  which  by  the  addition  of  aqua  ammonia, 
becomes  purple.  The  presence  of  uric  acid  and  urates  can  be 
readily  determined  by  this  procedure,  which  is  usually  known  as 
the  murexide  test.  The  amount  of  uric  acid  in  the  urine  can  be 
determined  approximately,  at  least,  by  Haycraft's  method.^  This 
consists  in  making  the  urine  first  alkaline  ;  precipitating  with  an 
ammoniacal  silver  solution,  dissolving  the  precipitate  on  nitric  acid 

(30  p.  c.)  and  then  titrating  the  solution  Math  a  T---sulpho-cyanide 

solution,  1  c.  c.  of  the  solution  corresponding  to  0.00168  grammes 
uric  acid.  The  uric  acid  excreted  in  human  urine  amounts  on  the 
average  during  twenty-four  hours  upon  a  mixed  diet  to  about  0.7 
grammes  (11  grains).  The  amount  eliminated  varies  considerably, 
however,  with  the  kind  of  food  taken,  O.o  grammes  (8  grains)  upon 
a  non-nitrogenous  diet,  2  grammes  (31  grains)  upon  a  nitrogenous 
one,  and  O.'i  grammes  (0.3  grains)  during  starvation,  the  body  sup- 
plying in  the  latter  case  the  nitrogenous  material.  It  would  ap- 
pear, therefore,  that  uric  acid  like  urea  is  derived  from  the  disinte- 
gration of  nitrogenous  food  rather  than  of  tissue.  Uric  acid  is  not 
only  found  in  the  urine  but  also  in  small  amounts  in  the  spleen, 
lungs,  heart,  pancreas,  liver,  blood  (especially  in  gout).  While 
uric  acid  like  urea  is  derived  from  nitrogenous  tissue  or  food,  con- 
siderable difference  of  opinion  still  prevails  among  chemists  as  to 
exactly  how  or  where  in  the  system  it  is  produced.  From  such 
facts  as  that  feeding  an  animal  upon  uric  acid  increases  the  amount 
of  urea  excreted,  the  uric  acid,  through  hydrolysis  and  oxidation, 
splitting  into  urea  and  carbon  dioxide 


Uric  acid.                 Water.          OxTgen. 

Urea. 

Carbon  dioxide. 

C^X^H  O3  +   2(H,0)  +  03  = 

2C0N^H^ 

^  3CO^ 

that  in  reptiles  where  oxidation  is  less  rapid  than  in  mammals  and 
in  birds  when  any  saving  of  oxidation  is  of  advantage,  urea  in  the 
urine  is  replaced  by  uric  acid,  that  the  molecule  of  uric  acid  con- 
tains the  residues  of  two  molecules  of  urea  as  shown  by  the  for- 
mula expressing  its  chemical  constitution 

NH  —  CO 

I  I 

CO         C  —  NHv 

1  II  )  CO  =  C,H,N,03 

XH  —  C  —  NH/ 

it  has  been  held  that  uric  acid  must  be  regarded  as  imperfectly  oxi- 
dized urea.  On  the  other  hand,  it  is  considered  by  many  chemists 
that  uric  acid  cannot  be  an  antecedent  of  urea,  being  formed  by  a  syn- 
thesis, possibly  of  lactic  acid  and  ammonia,  in  the  liver  or  elsewhere, 
rather  than  by  the  imperfect  oxidation  of  proteid  matter.  Accord- 
1  British  MedicalJournal,  1885,  p.  1100. 


HIP  PUBIC  ACID. 


All 


ing  to  this  point  of  view  the  relative  production  of  uric  acid  and 
urea  in  different  animals  depends  not  upon  the  extent  of  oxidation, 
but  on  the  structure  of  the  uriniferous  tubules,  the  amount  of  water 
absorbed,  the  general  physical  conditions  involved,  etc.,  being  better 
adapted  to  the  excretion  of  uric  acid  in  one  kind  of  animal  and  of  urea 
in  another.  It  must  be  admitted,  however,  that  neither  of  these  ex- 
planations offers  a  satisfactory  answer  as  to  why  the  principal  nitrog- 
enous constituent  in  the  urine  of  reptiles  and  birds  should  be  uric 
acid  and  of  mammals  urea.  In  this  connection  it  will  be  recalled 
as  already  mentioned  that  a  number  of  substances  closely  allied  in 
chemical  constitution  to  uric  acid,  such  as  xanthin,  guanin,  hypo- 
xanthin,  adenin,  etc.,  are  found  in  small  quantities  in  the  urine  and 
which  constitute  when  taken  together  the  so-called  xanthin  group. 
Allantoin  (C^HgN^g),  found  in  the  urine  of  children  within  a  few 
days  after  birth,  and  in  very  small  quantities  in  that  of  the  adult 
in  the  allantoic  fluid  (hence  its  name),  is  also  a  derivative  of  uric 
acid,  being  derived  by  the  oxidation  of  the  latter. 

Hippuric  Acid. — Hippuric  acid,  or  benzoyl-amido  acetic  acid 
(CgHgNOg),  Is  owQ  0^  i^Q  few  important  constituents  of  the  urine  that 
is  produced  in  the  kidneys  themselves,  being  formed  in  these  organs 
by  the  union  of  benzoic  and  amido  acetic  acids  (glycin,  glycocoll) 
with  dehydration. 

Benzoic  acid.  Glvcin.  Water.      Hippuric  acid. 

C,Hp^ -h  C^H.NO^  —  H^O  =  C\H3N03 

That  such  is  the  origin  of  hippuric  acid  within  the  economy  ap- 
pears from  the  fact  that  if  arterialized  blood  containing  benzoic  acid 
be  passed  through  the  blood  vessels  of  a  freshly  excised  "  surviving  " 
dog's  kidney,  hippuric  acid  will  be  found  in  the  perfused  blood. 

On  the  other  hand,  as  in  jaun- 
diced patients,  and  in  animals  Fig.  225. 
in  wdiicli  the  liver  is  extirpated, 
or  the  ductus  communis  is  li- 
gated,  the  benzoic  acid  admin- 
istered passes  out  of  the  body  as 
such,  one  w^ould  be  led  to  sup- 
pose that  the  synthesis  with 
glycin  takes  place  in  the  liver. 

It  would  appear,  therefore, 
that  hippuric  acid  may  be  pro- 
duced by  the  synthesis  j  ust  men- 
tioned in  different  parts  of  the 
body,  more  particularly  in  the 
dog  in  the  kidney,  in  the  rabbit 
in  the  liver,  and  in  man  in  one 
or  both  organs.  As  a  further 
confirmation  of  the  synthetic  origin  of  hippuric  acid,  it  may  be  men- 
tioned that  when  benzoic  acid  is  taken  internally  the  amount  of  hip- 


'=?f\ 


^ 


Hippuric  acid.     (Lasdois.) 


472 


THE  KIDNEYS  AND   URINE. 


puric  acid  excreted  in  the  urine  is  increased/  It  is  also  well  known 
that  a  benzoic  acid  residue  exists  in  the  fodder  of  ruminants,  and 
which  accounts  in  the  above  supposition  for  hippuric  acid  replacing 
uric  acid  in  the  urine  of  such  animals.^  As  hippuric  acid  is  found, 
however,  in  the  urine  of  a  starving  man,  or  of  one  upon  a  meat 
diet,  though  in  less  quantity  than  when  on  a  vegetable  or  mixed 
one,  the  benzoic  acid,  like  the  glycin,  must  be  derived  from  the  dis- 
integration of  proteid  materials.  Hippuric  acid  (Fig.  225)  crystal- 
lizes in  semi-transparent,  four-sided  rhombic  prisms  or  columns,  or 
in  needles  if  the  crystallization  is  rapid. 

The  hippuric  acid  excreted  in  the  urine  during  twenty-four  hours 
amounts  upon  a  mixed  diet  to  about  0.7  grammes  (10.8  grains).  If 
the  food  consists,  however,  of  fruit,  especially  plums,  it  may  then 
amount  to  as  much  as  2  grammes  QjO  grains). 

Creatinin. — Creatinin  (C^H^N.^O),  regarded  as  being  the  anhydride 
of  creatin  (C^HgNgOg),  appears  in  the  urine  in  the  form  of  color- 
less, shining,  monoclinic  prisms. 

The  quantity  of  creatinin  excreted  in  the  urine  in  twenty-four 
hours  amounts  on  the  average  to  about  one  gramme.  While  the 
amount  excreted  depends  to  a  great  extent  upon  the  quantity  of 
meat  eaten,  the  creatin  of  the  latter  being  converted  into  creatinin 
and  eliminated  in  that  form,  part  is  also  derived  from  the  proteid 
of  the  body,  as  creatinin  is  still  found  in  the  urine  of  the  starving 
man  even  if  in  diminished  amount. 


Fig.  226. 


Fig.  227. 


Creatinin,  crystallized  from  Lot  water. 
(Lehmann.) 


Calcium  oxalate.    Iieposited  from  liealthy  urine. 


Oxalic  Acid. — Oxalio  acid  (CJi.f)^)  occurs  in  the  urine  in  very 
small  amounts  (0.02  gramme  (0.3  grain)  per  day)  as  calcium  oxalate 
which  is  kept  in  solution  by  the  acid  sodium  phosphate.  When 
deposited  in  the  urine  in  consequence  of  ammoniacal  fermentation, 

1  Matschersky,  Virchow's  Archiv,  1803,  s.  .528. 

2  MeLssner  and  Shepard,  Centralblatt,  1866,  Nos.  43  and  4-1. 


CONJUGATE  SULPHATES.  473 

calcium  oxalate  crystallizes  (Fig.  227)  as  regular  octohedra  or 
double  quadrangular  pyramids  united  base  to  base. 

Oxalic  acid,  as  already  stated/  appears  to  be  derived  from  the 
food,  cabbage,  spinach,  asparagus,  apples,  grapes,  etc.,  containing 
it.  It  should  bo  mentioned,  however,  that,  according  to  Hammar- 
sten,^  oxalic  acid  has  been  found  in  the  urine  during  starvation,  and 
also  upon  a  diet  consisting  exclusively  of  flesh  and  fat,  which  if 
the  case  shows  that  it  may  be  derived  to  some  extent,  at  least,  from 
the  tissues. 

Conjugate  Sulphates. — The  phenol  (C,,H,pS0.3H)  and  cresol 
(CH^SO.^H^)  sulphuric  acids,  and  indoxyl  (C^H^NSO  j  and  skatoxyl 
(CgHj,NSO  j)  sulphuric  acids  that  occur  in  small  quantities  as  alkaline 
salts  in  the  urine  are  derived  as  already  mentioned  ^  from  the  phenol 
(CgH.OH)  and  cresol  (C.H.OH)  and  indol  (C,H„N)  and  skatol 
(CgH.jN)  tliat  are  produced  in  the  intestines  by  the  putrefaction  of  pro- 
teids,  and  which  l)eing  carried  to  the  liver,  the  indol  and  skatol  l)ecom- 
ing  through  oxidation  indoxyl  and  skatoxyl,  couple  with  sulphuric 

Indol.  Indoxvl. 

C3H,N  +  0  =  C3H,(0H)N 

acid  to  form  the  ethereal  or  conjugate  sulphates  and  are  in  that 
form  eliminated  by  the  kidneys.  The  presence  in  the  urine  of 
potassium  indoxyl  sulphate,  or  indican,  as  it  is  usually  called,  can 
be  readily  shown  by  mixing  equal  volumes  of  urine  and  hydrochlo- 
ric acid  and  adding  two  or  three  drops  of  a  solution  of  chlorinated 
lime,  whereby  oxygen  being  liberated,  the  indican  is  decomposed 
into  indigo  blue  and  potassium  acid  sulphate. 

Indican.  Indigo  blue.  Potas.sium  acid  sulphate. 

2C3H^NKSO^      +      O^      =      C\^H,„N^O,      +      2HKS0^ 

By  adding  chloroform  and  shaking  the  mixture  vigorously  for 
some  time,  the  blue  coloring  matter  is  dissolved,  and  after  the  chlo- 
roform evaporates  remains  as  a  deposit.  The  amount  of  indican 
found  in  the  urine  is  very  small,  0.005-0.02  gr.  (0.07-0.3  grains) 
only  being  excreted  in  twenty-four  hours.  It  may  be  mentioned  in 
this  connection,  as  an  interesting  fact,  that  25  times  as  much  indican 
occurs  in  the  urine  of  the  horse  as  in  that  of  man.  Aromatic 
oxyacids,  such  as  paraoxyphenyl  acetic  acid  (C,.HpHC.,H.p.,)  and 
paraoxyphenol-propionic  acid  (C,.H^OHC3H.02),  derived  from  tyro- 
sin  as  intermediate  steps  in  the  putrefaction  of  proteids  in  the  intes- 
tines, are  also  found  in  small  quantities  in  the  urine,  together  with 
some  other  organic  substances,  which  have  been  already  referred  to 
in  our  account  of  the  chemistry  of  the  body. 

Inorg-anic  Constituents  of  the  Urine. — Of  these,  water  is  the  most 

important,  constituting   95.4  per  cent,   of  the  whole  urine,  1572 

grammes  of  urine  containing   1500  grammes  of  water.     The  salts 

of  the  urine  are  taken  into  the  body  with  the  food  and  pass  out  of 

^P.  50.  2  Op.  cit.,  p.  357.  »Pp.  82,  109,  225. 


474  THE  KIDNEYS  AND  URINE. 

it  as  such  in  the  urine  unchanged,  or  they  are  produced  within  the 
system  through  oxidation  of  the  sulphur  and  phosphorus  either  of 
the  food  or  tissue,  the  sulphuric  and  phosphoric  acids  combining 
with  bases  to  form  salts.  The  amount  of  salts  excreted  daily  in  the 
urine  upon  a  mixed  diet  varies  from  9  to  25  grammes  (139  to  386 
grains).  It  is  impossible  as  yet  to  state  exactly  the  manner  in 
which  the  chemical  elements  are  combined  with  each  other  or  the 
acids  with  the  bases,  since  the  composition  of  the  ash  corresponds 
almost  exactly  with  the  direct  analysis  of  the  urine.  It  is  for  this 
reason  that  the  amounts  of  chlorine  and  sodium,  for  example,  oc- 
curring in  the  urine  are  stated  separately  in  an  analysis  of  the  latter 
rather  than  as  combined  as  sodium  chloride.  It  is  very  probable, 
however,  that  the  sodium,  and  potassium  also,  occiu'ring  in  the 
urine  do  exist  there  as  chlorides ;  phosphoric  acid  in  combination 
with  sodium  and  potassium  as  alkaline,  and  with  calcium  and  mag- 
nesium as  earthy  phosphates  ;  sulphuric  acid  with  sodium  and  po- 
tassium as  alkaline  sulphates  ;  uric  acid  as  sodium  urate.  With  the 
exception  of  water,  sodium  chloride  constitutes  by  far  the  greatest 
part  of  the  inorganic  principles  of  the  urine,  as  much  as  from  10  to 
15  grammes  (154  to  231  grains)  being  excreted  in  twenty-four 
hours.  The  amount  of  sodium  chloride  occurring  in  the  urine  de- 
pending almost  entirely  upon  that  contained  in  the  food,  the  chlo- 
rine estimated  as  such  will  vary  therefore  proportionally. 

The  phosphoric  acid  of  the  urine  is  excreted  principally  in  the 
form  of  potassium  and  sodium  phosphate.  The  amount  of  alkaline 
phosphates  excreted  in  twenty-four  hours  (2.6  grammes,  45  grains) 
varies  with  the  kind  of  food  taken,  being  greater  on  an  animal  than 
on  a  vegetable  diet,  the  former  being  richest  in  soluble  phosphates 
or  substances  yielding  readily  phosphoric  acid.  The  earthy  phos- 
phates, calcium  and  magnesium  phosphate,  while  derived  principally 
from  the  food,  are  no  doubt  formed  also  within  the  system  through 
the  decomposition  of  lecithin,  nuclein,  etc.  The  earthy  phosphates 
excreted  in  twenty-four  hours  amount  to  about  2.3  grammes 
(35.5  grains).  The  alkaline  sulphates  excreted  in  the  urine  amount 
in  twenty-four  hours  to  about  2.5  grammes  (40  grains).  The  sul- 
phuric acid  excreted  in  the  urine  is  derived  from  the  food  only  to 
a  very  small  extent,  the  greatest  part  being  formed  within  the  body 
by  the  burning  of  the  tissues.  It  is  for  this  reason  that  the  total 
destruction  of  body  proteid  can  be  estimated  from  the  amount 
of  sulphur  eliminated  in  the  urine '  as  well  as  from  the  nitrogen. 
The  sulphuric  acid  eliminated  is,  as  regards  the  nitrogen  in  the 
ratio  of  1  to  5.  Sulphur  occurs  in  the  urine  not  only  in  the  form 
of  sulphates  and  ethereal  sulphates,  but  also  as  "  neutral  sulphur  " 
in  which  form  it  is  found  in  cystin  and  sulphocyanides.  In  ad- 
dition  to   the   constituents  already  mentioned   the   urine  contains 

1  Proteid  :  sulphur  ::  100  :  2.2. 

Proteid  =  S  X  2^5  =  45.-1. 


FEE.VEXTATIOX  OF  THE  UEIXE. 


475 


usually  traces  of  nitric  and  slicic  acids,  ammonia  and  iron,  carbon 
dioxide  in  varying  amounts,  nitrogen  in  small  quantities  (0.8  vol. 
per  cent.)  and  oxygen  in  traces. 

Fermentation  of  the  Urine. — In  concludinof  our  account  of  the 
urine,  the  changes  produced  in  it  by  standing  may  be  here  briefly 


Fig.  228. 


Fig.  229. 


Micrococcus  ureje.     (Landois. 

alluded  to.  It  "will  be  re- 
membered that  the  urine, 
when  first  passed,  is  acid,  the 
acidity  being  due  to  the  acid 
sodium  phosphate.  AVithin 
twelve  or  twenty-four  hours, 
however,  through  the  devel- 
opment of  a  lactic  or  acetic 
acid  fermentation,  Ijrought 
about  by  mucus  or  fungi,  uric 

acid  and  acid  urates  are  precipitated,  and  the  urine  undergoes  the 
so-called  "  acid  fermentation." 

After  a  few  days  this  acid  fermentation  ceases,  through  the  con- 
version of  urea  by  the  addition  of  water  into  carbonate  of  ammonium. 

Urea.  Water.  Ammonium  carbonate. 

CON^H^     +     2(ap)     =     (NHJ„C03 

the  changes  being  brought  about   by  the  action  of  the  micrococcus 
urere  (Fig.  228). 

The  acid  sodium  phosphate  being  then  neutralized  by  the  ammo- 
nium carbonate  so  formed,  the  urine  becomes  alkaline. 


Ammonium  magnesium  phosphate.    Deposited  from 
healthy  urine,  during  alkaline  fermentation. 


Acid  sodium  phos. 

2NaH  PO. 


Ammon.  carb. 

(^^HJ,C03 


Ammon.  sodium  phos. 

=    2XaXH,HP0. 


Carb.  dioxide. 


Water. 

HO 


With  the  alkalinity  of  the  urine,  the  earthy  phosphates,  being 
only  soluble  in  acid  flnids,  are  precipitated,  and  in  combining  with 
the  ammonia  give  rise  to  the  formation  of  the  triple  phosphate  or 
ammonium  magnesium  phosphate  (Fig.  229). 


Magnesium  phos. 

2MgHP0^    + 


Ammon.  carb.  Ammon.  mag.  phos. 

(NHJ^CO^     =    2MoXH^P0^ 


Carb.  dioxide.        Water. 

C0„       +     H„0 


As  decomposition  goes  on,  the  ammonium  carbonate,  after  satu- 
rating the  elements  with  which  it  is  capable  of  uniting,  is  given  oflP 
free,  giving  rise  to  the  ammoniacal  odor  of  the  urine,  and  this  con- 
tinues until  all  of  the  urea  has  disappeared. 


CHAPTER  XXVT. 

THE  NEEVOUS  SYSTEM. 

Ix  describing  the  manner  in  which  food  is  digested,  absorbed, 
and  circulated  through  the  economy  as  Wood,  supplying  the  mate- 
rial for  the  repair  of  the  tissues  and  the  production  of  energy,  of  the 
absorption  of  oxygen,  and  exhalation  of  carbon  dioxide,  water,  urea, 
etc.,  the  influence  exerted  by  the  nervous  system  upon  these  pro- 
cesses has  only  been  alluded  to,  if  at  all,  in  an  incidental  manner. 
That  the  phenomena  of  nutrition  are  not  dependent  upon  the  nerv- 
ous system,  however  much  it  may  be  influenced  by  the  latter,  is 
shown  from  the  fact  that  the  nutrition  of  the  lower  animals,  in 
which  the  nervous  system  is  but  little  developed,  and  of  plants,  in 
which,  with  but  few  exceptions,  so  far  as  is  known,  it  is  altogether 
absent,  does  not  differ  from  the  higher  forms  of  animal  life.  In- 
deed, the  essential  difference  between  the  nutrition  of  plants,  as 
compared  with  animals,  consists  of  the  deoxidation  by  plants  of  the 
water,  carbon  dioxide,  and  ammonia  constituting  their  food,  into 
starch,  sugar,  fats,  albumin,  and  the  storing  up  of  energy,  and  the 
oxidation  by  animals  of  the  latter  substances  constituting  their  food, 
into  carbon  dioxide,  water,  and  ammonia,  and  the  expenditure  of 
energy.  But  while  such  a  broad  distinction  exists  between  plants 
and  animals,  as  compared,  on  the  whole,  nevertheless,  it  must  not 
be  lost  sight  of  that  oxidations,  analytical  processes,  are  going  on 
in  the  economy  of  plants  incidental  to  the  elaboration  and  circula- 
tion of  the  sap,  the  production  of  heat,  in  budding,  flowering,  etc., 
and  deoxidations,  synthetical  processes  in  the  economy  of  animals. 
Indeed,  as  has  already  been  mentioned,  no  sharp  line  of  demarca- 
tion can  be  drawn  between  vegetable  and  animal  life.  While  nu- 
trition is  not  actually  dependent  upon  the  nervous  system,  never- 
theless every  one  is,  however,  conscious  of  the  extent  to  which  it 
influences  nutritive  processes.  The  sudden  manner  in  which  diges- 
tion is  brought  to  a  stop  by  a  piece  of  bad  news,  the  weakness 
of  the  heart  induced  by  nervous  shock,  the  sudden  blush  or  pallor 
due  to  emotion,  are  familiar  illustrations.  The  flow  of  the  secre- 
tions into  the  alimentary  canal  in  response  to  food,  the  rhythmical 
action  of  the  heart  and  lungs,  though  unconsciously  brought  about, 
are  due  equally  to  the  action  of  the  nervous  system.  The  influence 
of  the  nervous  system  upon  nutrition  has  often  been  compared  to 
that  exercised  by  the  rider  upon  the  movements  of  a  horse,  the  en- 
ergy being  put  forth  by  the  latter,  but  controlled  with  bit  and  spur 
by  the  former.  Man,  like  other  animals,  is,  however,  something 
more  than  a  mere  nutritive  machine,  becoming  conscious,  through 


STRUCTURE  OF  THE  NERVOUS  SYSTEM. 


477 


liis  uervoiis  system,  of  an  external  world.  Impressions  made  upon 
afferent  nerves  by  heat,  light,  sound,  etc.,  when  conveyed  to  the 
sensorium,  give  rise  there  to  sensations,  out  of  which  are  developed 
in  still  higher  centers,  emotions,  desires,  ideas,  while  voluntary  im- 
pulses are  transmitted  in  the  reverse  direction  by  efferent  nerves  to 
the  muscles.  In  a  word,  it  is  by  means  of  the  nervous  system  that 
the  various  nutritive  processes  that  we  have  studied  are  brought 
into  relation  with  each  other — are  coordinated — that  we  feel,  think, 
will. 

Structure  of  the  Nervous  System. 

The  nervous  system  consists  morphologically  of  an  association 
of  numerous  and  independent  neurons,  that  is,  of  nerve  cells  and 
their  outgrowths.  The  nerve  cells  are  confined  in  a  great  measure 
to  the  cerebro-spinal  axis  and  ganglia  ;  the  outgrowths  are  found, 
however,  throughout  the  body.     Xerve  cells  (Fig.  230)  are  nucle- 


Fu;.  230. 


Fig.  231. 


Nerve  cells,  from  the  anterior  horn  of  gray 
substance  of  the  spinal  cord. 


Neuron  with  short  axon  immediately  break- 
ing up  into  numerous  fine  filaments,  n  c. 
Nerve-cell  proper,  x.  Axon.  d.  Dendrites. 
From  the  cerebellum.     (Andeiezen.) 


ated  cells  usually  more  or  less  ovoid  in  shape,  and  differ  considerably 
in  size,  varying  in  diameter  from  the  j^  to  the  ^  of  a  millimeter 
(2'"5Vo  ^^  sio^  ^^  '"^^  inch).  According  to  recent  researches  ^  a  nerve 
cell  appears  to  consist  of  a  kind  of  framework,  continuous  with  the 
fibrilhe  of  the  nerve  fiber,  in  the  meshes  of  which  are  contiiined 
small  masses  or  granules  readily  stainable  with  basic  aniline  dye. 
Nerve  cells  occur  not  only  separately,  but  in  many  cases  are  aggre- 
gated together  as  ganglia.  The  latter  are  generally  provided  with  a 
thin  but  strong  and  closely  adherent  capsule  or  sheath  continuous 
with  the  epineurium  or  supporting  framework  of  the  nerve  fibers. 

'Nissl,  Allgemein  Zeits  fiir  Psychiatrie,  Band  52,  1890,  s.  1147. 


478 


THE  NERVOUS  SYSTEM. 


Fig.  232. 


Mhi 


Neuron  with  long  axon  proceeding  as  an  axis 
cylinder  of  a  nerve  fiber,  n  c.  Nerve-cell 
])"roper.  rf.  Dendrites,  j-.  Axon,  d  jr.  Dendrite 
sliowing  gemmula;.  a  d  <j.  Apical  dendrite 
with  gemmulse.  c.  Collaterals,  e.  End  tufts. 
Pyramidal  cell  of  the  cerebral  cortex.  (.S.  Ra- 
m6x  y  Cajal.) 


From  mo.st  nerve  cells,  in  mam- 
mals at  least,  there  arises  one 
principal  branch  or  process,  the 
axon.  Such  cells  are  called, 
therefore,  monaxonic.  In  some 
of  the  lower  animals,  however, 
the  nerve  cells  giving  rise  to  two 
or  more  axons  are  therefore  di- 
axonic  and  polyaxonic.  The 
axons  differ  very  much  in 
length,  those  of  the  cerebellum 
(Fig.  2."31),  being  less  than  a 
millimeter,  those  of  the  pyram- 
idal cells  of  the  cerebral  cortex 
(Fig.  232,  x)  as  much  as  60  cent. 
(24  inches)  long.  Indeed,  the 
axons  extending  from  the  lum- 
bar region  of  the  cord  to  the  feet 
attain  a  length  of  100  cent.  (40 
inches).  The  volume  of  the 
axons  in  reference  to  the  cells  of 
which  they  are  the  outgrowths  is 
also  very  variable.  Thus,  while 
the  volume  of  the  axon  in  the 
cerebral  cortex  has  been  esti- 
mated as  being  220  times  that  of 
the  cell,  the  volume  of  the  axon 
in  the  lumbar  portion  of  the 
cord  may  be  1570  times  as  great. 
In  most  cases  the  axons  give  off 
both  near  their  origin  and 
throughout  their  course  collat- 
eral branches  (Figs.  231,  232  e), 
the  so-called  paraxons,  fine  fila- 
mentous processes  which  leave 
the  parent  l^ranch  at  right 
anoles  and  terminate  in  end  tufts 
(Fig.  232).  The  axon  itself 
terminates  always  in  a  free  ex- 
tremity. The  latter  may  con- 
sist of  a  free  undivided  filament, 
but  more  usually  splits  up  into 
a  number  of  very  fine  filaments 
or  end  tufts  (Fig.  232)  similar 
to  those  terminating  the  par- 
axons. 

From  nerve  cells  there  arise 
not  only  axons  but  other  out- 


NEUROBLASTS. 


479 


growths,  which,   dividing  dichotomously,   present  a   tree-like  ap- 
pearance ;  hence  the  name  of  dendrites  or  dendrons  (Figs.  231  and 


Fig.  233. 


Fig.  234. 


Ontogenetic  development  of  a  neuron  (pyramidal 
cell  of  the  cerebral  cortex)  in  a  typical  mammal. 
a.  Neuroblast  with  primitive  axon  (ai)  and  without 
dendrons  (dendrites),  h.  Commencing  dendrons. 
c.  Dendrons  further  developed,  d.  First  appearance 
of  collaterals,  e.  Further  development  of  collaterals 
and  dendrons.     (S.  Ramon  y  Cajai,.) 


Medulated  nerve  fiber. 
A.  Xode  of  Ranvier.  B. 
Xucleiis  belonging  to  the 
neurilemma.  ''.  Axis-cyl- 
inder. P.  Neurilemma 
rendered  distinct  by  the 
retraction  of  the  myelin 
of  the  medullary  sheath. 
In  the  left-hand  figure  the 
clefts  of  Lantermann  are 
shown  as  white  lines  in 
the  dark  myelin.  The  fig- 
ures are  taken  from  speci- 
mens treated  with  osmic 
acid. which  colors  the  fatty 
constituent  of  the  myelin 
a  dark  brown  or  black. 
(Key  and  Retzr's.) 


232,  d)  by  which  they  are  usually 
designated.  The  dendron.s,  while  de- 
scribed as  outgrowths  or  processes  of 
the  nerve  cell,  should  rather  be  re- 
garded morphologically  as  the  split-up  portion  of  its  pe- 
riphery than  as  differentiated  processes  like  the  axons.  In 
many  instances  there  ari.se  from  the  dendrons  short  rec- 
tangular or  oblique,  lateral  projections  or  buds,  the  so- 
called  gemmulse  (Fig.  232),  etc.  The  nerve  cells  with 
their  outgrowths  are  derived  from  the  spherical  cells 
which  appear  during  the  third  or  fourth  month  of  intra- 
uterine life  ^  among  the  columnar  epiblastic  cells  "which 
form  the  primitive  medullary  tube.  These  cells  divide  in 
such  a  way  that  of  two  daughter  cells  resulting  from 
division,  while  one  remains  as  a  germinal  cell  the  other 
becomes  a  neurobla.st  and  moves  away.  It  is  an  interest- 
ing fact  that  the  power  of  moving  possessed  by  the  nerve 
cells  at  this  early  period  of  their  existence  appears,  from 
recent  researches,"  to  be  retained,  to  some  extent  at  least, 
throughout  life.  The  neuroblasts  so  produced  soon  lose 
their  spherical  shape  and  become  pyriform,^    In  the  mean- 

^His,  Du  Bois  Reymond's  Archiv,  1889. 

^F.  X.  Dercum,  Unir.  Medical  Magazine,  April,  1897. 

'  Ramon  y  Cajal,  El  nuevo  concepto  de  la  liistologia  de  los  centres 
nerviosos,  Revista  De  Ciencias  De  Barcelona,  Tomo  xviii.,  1892,  pp. 
361-457. 


iSf.  it. 


480  THE  NERVOUS  SYSTEM. 

time  a  protuberance  appears  at  one  point  of  the  periphery  of  what 
may  be  now  called  the  nerve  cell,  and  which,  gradually  elongating, 
becomes  the  primitive  axon  (Fig.  233,  ax),  while  from  the  opposite 
pole  of  the  cell  arise  the  dendrons.  With  the  assumption  of  the 
nerve  cell  of  its  typical  form  and  the  production  of  chromatic  and 
pigmentary  materials,  etc.,  its  branches  groAV,  increasing  in  length 
and  diameter,  the  axon  being  gradually  converted  into  a  naked,  gray 
axis-cylinder  (Fig.  234),  or  that  portion  of  the  ultimate  nerve  fiber 
which  conveys  the  nervous  impulse  from  the  brain  and  cord  to  the 
periphery  or  in  the  reverse  direction.^  DifFerence  of  opinion  still 
prevails  among  histologists  as  to  the  structure  of  the  axis-cylinder, 
according  to  some  ^  it  being  composed  of  slender  fibrill?e  floating  in  a 
coagulable  plasma,  to  others  ^  of  a  spongy  framework,  in  the  meshes 
of  which  is  a  semi-fluid  plasma,  the  nervous  impulse  being  trans- 
mitted through  the  fibrillse,  according  to  the  one  view,  and  through 
the  plasma,  according  to  the  other.  The  axis-cylinder  appears  to 
be  chemically  of  an  albuminous  nature,  insoluble  in  water,  alcohol, 
and  ether,  but  soluble  in  a  boiling  solution  of  sodium  hydrate. 
As  development  advances  the  naked,  gray  axis-cylinders,  or  fibers 
(Fig.  234,  C),  become  invested  in  the  brain  and  spinal  cord,  except 
at  their  origin  and  termination,  with  a  white  medullary  sheath,  the 
myelin,  or  so-called  white  substance  of  Schwann  (Fig.  234),  a 
transparent,  highly  refractive  oleaginous  material,  and  to  which  the 
white  glistening  aspect  of  the  nerve  fiber  is  due.  In  the  case  of  the 
peripheral  nerves  the  white  substance  of  Schwann  becomes  covered 
in  turn  by  a  membranous  sheath,  the  neurilemma,  tubular  mem- 
brane, or  sheath  of  Schwann  (Fig.  234,  P),  a  colorless,  transparent, 
somewhat  elastic,  almost  homogeneous  membrane,  the  neurilemma, 
bears  to  the  nerve  fiber  in  its  general  ])roperties  very  much  the  same 
relation  that  sarcolemma  does  to  muscular  fiber,  and  serves,  without 
doubt,  as  a  protective  covering  to  the  white  substance  of  Schwann, 
and  the  axis-cylinder  enclosed  by  the  former.  At  regular  intervals, 
along  the  neurilemma,  may  be  observed  indentations,  the  so-called 
constrictions,  or  nodes  of  Ranvier  (Fig.  234,  A).  At  these  nodes 
the  white  substance  of  Schwann,  or  medullary  sheath,  is  indented  to 
such  an  extent  that  the  neurilemma,  or  sheath  of  Schwann,  comes 
in  contact  with  the  axis-cylinder,  the  spaces  outside  the  neurilemma 
being  filled  in  with  a  cement-like  substance.  From  the  fact  that 
a  substance  like  picro-carmine  difliises  into  the  axis-cylinder  only 
at   the   nodes,    but   not   into   the   whole    substance,    it   is   possible 

'  Since  tlie  above  was  written  there  has  appeared  an  article  by  Apathy  ( Mittheil 
aus  der  zoo  Station,  zu  Neapel,  V.  12,  1897),  in  which  it  is  held  that  while  the 
nerve  cell  produces  neuro-tibrils,  the  ganglion  cell  produces  the  force  whicli  is  to  be 
conducted,  the  neuro-tibrils  traversing  the  ganglion  cells  and  terminating  in  or 
around  a  muscle  or  sense  cell.  According  to  the  same  author  the  cell  process  of  a 
ganglion  cell  not  only  contains  both  cellulipetal  (centripetal)  and  cellulifugal  (cen- 
trifugal) fi})ers,  but  the  nerve  processes  ana-stomose.  If  these  views  be  substantiated 
the  conception  of  a  neuron  will  have  to  be  modified  or  even  abandoned. 

^Kuppferu.  Boveri,  Abhandl.  d.  k.  bayer.  Akad.  d.  Wissen.,  1885. 

''Schiifer,  Quain's  Anatomy,  10th  edition.  Vol.  i.,  1891. 


MEDULLARY  XERVE  FLEERS. 


481 


that  it  is  at  such  points  that  nutritive  material  finds  its  way  into 
the  axis-cylinder  and  effete  matter  a  way  out.  Each  interannular 
segment  of  that  part  of  the  nerve  fiber  below  the  nodes  exhibits, 
when  stretched,  oblique  lines  running  across  the  white  substance, 
and  known  as  the  incissures  of  Lantermann.  Oval  nuclei  (Fig. 
234,  B)  may  also  be  seen  at  intervals  between  the  neurilemma  and 
the  white  substance  of  Schwann. 

The  aggregation  of  medullary  nerve  fibers  such  as  those  just  de- 
scribed into  bundles  and  the  further  union  of  such  bundles  into 
larger  ones  give  rise  to  the  peripheral  nerves,  the  ultimate  nerve 
fibers  of  the  latter  being  separated  from  each  other  by  the  endo- 
neurium  (Fig.   235,  ed),  each  bundle  of  nerve  fibers  being  sur- 


FiG.  235. 


Fig.  236. 


a 


Transverse  section  of  part  of  the  median  nerve,  ep.  Epineurium. 
pe.  Perineurium,  ed.  Endoneurium.  (After  Eichhorst.)  a,  a.  Fu- 
niculus.    (Landois.) 


u  ■ 


Fibers  of  Eemak ; 
magnified  300  diame- 
ters. With  the  gelati- 
nous fibers  are  seen  two 
of  the  ordinary,  dark 
bordered  nerve  fibers. 
(Robin.) 


rounded  by  its  perineurium  pe,  and  the  bundles 
or  funiculi  being  supported  by  the  perineurium. 
The  axis-cylinders  that  occur,  however,  largely 
in  the  sympathetic  and  to  some  extent  also  in  the 
cerebro-spinal  nerves  differ  from  those  just  described  in  not  being 
invested  with  a  medulla,  though  covered  with  a  neurilemma,  or 
membranous  sheath.  The  non-medullated,  gelatinous  nerve  fibers, 
or  fibers  of  Eemak  (Fig.  236)  as  they  are  often  called,  are  pale, 
flattened,  gray,  granular  fibers  presenting  well-marked  oval  nuclei. 
It  is  impossible  to  say  at  present  whether  the  non-medullated  nerve 
fibers  have  different  functions  from  those  of  the  medullated  ones, 
or  to  assign  any  definite  function  to  the  medulla  when  present. 
From  the  fact  that  the  axis-cylinder  is  the  only  constant  portion  of 
the  ultimate  nerve  fiber,  the  intermediate  white  substance  and  ex- 
ternal sheath  being  absent  at  the"  origin  and  termination  of  the  lat- 
ter, there  can  be  no  doubt  that  it  is  the  most  important,  indeed,  the 
31 


482 


THE  NERVOUS  SYSTEM. 


essential,  portion,  functionally,  of  the  nerve  fiber,  the  remaining 
portions  having  accessory  functions  no  doubt  of  some  kind.  Inas- 
much as  up  to  the  fifth  month  of  intrauterine  life  the  nerves  gen- 
erally have  essentially  the  same  structure  as  the  so-called  gelati- 
nous fibers  of  the  adult,  and  as  during  the  regeneration  of  nerves 
after  injury  or  division  the  new  elements  pass  in  their  development 
through  a  transitory  stage  comparable  in  structure  to  that  of  the 
gelatinous  fibers,  the  latter  may  be  regarded  perhaps,  morpholog- 
ically, as  undeveloped  medullated  or  non-medullated  fibers. 

If  the  nerve  fibers  be  traced  from  their  origin  in  the  nerve  cells 
of  the  cerebro-spinal  axis  to  their  termination  in  muscles,  glands 
of  the  periphery,  or  in  the  reverse  direction  from  the  sensory  or- 
gans to  their  termination  in  the  cells  of  the  cord  and  brain,  it  will 
be  observed  as  already  mentioned  that  the  only  part  of  the  ulti- 
mate nerve  fiber  found  at  either  origin  or  termination  is  the  axis- 
cylinder.  Thus  in  the  termination  of  nerve  fibers  in  muscles  where 
the  axis-cylinder  passes  into  the  latter,  expanding  into  the  motor 
plate  (Fig.  237),  the  neurilemma  of  the  nerve  fibers  becomes  con- 

FiG.  237. 


Nerve-ending  in  muscular  fiber  of  a  lizard.  (Lacerta  viridis.)  a.  Eud-plate  seen  edgeways. 
6.  From  the  surface.  <V,  ,S'.  Sarcolemma.  P,tP.  Expansion  of  axis-cj'linder.  In  6  the  expansion 
of  the  axis-cylinder  appears  as  a  clear  network  branching  from  the  divisions  of  the  medullated 
fiber.    Highly  magnified.     (Kuhne.) 


tinuous  with  the  sarcolemma  of  the  muscle,  while  the  white  sub- 
stance of  Schwann,  though  continuing  to  the  muscle,  does  not, 
however,  penetrate  into  it,  and  while  there  may  be  still  doubt  pre- 
vailing as  to  whether  the  axis-cylinder  passes  into  the  nuclei  of  the 
cells  of  a  gland  in  the  manner  supposed  to  be  the  case  by  Pfliiger 
and  others,  in  the  salivary  gland,  for  example,  there  is  no  doubt 
that,  however  exactly  the  axis-cylinder  does  terminate  in  glands,  it 
is  the  only  part  of  the  nerve  fiber  that  actually  reaches  the  cells, 
of  which  such  organs  consist.  Such  is  essentially,  also,  the  dispo- 
sition that  obtains  in  the  case  of  sensory  organs,  so  far  as  has  been 
established.     Thus,  whether  it  be  a  Pacinian  corpuscle  attached  to 


TACTILE  CORPUSCLES. 


483 


sensor}^  nerves  (Fig.  238,  A,  B),  or  a  tactile  corpuscle  (Fig.  239), 
as  we  shall  see,  are  present  in  the  skin,  or  an  end  bulb  (Fig.  240) 


A 


Fig.  238. 


A  nerve  of  the  middle  finger,  with  Pacinian 
bodies  attached.   Xatural  size.    (He>"le  and  Kol- 

LIKER.) 

such  as  is  found  in  the  conjunc- 
tiva ;  in  each  instance  the  neuri- 
lemma of  the  nerve  fiber  becomes 
continuous  with  the  capsule  en- 
closing such  bodies,  the  white  sub- 
stance of  Schwann  remains  with- 
out the  latter,  the  axis-cylinder 
alone  penetrating  within. 

"Rvnprimpnfql     in  vpi;ticrnfinn      qc;    sue  envelope,    e.  Axis-cylinder,  with  its  end 

jLxpeiimtniai    inxcsugaiion,   as   provided  at/.    (Qualv.) 
well  as  morphological  considera- 
tions, proves  that  the  axis-cylinders  of  the   nerve  fibers  are  the 
avenues  by  which  nervous  impulses  emanating  from  the  cells  of  the 


Vater's  or  Pacini's  corpuscle,    a.  Stalk.    6. 
Nerve  fiber  entering  it.    a,  d.  Connective  tis- 


FlG.  239. 


Fig.  240. 


\ 


a.  Tactile  corpuscle.    6.  Xerve.     (Qcaix.) 


Three  nerve-end  bulbs  from  the  human  con- 
junctiva, treated  with  acetic  acid.  Magnified. 
300  diameters.     (Quaix.  ) 


brain  and  cord  are  transmitted   as  eflPerent  impulses  to  muscles, 
glands,  etc.,  and  by  which  impressions  made  upon  the  skin,  sensory 


484 


THE  NERVOUS  SYSTEM. 


organs  are  transmitted  as  afferent  ones  to  the  cells  of  the  cord  and 
brain.  As  the  neurons  of  which  the  nervous  system  is  composed 
are,  however,  entirely  independent  of  each  other,  never  absolutely 
continuous,  it  must  be  admitted  that  even  though  a  nervous  im- 
pulse may  pass  continuously  from  the  cerebral  cortex  (Fig.  241, 
/)  to  the  lumbar  enlargement  of  the  cord  4'  that  arriving  there 
it  must  pass  over  a  gap,  4'  to  5,  in  order  to  reach  the  next  neuron, 
N  I,  that  will  in  turn  carry  it  on  to  the  foot.  Or  let  us  suppose 
that  an  impression  made  upon  the  skin  (Fig.  242,  1)  is  transmitted 


Fig.  241. 


Fig.  242. 


ATJZ 


Diagrammatic  representation  of  cerebral  and 
spinal  motor  cells  with  axons.  1.  Cerebral  cell. 
2.  Axon.  .3,  4.  Collaterals.  4'.  End  tufts.  5. 
Spinal  cell.  6.  Axon.  7.  Limit  of  spinal  cord. 
jV/.  Motor  nerve.  8.  Muscle.  9.  Muscle-end  plate. 
(Raubek.  ) 


Diagrammatic  representation  of  cerebral 
and  spinal  sensor.v  cells  with  axons.  1.  Skin 
end  tufts.  2.  Limit  of  epidermis.  3.  Axon. 
4.  Common  stem.  5.  Cell  in  spinal  ganglion. 
6.  Axon.  7.  Limitof  sjiinal  cord.  8.  Ascend- 
Ingbranch.  9.  Descending  branch.  10.  End 
tufts.    11.  Si)inal  cell.  12.  Axon.    (Raubek.) 


continuously  to  a  cell  5  in  a  spinal  ganglion  and  thence  to  10  ;  on 
arriving  at  the  latter  point  it  must  pass  over  a  gap  in  order  to  reach 
the  next  neuron,  ^Y  11.^  It  will  be  observed  tliat  there  arises  from 
the  cell  5  (Fig.  242)  in  the  spinal  ganglion  one  outgrowth  or  nerve 
fiber  that  conducts  in  two  directions  towards  the  nerve  cell  and 
away  from  it,  presenting  apparcntly'an  exceptional  disposition  to 
that  already  described.  The  study  of  development  shows,  how- 
1  A.  Eauber,  Lclirbucli  Dcr  Anatomic  Des  Menschen,  Zweiter  Band,  1S98,  s.  270. 


CHEMICAL  COMPOSITION  OF  NERVOUS  TISSUES.       485 

ever,  that  such  a  nerve  fiber  consists  really  of  two  fibers,  afferent 
and  efferent,  which  have  become  so  closely  associated  that  their 
original  identity  is  lost.  Such  cells  do  not  differ,  therefore,  func- 
tionally from  those  in  which  the  outgrowths  are  situated  at  different 
points  of  the  cell.  Various  explanations  have  been  offered  as  to 
how  the  nervous  impulse  in  the  first  neuron  sets  up  an  impulse  in 
the  second  one.  It  has  been  urged  that  the  neurons  may  extend 
their  outgrowths  until  they  come  in  contact  temporarily  with  each 
other,  or  that  the  secondary  nervous  impulse  is  developed  through 
a  process  of  induction — or  that  the  tips  of  the  nerve  fibrils  cause 
some  chemical  change  in  the  intervening  substance  Avhich  gives  rise 
to  the  secondary  impulse.  It  must  be  admitted,  however,  that  these 
so-called  explanations  are  merely  hypotheses,  and  that  the  manner 
in  which  nervous  impulses  are  transmitted  from  neuron  to  neuron 
is  not  as  yet  understood.  Nerve  cells,  like  all  cells,  have  a  life  his- 
tory, and  as  recent  researches  ^  show,  in  old  age  the  chromatic 
substance  of  the  cells  diminish  while  the  pigment  increases,  the 
cytoplasm  becomes  vacuolated,  the  outgro^vths  atrophy,  and  in  some 
instances  the  entire  cell  is  absorbed. 

Chemical  Composition  of  the  Nervous  Tissues. — Less  is  known  of 
the  composition  of  the  nervous  tissues  than  of  any  other  tissues  of 
the  body.  They  appear,  however,  like  the  tissues  in  general,  to  be 
composed  largely  of  water,  which  enters  into  the  constitution  of  the 
white  matter  to  the  extent  of  70  per  cent,  and  into  that  of  the  gray 
to  about  75  per  cent.  Among  the  solid  constituents  of  the  nervous 
tissues  the  most  important  are  insoluble  albumin  and  connective 
tissue,  protagon,  cholesterin,  neurokeratin,  nuclein,  and  mineral 
bodies.^  Of  these  substances  albumin  and  connective  tissue  occur 
in  greater  quantity  in  the  gray  matter  than  in  the  white,  the  re- 
maining ones,  however,  in  greater  quantity  in  the  white  than  in  the 
gray.  Protagon  (C^.^H^^^j^X.POg.),  a  crystalline  substance,  consists, 
according  to  most  chemists,  of  lecithin  and  cerebrin.  Lecithin  ap- 
pears, as  already  mentioned,^  to  be  a  triatomic  alcohol  readily  break- 
ing up  into  fatty  acids,  glycero-phosphoric  acids,  and  cholin,  the 
latter  giving  rise  to  neurin,  Cerebrin  resembles  lecithin  in  being 
a  nitrogenous  substance,  but  differs  from  the  latter  in  not  contain- 
ing phosphorus  ;  it  appears  to  be  a  glucoside  yielding  that  form 
of  sugar  known  as  galactose.  The  cholesterin  found  in  the  nervous 
tissues  occurs  partly  free  and  partly  in  chemical  combination. 
Neurokeratin  is  found  in  the  peripheral  nerves  as  a  delicate  sheath 
coverinsT  the  axis-cvlinder  and  white  substance  of  Schwann.  Nuclein, 
or  the  substance  of  which  the  nucleus  of  the  nerve  cell  is  composed, 
appears  to  be  a  phosphorized  albuminoid.  The  mineral  bodies  oc- 
curring in  the  nervous  tissues  consist  of  the  salts  of  potassium, 
sodium,  magnesium,  calcium,  and  iron.  Extractives,  such  as  crea- 
tin,  xanthin,  hypoxanthin,  moist  lactic  acid,  leucin,  uric  acid,  and 
urea  are  found  in  small  quantities. 

'Hodge,  Journal  of  Physiology,  Vol.  xvii.,  1894. 
'^  Hammarsten,  op.  cit.,  p.  279.  ''See  p.  66. 


CHAPTER  XXVII. 

THE  NERVOUS  SYSTEM.— (Contiiiued.) 

BATTERIES.     OHMS   LAW.     INDUCTION  APPARATUS.     PEN- 
DULUM MYOGRAPH.     LATENT  PERIOD.     VELOCITY 
OF  CONDUCTION  OF  NERVOUS  IMPULSE. 

From  daily  observation  we  learn  that  all  our  actions  are  the  re- 
sult of  motives  or  stimuli.  Impressions  made  upon  the  surface  of 
the  body  and  transmitted  by  nerves  to  the  central  nervous  system 
and  there  giving  rise  to  sensations,  are  immediately  or  mediately 
followed  by  actions.  The  impressions  made  may  be  so  strong,  and 
the  corresponding  sensation  arising  so  acute,  that  action  instantly 
follows,  as  in  the  sudden  involuntary  shrinking  from  a  source  of 
pain,  or  the  sensation  giving  rise  to  an  idea,  a  longer  or  shorter  time 
may  intervene,  during  which  period  the  mind  has  time  to  reflect  as 
to  the  course  of  action,  the  individual  being  swayed  by  this  or  that 
idea  or  motive,  the  will  being  so  to  speak  in  abeyance. 

Sooner  or  later,  however,  one  motive  becoming  the  strongest, 
voluntary  action  follows,  or,  to  speak  in  ordinary  language,  the  will 
asserts  itself,  the  term  will  being  simply  a  convenient  one,  for  ex- 
pressing the  fact  that  action  is  the  result  of  the  strongest  motive, 
the  result  of  the  preceding  stimulus.  The  sole  difference  between 
these  two  actions,  the  involuntary  and  voluntary,  is  in  the  interval 
of  time  elapsing  between  the  application  of  the  stimulus  and  the  re- 
sulting action,  and  in  the  stimulus  being  some  external  exciting 
cause  other  than  that  of  the  will,  as  in  the  case  of  a  cough,  due  to 
a  crumb  of  bread  in  the  larynx,  rather  than  to  volition. 

In  addition,  however,  to  the  sensations,  or  ideas,  arising  within 
us  due  to  the  stimulation  of  nerves  from  without  inward  and  of  the 
involuntary  or  voluntary  actions  following  due  to  the  reflection  of 
the  impulses  from  such  stimulation  from  within  outward  of  which 
we  are  all  conscious,  there  are  similar  actions  following  the  stimu- 
lation of  nerves,  of  which  as  long  as  we  are  in  a  state  of  health  w^e 
are  entirely  unconscious.  'As  illustrations  of  such  actions  may  be 
mentioned  the  flow  of  the  gastric  juice  in  response  to  the  stimulus 
exerted  by  food  upon  the  nerves  distributed  to  the  stomach,  of  the 
dilatation  or  contraction  of  the  blood  vessels  brought  about  through 
the  influence  of  nervous  emotion,  of  the  contraction  of  the  iris  in 
response  to  light.  The  phenomena  of  secretion,  like  those  of  sensa- 
tion, involuntary  and  voluntary  movements,  result  from  the  appli- 
cation of  a  stimulus  to  peripheral  nerves,  which,  being  transmitted 
to  the  nervous  centers,  is  thence  reflected  to  the  parts  manifesting 


DANIELVS  ELEMENT. 


487 


the  phenomena.  That  it  is  by  means  of  the  nerves  connecting  the 
periphery  with  the  nervous  center,  and  the  center  with  the  organs 
manifesting  the  phenomena,  that  the  latter  are  produced  becomes 
at  once  evident  if  tlie  nerves  involved  be  destroyed,  whether  by 
disease,  injury,  or  experiment ;  sensation,  voluntary  movement,  se- 
cretion, etc.,  at  once  disappearing.  The  involuntary  muscular  con- 
traction, the  result  of  pain,  the  voluntary  one  made  in  the  carrying 
out  of  some  matured  plan,  and  the  flow  of  a  secretion,  are  equally 
illustrations  of  the  truth  of  all  nervous  action  being  of  this  reflex 
character.  In  every  instance  if  the  phenomenon  be  traced  to  its 
source  it  will  become  evident  that  an  action  apparently  due  to  an 
impulse  generated  from  within  and  transmitted  outward  is  in  real- 
ity due  to  an  impression  first  made  from  without  and  transmitted 
inward,  and  then  finally  reflected  outward.  That  nervous  energy, 
whatever  its  nature  may  be,  is  never  generated  spontaneously,  but 
must  be  of  this  reflex  character,  some  modified  preexistent  mode  of 
energy,  is  self-evident,  otherwise  nerve  energy  would  arise  out  of 
nothing.  Whatever  view  may  be  taken,  however,  of  the  origin  of 
ideas,  the  nature  of  the  will,  etc.,  it  will  not  affect  the  fact  that  the 
irritability  of  nerves,  like  that  of  other  tissues,  may  be  called  into 
excitement  by  appropriate  stimuli.  While  the  irritability  of  a  mus- 
cle, however,  shows  itself  by  its  contraction,  and  that  of  a  gland  by 
its  secretion,  that  of  the  nerve  is  not  manifested  by  any  ordinary 
visible  change  in  itself,  but  by  some  change  in  the  organ  to  which  it 
is  distributed.^  Of  the  different  stimuli, 
mechanical,  chemical,  and  electrical, 
available  in  calling  into  excitement  the 
property  of  irritability  possessed  by 
nerves,  the  electrical  is  by  far  the  most 
convenient,  and  since  the  contraction  of 
a  muscle  brought  about  indirectly  by 
the  stimulation  of  the  nerve  supplying 
it,  is  a  very  striking  phenomenon,  the 
muscular  contraction  may  be  taken  as 
an  evidence  and  measure  of  the  nervous 
irritability  causing  it. 

As  in  the  stimulation  of  nerves  we 
shall  usually  make  use  of  the  electricity 
supplied  by  a  Daniell  element,  a  brief 
description  of  the  same  does  not  appear 

superfluous.  A  single  Daniell's  element  consists  (Fig.  243)  of  a 
glass  vessel  S,  containing  a  saturated  solution  of  copper  sulphate,  in 
which  is  immersed  a  copper  cylinder  (A),  open  at  both  ends  and  per- 
forated with  holes,  and  provided  with  an  annular  shelf  supporting 
crystals  of  copper  sulphate  to  replace  the  solution  of  the  same  decom- 

^  We  shall  see  presently  that  the  nerve  does  undergo  a  change  in  its  electrical 
condition  when  excited,  but  which  can  only  be  detected  by  means  of  a  delicate  gal- 
vanometer, and  that  possibly  heat  is  also  produced. 


Fig.  243. 


Daniell's  elemeut.     (Ganot.) 


488  THE  NERVOUS  SYSTEM. 

posed  during  the  action  of  the  battery.  Within  the  copper  cylinder 
is  a  thin  porous  vessel  of  unglazed  earthenware,  containing  diluted 
sulphuric  acid,  in  which  is  placed  a  cylinder  of  amalgamated  zinc  Z. 
The  positive  electricity  generated  by  the  action  of  the  acid  upon  the 
zinc,  passing  through  the  liquid  of  the  battery  to  the  copper  cylinder, 
accumulates  at  the  end  of  the  wire  attached  by  the  binding  screw  to 
the  latter  (C),  the  ware  becomes,  therefore,  the  positive  pole  or  elec- 
trode, though  the  copper,  to  which  it  is  attached,  from  being  rela- 
tively little  acted  upon,  is  called  the  negative  or  collecting  plate  ; 
on  the  other  hand,  through  the  disturbance  of  the  electrical  equi- 
librium the  negative  electricity  developed,  passing  in  the  reverse 
direction  from  the  copper  to  the  zinc,  accumulates  at  the  end  of  the 
wire  attached  to  the  latter  (Z),  that  wire  becomes,  therefore,  the 
negative  pole  or  electrode ;  the  zinc,  however,  from  being  most 
acted  upon,  is  called  the  positive  or  generating  plate.  As,  how- 
ever, the  effect  of  the  battery  is  due  to  the  difference  of  electric 
potential  set  up  between  the  metals,  the  current  is  rather  regarded 
as  being  single  and  as  flowdng  from  the  zinc  or  positive  plate 
through  the  liquid  of  the  cell  to  the  copper  or  negative  one,  thence 
by  the  positive  pole  through  the  connecting  w'ire  to  the  negative 
pole  and  so  back  to  the  zinc  plate.  Such  being  the  disposition 
and  action  of  the  parts  of  a  Daniell's  element  when  closed,  the 
hydrogen  developed  by  the  action  of  the  dilute  acid  upon  the  zinc 
would  be  deposited  upon  the  copper  plate  were  it  not  for  the 
presence  of  the  copper  sulphate,  which  the  hydrogen  reduces  into 
copper  and  sulphuric  acid,  the  former  being  deposited  upon  the 
copper  plate,  and  the  latter  replacing  that  in  the  porous  cup  used 
up  in  acting  upon  the  zinc ;  the  constancy  of  the  battery  is  thus  in- 
sured for  several  hours  at  least,  upon  which  its  usefulness  for  our 
purpose  depends.  Did  the  hydrogen  gas  generated  settle  in  minute 
bubbles  upon  the  copper  plate,  which  it  otherwise  would  do  in  the 
absence  of  the  solution  of  copper  sulphate,  the  action  of  the  battery 
would  be  interfered  with  by  the  polarization  of  the  plate,  by  which 
is  meant  that  the  hydrogen  wdien  so  deposited  not  only  offers  a 
resistance  to  the  current  passing  from  the  zinc  to  tlie  copper,  but 
in  generating  a  counter  current  in  opposition  to  the  latter  propor- 
tionately weakens  it.  It  need  hardly  be  added  that  if  two  or  more 
Daniell  elements  are  used,  in  coupling,  the  zinc  jjlate  of  one  element 
must  be  connected  with  the  copper  plate  of  the  other  by  means  of 
a  copper  ware  or  stop  as  in  Fig.  245.  Among  the  other  forms  of 
batteries  often  used  for  physiological  purposes  may  be  mentioned 
those  of  Bunsen,  Smee,  Grenet,  Leclanche — differing  only  from 
the  Daniell  battery  in  the  character  of  the  metal  and  liquid  used, 
and  their  relative  arrangement.  In  describing  the  action  of  a 
Daniell  element  the  electricity  generated  was  spoken  of  as  if  flow- 
ing through  the  battery  to  the  poles,  as  one  might  speak  of  the  flow 
of  water  through  pipes,  just  as  if  there  was  an  actual  electrical  cur- 
rent present.     As  a  matter  of  fact,  it  is  needless  to  say  with  refer- 


ELECTRICITY  AS  A  XERVE  STIMULUS.  489 

ence  to  the  transmission  of  electricity,  there  is  no  evidence  of  a 
transference  of  particles  from  place  to  place  as  is  the  case  of  the 
flow  of  water.  It  will  be  found,  nevertheless,  since  the  molecular 
changes  incidental  to  the  production  of  electricity  are  yet  unknown, 
that  such  a  comparison  offers  an  extremely  convenient  way  of  pre- 
senting the  essential  facts,  of  representing  to  the  mind  in  a  con- 
nected way  results  brought  about  by  changes,  the  intimate  nature 
of  which  we  know  nothing.  It  might  be  supposed,  at  first  sight, 
that  the  consideration  of  this  subject  belongs  rather  to  the  domain 
of  physics  than  to  physiology ;  as  we  shall  soon  learn,  however, 
that  the  physiologist  not  only  continually  uses  electricity  as  a  nerve 
stimulus,  but  that  both  nerve  and  muscle  exhibit  electrical  currents, 
and  offer  a  resistance  to  the  passage  of  electricity,  etc.,  it  becomes 
indispensable  that  a  brief  account  of  the  principal  facts  of  elec- 
tricity be  offered,  sufficient  at  least  to  enable  the  student  to  under- 
stand the  terms  constantly  used  in  the  description  of  the  phenomena 
of  general  nerve  physiology. 

It  is  a  well-established  fact  that  when  two  metals  are  placed  in 
contact,  as,  for  example,  zinc  with  copper  or  platinum,  a  disturbance 
in  their  electrical  condition,  or,  as  it  is  called  by  physicists,  a  dif- 
ference in  potential,  ensues,  the  word  potential  being  used  in  elec- 
trical science  in  the  same  sense  as  level  or  head  of  water  in  hydro- 
dynamics. Xow  just  as  water  at  a  higher  level,  if  it  finds  a  channel, 
tends  to  fall  to  a  lower  one  until  equilibrium  is  established,  sim- 
ilarly if  two  bodies,  or  two  parts  of  the  same  body,  have  a  different 
potential — that  is,  are  at  different  electrical  levels,  so  to  speak — 
there  will  be  a  tendency  to  movement  from  the  body  having  a 
higher  potential  to  the  one  with  the  lower  until  electrical  equili- 
briiun  is  established.  The  agent  to  which  this  change,  movement, 
so-called  electrical  current,  is  due,  is  called  the  electromotive  force, 
and  while  its  nature  is  unknown,  it  can  be  measured  by  the  amount 
of  work  performed  in  the  j)assage  of  a  unit  of  electricity  from  one 
position  to  another,  just  as  the  potential  energy  of  water  can  be 
measured  by  the  amount  of  work  performed,  as  in  the  turning  of  a 
water-wheel,  etc.  Just  as  the  energy  exerted  in  a  definite  time  in 
raising  a  weight  against  gravity  may  be  stored  up  indefinitely,  to 
be  set  free  again  by  the  falling  of  the  weight,  and  applied  to  the 
performance  of  mechanical  work,  so  the  energy  expended  in  bring- 
ing up  a  body  against  another  similarly  electrified,  and  therefore  of- 
fering a  resistance  like  that  of  gravity,  may  be  temporarily  stored 
up,  and  with  the  setting  free  of  the  electricity  perform  work. 
While,  therefore,  the  principle  of  electrical  measurement  must  be 
the  same  as  that  of  other  measurements,  the  particular  standards 
used  Avill  not  only  differ  according  as  statical  or  dynamical  electric- 
ity is  being  considered,  but  as  to  what  shall  be  accepted  as  consti- 
tuting the  unit  of  time,  mass,  distance,  etc.  As  a  matter  of  fact, 
with  reference  to  statical  electricity,  each  of  two  equally  charged 
bodies  is  said  to  have  a  unit  of  electricity,  if  when  separated  by  a  dis- 


490  THE  NERVOUS  SYSTEM. 

tance  of  one  centimeter  the  one  will  repel  the  other  with  a  force 
which  will  impart  in  one  second  a  velocity  of  one  centimeter  per 
second  to  one  gramme  of  matter.  As  regards  the  galvanic  or  cur- 
rent electricity  with  which  we  have,  however,  more  particularly  at 
this  moment  to  do,  the  unit  of  electricity  is  usually  accepted  as  be- 
ing that  quantity  of  electricity  carried  in  one  second  by  a  current 
of  unit  strength.  The  latter,  however,  is  of  course  arbitrary,  but 
in  the  sense  just  used  is  one  such  that  if  a  conductor  one  centimeter 
long  be  bent  into  an  arc  of  one  centimeter  radius  it  will  exert  a 
force  of  one  dyne,  on  a  unit  magnet  pole  placed  at  the  center.  This 
is  called  the  electro-magnetic  unit  of  current.  For  convenience' 
sake,  however,  in  practice  a  hundred  millions  of  such  absolute 
electro-magnetic  units  are  taken  as  a  unit  constituting  the  so-called 
volt,  and  we  speak,  therefore,  of  the  electro-motive  force  of  a 
Daniell's  cell  being  equal  to  1.079  volts.  Furthermore,  the  elec- 
tro-mao-netic  unit  of  electro-motive  force  is  that  which  sends  a  cur- 
rent  of  unit  strength  through  a  unit  resistance,  and,  therefore,  a 
unit  quantity  in  a  unit  time,  and  this  definition  brings  us  now  to  a 
consideration  of  the  resistance  offered  by  the  conductors  in  the  pas- 
sage of  the  electricity  and  the  fixing  of  some  standard  for  the  same. 
As  the  unit  of  resistance  must  be,  of  course,  an  entirely  arbitrary 
one,  the  standard  of  resistance  ultimately  accepted  Avill  depend  upon 
what  is  considered  most  convenient  by  physicists.  As  a  matter  of 
fact,  at  the  present  time,  the  resistance  oifered  by  a  column  of  mer- 
cury about  106  cm.  long,  and  1  square  mm.  in  section  at  0°  C,  is 
accepted  as  the  unit  of  resistance  commonly  known  as  the  interna- 
tional unit,  or  one  ohm ;  or,  what  is  the  same  thing,  the  resistance 
offered  by  a  wire  made  of  an  alloy  of  silver  and  platinum  of  defi- 
nite length  and  thickness,  offering  the  same  resistance  as  the  column 
of  mercury  just  referred  to,  is  accepted  as  the  unit  of  resistance,  or 
one  ohm.  The  resistance  offered  by  different  bodies  to  the  passage 
of  an  electrical  current  varies  very  considerably,  according  to  the 
nature  of  the  body.  Metals,  being  the  best  conductors,  offer  the 
least  resistance  ;  liquids,  especially  those  of  a  saline  character,  con- 
duct, but  not  so  readily  as  metals.  Apart,  however,  from  the  con- 
ductibility  of  a  particular  substance,  which  is  constant  for  that 
substance,  the  resistance  offered  by  a  conductor  is  directly  propor- 
tional to  its  length,  and  inversely  proportional  to  its  cross-section — 
that  is,  the  longer  the  conductor  the  greater  the  resistance,  the  thicker 
the  conductor  the  less  the  resistance.  In  the  case  of  a  galvanic  ele- 
ment, however,  like  that  of  a  Daniell's  cell,  not  only  must  the  re- 
sistance offered  by  the  conducting  wires,  which  may  be  called  the 
external  resistance,  be  taken  into  consideration,  but  also  the  re- 
sistance offered  by  the  plates  and  liquid  within  the  cell,  and 
which  may  be  called  the  internal  resistance.  The  latter  is  directly 
proportional  to  the  distance  of  the  plates  from  each  other,  and  in- 
versely proportional  to  the  size  of  the  plates — that  is,  the  larger  the 
plates  the  less  the  resistance,  the  conducting  power  of  the  liquid,  of 


THE  RESISTANCE  BOX.  491 

course,  being  assumed  to  be  constant.  In  the  determination  of  the 
electro-motive  force,  resistance,  etc.,  of  nerves  it  will  be  found,  as  we 
shall  see  presently,  that  it  is  of  great  advantage  to  vary  by  known 
amounts  the  resistance  offered  to  the  passage  of  an  electrical  current. 
For  this  purpose  we  make  use  of  a  resistance  box,  wliicli  consists, 
essentially  (Fig.  244),  of  a  series  of  bobbins  (C  C)  on  which  are 
coiled  various  lengths  of  standard  insulated  wire,  the  latter  being  so 
disposed  in  the  box  that  two  ends  of  the  wire  of  each  bobbin 
(C  C)  are  connected  with  two  brass  plates  (B  B)  fitted  into  the  lid 
of  the  box,  the  resistance  offered  by  each  coil  of  wire  being  indi- 
cated in  ohms  on  the  lid  of  the  box.  Suppose,  by  means  of  the  two 
binding  screws  attached  to  the  lid  of  the  box,  a  current  of  electric- 
ity be  sent  through  the  coils  C  C,  the  resistance  encountered  will  be 
equal  to  the  total  resistance  offered  by  the  coils.  If,  however,  the 
space  intervening  between  the  brass  plates  be  plugged  up  by  tight- 
fitting  brass  plugs  (Fig.  244),  so  that  the  brass  plates  are  then  con- 
nected, the  current  will  take 

the  route  of  least  resistance,  Fig.  244. 

passing  simply  through  the 
brass  portion  of  the  lid  of 
the  box,  from  binding  screw 
to  binding  screw,  without 
traversing  the  coils  at  all. 
It  is  obvious,  therefore,  that  Eesistauce  box. 

the  amount  of  resistance  of- 
fered to  the  current  passing  through  the  resistance  box  will  depend 
upon  the  number  of  brass  plugs  taken  out.  We  have  just  seen  that 
the  passage  of  an  electrical  current  through  a  galvanic  circuit  is  due 
to  the  electro-motive  force  developed  by  the  element ;  and  further, 
that,  according  to  the  nature  of  the  circuit,  the  current  meets  with 
more  or  less  resistance.  It  follows,  therefore,  as  shown  by  Ohm,^  first 
from  theoretical  considerations,  and  subsequently  by  experiment,  that 
the  strength  of  the  current — that  is,  the  quantity  of  electricity  which, 
in  a  unit  of  time,  flows  through  a  given  section  of  the  circuit — must 
be  equal  to  the  ratio  of  the  resistance  to  the  electro-motive  force. 
This  important  result,  usually  known  now  as  Ohm's  law,  may  be  con- 

E 

veniently  expressed  by  the  equation  /=  —  (1),  in  which  /represents 

the  current  strength,  Et\\Q  electro-motive  force,  and  B  the  resistance. 
If  in  equation  {}.)  E,  or  the  electro-motive  force,  is  equal  to  1 
volt,  and  R,  or  the  resistance,  to  1  ohm,  then  /,  or  the  current 
strength,  will  be  equal  to  1  ampere,  and  the  quantity  of  electricity 
delivered  per  second,  1  coulomb,  or  per  hour,  3000  coulombs  (hour 
ampere).  As  Ohm's  law  is  a  most  important  one,  galvanic  batteries 
being  arranged  by  its  means  so  as  to  give  the  greatest  amount  of 
electricity  possible,  we  will  illustrate  its  application  in  this  respect 
by  a  few  examples. 

^  Die  galvanisclie  Kette  matliematisch  bearbeitet,  Berlin,  1827. 


492 


THE  NERVOUS  SYSTEM. 


It  -will  be  remembered  that  the  resistance  of  a  conductor  is  di- 
rectly proportional  to  its  length,  and  inversely  proportional  to  its 
conductivity  and  section.  If  now  the  length,  conductivity,  and  sec- 
tion be  represented  respectively  by  I,  c,  and  s,  then  the  resistance 

JR  will  be  equal  to  ^      ^  •     This  value  of  R  being  substituted  in 


c  X  s 


E      csE 
equation  (1)  we  shall  obtain  1=  —  =  ^^  (2)- 


-that  is  to  say,  the 


cs 


Fig.  2^5. 


intensity  of  a  current  is  directly  proportional  to  the  section  and 
conductivity  of  the  conductor,  but  inversely  proportional  to  its 
length.  In  the  case  of  a  galvanic  element,  as  we  have  seen,  the 
resistance  to  be  considered  is  not  only  that  of  the  conducting  wires, 
but  also  that  of  the  liquid  and  plates  of  the  element  itself.  Call- 
ing the  external  resistance,  that  of  the  wires,  r,  and  the  internal 
resistance,  that  of  the  element,  B,  we  obtain  from  equation  (1) 

JE 
I  =  ^5—; —  (o).     Xow  it  is  obvious  that  if  anv  number  of  similar 

K  -\-  r  ^  ■' 

elements  are  joined  together,  say  three,  as  in  Fig.  245,  there  is  n  times 

the  electro-motive  force,  but,  at 
the  same  time,  n  times  the  in- 
ternal resistance,  and  equation 

(8)   becomes    I  =  ~f^ (4). 

If,  however,  the  conduct- 
ing  wires  be  of  copper,  and 
short  and  thick,  then  the  ex- 
ternal resistance  r,  in  compari- 
son with  R,  may  be  neg- 
lected, and  equation  (4)  becomes 

nE      E 
1  =  -~7s  =  T^  (o)  —  that   is  to 
nR       R  ^ 

say,  when  the  internal  resistance  is  great  and  the  external  is  small,  a 
battery  consisting  of  several  elements — three,  in  this  instance — pro- 
duces no  greater  eflPect  than  one  element.  Suppose,  on  the  other  hand, 
that  the  conducting  wires  be  very  long  and  thin  and  the  external  re- 
sistance r,  therefore,  very  great,  so  much  so  that  the  internal  resist- 

nE 
ance  R  can  be  neglected  in  comparison;  then  /=     ^^    —  (4)  will 


Galvanic  batterv. 


become  /  = 


nE 


E 


(6),  or  as  I=-  1=  nJ  { 


nR  -f  r 
That  is  to  say,  when 


the  external  resistance  is  large,  and  internal  resistance  small,  the 
intensity  within  certain  limits  is  very  nearly  proportional  to  the 
number  of  elements — that  is,  a  battery  consisting  of  three  elements 
produces  nearly  three  times  the  effect  of  one  clement.  Instead  of 
increasing  the  numljcr  of  elements,  let  us  now  enlarge  the  plates, 
say  71,  or  three  times  that  of  a  single  element  (Fig.  240),  or  join 


OHM'S  LAW.  493 

all  the  copper  plates  and  all  the  zinc  plates  together,  as  in  multiple 
arc  and  consider  what  effect  will  be  obtained  according  to  Ohm's  law. 
The  electro-motive  force  under  these  circumstances,  will,  of  course, 
remain  unchanged — that  is,   not  increased,  since  it  depends  upon 
the  nature  of  the  plates  and  the  liquid,  and  not  upon  the  size  of  the 
element,  just  as  the  head  or  force  of  the  water  comparable  to  the 
electro-motive  force  is  not  increased  as  long  as  the  level  remains 
unchanged,  however  much  the  amount  of  water  may 
be  increased,  for  though  there  are  n  times  as  many        Fig.  246. 
regions,  in  this  case — three,  where  the  electro-motive 
force  acts  side  by  side — they  do  not  assist  one  another 
any  more  than  the  neighboring  vertical  columns  of 
water  in  a  reservoir  affect  the  pressure  on  the  exit 
pipe.     Nevertheless,  just  as  in  the  previous  instance, 
in  which  the  battery  was  supposed  to  consist  of  three 
elements,  there  will  be  a  difference  in  the  effect  pro- 
duced according  to  whether  the  external  or  internal 
resistance   is   neglected,  since  although  the  electro- 
motive  force  does   remain   unchanged,  the   increase 
in  the  size  of  the  plates    must   be    followed  by  a    oaivank  element. 
proportional   diminution   in   their    resistance    which 
permits  a  proportional  quantity  of  electricity  to  pass  through  them. 
Let  us  first  suppose  that  the  external  resistance,  or  r,  be  so  much 
smaller  than  the  internal  or  i?,  that  it  can  be  neglected,  and  that 
the  plates  have  been  enlarged  three  n  times,  then  we  will  obtain 

E  nE 

from  equation  J=  p -_  (3)  J=  -v/  =  nI{S).     That  is  to  say,  by 

enlarging  the  plates  of  the  element  n,  or  three  times  (Fig.  246),  when 
the  external  resistance  is  small,  the  intensity  is  increased  corre- 
spondingly.    On  the  other  hand,  suppose  the  internal  resistance,  or 

E 

R,  is  so  small  that  it  can  be  neglected,  then  equation  /=  ^ (3) 

771 
will  become  /=  —  or  J=  J  (9).     That  is  to  say,  by  enlarging  the 

plates  of  the  element  n,  or  three  times,  when  the  internal  resistance 
is  small  the  intensity  is  not  increased.  Resuming  what  has  just 
been  said,  we  learn  by  Ohm's  law  that  if  the  internal  resistance 
be  small,  it  is  of  advantage  to  increase  the  number  of  cells  ;  on  the 
other  hand,  if  the  internal  resistance  be  large,  while  it  is  of  no  ad- 
vantage to  increase  the  number  of  cells,  it  is  of  advantage  to  enlarge 
the  plates  of  the  cell,  nothing,  however,  being  gained  by  enlarging 
the  plates  if  the  internal  resistance  be  small.  It  need  hardly  be 
added  that  while  the  intensity  or  quantity  of  electricity  flowing 
through  the  circuit  in  a  given  time  remains  the  same,  the  density 
of  the  current  may,  however,  vary,  the  latter  being  inversely  as  the 
cross  section  of  the  conductor — that  is,  the  less  the  cross  section, 
the  greater  the  intensity. 

As,  in  the  stimulation  of  the  nerves  by  electricity  derived  from 


494 


THE  NERVOUS  SYSTEM. 


the  batteries  just  described,  we  ordinarily  make  use  of  the  induc- 
tion apparatus,  of  Du  Bois  Reymond/  a  brief  description  of  that 
most  useful  instrument  in  this  connection  appears  appropriate.  As 
its  name  implies,  it  is  an  apparatus  (Fig.  247)  by  means  of  which 
an  induced  current  can  be  applied  to  a  nerve,  and  in  order  that  the 


Fig.  247. 


Du  Bois  Reymond's  induction  apparatus.     (La:ndois.) 

strength  of  the  current  may  be  varied  at  pleasure,  the  secondary 
coil  8,  to  which  the  electrodes  I  L  are  attached,  is  placed  upon  a 
graduated  slide  ( Q),  so  that  it  can  be  made  to  approach  or  recede 
from  the  primary  coil  P,  as  near  or  far  as  desired.     The  current 

Fig.  248. 


Schema  of  Du  Bois  Reymoud's  induction  apparatus.     (Landois.) 

from  the  battery  B  (Figs.  247  and  248),  entering  the  apparatus  at 
the  binding  screw  a,  passes  up  the  pillar  h  and  through  the  German 
silver  spring  rf,  then  through  the  primary  coil  P,  and  the  coil  F^ 
returning  to  the  battery  by  the  binding  screw  p.  As  the  current 
enters  the  primary  coil  P,  an  induced  closing  or  making  current  is 
for  the  moment  developed  in  the  secondary  coil  /S',  and  in  an  oppo- 
site direction  to  the  primary  current.  During  the  passage  of  the 
current,  however,  tlirough  the  coil  P,  the  iron  core  within  the  latter 
becoming  magnetized,  the  spring  d  is  pulled  down  from  the  screw/, 
the  result  of  which  is  that,  the  primary  current  being  interrupted, 

'  Untersuchungen   iiber  thierische  Electricitat,   Zweiter  Band,  s.  393.     Berlin, 
1849. 


DU  BOIS  REYMOND  INDUCTION  APPARATUS. 


495 


there  is  developed  for  a  moment  in  the  secondary  coil  S  an  induced 
breaking  or  opening  current  in  the  same  direction  as  that  of  the 
primary  current.  As  the  iron  cores  within  the  coil  F  under  these 
circumstances  become  demagnetized  through  the  absence  of  the 
current,  the  spring  d  flies  up  again  ;  contact  being  again  made  with 
the  screw/,  the  current  passes,  as  before,  through  the  primary  coil, 
to  be  again  broken  with  the  magnetization  of  the  core  within  the 
coil  F,  and  to  be  again  made  with  the  demagnetization  of  the  same, 
and  so  on  indefinitely.  The  effect  produced  by  the  iron  core  within 
the  primary  spiral  is  the  same  as  that  of  the  primary  spiral  itself, 
since  in  being  magnetized  and  demagnetized  tlu-ough  induction  by 
the  making  and  breaking  of  the  primary  circuit,  the  core  induces 
closing  and  opening  currents  in   the    secondary  spiral    similar   to 

Fig.  249. 


Iiu  Bois  Reymond's  key. 

those  due  to  the  making  and  breaking  of  the  current  in  the  primary 
one.  By  applying  the  electrodes  I  L  attached  to  the  secondary 
coil,  to  the  nerve,  the  latter  will  be  stimulated  by  the  making  and 
breaking  induced  currents,  and  which  so  rapidly  succeed  each  other 
that  the  muscle  is  soon  brought  into  a  state  of  tetanus.  If,  how- 
ever, it  is  desired  to  stimulate  the  nerve  by  a  single  induction  shock 
— that  is,  by  one  closing  and  one  opening  induced  current,  then  the 
wire  of  the  l^atterv  must  be  attached  to  the  l^indiner  screw  .S'  instead 
of  to  a  (Fig.  247),  a  Du  Bois  Reymond  key  (Fig.  249)  having  also 
been  inserted  A\itliin  the  circuit  of  the  primary  coil.  The  key  being 
down,  the  current  will  then  be  short-circuited — that  is,  will  pass 


496 


THE  NERVOUS  SYSTEM. 


directly  back  to  the  battery  E,  since  the  resistance  offered  by  the 
key  is  less  than  that  oifered  by  the  nerve. 

With  the  elevation  of  the  key,  however  (Fig.  249),  the  current  Avill 
pass  through  the  primary  coil  p,  developing  the  closing,  or  making 
induced  current  in  the  secondary  coil  S  as  before  ;  but,  as  the  current 
through  the  primary  coil  is  not  broken  through  the  fall  of  the  spring, 
the  wire  being  attached  in  this  experiment  to  ^'  (Fig.  247),  there  will 
be  no  opening  or  breaking  current  induced  in  the  secondary  coil. 
The  latter  is,  however,  at  once  developed  in  the  secondary  coil  by 
simply  depressing  the  key,  the  current  being  then  short-circuited 
again,  it  returns  back  to  the  battery  Avithout  passing  through  the 
primary  coil.  It  ^\\\\  be  observed  that  when  the  induction  appa- 
ratus is  so  arranged  and  used,- that  the  nerve  is  stimulated  once  by 
the  current  induced  by  the  closing  of  the  primary  circuit,  and  once 
by  the  opening  of  the  same.  Suppose,  however^  it  be  desired  to 
stimulate  the  nerve  by  only  the  closing  or  the  opening  current? 
To  accomplish  this,  a  second  Du  Bois  Rcymond  key  (Fig.  250,  a) 
must  be  also  inserted  within  the  circuit  of  the  secondarv  coil  S,  and 
the  two  keys  worked  in  the  following  manner  :  A^  e  will  suppose, 
at  the  beginning  of  the  experiment,  that  the  key  b,  within  the  cir- 


FiG.  250. 


stimulation  of  nerve  by  closing  or  opening  current. 

cuit  of  the  primary  coil  P,  is  down,  and  the  key  a,  within  that  of 
the  secondary  coil  S,  is  up,  then  with  the  elevation  of  tlie  key  h,  and 
the  passage  of  the  current  from  the  battery  through  the  primary  coil, 
there  will  be  developed  for  an  instant  in  the  secondary  coil  an  in- 
duced current,  and  the  nerve  will  be  stimulated  by  a  closing  or 
making  single  induction  shock.  The  key  a  should  now  be  de- 
pressed so  that  the  nerve  will  not  be  stimulated  by  the  opening  or 
breaking  of  the  current  in  the  primary  coil,  due  to  the  depressing 
of  the  key  6,  and  the  consequent  short-circuiting  of  the  current. 
The  nerve  has  then  been  stimulated  by  the  closing  of  the  current 
only.  Supposing  the  two  keys  to  be  both  down,  let  us  now  elevate 
the  key  h  ;  the  secondary  current  developed  in  consequence  will  not 
influence  the  nerve  as  in  the  preceding  experiment,  since  the  key  a 
being  down,  the  secondary  current  is  short-circuited.  If,  however, 
now  the  key  a  be  elevated,  and  the  key  b  depressed,  the  secondary 


SIMPLE  FRICTIOX  KEY 


497 


current  developed  through  the  breakiug  of  the  primarv  current  will 
be  transmitted  to  the  nerve,  and  the  latter  \\i\\  be  stimulated  bv  the 
opening  or  breaking  current  only.  Whether  it  be  desired  to  stimu- 
late the  nerve  by  a  single  induction  shock,  or  many  successive  ones, 
or  bv  the  secondary  current  induced  through  the  making  or  break- 
ino-  of  the  primary  one,  the  key  should  always  be  used  as  a  short- 
circuiting  one  (Fig.  250)  rather  than  as  a  simple  friction  key  (Fig. 
251),  since  in  the  latter  case  muscidar  contraction  maybe  produced 

Fin.   251. 


Simple  friction  key. 

bv  unipolar  induction.  While  no  secondary  current  is  induced  in 
S  (Fig.  251)  by  that  in  the  primary,  the  secondary  circuit  being 
broken  through  the  key  being  open,  free  static  electricity  may  be 
given  off  at  the  end  of  the  single  electrode  fL),  and  transmitted 
through  the  nerve  to  the  muscle,  the  electricity  previously  acciunu- 
lated  at  the  end  of  the  electrode  being  due  to  the  decomposition  of 
the  neutral  electricity  in  the  secondary  coil,  induced  by  that  in  the 
primary  coil,  as  takes  place  in  the  prime  conductor  in  working  the 
ordinary-  electrical  machine.  If,  however,  the  secondary  coil  be 
short-circuited  by  a  Du  Bois  Reymond  key,  as  in  Fig.  250,  the 
key  being  down,  then  the  secondary  circuit  being  perfectly  closed, 
a  secondary  current  will  be  developed,  and  unipolar  induction  pre- 
vented, the  current  passing  directly  back  through  the  coil,  and  none 
passing  into  the  nerve,  which,  as  we  have  just  seen,  is  not  the  case, 
the  key  being  used,  as  a  friction  key  (Fig.  251),  and  open.  When, 
however,  the  short-circuiting  key  is  opened,  and  the  secondary 
32 


498 


THE  NERVOUS  SYSTEM. 


circuit  is  completed  by  the  nerve  intervening  between  the  elec- 
trodes, the  circuit  being  but  imperfectly  closed,  unipolar  induction 
may  occur  even  then,  as  when  the  key  is  used  as  in  Fig.  251. 
If,  however,  there  be  any  doubt  as  to  whether  the  muscular  con- 
traction be  due  to  the  stimulus  exerted  by  the  nerve  excited 
by  the  secondary  current,  or  to  the  unipolar  induction  shock — 
that  is,  the  direct  transmission  of  the  static  electricity  through 
the  nerve  to  the  muscle — it  can  be  at  once  decided  by  simply 
dividing  the  nerve  between  the  lower  electrode  and  the  muscle, 
since,  if  contraction  then  ensues,  the  ends  of  the  nerves  being 
approximated,  it  must  be  due  to  unipolar  induction,  and  not  to 
the  nerve,  as  the  division  of  the  nerve  does  not  interfere  with  the 
transmission  of  the  electricity,  but  makes  impossible  that  of  the 
nerve  force.  It  may  be  mentioned,  in  this  connection,  that  the 
surest  way  to  avoid  unipolar  induction  is  to  put  the  upper  electrode 
in  communication  with  the  earth  through  the  gas  or  water  pipe  of 
the  laboratory  by  a  good  conductor,  and  in  so  leading  the  free  elec- 
tricity off,  prevent  it  influencing  the  muscle,  and  so  eifecting  the 
contraction  due  to  nerve  excitement,  as  brought  into  activity  by  the 
secondary  current  alone.  It  will  be  seen,  presently,  that  if  a  nerve 
be  stimulated  first  by  a  closing,  and  then  by  an  opening  induced  cur- 
rent, that  the  physiological  effect  due  to  the  latter,  as  shown  by  the 
extent  of  the  muscular  contraction,  is  greater  than  that  due  to  the 

Fig.  252.1 


Graphic  rciiresentation  of  effect  of  the  extra  curreuts  on  the  induction  currents. 


former.  Now,  it  is  desirable,  under  certain  circumstances,  that  the 
two  currents  should  be  equalized  as  far  as  possible.  To  appreciate 
the  manner  in  which  tliis  is  accomplished,  it  will  be  first  necessary, 
however,  to  explain  briefly  why  the  induced  opening  current  is 
more  powerful  than  the  closing  one.  Inasmuch,  as  with  the  closing 
of  the  current  in  the  primary  coil,  there  is  developed,  momentarily, 
a  current  in  the  secondary  one,  opposite  in  direction  to  that  of  the 
primary,  it  might  be  supposed  that,  in  a  similar  manner,  the  indi- 

1  Du  Bois  Keymond,  Gesammelte  Abhandlunwn,  Erster  Band,  s.  236.    Leipzig, 
1875.  ^   ^ 


MODIFICATION  OF  INDUCTION  APPARATUS. 


499 


Fig.  253. 


vidual  coils  of  the  primary  current  would  act  inductively  on  each 
other.  Such  ivS  found  to  be  experimentally  the  case,  the  current  so 
produced,  and  opposite  in  direction  to  that  of  the  inducing  current, 
l)eing  known  as  the  inverse  extra  current.  The  latter,  being  oppo- 
site in  direction  to  that  of  the  inducing  current,  must  weaken  it, 
and  it  is  on  account  of  this  retarding  influence  of  the  inverse  extra 
current  that  the  closing  primary  current  only  gradually  attains  its 
maximum  intensity,  as  may  be  represented  graphically  (Fig.  252) 
by  the  curve  line  G  E,  in  which  the  horizontal  line  T  represents 
the  duration  of  the  current.  The  corresponding  closing  current, 
induced  in  the  secondary  coil,  may  in  the  same  manner  be  repre- 
sented by  the  curve  I)  s  h  only  the  ordinate  o  -s  must  be  drawn  be- 
low the  line  D  J,  since  the  current  is  in  the  opposite  direction  to 
that  inducing  it.  In  a  similar  manner,  at  the  moment  of  the  open- 
ing of  the  primary  current,  there  is  developed  within  the  primary 
coil  a  direct  extra  current,  so  called  on  account  of  it  being  in  the 
same  direction  as  the  current  inducing  it,  and  therefore  intensifying 
it.  But,  as  there  is  no  arraugement  in  the  ordinary  induction  appa- 
ratus by  which  the  primary  current  is  maintained,  the  direct  extra 
current  is  suppressed  at  the  opening  of  the  primary  current,  the 
latter  is  therefore  suddenly  inter- 
rupted Avhen  at  its  full  strength, 
and  may  be  represented  graphically 
by  the  perpendicular  line  E  I,  and 
the  opening  current  in  the  secon- 
dary coil  by  the  perpendicular  /  /, 
it  beins;  in  the  same  direction  as 
that  in  the  primary,  and  which, 
havins:  attained  its  maximum  sud- 
denly,  falls  off"  more  gradually,  as 
shown  by  the  curve  line  /  K. 
From  the  sudden  manner  in  which 
the  opening  current  developed  in 
the  secondary  coil  attains  its  maxi- 
mum intensity  -/  /,  as  compared 
with  the  gradual  increase  of  the 
closing  one  D  b,  it  becomes  evident  why  the  effect  of  the  stim- 
ulation by  the  former  current  is  greater  than  that  by  the  latter. 
Such  being  the  case,  the  induction  apparatus  being  used  as  just 
described,  let  us  modify  the  instrument  a  little,  as  done  by 
Helmholtz,^  by  connecting  the  binding  screw  a  (Fig.  253),  by 
means  of  a  wire  {w),  with  the  binding  screw  >S',  and  lowering  the 
silver  spring  (d)  away  from  the  point  of  the  binding  screw,  the  current 
will  then  pass  by  the  connecting  wire  to  directly  into  the  primary 
coil  P  without  passing  first  along  the  spring,  and  from  the  primary 
coil  back  to  the  battery  by  the  coils  g  h  ;  but  with  the  magnetiza- 
tion of  the  core  within  the  latter  the  spring  will  be  lowered,  and 
^  Du  Bois  Keymond,  op.  cit.,  s.  231. 


Helmholtz's  modification  of  induction  ap- 
paratus. 


500 


THE  NERVOUS  SYSTEM. 


the  greater  part  of  the  current  being  short-circuited  will  then  pass 
directly  back  to  the  battery  by  the  spring  d  and  pillar  m  ;  the  pri- 
mary current  being  then  weakened,  as  represented  graphically  to  the 
extent  of  the  lines  A  B  (Fig.  252),  the  magnetization  of  the  core 
within  the  coils  g  h  (Fig.  253)  will  not  be  sufficient  to  keep  the 
spring  do\A'n,  the  short  circuit  current  will  be  reopened,  and  all 
the  current  will  pass  through  the  primary  coil  again.  The  Helm- 
holtz  modification  of  the  induction  apparatus  being  used,  as  just 
described,  it  will  be  observed  that,  as  the  current  in  the  pri- 
mary coil  is  never  entirely  interrupted,  the  direct  extra  current 
developed  at  the  moment  of  the  opening  of  the  primary  current 
within  the  latter  Mill  reinforce  the  primary  current,  the  two  cur- 
rents having  the  same  direction.  The  partial  interruption  of  the 
primary  current,  and  the  development  of  the  opening  secondary 
current  will,  therefore,  be  both  gradual,  as  shown  by  the  curves 
E  31  and  J  L,  respectively,  which  is  not  the  case,  as  we  have  seen, 

Fia.  254. 


The  moist  chamber,  with  the  nerve-muscle  preparation,  non-polarizable  electrodes,  and  lever  in 
position  ready  for  an  observation.     The  glass  cover  is  not  shown. 


when  the  ordinary  induction  apparatus  is  used,  since  the  primary 
current,  being  entirely  interrupted,  the  direct  extra  current  cannot 
make  this  reinforcing  effect  felt.  The  opening  secondary  current 
./  L,  with  Helmholtz's  modification,  attaining  then  its  maximum 
intensity,  gradually,  like  that  of  the  closing  secondary  one  D  H  b, 
differs  but  little  in  its  physiological  effects  from  the  latter  when  used 
as  a  stimulus. 

That  part  of  the  sciatic  nerve  supplying  the  gastrocnemius  mus- 
cle in  the  frog  being  the  one  that  we  shall  make  use  of  in  our  ex- 
periments, on  account  of  its  length  and  the  readiness  with  which  it 


NON-POLARIZABLE  ELECTRODES.  501 

is  exposed,  it  may  be  mentioned  that  in  preparing  the  nerve  it 
should  be  touched  as  little  as  possible,  and  never  seized  with  a  pair 
of  forceps,  though  it  must  be  completely  separated  from  the  adja- 
cent nerves.  The  gastrocnemius  muscle,  the  contraction  of  which 
we  take  as  a  measure  of  the  stimulation  of  the  nerve,  having  been 
cut  through  at  its  insertion  the  tendo  Achillis,  must  be  completely 
freed  up  to  its  origin  at  the  end  of  the  femur ;  of  the  latter  enough 
should  be  left  so  that  it  can  be  firmly  clamped  to  the  bar  A  (Fig. 
254),  of  the  upright  B,  the  tibia  and  fibula  being,  however,  entirely 
removed.  If  the  nerve-muscle  preparation  so  prepared  and  clamped 
be  covered  with  a  glass  bell  fitting  into  the  rim  of  the  disk  D,  of 
ebony  or  other  hard  wood  a  few  pieces  of  wet  blotting  paper,  having 
been  previously  placed  upon  the  disk,  the  nerve  and  muscle  will  be 
prevented  from  getting  dry.  The  disk  is  also  provided  with  binding 
screws  for  receiving  the  wires  from  the  secondary  coil  of  the 
induction  apparatus,  and  from  the  electrodes  E  supporting  the 
nerve  N.  The  electrodes  should  be  non-polarizable — that  is,  elec- 
trodes which,  while  transmitting  the  current  from  the  secondary 
coil  of  the  induction  apparatus,  will  not  generate  a  current  by  con- 
tact with  the  nerve.  Of  the  different  forms  of  non-polarizable 
electrodes  a  convenient  one  is  that  consisting  of  a  glass  tube  (Fig. 
254,  E),  bent  and  plugged  up  at  one  end  by  a  putty  made  of  china 
clay  and  0.75  per  cent,  solution  of  sodium  chloride,  and  containing 
a  saturated  solution  of  zinc  sulphate,  into  which  is  immersed  to  a 
depth  of  about  -3  mm.  a  slip  of  thoroughly  amalgamated  zinc.  The 
wires  AV  AV  leadins:  to  the  bindinti;  screws  are  attached  to  the  latter, 
which  is  usually  sufficiently  strong  to  hold  up  the  electrodes  ;  if  not, 
the  latter  can  be  movably  clamped  to  the  upright  B,  or  supported  as 
in  Fig.  254,  by  an  electrode  bearer  S.  The  glass  tube  is  often 
closed  at  its  extreme  point,  the  plug  of  clay  being  exposed  only 
where  the  small  orifice  has  been  drilled.  Through  an  opening  in 
the  disk  of  the  moist  chamber  the  muscle  can  be  attached  to  a  lever 
(Fig.  254,  L),  and  its  contractions  made  very  evident  by  the  eleva- 
tion of  the  latter.  If  the  point  of  the  lever  be  terminated  by  a 
brush  or  pen,  by  means  of  the  l>lackened  cylinder  already  described, 
a  graphic  representation  of  the  muscular  contraction  can  be  obtained 
and  preserved  for  future  reference.  The  lever  consists  of  a  thin 
slip  of  wood,  the  portion  near  the  fulcrum  being  of  metal  and  per- 
forated or  notched  to  receive  the  hook  attached  to  the  tendon  of 
the  muscle,  and  has  usually  suspended  from  it  a  scale  pan  con- 
taining counterpoising  weights  varying  from  between  10  to  200 
grammes.  The  moist  chamber  being  so  attached  to  the  recording 
apparatus  by  means  of  its  upright,  that  the  point  of  the  lever  is 
brought  in  contact  with  the  blackened  surface  of  the  cylinder,  the 
latter  is  made  to  rotate  for  a  moment  so  as  to  obtain  first  a  base 
line.  The  nerve  is  now  stimulated  by  the  induction  apparatus,  first 
by  a  closing  and  then  by  an  opening  shock,  without  Helmholtz's 
modification  being  used,  and  the  cylinder  being  made  to  rotate  rap- 


502 


THE  NERVOUS  SYSTEM. 


idly  it  will  be  observed  that  the  lever  is  elevated  higher  in  the  lat- 
ter case  (Fig.  255)  than  in  the  former  (Fig.  256),  the  effect  of  the 
opening  shock  being  greater  than  that  of  the  closing  one  for  the  rea- 
sons already  given. 

Fig.  255. 


Opening  shock. 


Fig.  256. 


Fig.  257. 


closing  shock. 


Curve  of  tetanus 


Fig.  258. 


If,  however,  the  nerve  be  stimulated  by  a  series  of  closing  and 
opening  shocks  the  magnetic  interruptor  of  tlie  induction  apparatus 
being  used,  the  lever  is  observed  to  remain  elevated  (Fig.  257),  the 

interval  between  eacb  shock  being  of 
so  short  a  duration  that  the  lever  de- 
scends but  a  little  distance  when  it  is 
elevated  again.  The  elevations  and 
depressions  of  the  lever  due  to  the  in- 
dividual contractions  of  the  muscle 
when  so  rapidly  produced,  are,  how- 
ever, soon  lost  to  view,  becoming  so 
fused  together  that  they  are  not,  tlicre- 
fore,  apparent  in  the  trace  of  the 
muscle  curve  of  tetanus.  The  slight 
fall  and  rise  of  the  lever  Ijccome, 
however,  quite  evident  if  the  primary  current  be  interrupted,  not 
by  the  magnetic  arrangement  (</,  Fig.  24.S),  but  ])y  a  reed  like  that 


Mu.scle  curve.    Primary  current  inter- 
rupted sixteen  times  a  .second. 


TEE  MASKING  LEVER.  503 

already  described,  vibrating  at  the  rate  of  sixteen  times  a  second, 
placed  between  the  primary  coil  and  a  key,  as  shown  by  the  trace 
(Fig.  258),  obtained  in  this  manner. 

It  will  be  obser\-ed  that  in  the  preceding  experiments  in  which 
electricity  was  made  use  of  as  the  stimulant  to  call  into  activity  the 
nervous  irritability,  muscular  activity  being  taken  as  the  measure  of 
the  latter,  that  three  distinct  forms  of  energy  are  involved,  electricity, 
nervous,  and  muscular.  That  the  electricity  acts  simply  as  a  stimu- 
lant is  evident,  since  it  is  only  transmitted  across  the  nerve  trans- 
versely from  electrode  to  electrode,  and  that  the  nerve  impulse  is 
gradually  transmitted  from  the  point  where  the  nerve  is  first  ex- 
cited by  the  electricity  to  the  muscle,  is  proved,  as  mil  be  sho\vn 
presently,  by  the  length  of  time  that  is  required  by  the  ners'c  force 
to  traverse  the  nerve  to  the  muscle,  and  from  the  death  of  the  nerve 
progressing  gradually  from  its  cut  end  to  the  periphery.  Further, 
just  as  electricity  is  to  be  distinguished  from  nerve  force,  so  is  the 
latter  to  be  distinguished  from  muscular  force.  Indeed,  the  effect  of 
nerve  force  can  be  prevented  by  curara,  the  latter  substance  prob- 
ably acting  by  destroying  the  nerve  endings,  the  muscular  force, 
however,  remaining  unaffected,  whereas  the  latter  force  is  de- 
stroyed by  sulphocyanide  of  potassium,  the  nerve  force  being  un- 
affected.^ 

If  in  stimulating  a  nerve  the  electrodes  be  applied  to  the  latter 
as  near  as  possible  to  the  muscle,  a  marking  lever  (Fig.  259)  and 

Fig.  259. 


The  marking  lever. 

chronographic  apparatus  being  used  at  the  same  time,  the  moment 
at  which  the  nerve  is  stimulated  will  be  recorded  upon  the  cylinder 
by  the  depression  of  the  point  of  the  lever,  the  current  previously 
short-circuited  through  C  A  B  E  being  then  thrown  into  the  pri- 
mary circuit  C  H  P  E  and  inducing  a  current  in  the  secondary  one. 
The  marking  lever  having  been  placed  in  contact  with  the  cylinder 
above  the  pen  of  the  chronograph  and  below  that  of  the  muscle 
lever  (Fig.  260)  it  will  be  observed  that  usually  0.01  sec.  to  0.004 

1  Bernard,  Svsteme  Xerveux,  T.  i.,  p.  198.     Paris,  1858.     Yulpian,  Phvsiologie 
et  comparee  du  Svsteme  Xerveux,  p.  186.     Paris,  18G6. 


504 


THE  NERVOUS  SYSTEM. 


sec.  elapses,  as  determined  by  the  chronograph  between  the  stimula- 
tion of  the  nerve  and  the  contraction  of  the  muscle,  the  short  period  of 
time  so  intervening  being  known  as  the  "  latent  period."     In  order 


f}e>o  tA  e/'  a.  sec. 


Diagram  of  a  muscle  curve  as  drawn  on  a  traveling  surface,  c.  The  line  described  by  the  point 
of  the  lever  connected  with  the  muscle,  a.  The  line  described  by  marking  lever,  ft.  The  line 
described  by  the  tuning-fork.  The  vertical  line  m  marks  the  moment  of  stimulation,  m',  the 
beginning  ;  nfl,  the  maximum  ;  and  iiv^,  the  end  of  the  contraction  of  the  muscle.     (Foster.) 

to  avoid  misunderstanding,  it  may  be  mentioned  in  this  connection 
that  a  distinction  is  often  made  between  the  so-called  electrical  latent 
period  and  the  mechanical  one  just  referred  to,  the  former  lasting  in 


Whiiijie. 

the  striated  muscles  of  the  frog  a  shorter  time  (0.002  sec.)  than  the 
latter  (0.004  sec.).^     If  the  nerve  be  stimulated  not  where  it  passes 

^  W.  Biedermann  Electrophysiologie,  1895,  s.  48.  Burdon  Sanderson,  Central- 
blatt  fiir  Physiologic,  1890,  — .  Tigerstedt,  Archiv  fiir  Anat.  u.  Phys.,  1885,  s. 
111. 


VELOCITY  OF  A  XERVOUS  IMPULSE.  505 

into  the  muscle,  but  at  some  distance  from  the  latter,  2.5  cent. 
(1  inch),  say,  as  at  A  (Fig.  261),  which  can  be  readily  done  by 
simply  placing  the  wires  C  D  of  the  whippe  (the  cross  piece  being 
left  out)  in  the  mercury  cups  in  connection  with  the  binding  screws 
5  and  6,  it  will  be  observed  that  not  only  0.01  sec.  (Fig.  262,  a  b) 
elapses  between  the  stimulation  of  the  ners-e  and  the  contraction 
of  the  muscle,  but  an  additional  very  small  period  of  time  (0.0008 
sec,  66',  Fig.  262 j  inter\'enes,  which  precedes  that  of  the  latent 
period.  The  difference  in  the  interval  of  time  elapsing  between 
the  stimulation  and  the  contraction  in  the  two  cases  is  e\adently 
due  to  the  fact  that  in  the  case  of  the  nerve  being  stimulated  at  A 
rather  than  at  B,  Fig.  261,  the  impidse  must  travel  through  a  dis- 
tance of  2.5  cent.  (1  inch)  before  it  reaches  the  muscle,  and  as  in 
doing  this  0.0008  sec.  elapses,  it  may  be  inferred  that  nerve  energy 
is  propagated  approximately  at  the  rate  of  28  meters  (91.8  feet) 
per  second. 

Fig.  262. 


a    66 


Curves  illustrating  the  measurement  of  the  velocity  of  a  nervous  impulse.  (Diagrammatic.) 
To  be  read  from  left  to  right,  ab.  The  interval  of  time  elapsing  between  moment  of  stimulation 
and  contraction  of  muscle  when  nerve  stimulated  at  entrance  of  latter  into  muscle,  ab'.  The 
interval  when  nerve  stimulated  at  some  distance  from  muscle,  ab.  Latent  period  in  both  cases. 
hb'.  Interval  of  time  during  which  nervous  impulse  travels  along  nerve  to  muscle.  It  is  to  be 
understood  that  the  interval  of  time  bb'  precedes  that  of  ab,  the  nerve  being  stimulated  at  a. 
(Foster.) 

The  nerve  force  is  probal)ly,  however,  transmitted  at  a  slower 
rate  in  the  nerves  of  the  frog  than  that  just  given,  since,  if  a  long 
nerve  be  stimulated  in  three  different  places,  near  the  muscle,  mid- 
way, and  above,  the  curves  show  that  more  than  double  the  time 
elapses  during  the  pas.-^age  of  the  nerve  force  through  the  whole 
nerve  than  from  the  middle  point  to  where  the  nerve  passes  into 
muscle.^  While  the  latent  period  and  the  velocity  with  which 
nerve  force  is  transmitted,  can  be  determined  in  the  manner  just 
described,  a  more  accurate  method  is  by  means  of  the  pendulum 
myograph. 

The  pendulum  myograph  (Fig.  263)  consists,  as  its  name  implies, 
of  a  pendulum  suspended  by  a  knife  edge,  working  upon  a  support 
firmly  fixed  by  a  frame  imbedded  in  the  wall  of  the  laboratory. 
The  pendulum  carries  two  glass  plates,  the  outer  smoked  one.  A, 
ser\'ing  as  a  recording  surfoce,  the  inner  one,  not  seen  in  the  figure, 
as  a  counterpoise.  The  plate  A,  as  the  pendulum  vibrates,  pushes 
aside  by  its  tooth  a'  the  bar  e,  thereby  interrupting  the  primary 
current  xcdj/  of  the  induction  apparatus,  and  also  a  current  passing 
through  the  small  electro-magnet,  to  which  is  attached  a  pen  serv- 


506 


TEE  NERVOUS  SYSTEM. 


ing  as  a  marking  lever.  The  pendulum,  having  reached  h' ,  is  held 
there  by  a  catch  similar  to  that  which  held  it  at  a  before  its  vibra- 
tion began. 

Fig.  263. 


rendulum  myographion.     (Foster.) 


With  the  interruption  of  the  primary  current  I  (Fig.  264),  the 
nerve  is  stimulated  by  the  opening  shock  of  the  secondary  current 


THE  PENDULUM  MYOGRAPH. 


507 


II,  transmitted  to  the  electrodes,  the  moment  of  stimulation  being 
determined  by  the  moving  of  the  pen  acting  as  a  marking  lever, 
due  to  the  simultaneous  interrupting  of  the  current  passing  through 
the  small  electro-magnet.  The  time  elapsing  is  determined,  as  in 
the  preceding  experiment,  by  the  electro-magnetic  chronograph  /. 
In  using  the  pendulum  myograph  the  muscle  m  is  attached,  as  in 

Fig.  264. 


Schema  for  measuring  the  velocity  of  the  nerve  impulse  with  pendulum  myograph.  /.  Clamp 
for  femur,  m.  Muscle.  N.  Nerve;  a,  near,  6,  removed  from  C,  whippe.  II.  Secondary;  I,  pri- 
mary spiral  of  induction  apparatus.  B.  Battery.  1,  2.  Key.  3.  Tooth  on  the  smoked  plate. 
(Landois.) 

the  preceding  experiment,  to  a  lever  ;  the  latter  is,  however,  in  this 
case  much  heavier,  and  is  provided  with  a  projecting  steel  point, 
which,  in  being  pressed  against  the  smoked  plate  P,  makes  the 
curved  line,  as  the  plate  is  carried  past  by  the  vibration  of  the  pen- 
dulum. To  demonstrate  the  rapidity  with  which  the  nerve  force  is 
transmitted,  we  make  use  of  the  whippe,  as  in  the  preceding  experi- 
ment, throwing  the  current,  by  means  of  the  latter,  into  the  nerve 
at  6,  a  definite  distance  from  the  point  first  stimulated  a.  The 
result,  as  shown  by  a  tracing  (Fig.  265)  taken  with  the  pendulum 
myograph,  is  the  same  as  when  obtained  by  the  cylinder.  In  order 
to  preserve  the  tracing  on  the  smoked  glass  the  latter  is  placed  upon 
sensitive  paper  and  exposed  to  sunlight. 

The  rate  at  which  nerve  force  is  transmitted  has  been  determined 
by  Helmholtz  and  Baxt,^  in  man  as  well  as  in  the  lower  animals.  In 
the  case  of  the  motor  nerves  this  was  accomplished  by  applying  elec- 
trodes to  the  skin  over  the  median  nerve  at  the  wrist,  elbow,  and  up- 
per arm,  the  arm  being  firmly  surrounded  by  gypsum,  except  at  the 
points  stimulated.  The  time  elapsing  between  the  application  of  the 
electrodes  and  the  muscular  contraction,  the  latter  being  evinced  by 
the  swelling  of  the  muscles  of  the  ball  of  the  thumb  against  a  delicate 
lever,  was  greater  when  the  stimulus  was  applied  to  the  upper  arm 
than  at  the  wrist.  The  average  rate  of  transmission  was  deter- 
mined to  be  about  33.9  meters  (111  feet)  per  second,  varying,  how- 
iMonatsber.  d.  Berliner  Acad.,  1807,  s.  228;  1870,  s.  184. 


508 


THE  NERVOUS  SYSTEM. 


ever,  according  to  the  temperature  ;  being  more  rapid  at  a  high 
than  at  a  low  one.  The  rate  of  transmission  of  the  nerve  force  in 
sensory  nerves  was  also  determined  by  Helmholtz  ^  in  essentially  a 
similar  manner.  A  tactile  impression  being  made  successively  upon 
the  foot,  thigh,  and  loins,  the  moment  at  whicli  the  sensation  is  felt 
is  indicated  in  each  instant  by  a  movement  of  the  finger.  Now, 
since  the  time  elapsing  during  M'hich  the  impression  becomes  con- 
scious perception  in  the  brain,  as  well  as  that  during  which  the 
nerve  force  is  transmitted  by  the  motor  nerve  to  the  finger,  is  the 


ioij>        5T5.  5'e,  of  a  second. 

A  muscle-curve  obtained  by  means  of  the  pendulum  myograph,  the  nerve  being  stimulated  at  a 
(Fig.  264).  To  be  read  from  left  to  right,  a  indicates  the  moment  at  which  the  induction-shock 
is  sent  into  the  nerve,  b  the  commencement,  c  the  maximum,  and  d  the  close  of  the  contraction. 
The  two  smaller  curves  succeeding  the  larger  one  are  due  to  oscillations  of  the  lever.  Below  the 
muscle-curve  is  the  curve  drawn  by  a  tuning-fork  making  180  double  vibrations  a  second,  each 
complete  curve  representing  therefore  ii,,th  <<(  a  second.  It  will  be  observed  that  the  plate  of  the 
myograph  was  travelling  more  rapidly  towanl  the  close  than  at  the  beginning  of  the  contraction, 
as  shown  by  the  greater  length  of  the  vibration  curves.     (Foster.) 

same  in  all  three  cases,  the  differences  observed  in  the  successive 
observations  must  be  due  to  the  different  lengths  of  the  sensory 
nerves  transmitting  the  impression,  the  average  rate,  according  to 
Helmholtz,  being  about  60  meters  (196  feet)  per  second,  modified 
by  the  temperature,  as  in  the  case  of  motor  nerves. 

It  would  appear,  however,  from  recent  researches  ^  that  the  rate 
of  conduction  of  nervous  impulses  is  about  the  same  in  sensory  as  in 
motor  nerves,  viz.,  35  meters  (115  feet)  per  second. 

Knowing  the  rapidity  with  which  nerve  force  is  transmitted 
through  the  peripheral  nerves,  its  rate  of  transmissiou  through  the 
spinal  cord  in  man  can  be  inferred  from  the  difference  in  time 
elapsing  during  the  passage  of  a  voluntary  impulse  from  the  brain 
through  the  cord  to  the  upper  and  to  the  lower  extremity,  or  in  the 
reverse  direction,  of  an  impression  made  upon  the  periphery,  giv- 
ing rise  in  the  brain  to  a  sensation.  Thus,  in  the  case  of  the  mo- 
tor fibers  of  the  cord,  if  the  hand  be  moved  first  in  obedience  to 
the  will,  and  then  the  foot,  it  is  evident  that  a  longer  period  will 
elapse  between  the  application  of  the  stimulu.'^,  the  will,  and  the 
muscular  contraction,  in  the  latter  case  than  in  the  former,  since, 

iPhyso-Ocon  Ges.  zu  Konig.sberg,  1850,  Dec.  13. 

^Oehl,  Archiv  italiennes  de  Biologic,  xxi.,  3,  1895,  p.  401. 


TBANSMISSION  OF  NERVE  FORCE.  509 

in  the  transmission  of  the  nerve  force  through  the  spinal  cord  to 
the  sciatic  nerve,  three  times  the  distance  has  been  traversed  as  in 
its  transmission  to  the  median  nerve.  In  this  way  it  has  been 
shown  by  Burckhardt  ^  that  the  average  rate  of  transmission  of  the 
nerve  force  through  the  motor  fibers  of  the  cord,  is  about  10  meters 
(33  feet)  per  second,  or  about  one-third  of  that  of  the  motor  fibers 
of  the  peripheral  nerves.  On  the  supposition  that  0.08  sec.  elapses 
during  the  passage  of  the  nerve  force  from  the  brain  to  the  foot, 
one-half  of  that  time  is  consumed  in  its  transmission  tlirough  the 
cord,  and  one-half  through  the  nerves.  The  rate  of  transmission 
through  the  sensory  fibers  of  the  cord  does  not  differ  very  much, 
however,  from  tliat  of  the  sensory  fibers  of  the  peripheral  nerves. 
Supposing  that  the  distance  traversed  through  the  sciatic  nerve  and 
cord  from  the  periphery  to  the  sensorium  by  a  sensory  impulse  be 
the  same  as  that  of  the  motor  impulse  just  referred  to,  the  time 
elapsing  between  the  application  of  the  stimulus  and  the  resulting 
sensation  would  be  about  0.025  sec. 

As  an  illustration  of  the  relative  slowness  with  which  nerve  force 
is  transmitted,  it  may  be  mentioned  that  a  whale  one  hundred  feet 
long  would  not  feel  the  wound  of  a  harpoon  until  one  second  after 
the  weapon  was  thrust  into  its  tail,  and  that  in  response  to  a  volun- 
tary impulse,  about  one  second  would  elapse  before  the  tail  would 
be  moved,  supposing  that  the  nerve  force  is  transmitted  in  the  huge 
cetacean  at  the  same  rate  as  in  man.  It  should  be  mentioned,  how- 
ever, in  this  connection  according  to  Burckhardt,  that  tactile  im- 
pressions appear  to  be  transmitted  much  more  rapidly  through 
the  spinal  cord  than  painful  ones,  the  former  at  the  rate  of  42 
meters  (137  feet),  the  latter  13  meters  (42  feet)  per  second.  The 
latent  period  and  the  velocity  with  which  the  nerve  force  is  trans- 
mitted through  the  spinal  cord  being  known,  it  becomes  possible 
to  determine  approximately  at  least  the  time  required  for  the 
apprehension  or  perception  by  the  brain  of  an  impression  and 
volition.  Thus,  supposing  the  interval  of  time  elapsing  between 
the  production  of  a  sound  and  the  hearing  of  the  same  has  been 
determined  to  amount  to  0.198  sec,  it  follows  that  if  we  deduct 
from  the  latter  the  time  during  which  the  nervous  impulse  is 
transmitted  through  the  acoustic  nerves,  spinal  cord,  motor  nerves 
and  latent  period,  0.086  sec,  the  remainder,  0.112  sec,  will  be 
the  time  required  by  the  brain  for  perception  and  volition. 

Transmission  through  acoustic  nerve  .         .  0.010  sec. 

Pei'ception  and  volition     .         .         .         .         .  0.112    " 

Transmission  through  spinal  cord     .         .         .  0.022    " 

"  "         motor  nerve  .         .  0.044    " 

Latent  period 0.010    " 


0.198    " 


The  interval  of  time  (0.198  sec.)  elapsing  between  the  production 
of  a  sound  and  the  hearing  of  the  same  may  be  determined  among 

'  Die  Physiologische  Diagnostik,  s.  32,  Leipzig,  1875. 


510 


THE  NERVOUS  SYSTEM. 


other  methods  by  means  of  the  apparatus  (Fig.  266)  in  which  the 
clock-work  of  the  Hipp's  chrouoscope  H,  held  by  an  electro-mag- 
netic anchor  is  set  going  through  the  weaking  of  the  current 
Klmn2H3Z^  when  the  latter  is  short-circuited  through  Kfia6JZ4. 
by  the  tilting  up  of  the  board  through  the  electrodes  JZ  by  the 
falling  of  the  ball,  the  cause  of  the  sound  and  which  is  stopped  by 
the  voluntary  elevation  of  the  lever  h  at  the  instant  that  the  sound 
is  heard. 

Fig.  2G6. 


Apparatus  for  determining  the  interval  elapsing  between  the  production  and  hearing  of  a 
sound.     (WuxDT.) 

The  determination  of  the  interval  between  the  production  of  a 
light  and  the  seeing  of  the  same  can  be  determined  in  a  similar 
manner  by  suitable  apparatus.  Such  determinations,  apart  from 
their  j^hysiological  interest,  are  also  of  ])ractical  importance  to 
astronomers,  it  being  well  known  to  the  latter  that  considerable 
difference  exists,  amounting  in  some  instances  to  as  much  as  one 
second,  between  observation  made  upon  the  transit  of  a  star  for 
example,  the  object  being  seen  by  one  observer  sooner  than  the 
other.  Indeed,  it  was  such  discrepancies  that  led  Hirsch  ^  to  de- 
termine, as  far  as  possible,  the  "  reaction  time,"  that  is  the  interval 
which  elapses  between  the  application  of  the  stimulus  and  the  mak- 
ing of  the  signal  when  the  sensation  is  felt,  of  the  rapidity  with 
which  impressions  are  transmitted  through  the  optic  and  acoustic 
nerves  and  perceived  by  the  brain,  and  of  so  ascertaining  the  per- 
sonal error  due  to  individual  peculiarities,  and  by  means  of  which 
the  observation  could  be  corrected  by  the  personal  equation,  as  it  is 
called. 

The  determination  of  the  rapidity  with  which  nerve  force  is 
transmitted  is  a  striking  illustration  of  the  advances  made  in  phys- 

^BuU.  de  la  Soc.  des  Sciences  nat.  de  Neufchatel,  1862. 


RAPIDITY  OF  NERVE  ACTIOX.  511 

iology,  due  to  the  introduction  in  its  study  of  physical  methods. 
In  the  year  1<S44  Johannes  ]\Iuller  expressed  the  view  that  "  we  shall 
never  have  the  means  to  determine  the  rapidity  of  nerve  action, 
as  the  comparison  of  immense  distances  is  wanting,  by  which  the 
rapidity  in  the  nerves  can  be  calculated  in  the  same  respect  as  in 
the  case  of  light,"^  and  yet  within  six  years  of  this  period  what 
was  considered  impossible  by  one  of  the  greatest  biologists  was 
actually  accomplished,  as  we  have  seen,  by  Helmholtz.^ 

1  Physiologie,  i.,  4  Aufl.,  s.  581.     Coblenz,  1S44. 
^Monatsber.  d.  Berliner  Acad.,  1850,  s.  14. 


CHAPTER   XXVIIL 

THE    NERVOUS   SYSTEM.— {Continued.) 

GALVANOMETERS.      NON-POLARIZABLE     ELECTRODES. 

ELECTRICAL  CURRENT.     ELECTRO-MOTIVE  FORCE 

AND    RESISTANCE   OF    NERVES.     CAUSE    OF 

ELECTRICAL    CURRENT  OF    NERVES. 

It  will  be  observed,  in  the  precediug  experiments,  performed 
M'ith  the  view  of  demonstrating  nervous  irritability,  that  the  mus- 
cular contraction  following  the  stimulation  of  the  nerve  is  the  only 
visible  positive  evidence  that  we  have  obtained  so  far  of  the  nerve 
having  been  modified  in  any  way  by  the  application  of  the  stimu- 
lus. That  some  change,  however,  must  be  set  up  at  the  point  of 
irritation  and  transmitted  thence  through  the  nerve  is  evident  from 
the  fact  of  the  nuiscle  contracting  in  response  to  the  stimulus, 
though  the  latter  be  applied  to  the  nerve  at  a  distance  from  the 
muscle,  while  from  the  slowness  with  which  the  irritation  is  trans- 
mitted thence  through  the  nerve,  it  is  to  be  also  inferred  that  the 
change  in  its  condition  during  a  state  of  activity,  whatever  the  na- 
ture of  the  change  may  be,  is  of  a  gradual  character.  If,  however, 
the  electrical  condition  of  the  nerve  be  examined  in  a  state  of  rest, 
and  in  one  of  activity,  it  will  be  learned  that  the  change  induced 
in  a  nerve  through  its  stimulation,  is  a  change  partly  at  least  in  its 
electrical  condition,  since  the  natural  electrical  current  that  is  pres- 
ent in  a  cut  nerve  during  a  state  of  rest,  disappears  during  one  of 
activity.  Indeed,  it  can  be  shown  that  as  rapidly  as  the  electrical 
current  disappears  in  the  nerve,  the  nerve  current  or  irritability  of 
the  nerve  appears,  and  it  may  be  incidentally  mentioned  here,  as 
confinnatory  of  what  has  just  been  said  with  reference  to  the  dis- 
appearance of  the  electrical  and  the  appearance  of  the  nerve  im- 
pulse, that  the  fact  of  the  velocity  of  electricity  and  of  the  nervous 
impulse  being  at  the  rate  of  28 H, 000  miles  a  second  and  of  100 
feet  a  second  respectively,  also  proves  the  non-identity  of  the  two. 
To  appreciate,  however,  the  change  in  the  electrical  condition  of  a 
nerve  brought  about  during  its  state  of  excitement  through  the  ef- 
fect of  a  stimulus,  it  will  be  first  necessary  to  explain  the  construc- 
tion of  the  galvanometer,  by  means  of  which  the  presence  of  an 
electrical  current  in  a  cut  nerve  during  a  state  of  rest,  and  in  an 
uninjured  one  of  activity,  cannot  only  be  demonstrated,  but  also 
the  amount  and  direction  of  the  same  determined. 

The  construction  of  a  galvanometer  is  based  upon  the  fundamen- 
tal fact  discovered  by  Oersted,  in  1819,  of  a  magnetic  needle  being 


DEFLECTION  OF  MAGNET  BY  CURRENTS. 


513 


deflected  out  of  the  magnetic  meridian  by  a  current  of  electricity 
passed  along  a  wire  parallel  to  it.  Thus,  for  example,  if  an  elec- 
trical current  be  passed  above  the  magnetic  needle  from  south  to 
north  as  indicated  by  the  direction  of  the  arrows  (Fig.  267,  a  6), 
the  north  pole  n  of  the  needle  will  be  deflected  toward  the  west, 
while  if  in  the  reverse  direction,  from  north  to  south  (Fig.  268,  a  b), 
the  north  pole  n  of  the  needle  will  be  deflected  toward  the   east. 


Fig.  267. 


Fig.  268. 


C  a 


Deflection  of  magnet  by  currents. 


Deflection  of  magnet  by  currents. 


On  the  other  liand,  if  the  current  be  transmitted  from  north  to 
south  but  below  the  needle,  then  the  north  pole  of  the  needle  will 
be  deflected  toward  the  west,  as  in  Fig.  267,  but  if  in  the  reverse 
direction  toward  the  east,  as  in  Fig.  268.  The  direction  according 
to  which  the  needle  is  deflected  in  either  of  the  above  cases  may  be 
easily  remembered  by  the  memoria  technica  of  Ampere,  according 
to  which  the  north  pole  of  the  needle  is  always  deflected  toward 
the  left  of  an  individual  supposed  to  be  swdmming  in  the  electrical 
stream,  and  always  facing  the  needle,  the  current  entering  the  feet 
and  leaving  the  head  of  the  individual  so  disposed.  That  is  to 
say,  the  north  pole  of  the  needle  is  always  deflected  toward  the  left 
of  the  current.  It  is  evident,  therefore,  if  a  current  be  transmitted 
through  a  wire  passed  around  a  needle  so  that  the  current  enters  the 
wire  at  a  and  leaves  it  at  b  (Fig.  267),  that  not  only  will  the  north 
pole  of  the  needle  be  deflected  toward  the  west  as  the  current  passes 
above  the  needle  from  south  to  north,  but  still  also 
to  the  west,  as  the  current  is  transmitted  below  the  Fig.  269. 
needle  from  north  to  south,  and  that  if  the  wire  be 
coiled  again  and  again  around  the  needle  and  prop- 
erly insulated,  the  deflection  of  the  needle  will  be 
proportionally  intensified.  It  need  hardly  be  ad- 
ded that  if  the  current  be  transmitted  in  the  re- 
verse direction,  entering  the  wire  at  c  and  leaving  Multiplier. 
it  at  b  (Fig.  268),  the  needle  will  be  deflected  to 
the  east.  Hence,  the  name  of  multiplier  given  to  such  an  instru- 
ment (Fig.  269),  as  invented  in  1829,  by  Schweigger. 
33 


514 


THE  NERVOUS  SYSTEM. 


The  magnetic  needle  is  kept  in  the  magnetic  meridian  by  the 
magnetic  current  of  the  earth,  the  latter,  in  circulating  around  the 
globe  from  east  to  west,  bringing  parallel  to  itself  and  in  the  same 
direction  the  magnetic  currents  of  the  under  surface  of  the  needle, 
the  latter  finally  coming  to  rest  with  the  currents  of  its  north  pole, 
opposite  in  direction  to  that  of  the  hands  of  a  watch,  and  those  of 
its  south  pole  in  the  same  direction,  the  needle,  therefore,  pointing 
north  and  south,  with  its  currents  at  right  angles  to  its  long  axis. 
It  is  obviously  of  advantage,  therefore,  in  the  construction  of  a 
galvanometer  that  the  directive  influence  of  the  earth's  currents, 
exercised  upon  those  of  the  needle  be  eliminated,  as  the  deflection 
of  the  needle  by  the  directive  influence  of  an  electrical  current 
passed  through  the  surrounding  wire  will  be  then  still  more  inten- 
sified. This  was  accomplished  by  Nobile,  in  1827,  by  rendering 
the  needle,  or,  rather,  the  needles,  astatic,  as  it  is  called — that  is  to 
say,  two  needles  (Fig.  270)  N S  and  S  N,  are  connected  together,  and 


Fig.  270. 


Fig.  271. 


Thcimson'.s  galvanometer. 


Astatic  needles. 

suspended  by  a  fine  silk  filament,  the 
lower  one  within  the  electrical  circuit, 
the  upper  one  above  it,  so  that  the  north 
pole  iV^  of  the  lower  needle  is  opposite 
the  south  pole  S  of  the  upper  one,  and 
the  south  pole  /S'  of  the  lower  needle  is 
opposite  the  north  pole  X  of  the  upper 
one.  Such  being  the  disposition  of  the  needles,  the  influence  of  the 
earth's  magnetism  exerted  upon  the  north  pole  (^Y)  of  the  lower 
needle  is  more  or  less  neutralized  through  the  same  being  exerted 
upon  the  south  pole  (/S')  of  the  upper  one.  In  sensitive  galvanom- 
eters this  latter  effect  is  still  more  thoroughly  accomplished  by 
placing  a  magnet  D  (Fig.  271),  above  the  upper  needle. 

It  hardly  need  be  mentioned  that,  according  to  the  Amperian 


SCALE  AND  LAMP  FOR  GALVANOMETER. 


515 


rule,  the  north  end  X  ni'  the  h)wer  needle^  and  the  south  end  S  of 
the  upper  one  will  move  together,  and  toward  the  west,  if  the  elec- 
trified current  directing  them  be  transmitted  in  the  direction  indi- 
cated by  the  direction  of  the  arrows,  for,  though  the  upper  needle 
S  X  is  subjected  to  the  action  of  the  two  contrary  currents  below 
it,  the  action  of  the  upper  current  being  the  nearest  will  influence 
it  to  the  greatest  extent.  Upon  the  principles  just  enunciated  are 
constructed  the  Thomson  and  Wiedemann  galvanometers,  both  of 
which  the  author  makes  use  of  in  determining  the  presence,  intensity, 
and  direction  of  the  electrical  currents  of  nerves.  In  Thomson's  gal- 
vanometer (Fig.  271),  the  magnetic  needles  are  very  small  and 
light,  but  highly  magnetized,  and  are  disposed  in  an  upper  and 
lower  set,  connected  by  an  aluminium  rod,  and  arranged  astatically. 
Each  needle  is  separately  surrounded  by  numerous  coils  of  very 
fine  wire,  ending  in  the  binding  screws,  the  course  of  the  lower 
coil  being  opposite  in  direction  to  that  of  the  upper  one.  To  the 
upper  set  of  needles  is  fixed  a  slightly  concave  mirror  about  6  mm., 
or  one-fourth  of  an  inch  in  diameter,  serving  to  reflect  the  beam 
of  light  back  to  the  scale  B  (Fig.  272),  the  light  being  transmitted 
from  the  lamp  through  the  narrow  slit  F  under  the  scale,  and  the 


Fig.  272. 


Fig.  273. 


Scale  and  lamp. 


Lamp  and  scale  for  Thomson's 
galvanometer. 


lamp  placed  back  of  the  scale  (Fig.  273).  The  astatic  system  of 
needles  is  suspended  by  a  single  fiber  of  silk  from  a  brass  pin  fixed 
to  the  top  of  the  vulcanite  frame  of  the  coils.  The  latter  are  sup- 
ported upon  brass  uprights,  and  are  covered  by  a  glass  shade  fitting 
into  the  rim  of  a  vulcanite  disk,  brass  bound,  which  is  levelled  by 
three  screws  (CC).  The  brass-bound  glass  shade  covering  the  up- 
rights, supports  a  brass  rod  E,  upon  which  slides  a  curved  and 
weak  magnet  (i)),  serving  to  neutralize  the  earth's  magnetism. 
When  used,  the  galvanometer  should  be  so  placed  that  its  mirror 
faces  west,  the  light  and  scale  being  opposite  the  latter,  and  l^ctween 
two  and  three  feet  distant.  The  electrodes  being  attached  to  the 
outer  two  (b  b)  of  the  four  binding  screws,  and  the  two  intermedi- 


516  THE  NERVOUS  SYSTEM. 

ate  ones  (a  a)  being  connected  together,  the  current  to  be  investi- 
gated will  pass  through  the  coils,  the  light  moving  from  the  zero 
along  the  scale  to  the  left  or  right,  according  to  the  direction  of  the 
current. 

If  it  be  desired  to  compare  the  intensities  of  two  electrical  cur- 
rents, then  the  connection  between  the  two  intermediate  binding 
screws  a  a  being  unmade,  the  two  electrodes  conveying  one  of  the 
currents  must  be  attached  to  one  of  the  outer  binding  screws  (6),  and 
the  adjacent  inner  one  (d),  the  other  two  electrodes  similarly  to  the 
other  outer  binding  screw  (6)  and  the  adjacent  inner  one  (a).  If  the 
currents  be  equal  in  intensity,  and  opposite  in  direction,  the  mirror 
will  be  unaffected,  and  the  light  will  remain  at  zero,  only  moving 
to  the  right  or  left,  according  as  one  or  the  other  of  the  currents 
preponderates.  It  scarcely  need  be  added  that  if  a  Thomson  gal- 
vanometer be  used  in  determining  the  presence,  etc.,  of  nerve  cur- 
rents, the  room  must  be  darkened.  Inasmuch 
Fig.  274.  as  this  galvanometer  is  an  exceedingly  sensi- 

tive instrument,  it  is  often  desirable  to  allow 
only  a  fractional  part  of  the  current  of  elec- 
tricity studied  to  pass  into  it,  the  remaining 
part  of  the  current  being  shunted  oiF.  In  ac- 
complishing this  object  we  make  use  of  the 
electrical  shunt.  This  instrument  (Fig.  274) 
consists  of  a  series  of  brass  plates,  separated 
from  one  another,  but  connected  by  wires  of 
different  lengths,  which  offer,  therefore,  more 
or  less  resistance  to  a  current  traversing  them. 
The  plates  are,  however,  also  capable  of  be- 
>.;ij„Qt  ing  more  directly  connected   by  means  of  a 

brass  plug.  The  shunt  is  provided  with  two 
binding  screws,  to  which  are  attached  the  t^vo  wires  from  the  outer 
binding  screws  of  the  galvanometer  and  the  two  electrodes  convey- 
ing the  current,  a  part  of  which  is  to  be  diverted  from  the 
galvanometer. 

The  two  binding  screws  of  the  shunt  can  be  brought  into  direct 
connection  by  turning  down  a  brass  bar ;  if  this  be  done,  the  cur- 
rent from  the  nerve,  for  example,  will  be  short-circuited,  it  passing 
from  one  binding  screw  to  the  other,  back  to  where  it  came  from, 
none  of  the  current  going  to  the  galvanometer,  owing  to  the  re- 
sistance offered.  If,  however,  the  connection  between  the  binding 
screws  be  unmade  through  the  raising  of  the  bar,  and  the  i)lug  not 
placed  in  any  of  the  holes  of  the  shunt,  then  the  current,  not  be- 
ing able  to  pass  directly  across  from  one  binding  screw  to  the  other, 
will  traverse  the  galvanometer.  The  coils  of  the  shunt  being 
graduated,  however,  according  to  tlie  resistance  of  the  galvanometer, 
by  means  of  the  plug,  we  can  vary  at  will  the  proportional  amount 
of  the  current  going  to  the  galvanometer  to  that  short-circuited, 
the  amount  depending  upon  the  ratio  of  the  resistance  of  the  gal- 


WIEDEMANN S  GALVAyOMETEB. 


517 


vanometer  to  that  of  the  shunt.  Thus,  for  example,  suppose  the 
plug  be  inserted  into  the  hole  marked  1,  then  such  resistance  is 
oifered  in  the  short  circuit  that  only  J^  of  the  total  current  goes  to 
the  galvanometer,  the  remaining  ^^^  being  short-circuited  ;  if  in 
the  hole  marked  gL,  or  g-i^,  then  only  yi^  or  y-Q^ q,  respectively, 
of  the  current  traverses  the  galvanometer,  the  remaining  -^-^^,  or 
tVo^O'  t»eing  short-circuited. 

Weidemann's  galvanometer,  consists  of  a  thick  cylinder  of  cop- 
per (Fig.  275),  through  which  a  tunnel  is  bored,  the  latter  capable 
of  being  closed  at  each  end  by  either  a  cover  with  glass  front,  or 
bv  a  solid  plug  of  copper.  Within  the  copper  tunnel  hangs  a  mag- 
netized ring  (Fig.  -75,  A),  of  such  size  that  it  can  just  swing  clear 

Fig.  275. 


Wiedemann's  galvanometer. 

of  the  sides.  The  object  in  making  the  magnet  ring-shaped  is  to 
make  it  stronger  in  proportion  to  its  size,  the  center,  or  inactive 
portion  of  the  magnet,  in  that  form  being  absent.  Connected  with, 
and  passing  upward  from  the  magnetized  ring  through  a  copper 
tube,  is  an  aluminium  rod,  terminating  in  a  light  frame  holding  a 
circular  plane  mirror,  facing  east  and  west  (B).  In  order  to  prevent 
currents  of  air  moving  the  mirror,  the  latter  is  inclosed  within  a  cir- 
cular brass  cover  (C)  having  a  circular  window  (W),  through  which 
the  mirror  can  be  viewed.  Above  the  mirror  is  screwed  a  long 
glass  tube  (T),  at  the  top  of  which  there  is  a  little  windlass,  sup- 
ported by  a  small  piece  of  ebonite,  whose  centering  on  the  glass  tube 
is  effected  by  three  screws.  On  the  windlass  a  single  fiber  of  silk 
is  wound,  passing  through  the  ebonite  and  down  through  the  glass 
tube,  by  means  of  which  the  magnet  and  mirror  are  suspended,  the 
frame  of  the  latter  being  pierced  with  an  eye  for  the  attachment  of 


518  THE  NERVOUS  SYSTEM. 

the  platinum  hook,  to  which  the  end  of  the  silk  fiber  is  looped. 
The  magnetized  ring  can,  by  this  means,  be  raised  or  lowered  or 
centered  in  the  copper  chamber,  the  latter  and  its  attachments  being 
supported  by  brass  columns  on  a  mahogany  plate,  leyelled  by  three 
screws.  The  coils  C  C,  the  turns  of  which  in  sensitiye  instruments, 
as  in  that  of  the  author,  may  amount  to  as  many  as  30,000,  and 
through  which  is  transmitted  the  electricity  exerting  a  directive  in- 
fluence upon  the  magnetized  ring,  are  placed  upon  a  sledge,  that 
they  can  be  so  approximated  as  to  meet  right  over  the  copper  cham- 
ber, and  when  so  disposed  completely  conceal  the  latter,  as  in  Fig. 
275.  Since  with  the  movement  of  the  magnetized  ring  induced 
currents  are  set  up  in  the  surrounding  copper  chamber,  opposite  in 
direction  to  those  of  the  needle,  the  oscillations  of  the  latter  are  so 
diminished  that  after  deflection  it  comes  quickly  to  rest.  The  cop- 
per chamber  is,  therefore,  called  the  damper,  the  close  fitting  of  the 
ring  within  the  latter  and  the  proximity  of  the  coils  materially  assist- 
ing in  the  dampening  by  it  of  the  oscillations  of  the  ring.  Further, 
in  order  to  render  tlie  magnetized  ring  within  the  copper  damper 
astatic,  we  make  use^  of  an  accessory  magnet  (M),  a  Hauy  bar,  placed 
in  the  magnetic  meridian  horizontal  to  the  needle,  with  its  north  pole 
pointing  north,  like  that  of  the  magnetized  ring,  and  supported  upon 
a  bar  (D)  directed  perpendicularly  to  the  coils,  and  in  a  line  with 
their  axis.  The  accessory  magnet  can  slide  up  and  down  the  bar 
within  its  support,  the  bar  being  divided  into  centimeters,  for  meas- 
uring the  extent  of  the  movement.  One  end  of  the  magnet  being 
caught  between  a  spring  and  a  screw,  and  the  latter  being  turned 
by  the  pulley  P\  the  magnet  can  be  moved  from  its  spring  end  on  the 
other  end,  forming  an  angle  with  the  plane  of  the  coils,  the  angular 
movement  being  effected  by  an  experimenter  seated  at  a  distance  by 
means  of  the  pulley  P-.  The  galvanometer,  being  properly  located, 
the  accessory  magnet,  just  descriljed,  is  fixed  upon  its  bar  (B)  by  a 
clamp  to  the  shelf.  The  magnet,  being  first  placed  at  the  end  of 
the  bar,  is  then  slowly  moved  down  it,  the  effect  being  gradually  to 
neutralize  the  magnetic  action  of  the  earth.  The  moment,  however, 
that  the  position  of  neutralization  is  passed  the  magnetic  ring  swings 
round,  carrying  the  mirror,  of  course,  with  it,  now  facing  north  and 
south,  so  that  its  opposite  poles  are  placed  against  the  poles  of  the 
magnet,  the  movement  involving  a  full  half  twist  on  its  fiber.  To 
prevent  this,  one  of  the  copper  plugs  should  be  put  in  one  of  the 
openings  of  the  chamber,  by  which  the  movement  of  the  magnetic 
ring  is  blocked,  the  other  opening  being  filled  with  a  glass  plug,  the 
movement  of  the  ring  can  be  seen.  This  twisting  tendency  being 
r)bserved,  the  accessory  magnet  should  be  moved  back  again  till  the 
tendency  disappears,  and  the  magnetic  ring  is  just  sufficiently  in- 
fluenced by  the  directive  action  of  the  earth  to  be  kept  in  the  me- 
ridian. The  instrimtient  will  then  be  found  to  be  very  sensitive. 
When  botli  coils  are  to  be  used,  they  must  be  connected  by  carry- 
1  Du  Bois  Keymond,  Abhandlungen,  s.  370. 


CAPILLARY  ELECTROMETER. 


519 


Fig.  276. 


ing  a  wire  from  a  binding  screw  of  the  one  to  a  binding  screw  of 
the  other,  according  to  the  coils  used,  the  remaining  free  binding 
screws  receiving  the  wires  conveying  the  current.  When  both  coils 
enclose  the  copper  chamber  the  most  intense  effect  is  obtained,  the 
recession  of  coils  from  the  chamber  diminishing  it. 

The  great  advantage  of  Wiedemann's  galvanometer  is  that  by  the 
copper  damper  the  disposition  of  the  coils  C,  and  the  accessory 
magnet  M,  the  magnetized  ring  is  made  aperiodic  or  dead  beat^ 
that  is  to  say,  the  magnetic  ring,  when  aifected  by  the  current, 
swings  around  comparatively  slowly,  until  the  maximum  deflection 
is  reached,  and  arriving  at  this  point  it  rests  there  without  oscilla- 
tion ;  the  current  being  withdrawn,  it  savings  back  again  to  zero, 
stopping  there  without  further  oscillation,  a  current  in  the  opposite 
direction  being  indicated,  should  it  pass  the  zero.  It  is  highly 
important  in  locating  the  galvanometer  that  no  iron  structures 
whatever  should  be  present  in  its  neighborhood.  The  instrument 
may  be  placed  upon  a  strong 
wooden  shelf  fixed  to  a  solid  dry 
wall,  or,  if  the  laboratory  or  lecture- 
room  be  upon  the  ground  floor,  upon 
a  pillar  of  concrete,  capped  with 
oak,  built  upon  a  solid  stone  foun- 
dation. In  using  Wiedemann's  gal- 
vanometer in  the  laboratory  the 
extent  of  the  deflection  of  the  mag- 
netized ring  is  observed  by  means 
of  an  astronomical  telescope,  and  of 
a  scale  (Fig.  276),  supported  by  up- 
right above  and  at  right  angles  to 
the  long  axis  of  an  astronomical  telescope,  the  scale  and  telescope 
being  placed  upon  the  same  table  to  which  the  pulley  P\  already 
referred  to,  is  attached,  and  which  ought  to  be  from  6  to  9  feet 
distant  from  the  galvanometer.  The  scale  being  directly  opposite 
the  mirror,  the  reversed  numbers  of  the  former  will  be  seen  in  the 
latter  in  their  natural  position,  and  with  the  deflection  of  the  needle 
the  numbers  will  appear  as  if  drawn  across  the  mirror,  the  amount 
of  the  deflection  being  indicated  by  the  number  seen  in  the  mirror 
when  the  needle  comes  to  rest.  For  lecture  purposes,  however,  the 
telescope,  etc.,  is  not  used,  a  beam  from  a  lime  or  electric  light 
being  received  upon  a  small  plane  luirror,  is  thence  reflected  to  the 
mirror  of  the  galvanometer,  and  from  the  latter  to  a  white  scale 
placed  at  a  distance  of  from  6  to  15  feet,  according  to  the  magni- 
fication desired.  In  this  way  the  deflection  of  the  magnetic  ring 
can  be  made  evident  to  a  large  audience. 

A  very  sensitive  instrument  often  made  use  of  in  determining 
the  presence  of  electrical  currents  in  nerves  is  the  capillary  elec- 
trometer of  Lippmann.  This  consists  (Fig.  277)  of  a  capillary 
glass  tube  (i?)  filled  from  above  with  mercury  and  from  below  with 


Telescope  and  scale. 


520 


THE  NERVOUS  SYSTEM. 


Fig.  277. 


dilute  sulphuric  acid,  and  T^-liicli  opens  by  its  lower  narrow  end  into 
a  wide  glass  tube  (c)  containing  mercury  (^)  and  sulphuric  acid  (s) 
and  conducting  wires  terminating  in  non-polarizable  electrodes. 
With  the  application  of  the  latter  to  the  nerve  any  electrical  current 
present  Avill  be  at  once  revealed  by  the  move- 
ment of  the  thread  of  mercury  in  the  direc- 
tion of  the  arrow,  as  observed  by  the  micro- 
scope, as  a  very  slight  difference  of  electrical 
potential  causes  a  change  in  the  surface  ten- 
sion of  the  mercury  sulphuric  acid  meniscus. 
Inasmuch  as  in  demonstrating  the  presence 
of  an  electrical  current  in  a  nerve  l)y  means 
of  galvanometer,  the  current  is  conveyed  by 
the  wires  passing  from  the  binding  screw^  to 
the  nerve,  it  is  obvious  that  these  wires  must 
terminate  in  non-polarizable  electrodes — that 
is  to  say,  as  has  been  incidentally  mentioned, 
in  electrodes  that  will  convey  an  electrical 
current  already  existing  in  the  nerve  ex- 
amined, but  will  not  generate  a  new  one  when 
placed  in  contact  with  the  latter,  since  the 
latter  current  so  generated,  extremely  weak 
though  it  may  be  in  deflecting  at  once  the 
needle,  the  galvanometer  being  so  sensitive, 
might  readily  be  mistaken  for  the  pre-existing 
current  whose  presence  we  wish  to  demonstrate. 
In  order,  however,  to  understand  the  manner  in  which  the  gen- 
eration of  the  current  is  prevented  by  the  contact  of  the  electrodes 
with  the  nerve  tissue,  it  Avill  be  first  necessary  to  explain  what  is 
meant  by  the  polarization  of  the  electrodes,  to  which  the  above 
effect  is  due.  Let  us  suppose  that  two  platinum  electrodes  have 
been  immersed  in  acidulated  water,  and  that  the  electricity  trans- 
mitted from  the  battery  has  decomposed  the  water,  the  positive  pole 
being  covered  with  bubbles  of  oxygen,  and  the  negative  with  bub- 
bles of  hydrogen.  If  suddenly,  now,  the  electrodes  be  disconnected 
with  the  battery,  and  connected  with  a  galvanometer,  the  direction 
in  which  the  needle  of  the  latter  is  deflected  will  indicate  the  pres- 
ence of  a  current,  opposite  in  direction  to  that  of  the  battery 
and  weakening  the  latter,  developed  through  the  fact  of  the  nega- 
tive pole  covered  with  hydrogen  becoming  positive  to  the  positive 
pole  covered  with  oxygen,  just  as  in  the  case  of  non-constant 
batteries  already  referred  to.  It  is  the  change  in  the  condition  of 
the  electrodes  which  is  known  as  their  polarization,  and  which 
occurs  in  a  similar  manner  if  a  nerve  be  placed  upon  two  copper 
wires.  We  shall  see  hereafter  that  when  a  fresh  muscle  is  con- 
nected with  the  galvanometer  by  copper  wires,  the  deflection  of  the 
needle  ensuing  indicates  the  presence  of  a  current,  but  which,  on 
account  of  the  polarization  of  the  electrodes,  may  be  as  much  due 


Capillary  eloctrumcter.  R. 
Mercury  in  tube  ;  eajjillary 
tube.  «.  Sulphuric  acid.  q. 
Mercury.  B.  Observer.  M. 
Microscope.     (Landois.) 


HOMOGENEOUS  DIVERTING   VESSEL. 


521 


to  the  generatiou  of  a  current  a.<  to  the  presence  of  a  preexisting 
one.  Even  perfectly  clean  platinum  electrodes  soon  become  differ- 
ently affected  by  contact  with  organic  tissues,  and  so  give  rise  to 
difference  in  electrical  tension  or  electro-motive  force.  Eegnauld, 
however,  showed  in  18-34,  that  a  strip  of  chemically  pure  zinc  im- 
mersed in  a  solution  of  neutral  zinc  sulphate,  and  Matteuci,  two 
years  later,  that  ordinary  zinc  amalgamated  and  immersed  in  a 
saturated  solution  of  the  same,  exhibited  no  polarization.  Du 
Bois  Reymond,  availing  himself  of  these  discoveries,  devised  non- 
polarizable  electrodes,  convenient  forms  of  which,  kno^^'n  as  di- 
verting vessels  and  diverting  cylinders,  are  represented  in  Figs. 
278  and  279,  and  by  which  no  currents  are  generated  when  nerve 
or  muscle  is  placed  in  contact  with  the  same,  A  diverting  vessel 
(Fig.  278j  consists  of  a  zinc   trough  (T),  containing   a  saturated 

Fig.  278. 


Homogeneous  diverting  vessel. 

solution  of  zinc  sulphate,  the  inner  surface  of  the  trough  being 
carefully  amalgamated,  and  the  outer  surface  coated  with  a  layer 
of  black  varnish,  the  object  of  the  latter  being  to  prevent  the  sul- 
phate solution  coming  in  contact  vd\h  any  unamalgamated  zinc. 

It  mav  be  mentioned  incidentally  in  this  connection  that  the 
amalgamating  fluid  used  is  that  known  as  Bergot's,  prepared  by 
dissolving:  at  a  srentle  heat  200  grammes  of  metallic  mercurv  in  a 
1000-gramme  mixture  consisting  by  weight  of  one  part  of  nitric 
acid  to  three  parts  of  hydrochloric  acid,  and  adding  then  1000 
grammes  of  the  latter  acid.  The  fluid  should  be  kept  in  a  cool, 
dark  place,  to  avoid  decomposition.  The  trough,  insulated  by  a 
base  of  vulcanite  (V),  and  provided  with  a  binding  screw  (K),  can 
be  lifted  by  a  handle  (R).  The  insulated  cushions  (C),  called  de- 
riving cushions,  are  made  up  of  a  series  of  layers  of  white  Swedish 


522 


TEE  NERVOUS  SYSTEM. 


filtering  paper,  wliicli  are  stitched  together  at  one  end  to  secure 
them,  and  their  sides  cut  perpendicularly  with  a  sharp  razor,  and 
soaked  in  the  zinc  solution  and  squeezed  so  as  to  get  rid  of  the 
bubbles  of  air  which  would  offer  resistance  to  the  current.  These 
cushions  fill  up  the  cavity  of  the  trough,  and  project  over  the  lip 
of  the  latter,  a  plate  of  ebonite  (E),  and  an  Indian-rubber  band 
(B)  retaining  the  cushion  in  this  position.  Inasmuch,  however,  as 
the  nerve  to  be  examined,  if  placed  directly  upon  the  deriving 
cushion  would  be  corroded  by  the  zinc  sulphate  solution  in  which 
the  cushion  has  been  soaked,  a  guard  (G)  is  made,  consisting,  as 
already  mentioned,  of  china  clay  worked  up  into  a  soft  mass  with 
a  0.5  or  1  per  cent,  solution  of  sodium  chloride,  which  when  freed 
of  bubbles  of  air  and  flattened  into  a  sheet  (G)  is  folded  over  the 

Fig.  279. 


Diverting  cyliDclcrs. 

cushion.  A  small  piece  of  mica  may  also  be  placed  upon  the  clay 
guard  to  limit  the  part  to  be  touched  by  the  tissue.  The  clay  guard 
not  only  prevents  the  corrosion  and  destruction  of  the  nerve,  but 
through  the  presence  of  the  salt,  the  secondary  resistance,  which 
would  otherwise  arise  between  the  liquid  conductor  and  the  tissue, 
and  diminish  the  intensity  of  the  current  to  be  examined  is  avoided, 
the  salt  at  the  same  time  being  a  good  conductor.  Two  diverting 
vessels  being  so  prepared,  a  fine  silk-covered  copper  wire  is  carried 
from  the  binding  screw  (K)  of  one  of  the  troughs  (T)  to  one  side 
of  the  Du  Bois  Reymond  key,  and  another  wire  from  the  other 
trough  (T'),  not  represented,  to  the  other  side  of  the  key,  wires  be- 
ing also  carried  from  the  key  K  to  the  binding  screws  of  the  gal- 
vanometer g,  as  in  Fig.  279.  Such  being  the  disposition  of  the 
diverting  vessel,  the  key  and  galvanometer,  if  the  key  be  down, 


ELECTRICAL  CURRENTS  OF  NERVE. 


523 


the  diverting  vessels  are  short-circuited,  but  if  up,  are  in  commu- 
nication with  the  galvanometer.  Finally  the  troughs  can  be  di- 
rectly connected  together  by  approximating  them  or  indirectly  by  a 
closing  cushion  made  out  of  blotting  jjaper  saturated  in  the  zinc 
solution,  etc.,  like  the  deriving  ones.  The  diverting  vessels,  key, 
and  galvanometer  being  so  disposed  before  performing  any  experi- 
ment, it  ought  to  be  first  shown  that  the  diverting  vessels  are  ho- 
mogeneous or  non-polarizable.  To  do  this,  the  key  being  down,  and 
the  needle  of  the  galvanometer  at  zero,  the  two  diverting  vessels 
are  connected  together,  and  the  key  opened ;  if  the  needle  still  re- 
mains at  zero  we  may  be  assured  that  there  is  no  electrical  current, 
that  the  diverting  vessels  are  homogeneous  or  non-polarizable. 

Apart  from  the  fact  that  the  nerve  whose  electricity  is  to  be  ex- 
amined cannot  always  be  placed  between  the  cushions  in  the  posi- 
tion desired,  it  is  also  often  impossible  to  bring  particular  points  of 
the  nerve  in  contact  with  the  latter.  We  frequently,  therefore, 
make  use  of  the  non-polarizable  electrodes  represented  in  Fig.  279, 
known  as  diverting  cylinders,  which  consist  of  a  flattened  tube  of 
glass  (a)  mounted  on  a  universal  joint  {in  I),  and  supported  on  a 
brass  upright  (A)  closed  at  one  end  (c)  by  moistened  china  clay  and 
filled  with  the  saturated  zinc  sulphate  solution  in  which  is  immersed 
the  slip  of  amalgamated  zinc  Z.  The  clay  (c)  projecting  from  the 
end  of  the  tube  can  be  sharpened  into  a  point  so  that  any  two  parts 
of  the  nerve  can  be  touched  that  is  desired.  That  no  polarization 
occurs  when  the  points  of  such  electrodes  are  placed  in  contact 
with  the  nerv^e  is  shown  by  the  absence  of  the  products  of  electro- 
lytic action  which  would  otherwise  accumulate  at  the  electrodes. 

Fig.  280. 


Electrical  currents  of  nerve. 


Such  electrodes  are  not  only  serviceable  in  diverting  an  electrical 
current  from  the  nerve  to  the  galvanometer,  but  can  be  also  used 
for  the  purpose  of  stimulating  a  nerve  by  electricity  in  the  same 
manner  as  already  described.     The  deriving  cushions  (Fig.  278),  or 


524 


THE  NERVOUS  SYSTEM, 


the  diverting  cylinders  (a),  and  the  key  (K)  and  galvanometer  (^r) 
having  been  connected  as  represented  in  Fig.  279,  and  a  freshly 
prepared  nerve  {n)  having  been  placed  upon  the  cushions  or  in  con- 
tact with  the  points  of  the  cylinders  so  that  its  transverse  section 
or  cut  end  is  in  contact  with  one  of  the  cushions  or  cylinders,  and 
its  longitudinal  uninjured  surface  at  the  equator  with  the  other,  with 
the  opening  of  the  key  the  needle  of  the  galvanometer  will  at  once 
be  deflected,  and  in  a  direction  which  shows  that  the  electrical  cur- 
rent in  the  nerve  passes,  as  indicated  by  the  arrows  (Fig.  280),  from 
the  longitudinal  surface  of  the  nerve  (a)  through  the  galvanometer 
to  the  transverse  cut  surface  {x  y),  the  remainder  of  the  circuit  be- 
ing completed  by  the  nerve  itself.  In  this  connection  it  may  be 
mentioned  that  the  galvanometer  is  not  indispensable,  if  we  wish 
simply  to  demonstrate  the  electrical  nerve  current,  as  it  may  be  ac- 
complished by  what  is  known  as  the  physiological  rheoscope,  which 
is  prepared  in  the  following  manner  : 

Upon  an  insulated  glass  plate  A  (Fig.  281)  arc  placed  two  pieces 
of  blotting  paper  (B  C)  soaked  in  salt  solution,  wdiich  support  two 

Fig.  281. 


Physiological  rhooscope. 

albuminous  guards  (D  E),  upon  which  rests  the  nerve  (N)  of  a 
nerve-mu.sclc  preparation,  the  cut  end  of  which  is  in  contact  with 
the  pad  D,  the  longitudinal  surface  with  the  pad  E,  the  muscle 
(M)  being  supported  by  the  glass  plate  F,  also  insulated. 

The  nerve  being  so  disposed,  with  the  alternate  connection  and 
disconnection  of  the  two  pieces  of  blotting  paper  (B  C)  by  a  third 
piece  (G),  the  muscular  contraction  that  follows  in  both  instances 
indicates  the  presence  of  an  electrical  current  in  the  nerve  passing 
in  the  direction  of  the  arrows. 

Returning  now  to  the  case  of  the  nerve  Avhen  in  connection  with 
the  galvanometer  (Fig.  280),  and  experimenting  a  little  further  by 


DU  BOIS  REYMOND'S  BOUND  COMPENSATOR.  525 

changing  the  position  of  one  or  both  of  the  electrodes,  it  will  soon 
be  learned  that  while  the  current  always  passes  from  the  longitudi- 
nal to  the  transverse  cut  surface,  the  amount  of  the  deflection  of 
the  galvanometer  needle  varies  very  much  according  to  the  position  of 
the  electrodes.  In  certain  positions,  indeed,  as  where  the  electrodes 
are  placed  on  different  sides  of  the  nerves  exactly  opposite  to  each 
other  {ah),  or  on  points  equidistant  from  the  equator  {ef),  the 
needle  is  not  deflected  at  all,  there  being  no  difference  of  electrical 
potential  at  such  places.  Such  was  also  supposed  to  be  the  case 
with  reference  to  the  ends  of  the  nerve.  It  has  been  shown,  how- 
ever, bv  Du  Bois  Eeymond  and  Mendelssohn^  that  a  current  passes 
through  the  nerve  from  transverse  section  to  transverse  section,  to 
Avhich  the  name  of  "  axial  stream"  has  been  given  by  these  obser- 
vers. On  the  other  hand,  if  one  electrode  remaining  at  the  cut 
surface,  we  move  the  other  along  the  longitudinal  surface  toward 
the  equator  the  deflection  of  the  needle  will  be  increased,  the  max- 
imum being  reached  when  the  electrodes  are  at  the  equator  of  the 
longitudinal  and  transverse  surfaces,  as  in  the  experiment  repre- 
sented in  Fig.  280,  ab.  Experimentally,  in  this  w^ay,  with  the 
galvanometer,  it  may  be  learned  that  all  parts  of  the  longitudinal 
surface  of  any  nerve  are  positively  electrified  with  reference  to  the 
transverse  cut  surface,  and  that  if  any  two  points  (e/)  of  the  longi- 
tudinal surface,  that  nearest  the  equator  of  the  nerve  (e)  is  posi- 
tively electrified  with  reference  to  that  more  distant  (/). 

That  a  similar  relation  exists  between  the  equator  of  the  trans- 
verse cut  surface  and  its  periphery,  though  not  experimentally  dem- 
onstrated, is  rendered  highly  probable  from  the  fact  of  such  a  re- 
lation having  been  demonstrated  in  the  case  of  muscles,  as  we 
shall  see  hereafter.  Further,  by  experimenting  with  different 
nerves  it  will  be  found  that  the  length  and  thickness  of  the  nerve 
influence  the  amount  of  the  electrical  current,  it  being  greater  in 
long,  thick  nerves  than  in  short,  slender  ones.  That  an  electrical 
current  exists  in  the  nerve  during  a  state  of  rest,  there  can  be  after 
what  has  been  said,  no  doubt,  whatever  the  subsequent  explanation 
of  the  phenomena  may  be ;  but  it  must  be  admitted,  and  the  ad- 
mission is  an  important  one  as  regards  any  inference  to  be  here- 
after drawn  as  to  the  relation  between  nerve  electricity  and  nerve 
force,  that  in  an  uninjured  nerve,  in  which  no  transverse  section 
has  been  made,  there  is  no  evidence  of  an  electrical  current,  that 
is  to  say,  the  nerve  is  isolectric. 

The  electro-motive  force  of  nerve  currents  such  as  those  just  de- 
scribed can  be  determined  by  means  of  a  galvanometer  and  round 
compensator  (Fig.  282),  the  principle  made  use  of  being  essentially 
the  same  as  that  by  which  a  body  is  weighed.  The  method  con- 
sists in  shunting  ofl'  by  means  of  the  compensator  (Fig.  283,  III), 
from  the  circuit  of  a  standard  element,  a  Daniell  cell  (D),  for  ex- 

^  Ueber  den  axialen  Nervenstrom,  Maurice  Mendelssohn,  1885,  Archiv  f.  Anat. 
und  Phys.  separat-abdruck. 


526 


THE  NERVOUS  SYSTEM. 


ample,  whose  electro-motive  force  is  known  (1.08  volts),  an  amount 
of  current  sufficient  to  neutralize  or  compensate  the  current  deflect- 
ing the  magnet  due  to  the  electro-motive  force  of  the  nerve  N,  which 
is  to  be  determined,  just  as  the  unknown  weight  of  a  body  is  learned 


Fig.  282. 


Du  Bois  Reymond's  rouud  compensator. 

from  the  known  weight  necessary  to  neutralize  or  balance  it.  Let 
us  suppose  that  the  electrical  current  diverted  by  the  now  polari- 
zable  electrodes  from  the  nerve  N,  the  sciatic  of  the  frog,  for  exam- 
ple, to  the  Wiedemann  galvanometer  G,  be  sufficient  to  deflect  the 
magnet  to  an  extent  corresponding  to  25  divisions  of  the  scale.     If 


^-(7)       XeXff^ 


Schema  for  determining  electro-motive  force  by  round  compensator. 

now  the  compensator  be  turned  until  the  wheel  reaches  III,  part  of 
the  current  from  the  Daniell  cell  will  return  through  IV,  II,  F, 
whence  it  came,  and  part  through  III,  Pg  to  the  nerve  N,  and  be- 


RESISTANCE  OF  NERVE. 


527 


ing  in  the  reverse  direction  to  the  current  clue  to  the  nerve  the  mag- 
net will  be  brought  back  to  zero.  Such  being  the  case  it  follows 
that  the  electro-motive  force  of  the  nerve  current  is  equal  to  that 
shunted  off  from  the  compensator  and  neutralizing  it,  and  which 
amounts,  the  wheel  being  at  III,  to  the  -^^  of  a  Daniell  or  0.02 
volt.^ 

Recent  researches  ^  have  shown  the  electro-motive  force  of  the 
currents  in  the  nerve  and  spinal  tracts  of  the  cat  to  be  0.01  and 
0.04,  and  in  the  corresponding  parts  in  the  ape  0.005  and  0.29  of 
a  Daniell  cell  respectively.  According  to  Mendelssohn  ^  the  electro- 
motive force  of  the  axial  current  of  the  posterior  roots  of  the  spinal 
nerves  of  frogs — that  is,  of  the  current  from  equator  to  central  or 
peripheral  transverse  section  amounts  respectively  to  0.00893  and 
0.00767  of  a  Raoul,  that  element  (copper  in  copper  sulphate  solu- 
tion, and  zinc  in  zinc  sulphate)  being  used  instead  of  a  Daniell. 

As  the  electrical  current  of  a  nerve,  after  passing  through  a  gal- 
vanometer, must,  in  returning  to  the  point  from  which  it  started, 
pass  through  the  nerve,  and  as  induced  and  constant  currents  are 


Fig.  284. 


Schema  for  determining  the  resistance  of  nerve. 

frequently  thrown  into  a  nerve,  the  resistance  offered  by  the  latter 
to  the  passage  of  an  electrical  current  must  also  be  determined. 
This  is  accomplished  by  essentially  the  same  method  as  ordinarily 
made  use  of  in  determining  the  amount  of  resistance  offered  by 
bodies  in  general  to  the  passage  of  electricity,  and  is  briefly  known 
as  that  by  the  Wheatstone  bridge.     This  method  is  based  upon  the 

1  For  the  method  of  fletermining  this,  as  well  as  for  the  constniction  and  manner 
of  using  the  compensator,  the  reader  Ls  referred  to  "Researches  upon  the  general 
physiology  of  nerve  and  muscle,"  Xo.  1,  by  H.  C.  Chapman  and  A.  P.  Brubaker, 
Proe.  of  Acad.  Nat.  Sciences,  Phila.,  18§!8,  p.  106. 

2GotchandHorsley,  Phil.  Trans.,  Vol.  182,  1891,  pp.  267-526, 

3  Op.  cit.,  s.  387. 


528  TEE  NERVOUS  SYSTEM. 

principle  of  so  disposing  the  body  whose  resistance  is  to  be  deter- 
mined, that  the  cnrrent  of  electricity  traversing  it  passes  through  a 
galvanometer  in  an  opposite  direction  to  that  traversing  a  body 
whose  resistance  can  be  varied,  until  the  current  traversing  the 
body  exactly  neutralizes  the  former  current,  as  shown  bv  the  gal- 
vanometer's needle  remaining  at  zero. 

Such  being  the  case,  the  unknown  resistance  is  then  equal  to  the 
known  one  ;  otherwise  there  would  be  a  deflection  of  the  magnetic 
needle  according  as  the  one  body  would  oifer  a  greater  or  less  re- 
sistance to  the  current  than  the  other.  Thus,  supposing  that  the 
apparatus  be  arranged  as  in  Fig.  284,  then  the  current  from  a 
Daniell's  element  D,  on  arriving  at  A,  the  end  of  the  long  wire 
A  B,  or  rheocord,  splits  into  two  branch  currents,  one  of  wdiich 
will  traverse  the  body  X,  a  nerve,  for  example,  whose  resistance  is 
to  be  determined,  and  the  other  the  wire  A  B.  Further,  the  first 
branch  current,  on  arriving  at  0,  will  divide  into  two,  one  of  which 
will  pass  into  the  resistance  box  R,  the  other  into  the  galvanometer 
CjT ;  the  latter  current  being  opposite  in  direction  to  that  coming 
from  *S',  one  of  the  two  branch  currents  into  which  the  current  A  S 
divides,  the  remaining  one  passing  from  S  to  B,  and  thence  back 
to  the  Daniell's  element.  But,  as  the  resistance  offered  to  the  cur- 
rent passing  from  A  toward  B  can  be  increased  or  diminished  by 
the  sliding  of  S  from  or  toward  A,  all  the  current  returning  to  the 
battery  when  the  slider  is  at  A,  by  varying  the  position  of  the 
slider  a  point  will  be  reached  on  the  wire,  as  at  S,  when  the  gal- 
vanometer needle  will  remain  at  zero,  showing  that  the  current 
passing  down  from  the  nerve  from  O  to  the  galvanometer  is  equal 
and  opposite  in  direction  to  that  passing  up  from  the  wire  at  S.  Such 
being  the  case,  then  the  resistance  offered  by  the  nerve,  or  x,  is  to 
that  of  the  resistance  box  B,  as  the  part  of  the  wire  A  S  is  to  the 
part  N  B — that  is,  x:  B  :  :  A  S :  S  B.  Now,  as  the  resistance  B  is 
learned  by  observing  the  number  of  plugs  out,  and  that  of  A  S  and 
SB  being  also  known,  the  rheocord  wire  having  been  previously 
graduated,  the  unknown  resistance  of  the  nerve,  or  .r,  is  given  in 
terms  of  B,  A  »S,  and  S  B,  as  shown  by  the  equation 

EX  AS, 


SB 

If  A  S  and  ;S'  B  be  constant  and  equal,  then  the  resistance  offered 
by  iV  equals  that  of  B,  and  can  be  inferred  directly  from  the  latter. 
The  method  just  described  of  determining  the  resistance  offered 
by  a  nerve,  for  example,  to  the  passage  of  a  current  of  electricity 
is  at  times  inconvenient,  even  quite  awkward,  on  account  of  the 
length  of  the  rheocord  wire  involved.  For  this  reason  we  make 
use  of  the  round  compensator  (Fig.  285)  with,  however,  the  acces- 
sory binding  screw  O.  The  principle  of  determining  the  resistance, 
it  is  needless  to  add,  however,  is  not  at  all  affected  by  this  modifi- 
cation for  determination  of  resistance  of  nerve,  the  difference  be- 


THE  ROUND  COMPENSATOR. 


529 


Fig.  285. 


tween  the  long  and  round  rlieocord  or  compensator  being  simply  in 
the  disposition  of  detail.  Thus,  if  Fig.  285,  a  schematic  repre- 
sentation of  the  round  compensator, be  compared  ^ith  that  of  Fig. 
284,  the  long  one,  it  will  be  observed  that  in  both  instruments  the 
current  from  the  Daniell's  element  D,  on  arriving  at  A  splits  into 
two  currents,  one  of  which  passes  to  the  wheel  or  slider  S,  the  other 
to  the  nerve ;  that  the  current  at  N  divides  into  two,  one  of  which 
passes  to  the  galvanometer  (l,  the  other  back  to  the  Daniell's  ele- 
ment ;  that  the  current 
after  traversing  the  nerve 
divides  into  two,  one  of 
which  passes  to  the  gal- 
vanometer 6r,  the  other  to 
the  resistance  box  B,  and 
thence  back  to  the  Dan- 
iell's element ;  that  the 
two  currents,  passing  in 
opposite  directions  through 
the  galvanometer  neutral- 
ize each  other.  It  follows, 
therefore,  that  in  using 
the  modified  round  com- 
pensator we  obtain  the 
same  proportion  as  in  using 
the  long  one,  viz.: 

X  :  R  :  :  AS  :  SB, 

Ry^AS 

The  value  of  x,  or  the 
resistance  of  the  nerve,  as 
obtained  by  this  method, 
we  have  determined  to  be 
in  a  portion  of  the  sciatic 
nerve  of  the  frog,  2  cm. 
long,  1  cm.  broad,  and  0.5  mm.  thick,  when  exerted  longitudi- 
nally, twelve  million  times  greater  than  mercury  when  taken  as 
unity,  and  when  transversely  thirty-two  million  times  greater.^ 

It  may  be  mentioned  in  this  connection  that  while  the  resistance 
oifered  by  the  human  body  to  the  passage  of  an  electrical  current  is 
very  great  in  a  state  of  health,  it  appears  to  be  diminished  in  certain 
kinds  of  disease,  so  much  so  in  Grave's  disease,  for  example,  as  to 
constitute  an  important  diagnostic  symptom. 

Having  considered  the  nerve  current  and  the  electro-motive  force 
of  the  nerve,  and  the  resistance  offered  by  the  nerve  to  the  passage 

^  Researches  upon  the  General  Physiology  of  Nerve  and  Muscle,  No.  2,  by  H. 
C.  Chapman  and  A.  P.  Brubaker,  Proc.  Acad.  Nat.  Sci.  Phil.,  1888,  p.  155. 

34 


Schema  of  round  compensator,  with  modification. 


530 


THE  NERVOUS  SYSTEM. 


of  electricity,  it  remains  for  us  now  to  offer,  if  possible,  some  ex- 
planation of  the  natural  nerve  current  based  upon  its  physical 
structure.  It  is  well  kno^\Ti  that  if  a  solid  copper  cylinder  (Cu, 
Fig.  286),  covered  except  at  its  ends  by  a  layer  of  zinc,  Zn,  be  im- 
mersed in  a  conducting  fluid  like  water,  that  electrical  currents  are 
developed,  which,  as  may  be  shown  by  the  galvanometer,  pass  from 
the  longitudinal  or  zinc  surface  to  the  transverse  copper  one,  and 


Fig.  286. 


Apparatus  for  the  development  of  electrical  currents. 

that,  according  as  the  electrodes  are  shifted  from  point  to  point  of 
its  copper  and  zinc  surfaces,  these  currents  become  stronger,  weaker, 
or  disappear  altogether,  and  that  while  if  the  copper  be  entirely 
covered  by  its  zinc  mantel  there  is  no  appreciable  electrical  current, 
however  the  electrodes  may  be  placed.  When  it  is  remembered  that 
the  ultimate  nerve  fiber  consists  histologically  of  the  axis-cylinder 
surrounded  by  the  white  substance  of  Schwann  and  neurilemma,  it 
might  appear  at  first  sight  that  one  or  the  other  of  these  two  mem- 
branes bears  to  each  other,  or  to  the  axis-cylinder,  the  same  rela- 
tion electrically  that  we  have  seen  the  outer  zinc  mantel  does  to  the 
copper  axis  of  the  simple  physical  apparatus  just  described. 

That  such,  however,  is  not  the  case,  is  proved  by  the  fact  that 
even  at  the  nodes  of  Ranvier  in  the  spinal  nerves,  and  in  the  sym- 
pathetic fibers  also,  where  the  white  substance  of  Schwann  is  absent, 
nevertheless,  electrical  currents  can  be  shown  to  exist,  evidently 
then  it  cannot  be  the  contact  of  the  substance  of  Schwann  with 
either  the  neurilemma  or  the  axis-cylinder  that  is  the  cause  of  the 
difference  in  the  electrical  potential,  while  the  presence  of  electrical 
currents  in  the  cord  in  the  absence  of  the  neurilemma  equally  shows 
that  the  contact  of  that  membrane  with  the  axis-cylinder  has  noth- 
ing to  do,  any  more  than  the  white  substance  of  Schwann,  with  the 
development  of  such  currents.     The  only  conclusion  to  be  drawn 


ELECTRICAL  CURRENTS  IN  NERVES. 


531 


from  such  facts  is  that  of  the  three  parts  of  which  the  nerve  con- 
sists, it  is  the  axis-cylinder  only  which  is  concerned  in  the  develop- 
ment of  the  electrical  current,  and  Avhich  confirms  the  conclusion 
that  we  have  come  to  upon  other  grounds  that  the  axis-cylinder  is 
functionally  the  most  essential  part  of  the  ultimate  nerve  fiber. 
Among  the  many  theories  that  have  been  oifered  as  explanations  of 
the  presence  of  electrical  currents  in  nerves,  it  has  been  held  for 
example  that  the  electrical  current  developed  in  a  nerve  in  which  a 
transverse  section  has  been  made,  is  due  to  the  fact  that  the  negatively 
electrified  axis-cylinder  is  then  exposed  to  the  positively  electri- 
fied nutritive  fluid  surrounding  it,  since,  as  we  have  just  seen,  the 
diflerence  between  the  longitudinal  and  cut  surfaces  electrically  can- 
not be  attributed  to  the  contact  of  cither  neurilemma  or  substance  of 
Schwann  wdth  the  axis-cylinder.  If  such  be  the  case,  it  becomes 
intelligible  why,  as  we  have  already  mentioned,  there  is  no  appreci- 
able electrical  current  in  the  uninjured  nerve — that  is,  in  one  Avithout 
a  transverse  cut  section,  since  under  such  circumstances  the  negative 
axis-cylinder  is  not  exposed  to  the  positive  nutritive  fluid  surround- 
ing the  nerve,  just  as  in  the  case  of  the  physical  apparatus  (Fig.  286) 
there  is  no  electrical  current  developed  as  long  as  the  negative 
copper  axis  or  core  is  completely  enveloped  by  the  positive  zinc 
mantel  or  hull. 

As  an  illustration  of  the  influence  of  the  contact  of  a  surround- 
ing fluid  upon  a  tissue  in  the  development  of  an  electrical  current, 
it  may  be  here  mentioned  that  if  the  transverse  cut  surface  of  a 
dried  muscle  be  placed  upon  the  surface  of  distilled  water,  that  an 
electrical  current  will  be  developed,  passing  from  the  longitudinal 
to  the  cut  surface  as  soon  as  the  muscle  begins  to  swell  through  im- 
bibition of  the  fluid  with  which  its  transverse  section  is  in  contact. 
While  the  explanation  just  oflfercd,  that  of  Gruenhageu,^  was  consid- 

FiG.  287. 


Electromotive  double  dipolar  molecules. 

ered  by  that  physiologist  as  satisfactorily  explaining  the  electrical 
condition  of  the  cut  nerve,  however  plausible  it  may  appear,  it  must 
be  mentioned  that  it  is  not  generally  accepted  by  physiologists. 
Thus,  Du  Bois  Reymond  ^  for  many  years  held  that  the  nerve  consists 

1  Funke,  Physiologie,  Erster  Band,  1876,  s.  487. 

^  Untersuchungen  iiber  Thierische  Electricitiit,   Zweiter  Band,  s.  323.     Berlin, 
1849. 


532  TEE  NERVOUS  SYSTEM. 

not  of  a  homogeneous  axis,  surrounded  by  a  hull  like  that  of  the 
physical  apparatus  just  described  (Fig.  286),  but  of  a  series  of 
electro-motive  double  dipolar  molecules,  imbedded  in  an  indijfferent 
and  imperfectly  conducted  medium  (Fig.  287),  each  double  molecule 
consisting  of  a  positive  and  negative  part,  the  two  positive  parts  placed 
together  within,  the  two  negative  parts  without,  the  double  mole- 
cule presenting  then  a  negative  surface  at  the  transverse  section  or 
cut  end,  and  a  positive  surface  at  the  longitudinal  surface  of  the 
nerve.  Regarding  the  double  molecule  as  a  minute  battery  whose 
positive  and  negative  poles  are  at  the  longitudinal  and  transverse 
surfaces,  respectively,  currents  will  be  developed  which  through  the 
imperfect  conductility  of  the  medium  will  circulate  in  more  or  less 
eccentric  lines  not  only  in  the  immediate  neighborhood  of  each 
molecule,  but  at  some  distance  from  the  latter,  from  the  positive 
middle  surface  to  the  negative  ends  of  the  nerve  as  indicated  by 
the  arrows,  and  giving  rise  to  the  deflection  of  the  galvanometer 
needle,  as  we  have  seen  is  the  case  when  the  electrodes  are  applied 
to  the  nerve.  Suppose  that  the  nerve  does  consist  according  to  this 
hypothesis  of  molecules,  such  as  just  described,  it  is  evident  that 
the  electrical  current  within  it  is  a  closed  one,  the  nerve  differing 
in  this  respect  from  the  zinc-copper  apparatus  as  regards  any  cur- 
rent diverted  into  the  galvanometer.  In  either  case  the  current 
can  only  be  a  partial  one,  the  deflection  of  the  needle  indicating 
the  presence  of  a  current,  but  in  no  wise  the  total  strength  of  the 
current  due  to  the  electro-motive  force  of  all  the  molecules. 

That  the  strength  of  the  latter  must  be  much  greater  than  the 
partial  current  deflecting  the  needle  is  shown  by  the  necessity  of 
using  such  sensitive  galvanometers,  and  is  implied  in  the  overcom- 
ing of  the  resistance  both  of  the  nerve  and  the  galvanometer  cir- 
cuit, which  is  considerable.  Indeed,  were  not  the  total  electric 
strength  of  the  molecules  much  greater  than  that 
Fig.  288.  of  the  partial  current,  the  latter  would  not  be  ap- 

preciated by  the  galvanometer  at  all.     It    is  for 
such  reasons  that  Du  Bois  Reymond  holds  that  the 
electro-motive  force  of  the  nerve  molecules  exceeds 
that    producing  all    other  known  currents,  and  is 
capable,  in  the  highest  degree,  of  producing  all  the 
known  effects  of  currents.     While  there  is  much  to 
be  said  in  favor  of  Du  Bois  lleymond's  view  of 
the  nerve  consisting  of  electro-motive  molecules,  it 
must  be  admitted  that  it  is  difficult  to  explain  on 
Leyden  jar.         such  a  theory  the  weak  currents  that  are  developed 
by  ])lacing  the  electrodes  upon  different  points  of 
the  longitudinal  surface,  and  why  currents  of  any  kind  are  only 
present  in  the  injured  nerve,  or  one  presenting  a  transverse  section. 
Indeed,  this  latter  fact,  equally  an  objection  to  the  view  offered  by 
Gruenhagen,  has  led  pliysiologists,  like  Hermann,^  to  deny  alto- 
^Handbuch,  Zweiter  Band,  Ei-ster  Theil,  s.  109.     Leipzig,  1879. 


ELECTRICAL  CURRENTS  IN  NERVES.  533 

gether  the  preoxistciicc  of  any  electrical  current  in  tlie  nerve,  at- 
tributing the  latter  to  the  death  of  the  transverse  cut  surface,  which, 
at  that  moment,  becomes  negative  to  the  longitudinal  surface.  On 
the  other  hand,  according  to  Radcliife,^  the  electrical  character  of 
the  nerve  current  is  rather  static  in  its  nature  than  voltaic,  the 
nerve  being  compared  on  this  view  to  a  charged  Leyden  jar  (Fig. 
288),  the  current  being  simj^ly  accidental,  and  due  to  the  applying 
of  the  electrodes  of  the  galvanometer  to  points  having  different 
electrical  tensions.  After  all,  however,  the  difference  between  static 
and  voltaic  or  current  electricity  is  not  a  profound  one,  being  rather 
one  of  degree  than  of  kind,  since  the  former  is  one  of  high  tension, 
but  small  in  quantity,  the  latter  of  low  tension,  but  large  in  quan- 
tity ;  by  tension  being  meant  the  tendency  of  the  electricity  accu- 
mulated at  the  extremities  of  the  electrodes  to  free  itself. 

'Dynamics  of  Xerve  and  Muscle,  p.  24.     Lonlon,  1871. 


CHAPTER  XXIX. 

THE  NERVOUS  SYSTEM.— (Continued.) 

CURRENTS  OF  REST  AND  OF    ACTION.       NEGATIVE    VARI- 
ATION.    ELECTROTONUS.     ELECTROTONIC  MODIFICA- 
TION OF  EXCITABILITY. 


Fig.  289. 


Whatever  view  may  be  held  as  to  the  nature  and  cause  of  the 
electrical  current  present  in  an  injured  nerve  during  rest,  there  is 
no  difference  of  opinion  as  to  the  fact  that  it  is  diminished  during 
activity.  The  deflection  of  the  galvanometer  needle  in  the  latter 
case  is  accounted  for,  however,  by  Du  Bois  Eeymond,  on  the  sup- 
position that  the  current  of  rest  undergoes  during  activity  a  diminu- 
tion, a  "  negative  variation,"  while  according  to  Hermann,  and 
most  physiologists,  it  is  due  to  the  development  of  an  "  action  cur- 
rent," independent  of  and  in  a  direction  opposite  to  that  of  the 
current  of  rest.  That  the  negative  variation  or  action  current  con- 
stitutes an  essential  feature  of  nervous  action,  is  shown  from  the 
intensity  of  the  one  varying  with  the  other,  and,  as  already  men- 
tioned, from  the  rate  at  which  it  travels  along  the  nerve  being  the 
same  as  that  at  which  the  nerve  impulse  itself  is  propagated.  While 
the  current  of  action  or  negative  variation  can  be  shown  by  stimu- 
lating the  nerve  with  a  single 
induction  shock  the  phenom- 
enon becomes  much  more 
evident  when  the  induction 
apparatus  is  used  with  the 
automatic  interrupter,  since 
the  shocks  thrown  into  the 
nerve  succeed  each  other  so 
rapidly  that  before  the  gal- 
vanometer needle  can  return 
to  its  first  position,  that  due 
to  the  current  of  rest,  it  is 
again  deflected  by  the  nega- 
tive variation  or  current  of 
action  and  consequently  re- 
mains in  one  position,  that 
due  to  the  latter.  Thus,  for 
example,  suppose  that  the 
transverse  section  of  the 
nerve  N  be  in  contact  with  one  of  the  diverting  electrodes  E' 
(Fig.  289),  and  the  longitudinal  surface  with  the  other,  and  that 


(^ 


Disposal  of   apparatus   to  show  the  current  action  or 
negative  variation. 


CURRENT  OF  ACTION. 


535 


(S^ 


Disposal  of  apparatus  to  show  that  the  current  of  ac- 
tion or  negative  variation  is  transmitted  in  both  direc- 
tions. 


the  deflection  of  the  magnetic  needle  at  G,  due  to  the  current  of 
rest,  amounts  to,  say  C.  Such  being  the  case,  if  now  the  nerve  N 
be  stimulated  by  the  induction  apparatus,  the  deflection  of  the 
needle  in  the  reverse  direction  back  towards  zero,  o  indicates  either 
the  presence  of  an  "  action  current "  or  that  the  current  of  rest  has 
been  diminished,  has  undergone  a  negative  variation.  If  now  the 
experiment  be  so  modified  (Fig.  290)  that  while  the  nerve  is  stimu- 
lated in  the  middle  X,  its  two  ends  (c  d)  are  in  contact  with  the 
electrodes  of  two  galva- 
nometers {G  G'),  it  will  be  Fig.  290. 
observed  that  there  is  a  cur- 
rent of  action  or  a  diminu- 
tion in  the  current  of  rest 
(a  —  0,  6  —  o)  of  the  nerve 
at  both  ends,  showing  that 
the  disturbance  in  the  elec- 
t  r  i  c  a  1  condition  of  the 
nerve,  whatever  its  nature 
may  be,  is  propagated  in 
both  directions,  from  the 
center  or  the  point  of  the 
application  of  the  stimulus  : 
a  very  important  fact,  since, 
if  the  current  of  action  or 

the  negative  variation  is  intimately  associated  with  that  of  the  de- 
velopment and  propagation  of  the  nerve  impulse,  it  proves  that  the 
latter  is  transmitted  from  the  point  of  stimulus,  both  to  the  central 
and  peripheral  ends  of  the  nerve,  confirming  the  view  already  ad- 
vanced, that  the  nerve  impulse  is  transmitted  in  both  directions 
and  that  the  function  of  a  nerve  depends,  not  upon  its  intrinsic 
structure,  but  whether  it  terminates  in  a  motor,  sensory,  or  glan- 
dular organ. 

By  extending  our  experiments  it  will  be  further  found  that  all 
kinds  of  nerves,  motor,  sensory,  secretory,  exhibit  the  phenomena 
of  negative  variation,  the  amount  of  the  latter  at  different  points 
of  the  nerve  depending,  however,  upon  that  of  the  preexisting 
current  of  rest.  If,  however,  the  latter  be  absent,  there  will  then 
be  no  negative  variation  though  there  may  be  currents  of  action 
independent  of  the  latter.  Thus,  if  the  diverting  electrodes  be 
placed  upon  two  points  of  the  longitudinal  surface  symmetrically 
disposed  with  reference  to  the  equator,  the  magnetic  needle  not 
being  then  deflected  by  the  nerve  current,  there  can  be  no  diminu- 
tion of  the  latter  or  negative  variation.  An  interesting  fact  as  re- 
gards the  phenomenon  of  negative  variation  is,  that  it  cannot  only 
be  produced  by  artificial  stimuli,  electrical,  chemical,  thermal,  and 
mechanical,  but  by  natural  ones  inherent  in  the  nervous  system  it- 
self by  stimuli  from  the  spinal  cord,  for  example.  Thus  it  is  well 
known  that  if  the  sciatic  nerve  of  a  living  frog  be  well  exposed ^ 


536 


THE  NERVOUS  SYSTEM. 


avoiding,  however,  the  injuring  of  the  blood  vessels  and  the  origin 
of  the  nerve,  and  the  nerve  be  cut  through  at  the  popliteal  space, 
and  the  electrodes  so  disposed  that  the  point  of  one  is  in  contact 
with  the  equator,  and  the  point  of  the  other  with  the  cut  surface 
of  the  nerve,  that  with  the  appearance  of  the  muscular  cramps  due 
to  the  subcutaneous  injection  of  strychnia,  the  electrical  current  of 
the  nerve  will  undergo  a  negative  variation.  The  significance  of 
this  experiment  will  be  better  appreciated,  however,  when  the  sub- 
ject of  reflex  action  has  been  considered  ;  since  the  muscular  con- 
traction in  strychnia  poisoning  is  due  to  an  impression  made  upon 
the  skin  and  transmitted  to  the  spinal  cord,  and  thence  reflected  by 
the  spinal  nerves  to  the  muscles. 

Fig.  291. 


Bernstein's  differential  rheotome.     Horizontal  view. 

Negative  variation  occurs  also  during  the  tetanus  brought  about 
by  the  mechanical  crushing  of  a  nerve,  the  destruction  of  the  latter 
by  heat,  or  when  induced  by  the  stimulation  of  cutaneous  branches, 
as  in  the  case  of  the  sciatic  nerve,  for  example. 

Recent  researches  ^  have  shown,  when  electrodes  connected  with 
a  capillary  electrometer  are  applied  to  the  motor  tracts  of  the  spinal 
cord,  spinal  nerve  roots,  or  peripheral  nerves,  that  with  stimula- 
tion of  the  cortical  motor  areas,  the  currents  of  rest  present,  undergo 
negative  variation,  or  are  neutralized  by  currents  of  action.     It 

iGotch  &  Horsley,  Phil.  Trans.,  Vol.  182,  1891,  pp.  207-526. 


BEEXSTEIX'S  DIFFERENTIAL  RHEOTOME.  537 

has  already  been  mentioned  that  the  rapidity  at  which  the  nega- 
tive variation  is  transmitted  is  the  same  as  that  of  the  nerve  im- 
pulse itself.  This  was  first  determined  by  Bernstein  ^  by  means  of 
his  differential  rheotome  (Fig.  291).  The  principle  of  this  instru- 
ment (Fig.  292)  consists  in  closing,  by  C  at  e,  the  primary  circuit 

Fig.  292. 


Schema  of  Bernstein's  differeutial  rheotome.  N n.  Nerve.  J.  Secondary  coil  of  induction 
machine.  G.  Galvanometer,  x, ;/.  Deflection  of  needle.  E.  Battery.  C  closes  primary  circuit 
at  e.  e  closes  galvanometer  circuit  at  /.  z  z.  Electrodes  in  galvanometer  circuit.  .S'.  Cord  from 
motor.    (Landois.) 

stimulating  the  nerve  through  .7,  and  that  diverting  its  current  of 
rest,  by  c  at  i,  by  a  wheel,  rotating  at  a  known  rate,  and  of  so  dis- 
posing the  two  pairs  of  electrodes  that  the  stimulating  circuit  is 
closed  before  the  diverting  one,  the  interval  of  time  elapsing  be- 
tween the  two — that  is,  the  time  during  which  the  nerve  impulse 
passes  from  n  to  ^" — being  determined  from  the  rate  at  which  the 
wheel  is  rotating. 

To  explain  the  manner  in  which  the  rapidity  of  the  propagation 
of  the  negative  variation  is  determined,  in  the  frog  for  example,  by 
means  of  the  differential  rheotome,  we  will  begin  at  the  moment  that 
the  rotating  wheel  C  (Fig.  292)  comes  in  contact  with  e.  At  that 
instant  the  primary  circuit  is  closed  and  the  nerve  being  stimulated 
by  /  at  ?i,  the  current  of  action  or  negative  variation  will  begin  at 
that  point  and  will  be  transmitted  to  the  other  end  of  the  nerve  iV, 
the  wheel  coming  in  contact  however  at  that  instant  through  e  with 
i  and  the  galvanometer  circuit  being  then  closed,  the  needle  will  be 
deflected  in  an  opposite  direction  to  that  due  to  the  current  of  rest, 
the  latter  having  undergone  negative  variation.  As  the  current  of 
action  or  negative  variation  is  transmitted  through  the  nerve  from 

'  Untei-suchungeii  iilier  den  Erregunsvorgang  im  Nerven-  und  Muskel-systeme. 
Heidelberg,  1871. 


538 


THE  NERVOUS  SYSTEM. 


Fig.  293. 


the  point  of  application  of  the  stimulus  at  n  to  that  of  the  divert- 
ing electrodes  at  X,  and  as  the  deflection  of  the  galvanometer  needle 
occurs  at  the  moment  that  the  diverting  circuit  is  closed,  the  rate 
at  which  the  current  of  action  or  negative  variation  is  propagated 
becomes  known  since  it  is  transmitted  from  n  to  N  in  the  same  time 
that  c  moves  to  i,  C  having  first  reached  e,  that  is  at  the  rate  of  28 
meters  per  second.  It  was  at  one  time  supposed  that  the  current 
of  action  or  negative  variation  occurs  during  the  latent  period,  and 
during  its  transmission  through  the  nerve,  preceded  the  nerve  im- 
pulse. It  is  more  probable, 
however,  that  the  two  move- 
ments accompany  each 
other,  as  it  has  been  shown 
that  the  current  of  action  or 
negative  variation  that  oc- 
curs in  muscle,  accompanies 
the  contraction  wave  of  the 
latter^  and  which  corres- 
ponds to  the  impulse  in  the 
nerve. 

It  will  be  seen  from  the 
disposition  of  the  apparatus 
represented  in  Fig.  293  that 
the  current  of  rest  is  com- 
pensated by  means  of  the 
Daniell  cell  and  rheocord. 
The  galvanometer  needle 
will  remain,  therefore,  at 
zero  until  the  current  of 
action  or  negative  variation 
reaches  the  end  of  the 
nerve  t,  when  the  needle 
will  be  deflected  by  it,  and 
in  the  opposite  direction  to 
what  it  would  have  been 
deflected  by  the  current  of 
rest  had  not  the  latter  been 

Disposal  of  differential  rheotome,  etc.,  for  determina-    Compensated, 
lion  of  rapidity  of  propagation  of  the  current  of  action  Tlio  r»l->ionf  nf  ca  nni-ni-»fin 

ornegative  variation.  -LUC  OUjetL  ui  bu  ouiiipeii- 

sating  the  nerve  current  in 
the  study  of  its  negative  variation  by  means  of  the  diiferential 
rheotome  is  that  the  movement  of  the  needle  should  always  begin  at 
the  same  point,  viz.,  zero.  It  will  be  noticed,  however,  that  the 
rheocord — that  of  Du  Bois  Reymond — differs  in  its  form  from  that 
previously  described,  though  the  latter,  for  the  present  purpose, 
might  have  been  just  as  well  used.  The  rheocord  (Fig.  294),  con- 
sists of  a  long  box,  at  the  edge  of  which  are  stretched  two  platinum 
1  Burdon  Sandei-son,  Proceedings  of  Eoyal  Society,  1890. 


THE  RHEOCORD. 


539 


The  rheocord. 


wires,  passing  through  the  connected  mercury  cups  m  m,  which  can 
be  pushed  to  the  other  end  of  the  box  along  the  scale  graduated  in 
millimeters  at  the  side.  When  the  mercury  cups  are  directly  in 
contact  with  the  brass  a,  the 

resistance    offered    by    the  Fig.  294. 

rheocord  to  the  Dauiell's 
circuit  is  practically  noth- 
ing as  compared  ^ith  that 
offered  by  the  nervous  cir- 
cuit, consequently  the  cur- 
rent from  the  Daniell's 
element  simply  passes 
through  the  rheocord  back 
to  the  cell,  none  being  di- 
verted into  the  nervous  cir- 
cuit. If,  however,  the 
mercury    cups    be    pushed 

away  from  the  brass  along  the  platinum  wires,  the  wires  offering  a 
resistance,  the  amount  indicated  by  the  scale,  358  mm.  =  1  ohm, 
and  there  being  no  passage  for  the  current  from  one  side  of  the  rheo- 
cord to  the  other,  except  through  the  parts  of  the  wires  lying  be- 
tween the  mercury  cups  and  the  Ijrass,  it  follows  that  a  proportional 
part  of  the  total  current  from  the  Dauiell's  element  is  thrown  into 
the  nervous  circuit. 

If  a  greater  amount  of  resistance  is  needed  than  that  obtained  by 
pushing  the  mercury  cups  through  the  whole  length  of  the  platinum 
wires,  then  the  plugs  lettered  b,  c,  d,  e,  f,  g,  or  numbered,  can  be 
drawn  out,  these  being  multiples  of  the  resistance  offered  by  the 
total  length  of  the  platinum  wires  traversed  by  the  mercury  cups, 
the  amount  of  current  thrown  into  the  nervous  circuit  will  be  then 
proportionally  increased.  Thus,  for  example,  if  the  plug  5,  letter 
g,  be  M'ithdrawn,  then  the  amount  of  current  thrown  into  the  nerve 
will  be  five  times  as  great  as  when  the  mercury  cups  were  at  the 
end  of  the  wire,  and  so  proportionally  for  the  remaining  plugs.  In 
fact,  the  rheocord  is  a  form  of  resistance  box,  such  as  already  de- 
scribed. 

The  wheel  of  the  differential  rheotome,  as  has  already  been  men- 
tioned, is  uniformly  rotated  by  the  electro-magnetic  rotation  appara- 
tus of  Helmholtz  (Fig.  295,  E).  The  latter  consists  of  four  electro- 
magnets, the  two  external  ones  (A'  1')  immovable,  the  two  internal 
ones  {UK)  movable  ;  the  latter  are  fixed  to  the  axis  by  their  dis- 
similar poles,  and  are  supplied  by  three  Daniell's  elements,  the 
external  ones  by  one.  As  the  two  internal  magnets  are  repelled 
and  attracted  by  the  external  ones,  the  axis  is  rotated,  and  with  it 
the  wheel,  through  which  it  passes,  and  around  which  passes  the 
thread  from  the  disk  of  the  rheotome. 

Although  the  phenomenon  of  the  negative  variation  is  a  momen- 
tary one  its  duration  has  been  determined  by  means  of  the  rheo- 


540 


THE  NERVOUS  SYSTEM. 


tome  to  amount  to  0.0007  second.     Such  being  the  case  it  follows 
that  during  the  0.0006  or  0.0007  second  that  the  point  a  of  a 


Fig.  295. 


Electro-magnetic  rotation  .aiiiiaratiis. 

nerve  (Fig.  29G)  undergoes  its  negative  variation  the  intermediate 
points  between  a  and  c  will  be  successively  affected  in  the  same 


WAVES  OF  NEGATIVE  VARIATION. 


541 


way,  the  poiut  c  passing  into  the  condition  of  negative  varia- 
tion at  the  end  of  the  0.0000  or  0.0007  second  as  the  point  a 
passes  out  of  it.  The  negative  variation  is  propagated,  therefore, 
in  the  form  of  a  wave,  and,  being  at  the  rate  of  28  meters  a  second, 
the  wave  must  be  18  mm.  long.     That  is  to  say,  if  the  current  of 

Fig.  296. 


Wave  of  ucgative  variation. 

action  or  negative  variation  travels  along  the  nerve  18  mm.  in 
from  0.0006  to  0.0007  second  it  will  travel  28  meters  in  1  second. 
Further,  if  it  be  supposed  that  while  the  negative  variation  travels 
at  the  rate  of  28  meters  a  second,  that  during  the  same  period  of 
time  the  nerve  be  stimulated  28  times,  then  a  nerve  28  meters  long 
would  exhibit  at  the  end  of  the  second  28  waves  of  negative  varia- 
tion, each  wave  being  separated  by  an  interval  of  1  meter  (Fig.  297). 


isttui: 


Fig.  297. 


fS-miL 


Waves  of  negative  variation. 

It  having  been  learned  by  the  rheotome  that  the  current  of  action 
or  negative  variation,  produced  by  successive  stimuli  following  each 
other  periodically,  is  propagated  in  the  form  of  a  wave  of  definite 
length  and  duration,  there  can  be  no  doubt  that  the  change  under- 
gone by  the  nerve  when  in  this  condition  is  of  a  vibratory  character. 
The  wave  of  negative  variation  or  the  current  of  action  resembles, 
therefore,  those  of  water,  sound  and  Hght,  with  this  difference,  how- 
ever, that  in  the  case  of  the  former  chemical  changes  are  probably 
going  on  in  the  nerve  substance  which  are  absent  in  the  latter,  and 
of  which  little  or  nothing  is  known. 

It  has  already  been  mentioned  that  uninjured  nerves  are  isolec- 
tric  ;  that  is,  do  not  exhibit  electrical  currents.  If  a  normal  nerve 
be  stimulated,  however,  a  difference  of  electrical  potential  at  once 
ensues,  and  a  current  flows  in  the  direction  of  the  arrow  (Fig.  298) 
B  to  A,  the  part  of  the  nerve  first'  traversed  by  the  impulse  becom- 
ing negative  electrically  to  the  succeeding  parts.     The  current  so 


542 


TEE  NERVOUS  SYSTEM. 


Fig.  298. 


developed  is  of  but  short  duration,  and  is  replaced  by  one  flowing 
in  the  opposite  direction,  A  to  B,  the  latter  being  rendered  nega- 
tive by  the  passage  of  the  nerve  im- 
pulse. The  current  of  action  in  the 
uninjured  nerve  is  therefore  diphasic 
in  character.  It  will  be  observed  that 
the  currents  of  action  in  the  unin- 
jured nerve,  are  produced  in  the  same 
manner  as  the  currents  of  rest  are 
supposed  by  Hermann  to  be  produced 
in  the  injured  ones  in  so  far  at  least 
as  one  part  of  the  nerve  is  rendered 
negative  to  a  succeeding  part,  in  the 
case  of  the  currents  of  action,  by  the 
transmission  of  the  nerve  impulse,  in 
that  of  the  currents  of  rest  by  injury. 
It  would  appear,  however,  that  while 
the  currents  of  action  of  the  injured 
as  well  as  of  the  uninjured  nerves  are  natural  physiological  currents, 
the  currents  of  rest  are  artificial  demarcation  currents  produced  by 
injury  and  without  functional  significance. 


stimulation  of  uninjured  nerve.    Elec 
trodes"  at  x. 


Electrotonus.^ 

Up  to  the  present  moment,  in  exciting  the  nerve  by  electrical 
stimuli  we  have  made  use  of  single  or  repeated  induction  shocks, 
and  this  not  only  for  convenience'  sake,  but  especially  on  account  of 
the  short  duration  of  induced  currents,  the  object  in  view  being  the 
avoidance  of  the  consideration  of  the  changes  undergone  by  the 
nerve  during  the  passage  of  a  constant  current,  and  which,  had 
they  been  present.  Mould  have  rendered  the  explanation  of  the 
changes  due  to  the  induced  current  a  more  difficult  one.  Such 
changes  as  are  induced  in  the  condition  of  a  nerve  through  the  pas- 
sage of  a  constant  current  passing  directly  to  the  nerve  without  the 
intervention  of  an  induction  apparatus  can  now,  however,  be  con- 
veniently considered.  Let  us  suppose,  then,  that  N  (Fig.  299) 
represents  a  nerve,  and  that  through  the  deviation  of  the  magnets 
of  the  galvanometers  GG'  we  learn  that  the  currents  of  rest  are 
present,  passing  from  the  longitudinal  surface  through  the  galva- 
nometers to  the  transverse  cut  surfiice  of  the  nerve,  through  the 
nerve  to  the  longitudinal  surface  again  in  the  direction  indicated  by 
the  arrows.  Let  now  the  nerve  JVbe  stimulated  through  the  non- 
polarizable  electrodes  p  p'  at  a  point  intermediate  between  its  ends, 
by  means  of  a  constant  current,  say,  from  a  Daniell's  element,  and 
which  we  will  hereafter  designate  as  the  polarizing  current,  the  de- 
flection of  the  galvanometer  needles  will  show  that  the  current 
passing  through  the  galvanometer  G'  is  increased  (r?)  constituting 

'  Du  Bois  Reymond,  Uiitersucliungen  iiber  thierische  Electric!  tlit,  1848,  Band  ii., 
8.  289. 


ELECTROTONUS. 


543 


Q^-t- 


/'^  - 


JV^ 


the  positive  phase,  the  current  through  G  is  diminished  (c)  consti- 
tuting the  negative  phase.  It  is  evident,  therefore,  that  the  elec- 
trical condition  of  the  nerve  is  not  only  modified  temporarily  by  the 
momentary  stimulus  of  the  constant  current,  l)ut  permanently  also 
during  the  passage  of  the  current  through  the  nerve  in  the  modi- 
fication of  its  electrical  condition  in  the  manner  just  mentioned.  It 
will  be  observed  from  an  inspection  of  Fig.  299  that  the  polarizing 
current  is  direct — that  is, 

as  it  passes  through  the  Fig.  299. 

nerve  from  the  anode  a, 
or  positive  pole,  to  the 
kathode  h,  or  negative 
pole,  it  flows  in  the  same 
direction  as  the  nerve 
force  itself.  Now  if  it 
be  assumed  that  the 
polarizing  current  de- 
velops outside  of  the  elec- 
trodes a  h,  a  new  current, 
the  electrotonic  current, 
having  the  same  direction 
as  itself,  it  is  evident  that 
the  increasing  or  dimin- 
ishing of  the  currents  of 
rest  by  the  electrotonic 
current,  according  as  the 
latter  is  flowing  in  the 
same  or  in  the  opposite 
direction,  will  account  for 
the  difference  in  the  elec- 
trical condition  of  the  nerve  outside  of  the  anode  a,  and  kathode  1:, 
the  former  being  positively,  the  latter  negatively,  electrified.  Such 
being  the  case,  we  may  call  that  part  of  the  electrotonic  current 
increasing  the  current  the  anelectrotonic,  that  diminishing  the 
same  the  katelectro tonic  current,  indicating  the  electrical  con- 
ditions of  the  two  currents  respectively  by  the  signs  plus  -f-  and 
minus  — .  If  now  the  position  of  the  two  electrodes  a  k  he.  re- 
versed so  that  the  polarizing  current  flows  through  the  nerve  in  the 
opposite  direction  to  that  of  the  nerve  impulse,  then  the  anelectro- 
tonic current  will  be  developed  at  p' ,  the  katelectrotonic  at  p,  and 
the  current  passing  through  the  galvanometer  G  will  be  increased, 
that  through  the  galvanometer  G'  diminished.  It  will  be  observed, 
therefore,  that  the  anelectrotonic  and  katelectrotonic  condition  just 
described  will  depend  upon  the  fiict  of  the  polarizing  current  pass- 
ing through  the  nerve  in  the  direct  or  reverse  direction.  In  either 
instance,  when  the  polarizing  current  is  broken  the  currents  of  rest 
previously  increased  or  diminished  are  for  a  brief  moment  dimin- 
ished or  increased.     It  need  hardly  be  added  that  the  electrotonic 


6^ 


Auelectrotonic  and  katelectrotonic  currents. 


544 


THE  NERVOUS  SYSTEM. 


currents  are  entirely  independent  of  the  currents  of  rest,  the  former 
being  present  even  when  the  latter  are  absent. 

By  further  experimentation  it  will  be  found  that  the  strength  of 
the  electro  tonic  currents  depends  upon  that  of  the  polarizing  cur- 
rent and  of  the  length  of  the  intrapolar  portion  of  the  nerve  ex- 
posed to  the  latter,  and  of  the  irritability  of  the  nerve,  a  dead  nerve 
not  exhibiting  the  electrotonic  current. 

Of  the  electrotonic  currents,  the  anelectrotonic  is  of  higher  po- 
tential than  the  katelectrotonic,  the  electro-motive  force  of  the  for- 
mer amounting  to  0.5  of  a  Daniell,  that  of  the  latter  to  0.05  T)} 
The  anelectrotonic  current  differs  also  from  the  katelectrotonic  cur- 
rent in  attaining  its  maximum  and  minimum  more  slowly.  It  is 
an  interestino-  fact  that  both  the  electrotonic  currents  undergo  a 
negative  variation  during  the  passage  of  an  impulse  through  the 
nerve.  It  may  be  also  mentioned  in  this  connection  that  the  with- 
drawal of  the  polarizing  current  gives  rise,  through  the  internal 
polarization  set  up  in  the  nerve,  to  "  after  currents,"  the  latter  be- 
ing positive,  that  is,  in  the  direction  of  the  polarizing  current  when 
the  current  is  strong,  and  negative  when  weak.  Considerable  dif- 
ference of  opinion  prevailed  at  one  time  among  physiologists  as  to 
whether  electrotonic  currents  are  due  to  some  especial  modification 
of  the  electro-motive  condition  of  the  nerve,  which,  like  the  current 
of  action,  is  transmitted  from  the  point  stimulated,  through  the 
nerve,  from  molecule  to  molecule,  or  are  due  to  the  direct  effect  of 
the  polarizing  current  through  an  escape  of  the  latter,  from  the 
electrodes  along  the  extra-polar  portions  of  the  nerve.  The  latter 
view  is,  however,  the  one  usually  accepted  at  the  present  day  as 

best    explaining    the    facts. 
Fig.  300.  At  least  currents  similar  to 

electrotonic  ones  can  be  pro- 
duced when  a  constant  cur- 
rent is  transmitted  through 
a  conductor  consisting,  like 
a  nerve,  of  three  parts,  such 
as  is  represented  in  Fig. 
300,  in  which  the  platinum 
axis  represents  the  axis- 
cylinder,  the  zinc  sulphate 
solution  the  substance  of 
Schwann,  and  the  clay  tube 
the  neurilemma.  The  leav- 
ing currents  in  such  a  con- 
ductor,  owing  to  the  substance  surrounding  the  axis  being  a 
better  conductor  than  the  envelope,  will  pass  from  the  anode  into 
the  former,  and  thence  into  the  axis,  and  so  return  by  the  latter  to 
the  kathode.  Further,  the  electrotonic  currents  so  developed  re- 
semble those  of  a  nerve  in  being  entirely  dependent  upon  the  polar- 
'  Du  Bois  Eeymond,  Gesammt.  Abliandl. ,  Band  ii. ,  s.  260. 


CUi^Tul><! 


Passage  of  current  through  platinum,  surrounded  hy 
zinc  suli)bate  and  clay. 


PASSAGE  OF  CURRENT  THROUGH  NERVES. 


545 


izing  current,  of  the  length  of  the  nerve  traversed  by  the  latter, 
etc.  If,  now,  such  a  lieterogeneous  conductor  be  divided  in  the 
middle,  and  the  cut  ends  be  joined  by  a  homogeneous  moist  con- 
ductor like  that  already  described,  no  electrotonic  currents  will  ap- 
pear for  the  reasons  already  given.  It  is  in  this  way,  probably, 
that  the  ligation  or  the  crushing  of  the  nerve  interferes  with  the 

Fig.  301. 


Passage  of  current  through  heterogeneous  conductor. 

development  of  such  currents,  the  nerve,  after  death,  being  changed 
from  a  heterogeneous  to  a  homogeneous  conductor.  Further,  as 
the  escape  of  the  polarizing  current,  either  in  the  nerve  or  the  het- 
erogeneous conductor,  appears  to  be  due  to  the  resistance  developed 
through  the  inner  polarization  set  up  between  the  core  and  the 
sheath,  it  is  to  be  expected  that  the  amount  of  polarizing  current 
escaping  along  the  extrapolar  portions  of  the  nerve  will  be  propor- 
tional to  such  resistance,  and  such  a  fact  is  found  to  be  the  case. 

An  interesting  illustra- 
tion of  the  diiference  in  Fig.  302. 
eifect  as  regards  the  de- 
velopment of  electrotonic 
currents  due  to  the  con- 
ductor being  homogeneous 
or  heterogeneous  can  be 
readily  shown  by  the  fol- 
lomng  simple  apparatus 
(Fig.  301),  which  consists 
of  a  glass  tube  through 
which  passes  an  axis  of 
amalgamated  zinc. 

If  the  -tube  be  filled 
with  zinc  sulphate  solu- 
t  i  o  n ,  the  galvanometer 
gives  no  evidence  of  elec- 
trotonic currents  ;  but  if  a  number  of  little  glass  beads  be  run 
along  the  axis,  the  spaces  between  the  beads  corresponding  to  the 
nodes  of  Ranvier  in  the  nerve,  the  galvanometer  will  be  at  once 
35 


Passage  of  current  through  nerve. 


546  THE  NERVOUS  SYSTEM. 

deflected,  the  conductor  having  been  converted  from  a  homogeneous 
into  a  heterogeneous  one.  The  diiferent  facts  just  referred  to,  es- 
tablished by  Funke,  Gruenhegen,  Hermann,  etc.,  all  go  to  show 
that  the  living  nerve  is  a  heterogeneous  conductor,  consisting  (Fig. 
302)  of  a  central  axis,  which  is  a  better  conductor  than  its  sur- 
rounding envelopes,  the  white  subtance  of  Schwann,  and  the 
neurilemma,  and  that,  owing  to  the  inner  polarization  set  up  be- 
tween the  axis  and  its  sheath,  a  resistance  is  offered  to  the  polar- 
izing current,  hence  its  escape  in  longitudinal  loops,  the  extent  of 
which  is  proportional  to  the  degree  of  polarization. 

Secondary  Electrotonus, 
Just  as  a  constant  polarizing  current  traversing  a  nerve  gives  rise 
to  an  electrotonic  current,  so  the  latter  gives  rise  to  a  secondary 
electrotonic  current  when  made  to  traverse  a  second  nerve.  Thus,  for 
example,  if  an  excised  nerve  N  (Fig.  303)  be  placed  in  contact  mth 
the  nerve  N'  of  a  nerve-muscle  preparation,  and  the  former  be  stimu- 
lated the  electrotonic  current  then  developed  in  N  will  produce  in 

Fig.  303. 


ak 


X 


Secondary  electrotonic  current. 

the  nerve  N'  with  which  it  is  in  contact  a  secondary  electrotonic  cur- 
rent which  in  stimulating  N'  causes  the  muscle  to  contract.  That 
the  contraction  of  the  muscle  is  not  due  to  a  variation  in  the  current 
of  rest  or  to  a  current  of  action  acting  as  stimuli,  as  might  be  sup- 
posed, but  to  the  secondary  electrotonic  current,  is  shown  by  the 
fact  that  stimulation  of  the  nerve  by  any  other  than  electrical 
means  will  not  cause  contraction. 

Electrotonic  Modification  of  Excitability  and  Conductivity. 

If  a  nerve  when  traversed  by  a  constant  polarizing  current  be 
still  further  tested  as  regards  its  excitability  and  conductivity,  it 
will  be  found  that  the  anodal  and  kathodal  regions  of  the  nerve 
differ  not  only  as  regards  their  electric  potential,  but  also  in  the  ex- 
citability and  conductivity  of  the  nerve  being  diminished  in  the 
anodal,  and  increased  in  the  kathodal  parts,  that  is  of  exhibiting 
the  conditions  known  as  anelectrotonus  and  katelectrotonus.^ 

The  anelectrotonic  and  katelectrotonic  conditions  are  not  only  in- 
teresting from  being  intimately  connected  in  so  many  respects  with 
the  anelectrotonic  and  katelectrotonic  currents,  the  latter,  indeed, 
being  so  named  for  this  reason  by  Du  Bois  Ileymond,  the  phcnom- 
1  Pfliiger,  Untersucliungen  iiber  die  Pliysiologie  des  Electrotonus,  1 859. 


ELECTROTONIC  CURRENTS.  547 

ena  of  anelectrotonus  and  katelectrotoniis  having  been  discovered 
first,  but  also  on  account  of  such  conditions  offering  an  exphuiation 
of  certain  well-established  facts  as  regards  the  excitability  of  nerves 
by  electrical  stimuli.  It  might  naturally  be  supposed  in  using  the 
constant  current  as  a  nervous  stimulant  that  the  current  would  ex- 
cite the  nerve  during  the  whole  time  that  it  was  applied,  that  so 
long  as  the  current  passed  through  the  nerve  successive  impulses 
would  be  generated,  with  the  effect  of  throwing  the  muscle  into  a 
kind  of  tetanus.  While  under  certain  circumstances  the  above  does 
take  place,  in  the  great  majority  of  cases,  however,  the  muscle  re- 
mains entirely  quiet  during  the  passage  of  the  current  through  the 
nerve,  provided  the  current  remains  constant,  contractions  taking 
place  at  the  making,  or  at  the  breaking,  or  at  both  the  making 
and  breaking,  according  as  we  shall  see  presently,  to  the  strength 
and  direction  of  the  current.  It  may  be  said,  therefore,  as  a  general 
rule,  that,  during  the  passage  of  a  constant  current  the  muscle  re- 
mains at  rest.  Nevertheless,  as  we  have  just  seen,  in  the  absence 
of  any  muscular  contraction,  the  nerve  is  profoundly  modified 
during  the  passage  of  a  constant  current  by  the  development  at 
the  anode  of  the  anelectrotonic  current  and  anelectrotonic  condi- 
tion and  at  the  kathode  of  the  katelectrotonic  current  and  katelec- 
trotonic  condition,  conditions  intimately  connected  with  the  peculiar- 
ities just  referred  to  as  regards  the  muscular  contraction  brought 
about  by  the  opening  and  closing  of  the  electrical  circuit. 

Before  considering,  however,  these  relations,  let  us  first  describe 
how  the  difference  already  mentioned  in  the  excitability  of  the  nerve 
at  the  anode  and  kathode,  respectively,  can  be  demonstrated.  With 
this  object,  we  will  dispose  the  necessary  apparatus,  as  represented 
in  Fig.  304,  and  let  us  suppose,  first,  that  the  polarizing  current 
thrown  into  the  nerve  by  the  opening  of  the  key,  and  whose  strength 
is  regulated  by  the  rheocord,  is  direct,  descending — that  is,  traverses 
the  nerve  in  the  same  direction  as  that  of  the  nerve  force — .4  being, 
therefore,  the  anode,  and  A"  the  kathode.  It  will  then  be  found 
that  if  the  nerve  be  stimulated  at  the  point  x  the  irritability  of  the 
nerve  will  be  increased  during  the  passage  of  the  polarizing  current 
as  shown  by  the  greater  elevation  of  the  lever  due  to  the  muscular 
contraction,  as  compared  with  the  average  elevation  previously  de- 
termined with  the  same  stimulus,  but  in  the  absence  of  the  polariz- 
ing current.  On  the  other  hand,  if  the  nerve  be  stimulated  at  the 
point  y  the  irritability  of  the  nerve  will  be  found  to  be  diminished. 
That  it  is  not  the  distance  of  the  point  y  from  the  muscle,  as  com- 
pared with  that  of  .r,  to  which  the  diminution  in  irritability  at  y  is 
due,  is  shown  by  reversing  the  polarizing  current  by  means  of  the 
whippe  (its  cross  piece  being  in),  so  that  the  current  becomes 
an  inverse  ascending  one,  the  anode  being  then,  therefore, 
nearer  the  muscle  than  the  kathode ;  even  then  the  irritability 
of  the  nerve  at  x  is  diminished,  and,  Avith  certain  qualifications,  to 
be  mentioned  presently,  that  at  y  is  increased.     In  this  way,  then, 


548 


THE  NERVOUS  SYSTEM. 


it  is  shown  that  during  the  passage  of  a  constant  current  the  irrita- 
bility of  the  nerve  at  the  kathode  is  increased  and  at  the  anode 
diminished,  the  change  in  the  condition  of  the  nerve  being  described 
as  that  of  katelectrotonus  and  anelectrotonus,  or  as  the  katelectro- 

tonic  increase,  and  anelec- 
FiG.  304.  trotonic  decrease  of  irri- 

tability. The  condition 
of  katelectrotonus  and 
anelectrotonus  not  only 
modifies  the  irritability  of 
the  nerve  as  regards  the 
originating  of  nervous 
impulses,  but  appears  also 
to  influence  their  propa- 
gation— at  least  it  may 
be  said  that  the  condition 
of  anelectrotonus  offers 
an  obstacle  to  the  passage 
of  a  nervous  impulse. 
The  condition  of  katelec- 
trotonus and  anelectro- 
tonus not  only  spreads 
out  along  the  extrapolar 
portions  of  the  nerve,  but 
extends  also  into  the  in- 
t  r  a  p  o  1  a  r  portion,  the 
point  where  they  merge 
into  each  other — that  is, 
where  the  irritability  is 
unchanged — being  known 
as  the  neutral  or  indiffer- 
ent point.  The  position 
of  the  latter  varies  some- 
M'hat,  according  to  the 
strength  of  the  current, 
with  a  strong  current  approaching  the  kathode,  with  a  weak  one 
the  anode.  AVhile  the  katelectrotonic  increase  and  anelectrotonic 
decrease  of  irritability  reach  a  maximimi  shortly  after  the  making 
of  the  polarizing  current,  and  then  gradually  diminish,  the  kat- 
electrotonic increase  attains  its  maximum  and  minimum  limits 
sooner  than  the  anelectrotonic  decrease.  The  strength  of  the  kat- 
electrotonic and  anelectrotonic  conditions  depends,  up  to  a  certain 
limit,  upon  the  strength  of  the  polarizing  current,  and  the  general 
irritability  of  the  nerve.  With  the  opening  of  the  polarizing  cur- 
rent the  phenomena  of  katelectrotonus  and  anelectrotonus  disap- 
pear, there  is,  however,  momentarily  an  increase  of  irritability  at 
the  anode,  a  decrease  at  the  kathode.  In  bringing  about  this  con- 
dition   of  katelectrotonus    and    anelectrotonus,  while    usually  the 


Disposal  of  apparatus  to  demonstrate  electrotonic  modifi- 
catiou  of  cxeitabilitv  of  nerve. 


KATELECTROTONUS  AND  AXELECTFOTOXUS.  549 

constant  current  is  made  use  of  as  the  stimulus,  as  in  the  pre- 
cedino-  instance,  this  is  not  indispensable,  an  induced  current 
producing  the  same  effect ;  this  is  as  might  be  expected,  since  a 
single  induction  shock  may  be  regarded  as  a  constant  current,  but 
of  very  short  duration,  developing  very  suddenly,  and  disappearing 
more  gradually.  Whether,  therefore,  the  constant  or  induced  cur- 
rent be  used  as  a  stimulus  the  nerve  is  thrown  into  the  condition  of 
katelectrotonus  and  anelectrotonus,  and  with  the  disappearance  of 
the  current,  as  just  mentioned,  there  is  a  rebound  at  the  poles,  their 
condition  being  then  momentarily  reversed.  It  will  be  also  partic- 
ularly observed  that  during  the  passage  of  the  current  through  the 
nerve  the  muscle  remains  quiescent,  contraction  only  taking  place  if 
the  strength  of  the  current  varies,  or  at  the  entrance  or  exit  of  the 
current  into  or  from  the  nerve.  The  stimulus  causing  the  nervous 
impulse  is  due  to  a  change  from  one  condition  to  another,  not  to  the 
condition  itself,  the  effect  not  depending  so  much  upon  the  inten- 
sity of  the  condition  as  on  variation  of  the  same.  Indeed,  if  the 
nerve  be  stimulated  with  a  current  the  strength  of  which  is  very 
o-raduallv  increased  or  decreased  the  excitement  o-enerated  will  not 
suffice  to  cause  muscular  contraction.  Further,  it  will  be  observed 
by  extending  the  experiments,  that  a  nervous  impulse  is  only  gen- 
erated when  the  nerve  passes  from  its  normal  condition  into  that  of 
katelectrotonus,  or  that  of  increased  irritability,  and  diminished 
electrical  potential,  or  passes  from  the  condition  of  anelectrotonus, 
that  of  diminished  irritability  and  increased  electrical  potential, 
back  to  the  normal  condition,  the  latter  normal  condition  being  then, 
relatively  at  least,  one  of  katelectrotonus,  as  compared  with  the  im- 
mediately preceding  anelectrotonic  condition.  As  might  be  ex- 
pected, however,  the  passage  of  the  nerve  from  the  anelectrotonic  to 
the  normal  condition  is  far  less  effective  as  a  generator  of  nervous 
impulses  than  that  from  the  normal  to  the  katelectrotonic  condition, 
since  the  return  from  the  anelectrotonic  to  the  normal  condition  is 
a  gradual,  not  a  sudden  one,  and  the  change  acts  as  a  stimulus,  at 
best  only  relatively.  Hence,  with  constant  currents  at  least,  the 
muscular  contraction  takes  place  usually  only  at  the  closing,  not  at 
the  opening  of  the  current. 

Let  us  now  modify  the  arrangement  of  the  apparatus  just  used  so 
that  (Fig,  305)  by  means  of  the  rheocord  we  can  modify  the  strength 
of  the  constant  current,  and,  by  the  whippe  (its  cross  piece  being  in), 
reverse  with  the  cross  in  the  direction  through  which  it  traverses 
the  nerve,  and  let  us  suppose  first  that  the  current  is  a  weak  one, 
descending  direct  at  the  moment  of  stimulation — that  is,  at  the 
making  of  the  circuit,  the  muscle  will  contract,  remaining  quiet, 
however,  during  the  passage  of  the  current  and  also  at  the  breaking 
of  the  same.  Let  us  now  reverse  the  direction  of  the  cm'rent,  so 
that  it  becomes  an  inverse  ascending  one  (Fig.  306),  then,  as  before, 
the  muscle  will  contract  only  at  the  making  of  the  circuit.  The 
effect  in  both  instances  being  the  same,  can  be  accounted  for  by 


550 


THE  NERVOUS  SYSTEM. 


supposing  the  katelectrotonic  condition  acts  as  a  stimulus,  the  im- 
pulse generated  at  the  kathode  in  the  case  of  the  inverse  current  be- 
ing still  effective,  even  though  the  distance  of  the  kathode  from  the 


Fig.  305. 


'nerve 
Disposal  of  apparatus  to  demonstrate  effect  of  direct  current  upon  excitability  of  nerve. 

muscle  is  increased.  Since,  however,  the  latter  impulse  generated  at 
the  kathode  has  to  traverse  the  anelectrotonie  portion  of  the  nerve  (a), 
which,  as  it  will  be  remembered,  offers  an  obstacle  to  the  propagation 
of  the  impulse,  the  muscular  contraction  due  to  the  making  of  the  in- 
verse current  will  be  less  than  that  due  to  the  making  of  the  direct 
one.  That  no  contraction  takes  place  at  the  breaking  of  the  circuit 
with  either  the  direct  or  inverse  currents  is  to  be  expected,  since,  with 
the  breaking  of  the  direct  current,  the  kathode  offers  an  obstacle, 
having  become  momentarily  the  anode,  to  the  propagation  of  the  im- 
pulse due  to  the  weak  katelectrotonic  condition  momentarily  de- 
veloped at  the  anode,  and,  with  the  breaking  of  the  inverse  current, 
the  fall  at  the  anode  from  anelectrotonus  to  the  normal  is  too  slight 
to  generate  an  impulse.  Let  us  now  intensify  the  current  and  re- 
verse its  direction  by  tlie  whippe,  so  that  it  is  again  a  direct  one 
(Fig.  305)  :  muscular  contraction  will  take  place  both  at  the  making 
and  breaking  of  the  circuit,  in  the  latter  case  the  effect  being  due  to 
the  passageof  the  anelectrotonie  condition  back  to  the  normal — that 
is,  relatively  to  a  condition  of  katelectrotonus.  Reverse  the  current 
so  as  to  make  it  an  ascending  one  (Fig.  30G),  and,  as  before,  we 
will  have  muscular  contraction  taking  place  both  at  the  making  and 


LAW  OF  MUSCULAR  CONTRACTION.  551 

breaking  of  the  circuit  ;  the  katelectrotonic  condition  generating 
the  impulse  at  the  making  and  the  return  of  the  anelectrotonic  con- 
dition to  the  normal  at  the  breaking  of  the  circuit.  Finally,  with 
a  very  strong  current,  if  the  latter  be  direct  (Fig.  305),  contraction 
takes  place  only  at  the  making  of  the  circuit,  and  with  the  inverse 

Fig.  306. 


Disposal  of  apparatus  to  demonstrate  effect  of  inverse  current  upon  excitability  of  nerve. 

current  only  at  the  breaking.  The  fact  of  there  being  no  contraction 
at  the  breaking  of  the  circuit  with  the  direct  current  may  be  ac- 
counted for,  l)y  partly  supposing  that  the  general  irritability  and  con- 
ductivity of  the  intrapolar  portion  of  the  nerve  has  been  depressed 
by  the  strong  current,  and  partly  h\  the  fall  of  anelectrotonus  not 
being  effective,  on  account  of  the  relative  anelectrotonic  condition, 
developed  through  the  fall  of  the  katelectrotonic  condition,  offering 
an  obstacle  to  the  transmission  of  the  impulse.  On  the  other  hand, 
with  the  ascending  current  (Fig,  306)  there  will  be  no  contraction 
at  the  making  of  the  circuit,  since  the  anelectrotonic  condition,  an 
obstacle  to  the  propagation  of  the  impulse  generated  at  the  kathode, 
intervenes  Ijetween  the  latter  and  the  muscle  ;  but,  ^^•ith  the  breaking 
of  the  circuit,  the  fall  of  the  anelectrotonus  to  the  normal  relatively 
katelectrotonus  will  generate  an  impulse,  since  no  obstacle  inter- 
venes then  between  the  point  of  stimulation  and  the  muscle,  and 
the  latter  will  contract.  The  above  facts,  established  among  others 
by  PfafF,  Ritter,  and  Pflliger,  may  be  summarized  as  a  law  of 
muscular  contraction,  under  the  following  formula,  in  which  the 
direct  and  inverse  currents  are  indicated  by  the  letters  D  and  /  and 
the  arrows,  and  the  making  and  breaking  of  the  circuits  by  the 
letters  J/ and  B,  and  the  contraction  and  rest  of  the  muscle  by  C 
and  R  respectively. 

Law  of  Musculab  Contraction. 

Weak  current.  Medium  current.  Strong  current. 

D    I  M  C,  B  B,  M  C,  B  C,  M  C,  B  B, 

I    I  M  C,  B  B,  M  C,  B  C,  M  B,  B  C, 

The  above  law  can  be  readily  remembered,  and  the  facts  ex- 
plained, if  it  be  admitted  that  muscular  contraction  only  takes 
place  when  there  is  a  rise  of  katelectrotonus  or  a  fall  of  anelectro- 


552 


THE  NERVOUS  SYSTEM. 


tonus  (relative  katelectrotonus) ;  but  not  by  the  rise  of  anelectro- 
tonus  or  fall  of  katelectrotonus  (relative  anelectrotonus).  Or,  in 
other  words,  that  the  nerve  impulse  starts  at  the  kathode  with  the 
closing  current  and  at  the  anode  with  tlie  opening  one.  It  may  be 
mentioned  in  this  connection  that  the  closing  and  opening  of  a  con- 
stant current  traversing  a  nerve  is  frequently  followed  by  a  series 
of  muscular  contractions,  respectively  known  as  the  closing  tetanus 
of  Wundt  and  the  opening  tetanus  of  Rutter. 

Electrotonus  in  Man, 

Inasmuch  as  the  statements  just  made  as  to  the  modification  of 
the  excitability  of  a  nerve  by  the  passage  of  a  constant  current  are 
based  entirely  upon  experiments  made  on  the  isolated  nerve  of  the 
frog,  it  is  not  to  be  expected  that  the  results  obtained  by  stimulating 
a  human  nerve  covered  by  tissue  and  skin  with  a  constant  current 
will  be  exactly  the  same.  Notwithstanding  however  the  difference 
of  the  conditions  in  the  two  cases,  it  has  been  shown  ^  that  super- 
ficially lying  motor  nerves  in  man  are  thrown  into  a  condition  of 
electrotonus  by  the  ajjplication  of  a  constant  current.  It  should  be 
mentioned,  however,  that  when  the  electrodes  of  the  polarizing  cur- 
rent are  applied  to  the  surface  of  the  body  as  the  current  density 
diminishes  in  proportion  to  the  distance  of  the  underlying  nerve 
from  the  surface,  the  intervening  tissues  being  good  conductors,  the 
current  soon  leaves  the  nerve,  in  consequence  of  which  the  kathode 
comes  to  lie  near  the  anode.  It  is  for  this  reason  that  the  electrodes 
of  the  polarizing  and  stimulating  currents  should  be  conjoined  in 
one  circuit  so  that  the  same  tract  of  nerve  can  be  stimulated  simul- 


FiG.  307. 


Scheme  of  the  distribution  of  aii  electrical  current  in  the  nerve  on  galvanizing  the  ulnar  nerve. 

(Lanuois.) 

taneously  or  consecutively."  In  considering  the  influence  exerted 
upon  the  excitability  of  a  nerve  by  the  transmission  of  a  constant 
current,  one  electrode  should  be  applied  first,  the  circuit  being  closed 

^Eulenberg,  Deutsches  Arcliiv  fur  klin.  Medecin,   Band  iii.,  1867,  s.  117  •  Erb 
Ebenda,  s.  238,  513.  nValler,  Phil.  Trans.,  1882,  p.  961.     ' 


ELECTROTONUS  IN  MAN. 


553 


► 


by  the  application  of  the  other  electrode  to  any  convenient  part 
of  the  body  and  the  effect  studied,  and  then  the  second  electrode 
should  be  applied,  the  circuit  being  closed  by  the  first  one.  Let  us 
suppose  that  the  anode  is  applied  first  to  the  surface,  for  example, 
of  the  arm  overlying  the  ulnar  nerve  (Fig.  307  -f ),  it  will  be  ob- 
served that  the  points  under  the  physical  anode  A  in  the  polar  re- 
gion, where  the  current  enters  the  nerve  constitute  a  group  of  physi- 
ological anodes  (Fig.  309,  A  A  A),  and  where  the  current  leaves  the 


Fig.  308. 
Peripolar   Region 


Fig.  309. 
Peripolar   Region 


\/ 


C+J 


A 


Anode 


Exit  of  current  from  arm. 


Entrance  of  current  into  arm. 


nerve,  in  the  peripolar  region,  a  group  of  physiological  kathodes 
KK K,  and  that  the  points  under  the  physical  kathode  K,  where 
the  current  enters  the  nerve  in  the  peripolar  region,  constitute  a 
second  group  of  physiological  anodes  (Fig.  308)  ^  ^  A,  and  where 
the  current  leaves  the  nerve  in  the  polar  region,  a  second  group  of 
physiological  kathodes  K  K  K. 

It  is  obvious,  therefore,  that  there  are  four  possible  cases  which 
can  be  tabulated,  the  muscular  contraction  being  taken  as  the 
measure  of  the  excitability  of  the  nerve,  as  follows  : 

1st.  Kathodic  closing  contraction  KCC,  i.  e.,  the  effect  of  the 
change  developed  at  the  physiological  kathode  beneath  the  phys- 
ical kathode.  2d.  Anodal  closing  contraction  ACO,  i.  e.,  the  effect 
of  the  change  developed  at  the  physiological  kathode  beneath  the 
physical  anode.  3d.  Anodal  opening  contraction  AOC,  i.  e.,  the 
effect  of  the  change  developed  at  the  physiological  anode  beneath 
the  physical  anode.     4th.     Kathodal  opening  contraction  KOC, 


554  THE  NERVOUS  SYSTEM. 

i.  e.,  the  eiFect  of  the  change  developed  at  the  physiological  anode 
beneath  the  physical  kathode.  These  four  contractions  differ  very 
much,  however,  in  strength,  owing  to  the  fact  that  with  a  closing 
current  the  excitement  starts  at  the  kathode,  but  with  an  opening 
current  at  the  anode,  that  the  excitement  developed  at  the  kathode 
on  closing  the  current  is  stronger  than  that  developed  at  the  anode 
on  opening  it,  and  that  the  effect  of  the  current  is  proportional  to 
its  density.  Thus,  for  example,  of  the  four  contractions  the  two 
closing  ones  KCC  and  ACC  are  stronger  than  the  two  opening 
ones  J.  0(7  and  A'OC  since  the  excitement  developed  at  the  physio- 
logical kathode  with  a  closing  current  other  things  equal  is  stronger 
than  that  developed  at  the  physiological  anode  with  an  opening  one. 
Of  the  two  closing  contractions  the  KCC  is,  however,  stronger  than 
the  A  CC  since  the  current  in  the  polar  region  at  the  physiological 
kathode  beneath  the  physical  kathode  is  denser  ^  than  in  the  peri- 
polar region  at  the  physiological  kathode  beneath  the  physical 
anode.  On  the  other  hand  of  the  opening  contractions  J.  0(7  is 
stronger  than  KOC  because  the  current  in  the  polar  region  at  the 
physiological  anode  beneath  the  physical  anode  is  denser  than  in 
the  peripolar  region  at  the  physiological  anode  beneath  the  physical 
kathode. 

The  above  conditions  may  be  briefly  tabulated  as  follows  •? 

Condition. 

Best  stimulus  in  best  region. 

"  "  worst  region. 

Worst  stimulus  in  best  region. 

"  "  worst  region. 

Finally,  if  instead  of  comparing  the  contractions  obtained  with 
a  current  of  constant  strength  the  order  in  which  they  appear  be 
observed  with  currents  of  gradually  increasing  strength,  it  will  be 
found  that  the  KCC  appears  first,  the  KOC  last,  the  formula  for 
contraction  being,  in  man,  as  follows : 

Weak  current,  KCC. 

Medium    "        KCC— ACC— AOC. 

Strong       "        KCC— ACC— AOC— KOC. 

In  concluding  our  account  of  general  nerve  physiology  it  re- 
mains for  us  now  to  say  a  few  words  with  reference  to  the  condi- 
tions influencing  the  general  irritability  of  nerves,  which  for  con- 
venience' sake  have  been  reserved  for  the  present  moment,  such  as 
the  influence  exerted  by  the  distance  from  the  muscle  of  the  point 
of  the  nerve  stimulated,  the  effect  of  the  angle  at  which  the  cur- 
rent enters  and  leaves  the  nerve,  the  duration  and  number  of  the 
stimuli,  the  temperature  and  blood  supply,  the  functional  activity, 

^  As  the  same  amount  of  electricity  always  flows  througli  any  given  transverse 
section  of  the  circuit,  the  density  of  tlie  current  will  be  greater  in  a  thin  conductor 
than  in  a  thick  one. 

2  Waller,  Human  Physiology,  1891,  p.  303. 


Current. 

stimulus. 

Region. 

KCC. 

Kathoclic. 

Polar. 

ACC. 

Kathodic. 

Peripolar. 

AOC. 

Anodic. 

Polar. 

KOC. 

Anodic. 

Peripolar. 

CO^WITIOXS  IXFLUEXCING  NERVE  IRRITABILITY.       OOO 

severance  from  the  central  nervous  system,  etc.  Thus,  if  two  pairs 
of  electrodes  are  placed  upon  the  nerve  of  a  freshly  prepared  nerve- 
muscle  preparation,  one  pair  near  the  muscle,  the  other  pair  near  the 
cut  end  of  the  nerve,  it  will  be  found  that  the  muscular  contraction 
is  greater  when  the  stimulus  is  applied  through  the  latter  pair  than 
when  throuo-h  the  former.  This  result  can  be  accounted  for  either 
on  the  supposition  that  the  nervous  impulse  gathers  strength,  ava- 
lanche-like, as  it  travels  from  the  cut  end  of  the  nerve  toward  the 
muscle,  or  that  the  central  end  of  the  nerve  is  more  irritable  than 
the  distal  end.  The  latter  view  is  the  most  probable,  since  the  cur- 
rent of  action,  or  negative  variation,  exhibits  no  such  avalanche-like 
increase  as  it  progresses,  wave-like,  from  the  point  stimulated  to 
the  muscle.  In  stimulating  a  nerve  it  is  important  that  the  elec- 
trode should  be  so  applied  that  the  current  will  pass  through  the 
nerve  as  nearly  longitudinally  as  possible,  not  transversely,  as  in 
the  latter  case  the  current  will  not  produce  any  eliect.^ 

It  has  been  shown  by  Konig  -  that  the  constant  current  if  used 
as  a  stimulus  must  last  at  least  the  0.0015  second  to  produce  a 
nervous  impulse,  and  by  Kroniker  and  Stirling,'^  that  inductive 
shocks  even  if  repeated  as  rapidly  as  2200  times  a  second  will 
throw  a  muscle  into  tetanus.  In  this  connection  it  may  be  men- 
tioned that  according  to  Helmholtz,*  that  if  maximum  induction 
shocks  be  throw^i  into  a  nerve  following  each  other  at  a  rate  of  less 
than  the  ^^  of  a  second,  half  tlie  shocks  will  produce  no  effect, 
the  muscle  being  devoid  of  irritability  for  the  g-^^  of  a  second  sub- 
sequent to  each  shock. 

The  influence  exerted  by  the  duration  and  change  of  intensity  of 
the  stimulus  upon  excitability  differs  in  nerves  as  compared  with 
striated  and  unstriated  muscles.  Thus,  for  example,  in  the  case  of 
nerves,  rapid  change  of  intensity  is  more  important  than  duration 
of  stimulus,  in  striated  muscles  the  reverse  obtains  while  in 
unstriated  muscles  duration  of  the  stimulus  is  the  all  important 
factor.-^  A  rise  of  temperature,  say  to  45°  C.  (113°  F.)  in 
the  case  of  the  frog's  nerve  favors  the  development  of  nerve  irri- 
tability, the  activity  of  the  molecular  processes  being  increased, 
nervous  impulses  are  generated  more  readily  by  stimuli,  and 
the  muscular  contractions  are  proportionately  greater.  On  the 
other  hand,  the  application  of  cold  benumbs  the  nervous  system, 
diminishes  nervous  irritability,  the  latter  disappearing  altogether  if 
the  temperature  be  reduced  to  0°  C.  (32°  F.).  Judging  from  what 
we  shall  learn  hereafter  from  the  analogous  case  of  muscle  there 
can  be  little  doubt  that  the  irritability  of  a  nerve  depends  upon  a 
full  supply  of  oxygenated  blood  and  that  through  prolonged  use  the 
nerve  becomes  exhausted.     Finally,  if  a  nerve  be  divided  in  the 

^Albrecht  V.  Mever,  Pfliiger's  Archiv,  Band  xxi.,  1880,  s.  462. 

2Wien.  Sitz.  Bericht,  Ixii.,  1870. 

'' Archiv  Anat.  u.  Phys.,  1878,'s.  1. 

*  Berlin  Monats.  Bericlit,  1854. 

^  Fick,  Beitriige  zur  Physiologie  der  irritabilen  Substanzen,  1863. 


556  THE  NERVOUS  SYSTEM. 

living  body  or  even  out  of  it,  it  will  be  observed  that  at  the  periph- 
eral end  of  the  cut  nerve  the  irritability  at  first  slightly  increases, 
then  diminishes,  and  finally  disappears,  the  changes  in  the  irrita- 
bility advancing  from  the  cut  end  of  the  nerve  toward  the  muscle. 
(Ritter-Valli  law.)  Coincidently  with  the  changes  in  the  irrita- 
bility of  the  nerve  just  mentioned,  a  degeneration  is  set  up  in  the 
substance  of  Schwann  and  the  axis-cylinder  extending  to  the  ter- 
minal filaments,  involving  even  their  endings  in  the  motor  plates. 
A  similar  degeneration  may  extend  also  centripetally  from  the  cut 
end,  but  not  beyond  the  first  node  of  Ranvier.  Beyond  this  point 
the  nerve  is  usually  found  normal. 


CHAPTER   XXX. 

THE  NERVOUS  SYQTBISL— (Continued.) 

THE  SPINAL  CORD.  ITS  STRUCTURE  AND  FUNCTIONS  AS  A 
CONDUCTOR  OF  EFFERENT  AND  AFFERENT  IMPULSES. 


The  spinal  cord  lying  in  the  vertebral  canal,  enveloped  within 
its  membranes,  extends  as  a  cylindrical  cord  of  from  37  to  45  cm. 
(15  to  18  inches)  in  length  from  the  medulla  oblongata,  with  which 
it  is  continuous,  at  the  level  of  the  occipital  foramen  to  the  lower 
part  of  the  first  lumbar  vertebra.  It  weighs  about  28  grammes 
(1  ounce).  If  a  transverse  section  of  the  cord  be  made,  it  will  be 
observed  (Fig.  310)  that  it 

consists    of    white    matter  Fig.  310. 

externally,  and  of  gray 
matter  intei'nally,  the  latter 
beino;  found  in  the  o-reatest 
amount  opposite  the  cervi- 
cal and  limibar  enlarge- 
ments, the  origin  of  the 
large  nerves.  The  gray 
matter  is  disposed  as  two 
crescents,  placed  back  to 
back,  somewhat  in  the  form 
of  the  letter  H  and  con- 
nected across  the  middle 
line  by  an  isthmus,  the 
gray   commissure,    each 

crescent  exhibiting  an  anterior,  a  posterior  cornu  or 
middle  part,  the  cervix  or  neck. 

The  gray  commissure  is  often  subdivided  into  the  interior  and 
posterior  gray  commissures  by  its  central  canal,  which,  as  we  shall 
see  hereafter,  is  the  remnant  of  the  primitive  neural  canal.  This 
peculiar  arrangement  of  the  gray  matter  within  the  spinal  cord 
serves  conveniently  to  subdivide  the  Avliite  portions  of  the  cord  into 
the  anterior,  lateral,  and  posterior  columns.  The  anterior  columns 
are  made  up  by  that  part  of  the  white  matter  of  the  cord  lying  be- 
tween the  anterior  median  fissure  and  the  anterior  cornu.  It  will 
be  observed,  however,  that,  as  the  anterior  median  fissure  does  not 
extend  into  the  anterior  gray  commissure,  a  band  of  white  matter, 
the  white  commissure,  intervening,  the  anterior  columns  run  into 
each  other,  and  that,  as  the  anterior  cornu  does  not  extend  to  the 
outer  edge  of  the  cord,  the  anterior  columns  pass  into  the  lateral 


Transverse  section  of  the  spinal  cord,  a,  b.  Spinal 
nerves  of  right  and  left  sides,  d.  Origin  of  anterior 
root.  e.  Origin  of  posterior  root.  c.  Ganglion  of  pos- 
terior root.     (Daltos.) 


horn,  and  a 


558 


THE  NERVOUS  SYSTEM. 


ones,  lying  between  the  two  crescents.  On  the  other  hand  the  pos- 
terior median  fissure  filled  up  with  the  inner  layer  of  the  pia  mater 
and  extending  down  to  the  posterior  gray  commissure,  and  the  pos- 
terior cornu  of  the  gray  matter  to  the  inner  edge  of  the  cord,  the 
posterior  columns  lying  between  them  are  completely  separated  from 
the  lateral  columns,  and  from  each  other.  In  certain  regions  of  the 
cord  each  posterior  column  is  further  subdivided  by  a  rather 
obscure  fissure  into  two  sub-columns,  the  one,  the  posterior  median 
column,  lying  immediately  next  to  the  posterior  median  fissure, 
often  called  the  column  of  Goll,  also  the  inner  root  zone  of  Charcot, 
the  other  the  posterior  external  column,  or  the  column  of  Burdach, 
or  the  outer  root  zone  of  Charcot,  the  two  columns  terminating  re- 
spectively in  the   clavate  and  the  cuneate  nuclei   of  the  medulla. 

The  white  matter  of  the  cord 
Fig.  311.  constituting    its    columns    as 

just  described  consists  princi- 
pally of  medullated  nerve 
fibers  which,  though  provided 
Avith  neurokeratin  sheaths,  do 
not  possess  a  neurilemma. 

The  course  of  the  fibers 
through  the  columns  of  the 
cord  is  generally  in  a  longi- 
tudinal direction,  those  decus- 
sating in  the  white  commissure 
and  in  the  gray  matter  as 
well  as  the  fibers  entering  into 
the  formation  of  the  roots  of 
the  spinal  nerves  are,  how- 
ever, transversely  or  obliquely 
disposed.  If  the  white  matter 
of  the  cord  be  viewed  in  trans- 
verse sections  with  the  micro- 
scope, the  nerve  fibers  will 
then  appear  like  small  circles 
of  different  sizes  (Fig.  311), 
with  a  rounded  dot  in  the 
center,  the  latter,  or  the  axis- 
cylinder,  being  very  distinct  if  the  preparation  be  stained  with  car- 
mine, while  between  groups  of  these  nerve  fibers  fine  septa  of  con- 
nective tissue  may  also  be  observed  supporting  delicate  blood  vessels. 
The  gray  matter  of  the  cord  consists  of  a  supporting  connective  tissue, 
the  neuroglia  of  A^irchow,  composed  of  a  fine  network  of  round  and 
large  branched  cells,  iml^cdded  in  a  homogeneous  matrix,  which, 
from  being  particularly  al)undant  at  the  sides  of  the  posterior  cornu, 
is  there  known  as  the  gelatinous  sul)stance  of  Rolando,  of  blood 
vessels  derived  from  the  vertebra)  and  partly  from  the  intercostal 
lumbar  and  sacral  arteries  of  nerve  cells  and  nerve  fibers. 


jy 


A^ 


Transverse  section  through  the  under  half  of  the 
human  cord.  a.  Central  canal.  6.  Anterior,  c, 
Posterior  fissure,  d.  Anterior  cornu,  with  large 
ganglion  cells,  e.  Posterior  cornu  with  smaller.  /. 
Anterior  white  commissure.  </.  Sustentaeular  sub- 
stance around  the  central  canal,  h.  Posterior  gray 
commissure.  ■(.  Bundles  of  the  anterior,  and  k  of 
the  posterior  spinal  nerve  roots.  /.  Anterior,  m, 
Lateral,    w,  Posterior  column.     (Deiteks.) 


CELLS  IN  THE  GRAY  MATTER. 


559 


The  cells  in  the  gray  matter  of  the  cord  are  of  two  kinds,  large 
multipolar  cells  (Fig.  811,  d),  such  as  are  found  in  the  anterior 
cornu,  and  small  spindle-shaped  cells  (e)  in  the  posterior  cornu. 
Large  multipolar  cells  are  also  found  principally  in  the  lower  part 
of  the  dorsal  region  of  the  cord,  behind  the  gray  commissure,  and 
on  the  inner  surface  of  the  posterior  cornu,  constituting  the  posterior 
vesicular  column  of  Clarke. 

The  gray  matter  of  the  cord  consists  also,  or  is  traversed,  rather, 
by  innumerable  delicate  non-medullated  nerve  fibers,  which  appear 
to  be  the  axons  or  the  outgrowths  of  the  cells  just  mentioned,  and 
which  pass  either  into  the  roots  of  the  spinal  nerves  or  into  the 
columns.  On  account,  however,  of  the  manner  in  which  the  sec- 
tions are  made  necessarily,  in  many  cases  it  is  impossible  to  say 
anything  positively  as  to  either  the  origin  or  termination  of  such 


Fig.  312. 


Transverse  section  of  half  of  the  spinal  cord  of  a  trout  embryo,  cc.  Central  canal,  mli.  Mem- 
brana  limitaus  interna,  g.  Germinal  cell.  sp.  Spongioblast,  nb.  Neuroblast,  wc.  White  columns, 
(Landois.) 

nerve  fibers.  Comparison  of  sections  made,  however,  both  in  a 
longitudinal  and  in  a  transverse  direction,  leads  to  the  supposition 
that  all  such  non-medullated  nerve  fibers,  or  axis-cylinders,  found 
in  the  gray  matter  of  the  cord,  originate  in  either  encephalic  or 
spinal  cells,  neuroblasts  (Fig.    312),    and,  directly   or  indirectly, 


560 


THE  NERVOUS  SYSTEM. 


through  spinal  nerves,  terminate  in  muscle,  gland,  sensory  organ, 
etc.  What  has  been  positively  learned  from  the  recent  histological 
researches  of  Lenhossek/  Obersteiner,"  Koelliker,'^  and  others  as  to 
the  origin  and  course  of  these  fibers  may  be  briefly  summed  up  as 
follows  :  The  axis-cylinders  of  the  anterior  roots  terminating  in  the 
muscle  end-plates^  pass  out  of  the  cord  continuously  as  tlie  axons,  of 
the  cells,  of  the  anterior  cornu,  the  latter  being  situated  near  the  end 
tufts  of  the  axons,  of  the  cerebral  cells.  Of  the  latter  axons  some 
(Fig.  313),  pass  through  the  white  commissure,  and  are  continued 

Fig.  313. 


Course  of  the  motor  and  sensory  paths  in  a  spinal  segment.  1.  Anterior  pyramidal  tract.  3 
Cro.ssed  pyramidal  tract.  4  and  5.  Sensory  paths  decussating  in  the  cord.  6.  Sensury  jiaths  which 
do  not  decussate  in  the  cord.  7.  Afferent  paths  leading  to  Clarke's  column  and  I'mm  thence  pass- 
ing as  uncrossed  fibers  upwards  via  the  direct  cerebellar  tract.  2.  Origin  of  a  motor  liber  from  a 
ganglionic  cell  of  the  anterior  cornu.     (Landois.) 

as  the  direct  pyramidal  tract  in  the  anterior  column  of  the  opposite 
side  of  the  cord,  while  others  3  (Fig.  313),  pass  into  the  lateral 
columns  of  the  same  side,  and  thence  to  the  medulla  oblongata,  where 
the  greater  portion,  decussating  with  the  corresponding  fibers  of  the 
opposite  side,  pass  as  the  crossed  pyramidal  tract  through  the  pons, 
crusta  of  the  cms  cerebri,  to  the  caudate  and  lenticular  nuclei  of  the 
corpus  striatum  and  by  the  anterior  two-thirds  of  the  posterior  seg- 
ment of  the  internal  capsule  to  the  motor  areas  of  the  cerebral  cortex 
(Fig.  314).     The  axis-cylinders  of  the  posterior  roots,^  after  enter- 

'Der  Feinere  Bau  ties  Ncrvensystems,  etc.,  Zweite  Auflage,  1895,  s.  248. 

^Anleitung  Beim  Studium  des  Baus  der  Nervosen,  Centralorgane,  etc.  Dritte 
Auflage,  1896,  s.  208. 

''Ilandbuch  der  Gewebelehre  des  Menschen,  Sechste  Auflage,  Zvveiter  Band, 
1896,  s.  55.  ^See  Fig.  241,  p.  484.  ^See  Fig.  242,  p.  484. 


STRUCTURE  OF  THE  BRAIN. 


561 


ing  the  spiual  cord,  divide  into  ascending  and  descending  branches, 
the  end  tufts  of  which  lie  in  close  proximity  to  cells  whose 
axons  cross  the  middle  line  of  the  cord  and  ascend  by  the  ante- 
rior  and   lateral   columns  of   the  opposite  side  (Fig.   313,    4,    5) 


Fig.   3U. 


Diagram  of  the  structure  of  the]^raiu.  C  C.  Cortical  substance  of  the  cerebral  hemispheres. 
C.  s.  Corpus  striatum.  N.  1.  Nucleus  lenticularis.  T.  o.  Thalamus  opticus.  V.  Corpora  quadri- 
gemina.  P.  Pedunculus  cerebri.  P.  Basis  or  crusta,  and  H,  tegmentum.  1,  1.  Fibers  of  the 
corona  radiata  of  the  corpus  striatum.  2,  2.  Those  of  the  lenticular  nucleus.  3.  Those  of  the 
optic  thalamus.  4,  4.  Those  of  the  corpora  quadrigemina.  5,  5.  Direct  strands  to  the  cortex 
cerebri  (I'lechsig).  6.  Fibers  from  the  corpora  quadrigemina  to  the  tegmentum.  7.  Fibers  from 
the  optic  thalamus  to  the  tegmentum,  m.  Further  course  of  these  fibers.  8.  Fibers  from  the 
corpus  striatum  and  lenticular  nucleus  to  the  pes  of  the  pedunculus  cerebri.  M.  Further  course 
of  these  fibers.  S,  S.  Course  of  the  sensory  tibers.  R.  Transverse  section  of  the  spinal  cord. 
V  W.  Anterior  roots,  h  W.  Posterior  roots  of  the  spinal  nerves,  a,  a.  Association  fibers,  c,  c. 
Commissural  fibers. 

through  the  medulla,  pons,  and  tegmentum  of  the  crus  to  the  thal- 
amus opticus  and  to  the  posterior  third  of  the  posterior  segment  of 
the  internal  capsule  or  the  "  sensory  cross- way "  to  the  sensory 
areas  of  the  cerebral  cortex.  The  fibers  just  described,  connecting 
36 


562 


THE  NERVOUS  SYSTEM. 


the  cerebral  cortex  and  the  anterior  and  posterior  roots,  we  shall  see 
presently,  constitute  the  avenues  by  which  motor  impulses  pass  from 
the  brain  to  the  periphery,  and  sensory  ones  from  the  periphery  to 
the  brain.  The  anterior  and  posterior  roots  consist,  as  incidentally 
mentioned,  not  only  of  motor  and  sensory  fibers  but  of  other  fibers 
as  well,  which  take  a  different  course  through  the  cord  and  have 
different  functions,  the  consideration  of  which  will  be  deferred,  how- 
ever, for  the  present. 

From  what  has  just  been  said,  it  is  obvious  that,  while  for  con- 
venience' sake,  the  spinal  cord  may  be  described  as  beginning  at 
the  great  foramen,  as  a  matter  of  fact,  it  passes  so  continuously 
into  the  medulla  that  the  latter  may  be  regarded  as  its  upper  ex- 
panded portion,  and,  since  the  medulla  is  largely  made  up  of  fibers 
passing  through  it  to  and  from  the  cortex,  corpora  striata,  thalami 
optici,  etc.,  the  cord,  physiologically,  may  be  regarded  as  beginning  in 
these  basal  ganglia  and  the  cortex  rather  than  at  the  great  foramen. 

The  medulla  oblongata  (Fig.  315)  is  of  a  pyramidal  form,  hav- 

FiG.  315. 


Inferior  surface  of  the  cerebellum  with  the  pons  Varolii  and  medulla  oblongata.  1.  Placed  iu 
the  notch  between  the  cerebellar  hemispheres,  is  below  the  inferior  vermiform  process.  2,  2. 
]Sredian  depression,  or  vallecula.  3,  3,  3.  The  biveutral,  slender,  and  posterior  inferior  lobules  of 
the  hemisphere.  4.  The  amygdala.  5.  Flocculus,  or  subpeduncular  lobule.  6.  Pons  Varolii. 
7.  Its  median  groove.  8.  Middle  peduncle  of  the  cerebellum.  0.  Medulla  oblongata.  10,  11. 
Anterior  part  of  the  great  horizontal  tissure.  12,  13.  Smaller  and  greater  roots  of  the  fifth  pair 
of  nerves.  14.  Sixth  pair.  1.5.  Facial  nerve.  16.  Pars  intermedia.  17.  Auditory  nerve.  18. 
Glosso-pharyngcal.  19.  Pneumogastric.  20.  Spinal  accessory.  21.  Hypoglossal  nerve.  (From 
Sappey,  after  Hirsciifeld  and  Leveille.  ) 


ing  its  broad  extremity  upward  and  expanded  laterally  at  its  upper 
part.  Its  length  is  about  an  inch  and  a  quarter,  its  breath  nearly 
an  inch,  and  its  thickness  about  three-quarters  of  an  inch.  Like  the 
spinal  cord,  tlie  medulla  presents  two  median  fissures.  The  anterior 
median  fissure  terminates  just  below  the  pons  in  a  recess,  the  foramen 
caecum  of  Vicq  d'Azyr ;  the  posterior  median  fissure  is,  however, 
continued  up  into  the  floor  of  the  fourth  ventricle,  where,  after  ex- 
panding into  a  superficial  furrow,  it  is  gradually  lost.  In  other  re- 
spects, however,  the  medulla  differs  entirely  in  the  arrangement  of 


MEDULLA  OBLONGATA.  563 

its  parts  from  the  spinal  cord,  each  of  its  halves  being  characterized 
by  four  eminences,  or  columns,  which  are  known  in  the  order  in 
which  they  present  themselves  from  before  backward  as  the  anterior 
pyramids,  the  olivary  bodies,  the  restiform  bodies,  and  the  posterior 
pyramids.  The  anterior  pyramids  are  situated  on  either  side  of  the 
anterior  fissure,  and  are  separated  from  the  olivary  bodies  by  a 
slight  depression.  Each  anterior  pyramid  consists  of  two  sets  of 
fibers,  inner  and  outer :  the  outer  fibers  are  continuations  of  those 
of  the  anterior  columns  of  the  cords  of  the  same  side,  and,  together 
with  the  decussating  fibers  from  the  opposite  side  of  the  cord,  pass 
upw'ard  through  the  pons  into  the  cerebral  peduncles  ;  the  inner  or 
decussating  fibers,  so  called  because  they  interlace,  to  a  considerable 
extent,  with  those  of  the  opposite  pyramid,  are,  in  reality,  almost 
entirely  derived  from  the  fibers  of  the  lateral  column  of  the  oppo- 
site side  of  the  cord,  the  anterior  pyramids  being  pushed  aside,  as 
it  were,  by  the  lateral  columns  inserting  themselves  between  them  as 
they  interlace  with  each  other.  The  anterior  pyramid  proper  con- 
tains no  o-rav  matter,  its  so-called  nucleus  consistino;  of  stellate  nerve 
cells  lying  behind  and  between  it  and  the  olivary  body.  The  oli- 
vary bodies  are  two  smooth,  oval  eminences  sunk  deeply  into  the 
medulla,  and  consist  of  both  white  and  gray  matter  ;  the  fibers  of 
the  former  run  in  a  longitudinal  direction.  The  gray  matter,  pre- 
senting a  very  characteristic  zigzag  contour  in  section,  is  known  as 
the  corpus  dentatum,  or  ciliare,  or  olivary  nucleus ;  while  the  gray 
lamina  above  the  latter  is  often  described  as  the  accessory  olivary 
nucleus.  The  fibers  of  the  anterior  columns  of  the  cord,  which, 
as  just  mentioned,  are  thrown  outward  as  they  are  continued  up  as 
the  outer  fibers  of  the  anterior  pyramids,  pass  partly  on  the  out- 
side of,  and  partly  beneath  the  olivary  bodies,  and  being  joined  by 
fibers  from  the  olivary  nucleus  pass  upward  as  the  olivary  fasciculus 
and  fillet  to  the  corpora  quadrigemina  and  cerebral  peduncles.  The 
restiform  bodies,  or  the  inferior  peduncles  of  the  cerebellum,  situ- 
ated behind  and  to  the  outer  side  of  the  olivary  bodies  (Fig.  316), 
w^hile  containing  a  considerable  quantity  of  gray  matter,  consist 
principally  of  white  fibers  continued  upward  partly  from  the  pos- 
terior column  of  the  cord,  and  partly  from  the  lateral  and  anterior 
columns  ;  the  latter  fibers,  a  small  band,  connect  the  anterior  column 
with  the  cerebellum.  The  posterior  pyramids  situated  on  either 
side  of  the  ])osterior  median  fissure,  containing  ranch  gray  matter, 
consist  of  white  fibers,  continuous  with  those  of  the  posterior  me- 
dian columns  of  the  cord  ;  ascending,  they  diverge  from  one  another, 
forming  the  lower  boundary  of  the  fourth  ventricle,  and  tapering  oif 
become  closely  a])plied  to  the  restiform  bodies. 

Resuming  what  has  just  been  said  with  reference  to  the  structure 
of  the  medulla,  it  will  be  seen  that  the  fibers  of  the  anterior  columns 
of  the  cord  pass  through  it  by  three  routes  :  1st,  as  the  fibers  of  the 
anterior  pyramids  to  the  cerebral  jjeduncles  ;  2d,  as  the  inner  fibers 
of  the  anterior  pyramids  (together  with  the  decussating  fibers),  as 


564 


THE  NERVOUS  SYSTEM. 


the  olivary  fasciculus  and  fillet  to  the  corpora  quadrigemina  and 
cerebral  peduncles ;  3d,  as  the  band  behind  the  olivary  body,  from 
the  restiform  body  to  the  cerebellum.  The  fibers  of  the  lateral 
columns  pass  through  the  medulla  also  by  three  routes  :  1st,  as  the 
decussating  fibers  (together  with  the  inner  fibers  of  the  anterior 
pyramids),  as  the  olivary  fasciculus  and  fillet  to  the  corpora  quad- 

FiG.  3ir). 


View  of  the  floor[of  the  fourth  ventricle  with  the  jiosteriur  surface  of  the  medulla  oblongata  and 
ncigliboring  parts. '^Ou  the  left  side  the  three  cerebellar  peduncles  have  been  cut  short;  on  the 
right  side  the  white  substance  of  the  cerebellum  has  been  preserved  in  connection  with  the  su- 
perior and  inferior  peduncles,  while  the  middle  one  has  been  cut  short.  1.  Median  groove  of  the 
fourth  ventricle  with  the  fasciculi  teretes,  one  on  each  side.  2.  The  same  groove  at  the  place 
where  the  white  striie  of  the  auditory  nerve  emerge  from  it  to  cross  the  floor  of  the  ventricle.  3. 
Inferior  peduncle  or  restiform  body."  4.  Posterior  pyramid  ;  above  this  the  calamus  scriptorius. 
o.  Superior  peduncle,  or  processus  a  eerebello  and  cerebrum  ;  on  the  right  side  the  dissection 
shows  the  superior  and  inferior  peduncles  crossing  each  other  as  they  pass  into  the  white  center 
of  the  cerebellum.  6.  iFillet  to  the  side  of  the  crura  cerebri.  7.  Lateral  grooves  of  the  crura 
cerebri.    8.  Corpora  quadrigemina.     (From  Sappey  after  Hirschfeld  and  Leveille.) 

rigemina,  and  cerebral  peduncles  ;  2d,  by  the  restiform  body  to  the 
cerebellum ;  3d,  by  the  fibers  in  the  floor  of  the  fourth  ventricle 
(fasciculus  teres)  into  the  cerebrum.  The  fibers  of  the  posterior 
columns  pass  through  the  medulla  by  two  routes  :  1st,  the  outer 
portions  of  the  columns  by  the  restiform  bodies  to  the  cerebellum  ; 
2d,  the  inner  portion  (fasciculus  gracilis),  by  the  posterior  pyramids 
to  the  cerebrum. 

The  fourth  ventricle  (Fig.  316),  just  alluded  to  incidentally,  is 
the  space  left  between  the  medulla  oblongata  in  front,  and  the 
cerebellum  behind.  It  is  bounded  laterally  ])y  the  superior  pe- 
duncles above,  and  l)y  the  diverging  posterior  pyramids  and  resti- 
form bodies  below,  and  is  covered  in  behind  by  the  valve  of 
Vieusscns  and  inferior  vermiform  process  of  the  cerebellum,  the 
floor  being  constituted  by  the  back  of  the  medulla  oblongata  and 
pons  Varolii,  marked  by  the  median  furrow  terminating  inferiorly 
as  the  calamus  scriptorius  ;  above  the  fourth  ventricle  communi- 
cates through  the  sylvian  aqueduct  or  iter  Avith  the  third  ventricle, 


FOURTH  VENTRICLE. 


565 


and  below  Avith  tlie  contnil  canal  of  the  spinal  cord  and  the  sub- 
arachnoid cavity  through  the  foramen  of  ]Magendie  in  the  pia  mater. 
The  gray  matter  of  the  floor  of  the  fourth  ventricle  disposed  as  a 
continuous  series  of  nuclei  extending  from  beneath  the  corpora 
quadrigemina  to  a  point  corresponding  to  the  decussation  of  the 
pyramids,  is  of  extreme  interest  physiologically  as  constituting,  as 
"sve  shall  see,  the  nuclei  of  origin  of  the  so-called  cranial  nerves  from 
the  third  to  the  twelfth  inclusive.  The  gray  matter  of  the  medulla, 
like  that  of  the  spinal  cord  proper,  differs  as  regards  its  form, 
amount,  etc.,  according  to  the  position  of  the  section.  Thus,  if  the 
latter  be  made  just  above  the  level  of  the  first  cervical  nerve  (Fig. 
317),  the  central  gray  substance  is  encroached  upon,  pushed  back 
by  the  decussating  fibers  from  the  lateral  columns,  which,  in  cours- 
ing inward,  separate  the  anterior  cornu  from  the  rest  of  the  gray 
substance,  while  if  the  section  be  made  through  the  loAvest  part  of 
the  olivary  bodies  (Fig.  ol8),  the  gray  matter  will  be  seen  to  be 

Fig.  317. 


Transverse  section  of  cord  just  above  level         Transverse  section  of  medulla  at  level  of  olivary 
of  first  cervical  nerve.  bodies. 


still  further  modified.  The  pons  Varolii  entering,  as  we  have  seen, 
into  the  formation  of  the  floor  of  the  fourth  ventricle,  consists  not 
only  of  the  longitudinal  fibers  passing  upward  through  it  from  the 
cord  and  medulla  to  the  crura  cerebri,  but  also  of  commissural 
fibers  connecting  the  lateral  halves  of  the  cerebellum  and  of  gray 
matter.  The  functions  of  the  latter  will  be  considered  after  those 
of  the  spinal  cord  and  medulla  have  been  treated  of. 

From  the  fact  of  the  spinal  nerves  being  distributed  in  general 
to  the  muscles  of  the  trunk  and  extremities,  the  sphincters,  and  to 
the  integument  covering  these  parts,  of  the  posterior  part  of  the 
head,  and  a  portion  of  the  mucous  membrane,  it  is  evident  that  a 
complete  account  of  their  functions  would  necessitate  not  only  a 
detailed  description  of  each  spinal  nerve,  but  of  the  parts  supplied 
by  the  latter.  Inasmuch,  however,  as  the  structure  and  functions 
of  any  one  spinal  nerve  are  essentially  the  same  as  those  of  the 
spinal  nerves  in  general,  a  brief-  description  of  these  nerves  only 
will  be  ffiven. 


566 


TEE  NERVOUS  SYSTEM. 


There  are  thirty-one  pairs  of  spinal  nerves,  eight  cer^^cal,  twelve 
dorsal,  five  lumbar,  five  sacral,  and  one  coccygeal.  Each  spinal 
nerve  (Fig.  'UO,  A  B)  arises  from  the  cord  by  an  anterior  and  a 
posterior  root,  tlie  latter  being  the  largest,  and  having  a  ganglion. 
Immediately  beyond  the  ganglion  the  two  roots  unite  into  a  single 
spinal  nerve,  which,  after  passing  out  of  the  spinal  canal  by  the  in- 
vertebral  foramen  (with  the  exception  of  the  sacral  and  coccygeal 
nerves,  which  divide  within  it),  divides  into  two  branches,  anterior 
and  posterior,  distributed  respectively  to  the  anterior  and  posterior 
portions  of  the  body,  the  anterior  branch  being  the  larger.  It  will 
be  observed  that  a  distinction  is  made  between  the  anterior  and 
posterior  roots  and  the  anterior  and  posterior  branches  of  a  spinal 
nerve.     This  distinction  is  a  most  important  one,  it  having  been 

Fig.  319. 


Different  views  of  a  portion  of  the  spinal  cord  from  the  cervical  region,  with  the  roots  of  the 
nerves  slightly  enlarged.  In  A,  the  anterior  surface  of  the  specimen  is  shown,  the  anterior 
nerve-root  of  its  right  side  being  divided  ;  in  B,  a  view  of  the  right  side  is  given  ;  iu  C  the  upper 
surface  is  shown  ;  in  D  the  uerve-roots  and  ganglion  are  sliowii  I'rom  below.  1.  The  anterior 
median  fissure.  2.  Posterior  median  fissure.  3.  Anterior  lateral  ikiiression,  over  which  the  an- 
terior nerve-roots  are  seen  to  spread.  4.  Posterior  lateral  groove,  into  which  the  posterior  roots 
are  seen  to  sink.  .'5.  Anterior  roots  passing  the  ganglion.  5'.  In  A,  the  anterior  root  divided.  6. 
The  posterior  roots,  the  fibers  of  which  pass  into  the  ganglion  6'.  7.  The  united  or  compound 
nerve.  7'.  The  posterior  primary  branch,  seen  in  A  and  1)  to  be  derived  in  part  from  the  anterior 
and  in  part  from  the  posterior  root.     (From  Quain.) 


well  established  that  the  anterior  root  is  purely  motor  in  function, 
and  the  posterior  root  purely  sensory,  whereas  the  anterior  branch, 
consisting  of  fibers  derived  from  both  the  anterior  and  posterior 
roots  will  be  found  to  be  both  motor  and  sensory  in  function,  and 
the  posterior  bran(!h  being  made  up  also  of  fibers  derived  from  both 
tlie  anterior  and  posterior  roots  is  also  motor  and  sensory  in  func- 
tion.    The  anterior  and  posterior  branches  of  a  spinal  nerve  are 


THE  SPINAL  COED  AND  NERVES. 


567 


therefore  mixed  in  their  function,  whereas  the  anterior  root  is  purely 
motor,  and  the  posterior  root  wholly  sensory. 

The  discovery  that  the  anterior  root  of  a  spinal  nerve  is  motor, 
the  posterior  root  sensory  in  function,  is  an  excellent  illustration  of 
the  indispensability  of  vivisection  as  a  means  of  research  in  physio- 
logical investigation — indeed,  it  is  difficult  to  conceive  how  the  dis- 
covery could  have  been  made  in  any  other  manner,  comparative 
anatomy,  from  the  nature  of  the  case,  throwing  no  light  upon  the 
question,  since  the  spinal  nerves  arise  Avith  the  exception,  perhaps, 
of  Amphioxus  in  a  similar  manner  in  all  vertebrates,  while  patholog- 
ical changes,  even  when  recorded  from  involving  both  roots  simul- 
taneously, rendered  such  data  of  little  or  no  use.  Such  being  the 
case,  the  only  available  means  of  investigation  was  experimental, 
and,  as  a  matter  of  fact,  it  was  by  such  means,  a  vivisection,  that 
Magendie  ^  first  demonstrated  the  function  of  the  roots  of  the  spinal 
nerves,  one  of  the  most  important  discoveries  ever  made  in  the 
whole  range  of  physiological  science.  The  experimental  procedure 
which  can  readily  be  repeated  is  as  follows :  The  vertebral  canal  being 
laid  open  and  the  spinal  cord  and  nerves  exposed  in  a  frog,  for  ex- 
ample, or  a  rabbit  or  dog,  the  anterior  roots  of  the  spinal  nerves  sup- 
plying the  lo\ver  extremity  are  divided.  Allowing  sufficient  time  to 
elapse  for  the  effect  of  shock,  hemerrhage,  etc.,  to  pass  off,  it  vnll 
be  observed  that  the  lower  extremity  on  the  same  side  as  that  on 
which  the  nerves  have 
been  divided  is  paralyzed 
so  far  as  regards  motion, 
sensation  remaining  intact. 
If,  however,  the  distal  end 
of  the  divided  anterior 
roots  (Fig.  320,  e)  be  now 
stimulated,  the  lower  ex- 
tremity will  be  at  once 
thrown  into  muscular  con- 
traction, whereas  no  effisct 
is  observed,  on  the  other 
hand,  of  a  motor  character, 
if  the  central  end  d  of  the 
divided  anterior  root  be 
stimulated.  These  |  facts 
show  conclusively  that  the 
functions  of  the  anterior 
roots  of  the  spinal  nerves 
are  motor,  and  that  the  stimulus  emanating  from  the  cord,  wdiatever 
its  nature  may  be,  is  transmitted  through  the  anterior  root  from  the 
center  to  the  periphery.  That  the  anterior  root  possesses  in  itself  no 
sensory  properties,  is  shown  from  the  fiict,  that  even  if  at  times  signs 
of  sensibility  manifest  themselves- on  its  stimulation,  such  sensibility 
1  Journal  de  Physiologie,  Paris,  1822,  Tome  ii.,  pp.  276-368. 


Fig.  320. 


Diagram  of  spinal  cord  and  nerves.     The  posterior  root 
is  seen  divided  at  a,  b,  the  anterior  at  c,  d. 


568 


THE  NERVOUS  SYSTEM. 


at  once  disappears  after  division  of  the  posterior  root.  The  sensi- 
bility occasionally  exhibited  on  stimulation  of  the  anterior  root  is 
due  either  to  muscular  cramp,  as  suggested  by  Brown-Sequard/  or 
to  the  recurring  fibers  passing  backward  from  the  anterior  root 
through  the  posterior  root  to  the  cord,  hence  the  name  of  "  re- 
current sensibility  "  given  to  the  phenomenon  by  Magendie  ^  and 
Longet.^  If,  now,  the  posterior  roots  of  the  spinal  nerves  in  the 
same  animal,  but  in  an  uninjured  one,  be  divided,  it  will  be  ob- 
served that  while  the  animal  retains  the  power  of  moving  the  lower 
extremity  it  has  lost  sensation  entirely  in  it,  and  that  while  no 
effect  is  observable  if  the  distal  end  (a,  Fig.  320)  of  the  divided 
posterior  root  be  stimulated,  sensibility  at  once  manifests  itself  if 
the  central  end  (6 j  of  the  same  be  stimulated,  showing  conclusively 
that  the  function  of  the  posterior  root  of  the  spinal  nerve  is  sensory, 
and  that  the  impression  made  upon  the  periphery  is  transmitted 
through  the  posterior  root  to  the  cord.  That  the  posterior  root 
possesses  in  itself  no  motor  properties  is  shown  from  the  fact  that 
if  the  anterior  root  be  divided  no  motion  ever  ensues  on  stimulating 
its  central  end  (b,  Fig.  320),  any  motion  ensuing  on  stimulation  of 
the  central  end  of  the  posterior  root  being  reflex  in  character,  a  kind  of 
recurrent  motility,  so  to  speak — that  is  to  say,  the  impression  made 
upon  the  central  end  of  the  divided  ])osterior  root  is  transmitted  to  the 
gray  matter  of  the  cord,  and  is  thence  reflected  out  through  the  an- 
terior root.  While  the  ganglion  already  mentioned,  so  characteristic 
of  the  posterior  roots  of  the  spinal  nerves,  does  not  appear  to  influ- 


FiG.  321. 


Degeneration  of  spinal  nerves  and  nerve  roots  after  section.  A.  Section  of  nerve  trunk  beyond 
the  ganglion.  B.  Section  of  anterior  root.  C.  Section  of  posterior  root.  D.  Excision  of  gan- 
glion,   a.  Anterior  root.    p.  Posterior  root.    (/.  Ganglion. 

ence  in  any  way  the  transmission  of  impressions  from  the  periphery 
to  the  centers,  it  does  exercise  a  very  great  influence  upon  the  nu- 
trition of  the  nerves  after  their  division.  Thus  it  has  been  shown 
by  Waller,^  if  the  anterior  root  be  divided  (B,  Fig.  321),  that  while 
the  central  end  of  the  anterior  root  preserves  its  normal  structure, 

'  Phyf^iologv  and  Pathology  of  the  Central  Nervous  System,  p.  8.  Philadelphia. 
1860.  '  K'omptesrendus,  T.  xxiv.,  p.  3.     Paris,  1847, 

'Bernard:  Sv.steme  Nerveux,  Tome  i.,  p.  35.  Paris,  1858.  Physiologie,  Tome 
iii.,  p.  115.     Paris,  1809. 

♦  Comptes  rendus,  Tome  xliv.,  p.  168.     Paris,  1857. 


FUNCTIONS  OF  SPINAL  GANGLIA.  509 

the  distal  end  degenerates,  exhibiting  the  usual  changes  undergone 
by  a  nerv^e  when  separated  from  its  center ;  whereas,  in  the  case  of 
the  posterior  root  being  divided  between  the  ganglion  and  the  cord 
(C,  Fig.  321),  it  is  the  distal  end,  that  attached  to  the  ganglion, 
which  remains  normal,  the  central  end  degenerating.  It  would 
appear,  therefore,  from  these  experiments,  that  the  ganglion  of  the 
posterior  roots  exerts  a  nutritive  influence  upon  the  sensitive  nerves, 
like  that  exerted  by  the  spinal  or  higher  centers  on  motor  ones,  and 
it  is  worthy  of  observation  that  the  degeneration  takes  place  in  the 
direction  in  which  the  nerve  force  is  transmitted.  In  this  connec- 
tion it  may  be  mentioned  also,  as  confirmatory  of  the  explanation 
offered  of  recurrent  sensibility,  that  if  the  posterior  root  be  divided 
beyond  the  ganglion  the  anterior  roots  will  then  be  found  to  contain 
degenerated  fibers,  showing  that  some  of  the  fibers  of  the  anterior 
root  at  least  are  really  derived  from  the  posterior  one. 

It  is  generally  held,  though  denied  by  some  physiologists,  that, 
while  the  gray  matter  of  the  cord  transmits  sensory  impressions,  it 
itself  appears  to  be  insensible  to  ordinary  mechanical  or  electrical 
stimuli,  since  it  may  be  pricked,  pinched,  or  electrically  stimulated 
without  the  animal  giving  any  signs  of  pain.  The  gray  matter 
can  be,  however,  excited  by  chemical  stimuli,  certain  poisons,  and 
venous  blood. 

It  has  already  been  mentioned  that  the  anterior  and  posterior  roots 
of  the  spinal  cord  do  not  consist  exclusively  of  purely  motor  and 
sensory  fibers.  Thus,  for  example,  the  vasomotor  and  sweat  fibers 
regulating  the  calibre  of  the  blood  vessels  and  the  production  of 
sweat,  leave  the  cord  by  the  anterior  root.  The  posterior  roots  con- 
tain also  fibers  which  pass  directly  or  indirectly  to  the  anterior  root, 
to  the  direct  cerebellar  tract  (Fig.  313),  and  through  the  column  of 
Burdach  to  the  column  of  Goll,  thence  to  the  clavate  nucleus  of  the 
medulla  ;  other  fibers,  ascending  the  posterior  columns,  cross  the 
middle  line  above  the  cuneate  and  clavated  nuclei  of  the  medulla 
and  pass  to  the  opposite  hemisphere. 

"While  there  can  be  no  doubt  that  the  spinal  cord  is  the  exclusive 
organ  of  communication  between  the  brain  and  the  periphery,  a 
complete  loss  of  sensibility,  voluntary  motion,  etc.,  following  its 
division,  compression,  or  disorganization,  there  still  prevails  some 
uncertainty  as  to  the  exact  routes  by  which  afferent  impressions 
made  upon  the  periphery  are  transmitted  from  the  posterior  roots 
through  the  cord  to  the  brain  and  efferent  impulses  in  the  reverse 
direction  through  the  anterior  roots  to  the  periphery. 

The  difference  of  opinion  held  in  this  respect  by  physiologists, 
the  diametrically  opposed  views  that  have  been  maintained,  are  no 
doubt  due  partly  to  the  fact  of  the  structure  of  the  spinal  cord  not 
yet  being  thoroughly  understood  either  in  man  or  animals,  but  also 
in  a  great  measure  to  the  conclusions  based  upon  exjieriments  per- 
formed upon  animals  being  applied  to  man  without  it  being  taken 
into  consideration  that  not  only  does  the  sjiinal  cord  of  animals  dif- 


570 


THE  NERVOUS  SYSTEM. 


fer  in  certain  respects  from  tliat  of  man,  but  that  it  varies  in  its 
structure  in  diiferent  parts  of  its  course  even  in  the  same  animal. 


Fig.  322. 


Pathways  of  Afferent  and  Efferent  Impulses  in  the  Cord. 

It  has  just  been  shown  by  histological  investigations  that  a  con- 
tinuous tract  of  nerve  fibers  exists  (Fig.  322),  extending  from  the 
cerebral  cortex,  ah,  through  the  corona  radiata,  internal  capsule, 

((ri),  crus,  pons  (P),  and  which 
arriving  at  the  medulla  traverses 
thence  as  the  direct  (6)  and  crossed 
pyramidal  tracts  (a),  the  anterior 
and  lateral  columns  of  the  cord, 
tlic  fibers  of  the  tracts,  or  rather 
tlieir  relays,  the  spinal  neurons, 
leaving  the  cord  (Fig.  313)  at  dif- 
ferent levels  as  the  anterior  roots 
to  terminate  in  striated  muscles. 
Such  being  the  disposition  of  the 
fibers  of  the  anterior  and  lateral 
columns  of  the  cord  in  reference 
to  the  anterior  roots  and  muscular 
system  it  might  be  inferred  that 
the  functions  of  these  columns  are 
to  a  great  extent  at  least  motor, 
subserving  the  transmission  of 
voluntary  impulses.  That  such  is 
the  case  is  shown  by  both  experi- 
mental and  pathological  evidence. 
Thus  if  a  section  be  made  of  the 
spinal  cord  of  an  animal,^  a  dog, 
rabbit,  or  guinea-pig  for  example, 
involving  only  the  lateral  col- 
umns, entire  loss  of  the  power  oi 
voluntary  motion  on  the  same 
side  will  be  observed  below  the 
level  of  the  section,  while  if  the 
columns  be  stimulated  at  their 
distal  ends,  the  muscles  supplied 
by  the  portion  of  the  cord  below 
the  section  will  be  thrown  into 
contraction. 

To  avoid  misunderstanding,  it 
may   be    stated    that    the   direct 
pyramidal  tract  exists  only  in  man  and  the  monkey,  that  it  extends 


A.R. 


Course  of  the  fibers  for  voluntary  move- 
ment, ah.  Path  for  the  motor  nerves  of  the 
trunk,  c.  Fil)urs  of  the  facial  nerve.  B.  Corpus 
callosum.  Nc.  Nucleus  caudatus.  Chi.  Interual 
capsule.  JV7,  Lenticular  nucleus.  P.  Pons ; 
Nf.  Original  of  the  facial.  I'y.  Pyramids  and 
their  discussion.  01.  Olive.  Gr.  Restiform 
body.  PR.  Posterior  root.  AR.  Anterior  root. 
X  crossed  and .-  direct  pyramidal  tracts.  (Lak- 

DOIS.) 


'In  making  sections  of  the  cord  in  an  animal  it  is  indispensable  that  the  spinal 
column  should  be  firmly  fixed,  and  that  the  cord  be  divided  witliin  certain  defined 
measurable  areas.  These  conditions  are  fulfilled  by  using  the  instrument  devised  by 
Ludwig  and  Woroschiloff,  and  described  in  Ludwig's  xVrbeiten,  1875,  s.  248. 


I 


EFFERENT  AND  AFFERENT  IMPULSES. 


oil 


in  man  only  to  aljout  the  middle  of  the  dorsal  region,  and  that  it 
contains  only  from  10  to  20  per  cent,  of  the  fibers  of  the  total  py- 
ramidal tract,  the  remaining  fibers  decussating  with  those  of  the 
opposite  side  as  the  crossed  pyramidal  tract.  Further,  as  the  vaso- 
motor and  sweat  fibers  traverse  the  lateral  columns,  leaving  the 
cord  by  the  anterior  roots,  division  of  those  columns,  as  in  the  case 
of  the  experiment  just  described,  will  involve  modifications  of  the 
blood  supply  and  the  production  of  sweat  below  the  level  of  the 
section.  Clinical  and  pathological  facts  also  confirm  the  view  that 
voluntary  impulses  are  transmitted  from  the  brain  to  the  periphery 
by  the  pyramidal  tracts.  Thus,  a  clot  in  the  internal  capsule  is 
followed  by  hemiplegia,  or  loss  of  voluntary  power  over  the  mus- 
cles of  the  opposite  side  of  the  body,  the  clot  blocking  the  trans- 
mission of  impulses  from  the  motor  areas  of  the  cortex  to  the  mus- 
cles. Further  destruction  of  the  motor  areas  of  the  cerebral  cortex 
involves  a  secondary  degeneration,^  which  progressing  downwards 
invades  successively  the  internal  capsule,  crus,  pons  medulla,  anterior 
columns  of  the  same  side,  and  the  lateral  columns  of  the  cord  of  the 
opposite  side  of  the  lesion,  the  nutrition  of  the  fibers  of  the  pyram- 
idal tract  being  governed  by  cerebral  cells,  just  as  the  fibers  of  the 
anterior  roots  are  governed  by  spinal  cells.  xVs  the  direction  in 
which  a  fiber  degenerates,  in  the  case  of  a  motor  nerve  at  least,  is 
the  same  as  that  in  which  it  conducts,  it  is  inferred  that  the  fibers 
of  the  pyramidal  tracts  are  efferent  in  function,  conducting  motor 
impulses  from  the  brain  to  the  periphery. 

It  is  interesting,  in  this  connection,  as  offering  an  explanation  of 
the  fact  that  the  movements  of  both  halves  of  the  body  are  con- 
trolled by  one  hemisphere,  that,  in  cases  of  secondary  descending 
degeneration    of    the    cord,    degenerated 
fibers    have  been  found    in  both   crossed  Fig.  .323. 

pyramidal  tracts,  the  pyramidal  fibers  ap- 
pearing to  divide  into  branches,  "  geminal 
fibers,"  ^  one  branch  passing  to  the  op- 
posite side  of  the  cord,  the  other  continu- 
ing: in  the  original  direction  on  the  same 


side.  Although  our  knowledge  of  the 
sensory  pathways  in  the  cord  is  far  less 
definite  than  that  of  the  motor  ones,  both 
experimental  and  clinical  investigation 
show  that  the  fibers  of  the  posterior  roots, 
which  cross  the  middle  line  of  the  cord 
and  ascend  in  the  anterior  and  antero- 
lateral columns  (Fig.  313,  4,  5),  are  those 
that  convey  afferent  impulses  to  the  sen- 
sory areas  of  the  brain.  Thus,  for  example,  a  hemisection  of  the 
cord  made  in  a  dog  at  the  level  of  3  (Fig.  323)  is  followed  by  loss 
of  sensibility  on  the  opposite  side  of  the  body  and  loss  of  voluntary 
'Turck,  Wiener  Sitzberichte,  1851,  s.  289.  ^  f^herriiigton. 


Diagram  showiug  the  course  of 
the  motor  and  sensory  fibers  in 
the  spinal  cord  and  medulla 
oblongata. 


572  THE  NERVOUS  SYSTEM. 

motion  on  the  same  side.  If  the  section  be  made,  however,  at  a 
higher  level,  as  at  1  or  2,  then  the  paralysis  of  both  motion  and 
sensation  will  be  on  the  same  side  of  the  body,  but  on  the  opposite 
side  to  that  of  the  section.  It  follows,  also,  that  if  the  spinal 
cord  be  divided  longitudinally  below  the  medulla,  that  while  the 
animal  is  able  to  stand  on  his  four  legs  and  make  voluntary  move- 
ments, as  first  shown  by  Galen,^  it  has  lost  all  sensibility  in  them, 
all  the  sensory  fibers  being  divided  at  their  decussation  in  the 
middle  line,  the  motor  fibers  remaining  uninjured  by  the  section. 

Unilateral  lesions  of  the  spinal  cord  in  man  confirm  the  view,  as 
learned  from  experiments  upon  animals,  that  the  sensory  pathways 
in  the  cord  lie  in  the  lateral  columns.  Thus,  in  the  case  reported 
by  Gowers,"  in  which  the  lateral  column  and  gray  matter  of  the 
upper  cervical  region  of  the  cord  was  wounded  by  a  spicule  of  bone, 
entire  loss  of  sensibility  to  pain  was  observed  on  the  opposite  side 
of  the  body. 

While  there  can  be  but  little  doubt  that  the  decussation  of  the 
sensory  fibers  in  the  spinal  cord  of  man  is  complete,  such  does  not 
obtain,  to  the  same  extent,  in  all  auimals,  the  decussation  being 
much  less  complete  in  mammals,  reptiles,  and  birds  than  in  man, 
and  less  in  the  lumbar  than  in  the  dorsal  portions  of  the  cord  in 
certain  animals.  In  connection  with  the  aniesthesia  of  the  opposite 
side  of  the  body  following  a  hemisection  of  the  cord  may  be  here 
appropriately  mentioned  the  hypersesthesia  usually  developed  in  the 
same  side  as  that  of  the  section.  This  remarkable  condition  of 
excited  sensibility,  made  quite  evident  within  a  few  hours  after  the 
operation  by  the  movements  of  the  animal  made  in  response  to  the 
slightest  pinching,  etc.,  of  the  skin,  and  lasting  often  for  weeks,  is 
probably  due  to  the  increase  in  temperature  and  vascularity  brought 
about  by  the  division  of  the  vasomotor  nerves,  or  the  nerves  regu- 
lating the  caliber  of  the  blood  vessels,  which,  we  shall  see  hereafter, 
descending  from  the  vasomotor  center  in  the  medulla  oblongata 
through  the, ante ro-lateral  columns,  but  is  also,  no  doubt,  to  be  at- 
tributed to  the  division  of  the  inhibitory  or  restricting  fibers,  whose 
influence  being  lost,  therefore,  upon  the  parts  below  the  section,  the 
latter  become  more  excitable,  more  susceptil^le  to  external  stimulus. 

Attempts  have  been  made  by  physiologists  to  prove  that  there 
exist  in  the  cord  distinct  pathways  for  the  impulses  giving  rise  to 
the  sensations  of  pressure,  heat,  and  cold,  entirely  independent  of 
those  transmitting  the  impulses  giving  rise  to  pain.  Even  if  such 
should  prove  hereafter  to  be  the  case,  it  is  more  probable  that  the 
above  sensations,  when  suflficieutly  intense,  give  rise  to  pain  than 

'De  Anat.  Administrat,  Lib.  viii.,  Caji.  v.,  Opera  Omnia,  T.  ii.,  p.  683.  Lips., 
1821.  Galen  does  not  appear,  however,  to  have  observed  the  h)ss  of  sensibility  in 
such  cases,  whicli  was  fii-st  observed  by  Fodera  in  1822,  Journal  de  Physiologie,  T. 
iii.,  p.  199.     Paris,  1823. 

2 Clinical  Society's  Trans.,  Vol.  xi.,  1878,  p.  24.  Since  the  above  was  written 
two  cases  of  pistol-shot  wounds  have  been  reported  l)y  D.  II.  W.  Cushing  (American 
Journal  of  the  Medical  Sciences,  June,  1898)  Avhicli  confirm  still  further  the  views 
expressed  in  the  text  as  to  the  avenues  of  tactile  sensations. 


PA  THWA  YS  OF  TA  CTIL  E  SENS  A  TIONS.  o  /  :3 

that  special  "specific"  pain  fibers  exist  in  the  cord.  A  very 
marked  distinction  exists,  however,  between  general  and  tactile 
sensibility — the  ability  to  feel,  to  appreciate — a  sensation  not  neces- 
sarily enabling  one  to  localize  it.  It  wonld  appear,  therefore,  that 
there  must  be  distinct  pathways  for  the  transmission  of  impulses 
giving  rise  to  tactile  sensations  and  such  seems  to  be  the  function 
of  the  fibers,  already  referred  to,  which,  traversing  the  posterior 
columns  of  the  cord,  cross  the  middle  line  high  up  above  the  cuneate 
and  clavate  nuclei  and  pass  to  the  opposite  hemisphere.  At  least 
in  cases  like  that  described  by  Miiller,'  in  which  the  whole  of  one- 
half  of  the  cord  and  the  posterior  column  of  the  other  half  was 
divided  by  a  stab-wound  ;  while  loss  of  sensibility  of  pain  was  con- 
fined to  the  side  opposite  the  lesion,  loss  of  the  sense  of  touch  ex- 


Transverse  section  of  spinal  cord,  showing  the  degeneration  tracts,  and  the  paths  that  do  not 
undergo  degeneration  in  the  cord.  A.VF.  Anterior  median  tissu re.  i>Pr  and  OPT.  Direct  and 
crossed  pyramidal  tracts.  AJi  and  PR.  Anterior  and  posterior  roots.  AAL  nud  DAL.  Ascend- 
ing and  descending  antero-lateral  tracts.  CT.  Cerebellar  tract.  D.  Comma-shaped  tract.  PMZ. 
Posterior  marginal  zone.  PEC.  Column  of  Burdach.  GC.  Column  of  Goll.  The  jjarts  left  white 
do  not  undergo  degeneration.     (Laxdois. ) 

isted  on  both  sides.  It  may  be  mentioned,  as  confirming  the  view 
that  the  avenues  for  tactile  semsation  lie  in  the  posterior  columns  of 
the  cord,  that  in  the  case  of  Gowers,  just  mentioned,  in  which  the 
posterior  column  was  only  cedematous,  tactile  sensibility  was  unim- 
paired. 

While  unilateral  lesions  of  the  spinal  cord,  such  as  those  just  men- 
tioned, show  that  in  man  at  least  the  paths  for  the  conduction  of  aU 
forms  of  sensory  impulses  decussate  in  the  cord,  clinical  and  ex- 
perimental investigations  prove  that  the  paths  for  the  impulses  from 
the  muscles  lie  in  the  columns   of  Goll  (GC,  Fig.  324),  of  the  same 

'  Beitriijfe  zur  Path.  Anat.  u.  Phvs.  der  Kiickenmark,  1871  ;  Kobner,  Deut. 
Arch.  f.  klin.  Med.,  Band  xix.,  1877,  s.  190. 


574 


rUE  NERVOUS  SYSTEM. 


Fig.    325. 


side  of  the  cord.  Thus,  if  the  posterior  roots  be  attacked  l)y  dis- 
ease, as  in  locomotor  ataxia,  or  divided  experimentally  in  animals, 
the  secondary  degeneration  so  arising  will  be  ascending,  will  pro- 
gress centripctally  along  the  nerve  roots  to  the  cord  upwards  through 
the  so-called  Lissauer's  zone  in  Burdach's  column  [PEC]  for  a  short 
distance,  and  passing  thence  into  the  columns  of  Goll  {GC),  will  as- 
cend on  the  same  side  of  the  cord  to  the  clavate  nucleus  of  the 
medulla.      It  is  an  interesting  fact  that  disease  of  the  columns  of 

Goll  is  followed  by  defect  of 
muscular  coordination,  re- 
sembling so  closely  that  due 
to  disease  of  the  cerebellum 
as  to  admit  of  no  doubt  that 
the  impulses  determining 
cerebral  coordination  pass 
from  the  muscles  by  the 
columns  of  Goll  to  the  cla- 
vate nucleus  of  the  medulla, 
and  thence  by  relay  fibers 
through  the  cerebellum  to 
the  cortex. 

If  the  disposition  of  the 
sensory  tracts  be  such  as  just 
described,  it  will  be  observed 
that  the  sensory  resemble 
the  motor  tracts  in  that,  of 
the  two  sensory  tracts,  one, 
the  sensory,  crossesthe 
middle  line  of  the  cord  at  all 
levels,  the  other,  the  tactile, 
at  the  medulla  in  black,  just 
as,  of  the  two  motor  tracts, 
one,  the  direct  pyramidal, 
crosses  the  middle  line  of  the 
cord  at  all  levels,  the  other, 
the  'irossed  pyramidal  tract, 
at  the  medulla  in  block. ^ 

That  such  is  the  case  is 
further  shown  l)y  the  fact 
that  division  of  the  columns 
of  Goll  in  animals  is  followed 
by  defects  of  coordination  similar  to  that  due  to  loss  of  the  cerebel- 
lum. While  the  function  of  the  direct  cerebellar  tract  (Fig.  324, 
CT)  cannot  yet  be  said  to  have  been  demonstrated,  the  fact  of  its 
fibers  passing  by  way  of  the  restiform  body  to  the  middle  lobe  of  the 
cerebellmn  and  thence  by  the  superior  peduncle  to  the  opposite  hemi- 

'  Van  Gehuchten,  Anatomic  Du  Systeme  Nerveux  De  L' Homme,   Deuxieme 
Edition,  1897,  p.  758. 


Diagram  showing  pathway  of  the  sensory  impulses. 
On  the  left  side  S  S'  represent  aflferent  spinal  nerve 
fibers  ;  (',  an  afferent  cranial  nerve  fiber.  These  fibers 
terminate  near  central  cells,  the  neuron  S  of  which 
cross  the  middle  line  and  end  in  the  opposite  hemi- 
sphere.    (Van  Geiiuciitkn.) 


FUyCTION  OF  COLUMXS  OF  COED.  0/0 

sphere,  render  it  highly  probable  at  least  that  they  also  convey  im- 
pulses from  the  muscles  of  the  lower  part  of  the  trunk,  and  from 
between  the  trunk  and  the  lower  limbs,  and  possibly  from  the  viscera. 
That  the  fibers  of  the  direct  cerebellar  tract  are  at  least  centripetal  in 
function,  convey  impulses  from  the  periphery  to  the  brain,  is  shown 
by  the  fact  that  secondary  degeneration,  when  arising  in  this  tract, 
ascends  to  the  medulla.  In  addition  to  the  fibers,  already  described, 
that  pass  continuously  from  the  posterior  roots  to  the  columns  of 
Burdach,  to  the  columns  of  Goll,  the  columns  of  Burdach  contain 
short  vertical  fibers  connecting  apparently  the  gray  matter  of  the  pos- 
terior cornu  at  different  Ijut  adjacent  levels,  which  possibly  have  a 
commissural  or  coordinating  function.  It  may  be  here  mentioned 
that  if  such  be  the  case  it  is  quite  possible  that  those  portions  of 
the  anterior  columns  not  containing  the  efferent  fibers  of  the  an- 
terior roots,  may  have  similiar  functions.  Of  the  functions  of  the 
remaining  tracts  of  the  cord,  still  undescribcd,  the  ascending  antero- 
lateral tract  (Fig.  324,  AAL)  of  Gowers  and  the  descending  antero- 
lateral tract  [DAL),  and  the  so-called  comma  tract  (D)  in  the  column 
of  Burdach,  little  or  nothing  is  known.  That  the  ascending  and 
descending  antero-lateral  tracts  convey  impulses  from  the  periphery 
to  the  brain  and  the  brain  from  the  periphery  respectively,  is  shown 
by  the  fact  that  secondary  degeneration  arising  in  these  tracts  pro- 
gresses centripetally  in  the  former  and  centrifugally  in  the  latter. 
It  is  possible,  therefore,  that  sensory  impulses  may  ascend  in  part 
through  the  ascending  antero-lateral  tract  of  Gowers.  The  de- 
scending comma  tract  hardly  deserves  the  name  of  a  tract,  extend- 
ing but  a  short  distance  through  the  cord  after  section,  and  consists 
probably  of  fibers  of  the  posterior  root,  which  take  a  descending 
course  after  entering  the  cord.  That  the  spinal  cord  consists  of 
tracts,  such  as  those  just  described,  is  further  proved  by  the  man- 
ner in  which  the  cord  develops.  Thus  it  has  been  shown  by  Flech- 
sig  ^  that  the  fibers  of  the  cord  get  their  covering  of  myelin  at  dif- 
ferent periods  of  development,  the  fibers  having  the  longest  course 
becoming  medullated  latest. 

In  conclusion  it  will  be  seen  from  Fig.  324  that  there  still  remain 
areas  of  fibers  (unshaded)  which  do  not  degenerate  after  section,  in- 
jury, or  disease  of  the  cord,  and  whose  functions  have  not  as  yet 
been  determined.  It  must  be  mentioned  in  connection  with  what  has 
been  said  as  to  the  result  of  division  and  disease  of  different  parts  of 
the  spinal  cord,  that,  from  the  fact  of  the  loss  of  the  power  of  volun- 
tary motion  and  sensation  being  frequently  restored,  there  must  ex- 
ist potentially,  so  to  speak,  a  vicarious  power  of  interchange  of 
function  between  different  parts  of  the  cord,  certain  fibers  being 
capable  of  assuming  the  transmitting  of  sensory  and  motor  impulses 
in  addition  to  their  ordinary  functions.  Although  the  distribution 
of  the  spinal  nerves  will  be  found  in  any  treatise  on  anatomy  a 
brief  resume  of  the  same  is  here  offered  as  illustrating  their  general 
*  Die  Leitungsbahnen  ini  Gehirn  und  Riickenmark  des  Meuschen,  1876. 


o76  THE  NERVOrS  SYSTEM. 

functions.  It  should  be  borne  in  mind  that  the  branches  of  the 
spinal  nerves,  whether  anterior  or  posterior,  are  in  their  functions 
mixed  nerves,  possessing  both  motor  and  sensory  properties.  The 
anterior  branches  of  the  four  upper  cervical  nerves  form  the  cervical 
plexus,  and  the  four  lower  cervical,  together  with  the  first  dorsal 
nerve,  the  bracliial  plexus.  From  the  cervical  plexus  are  derived 
the  superficial  cervical,  great  auricular,  small  occipital,  supracla- 
vicular, and  phrenic  nerves,  and  muscular  branches  ;  the  brachial 
plexus  supplying  mainly  the  upper  extremity,  but  giving  off,  also, 
the  supra-  and  subscapular  and  thoracic  nerves.  The  posterior 
branches  of  the  cervical  nerves,  with  the  exception  of  the  first,  after 
passing  backward  from  the  vertebral  canal,  divide  into  external  and 
internal  branches,  and  supply  the  muscles  and  integument  behind 
the  spinal  column,  the  posterior  branch  of  the  first  cervical  issuing 
between  the  arch  of  the  atlas  and  the  vertebral  artery,  being  dis- 
tributed to  the  contiguous  straight,  oblique,  and  complex  muscles. 
The  anterior  branches  of  the  dorsal  or  thoracic  nerves,  with  the 
exception  of  the  last  one,  pass  outwardly  in  the  intercostal  spaces, 
as  the  intercostal  nerves,  the  anterior  branch  of  the  last  dorsal,  be- 
ing situated  below  the  last  rib,  crosses  the  quadrate  lumbar  muscle 
as  it  advances  between  the  internal  oblique  and  transverse  muscle 
in  a  similar  manner  as  an  intercostal  nerve.  In  their  course  the 
intercostal  nerves,  as  they  supply  the  muscles,  give  off  lateral 
cutaneous  branches,  that  from  the  second  intercostal  or  the  inter- 
costo-humeral  nerve  being  an  important  one,  since  it  extends  across 
the  axillary  space,  running  in  juxtaposition  with  the  small  cuta- 
neous nerve  from  the  brachial  plexus,  and  supplies  the  skin  on  the 
inner  part  of  the  arm.  The  posterior  branches  of  the  dorsal  nerves, 
like  those  of  the  spinal  nerves  generally,  after  turning  backward 
between  the  transverse  processes  of  the  vertebra?,  divide  into  exter- 
nal and  internal  branches,  the  former  supplying  the  skin  contiguous 
to  the  angle  of  the  ribs,  the  longissimus  and  sacro-lumbar  muscles, 
the  latter  the  skin  over  the  spinous  processes  of  the  vertebrae,  the 
multifid  and  semispinal  muscles.  The  anterior  branches  of  the  up- 
per four  lumbar  nerves,  together  with  a  filament  from  the  last  dor- 
sal nerve,  constitute  the  lumbar  plexus,  and  which,  after  supplying 
the  psoas  and  quadrate  lumbar  muscles,  give  off  the  ilio-hypogas- 
tric,  ilio-inguinal,  genito-crural,  external  cutaneous,  obturator  and 
anterior  crural  nerves.  The  posterior  branches  of  the  lumbar 
nerves  pass  backward,  like  those  of  the  dorsal,  to  supply  the  longis- 
simus and  sacro-lumbar  muscles,  and  the  adjacent  skin.  The  ante- 
rior branches  of  the  up})er  four  sacral  nerves,  together  with  the  fifth 
and  part  of  the  fourth  lumbar  nerves,  form  the  sacral  plexus,  from 
which  are  derived  the  filaments  supplying  the  pyriform,  internal 
obturator  muscles,  etc.,  the  levator  and  sphincter  ani,  the  superior 
gluteal,  pudic,  and  great  and  small  sciatic  nerves.  The  sacral,  to- 
gether with  the  lumbar  plexus,  give  off  the  nerves  supplying  the 
lower  extremity.     The  anterior  branch  of  the  fifth  sacral,  a  small 


SPIXAL  NERVES.  577 

nerve,  emerges  from  the  end  of  the  vertebral  canal,  and  divides  into 
two  branches,  one  of  which  passes  with  a  filament  from  the  fourth  sa- 
cral to  end  in  the  sympathetic,  the  other  joining  the  coccygeal  nerve. 
While  the  posterior  branches  of  the  upper  four  sacral  nerves  pass 
out  of  the  vertebral  canal  by  the  corresponding  sacral  foramina,  the 
posterior  branch  of  the  fifth  sacral  emerges  from  the  end  of  the 
vertebral  canal  and  together  with  the  posterior  branch  of  the  coccyg- 
eal nerve  supplies  the  skin  and  muscles  of  the  back.  The  ante- 
rior branch  of  the  coccygeal  nerve  also  passes  out  of  the  end  of  the 
vertebral  canal,  is  joined  by  a  branch  from  the  fifth  sacral  after  perfo- 
rating the  coccygeal  muscle  and  the  great  sacro-sciatic  ligament,  and 
terminates  in  the  skin  of  the  buttock.  The  posterior  branch  of  the 
coccygeal,  like  the  anterior  branch,  emerges  from  the  end  of  the 
vertebral  canal ;  its  distribution  has  just  been  referred  to  in  con- 
nection with  that  of  the  posterior  branch  of  the  fifth  sacral. 

37 


CHAPTER   XX  XL 

THE  NERVOUS  SYSTEM.— {Continued.) 


DIVISION    OF    LABOR    IN    ANIMALS    AND    MAN.     REFLEX 

AUTOMATIC    AND    NUTRITIVE    FUNCTIONS    OF 

SPINAL    CORD. 

One  of  the  most  striking  differences  in  the  organization  of 
animals  is  the  extent  to  which  the  division  of  labor,  physiologically 
speaking,  is  carried.  Indeed,  the  lowest  forms  of  life,  such  as  the 
monera,  consisting,  as  we  have  seen,  of  mere  masses  of  protoplasm, 
are  so  utterly  unorganized  as  to  make  it  impossible  to  say  whether 
such  beings  should  be  assigned  genealogically  to  the  vegetable  or 
animal  kingdom.  It  is  true,  that  among  such  primitive  forms  of 
life  there  are  beings,  like  the  common  amoeba,  in  which  there  is 
a  slight  differentiation  of  structure,  in  that  not  only  a  nucleus 
and  nucleolus  are  present,  but  even  an  enveloping  membrane  or 
cell  wall  may  be  developed,  and  that  among  the  infusoria  are  also 
seen  forms,  like  paramcecium,  apparently  quite  organized  ;  never- 
theless, even  these  protozoan  animalculse,  so  much  more  complex 
in  their  structure  than  the  monera,  cannot  be  said  to  be  organized 
in  the  same  sense  that  the  remaining  members  of  the  animal  king- 
dom, or  metazoa,  are.  Even  the  infusoria,  apparently  complex  as 
they  are  in  their  structure,  are  morphologically  only  unicellular, 
and  never  passing  beyond  this  primitive  one-celled  stage  ;  tissues, 

and  still  loss  organs,  are  never  developed 
in  them  similar  to  those  of  which  the 
body  of  one  of  the  higher  animals  is  made 
up,  since,  as  we  have  already  seen,  the 
organs  in  the  latter  consist  of  tissues  and 
the  tissues  of  cells,  the  latter  resulting 
from  the  division  of  the  primitive  cell. 
Indeed,  it  is  not  until  we  reach  in  the 
tree  of  life  the  porifera,  actinozoa,  and 
hydrozoa,  of  which  the  sponge,  anemone, 
and  jelly  fish,  familiar  objects  at  the  sea- 
shore, are  examples,  that  we  meet  with 
anything  like  organization,  at  least  in  the 
true  morphological  sense  of  the  word — 
that  is  to  say,  of  an  animal  consisting  of 
organs,  made  uj)  of  tissues,  developed  out 
of  cells  resulting  from  the  segmentation 
of  a  primitive  cell,  or  ovum.  Suppose  that  the  structure  of  one 
■of  the  hydrozoa  be  considered,  as  tliat  of  the  common  green  hydra 
(Fig.  326),  found  during  the  summer  in  almost  every  fresh-water 


Fig.  326. 


Hydra.     (Milne  Kdwauds.  ) 


THE  HYDRA. 


579 


Fig.  327. 


pool,  and  therefore  an  object  for  study  accessible  to  all,  it  will  be 
found  that  the  animal,  about  half  an  inch  in  length  and  a  line  in 
diameter,  is  essentially  a  double-layered  tube,  closed  at  one  end  and 
open  at  the  other,  the  latter  serving  as  a  mouth  and  surrounded 
with  delicate  tentacles,  or  feelers,  by  means  of  which  it  seizes  its 
prey,  the  outer  layer,  or  ectoderm,  of  the  tube,  functionating  as 
skin,  the  inner  layer,  or  endoderm,  as  a  mucous  digestive  surface. 

Leaving  out  of  consideration  an  imperfectly  developed  neuro- 
muscular layer  or  mesoderm  intermediate  between  the  ectoderm  and 
endoderm  (absent  in  the  protohydra),  the  hydra  may  be  considered 
fanctionally  as  little  more  than  a  digestive  sac.  That  the  differen- 
tiation of  ectoderm  and  endoderm  is  very  incomplete,  is  shown  from 
the  fact  that  if  the  animal  be  turned  inside  out  the  skin  or  ectoderm 
becomes  digestive  in  function,  and  the  digestive  surface  or  endoderm 
epidermal,  just  as  the  mucous  membrane 
of  the  mouth  or  anus  in  man  may  become 
skin  if  everted,  or  the  skin  of  the  same 
parts  mucous  membrane  if  inverted.  This 
is,  however,  as  might  have  been  expected, 
since,  as  we  shall  see  hereafter,  there  can 
be  little  doubt  but  that  the  ectoderm  and 
endoderm  of  the  hydra  are  homologous 
with  the  epiblast  and  hypoblast  of  the  em- 
bryo, or  the  parts  corresponding  to  the 
skin  and  mucous  membrane  of  the  adult. 
Further,  that  no  one  part  of  the  hydra 
differs  essentially  from  any  other  part,  is 
shown  by  the  well-established  fact  that  if 
a  hydra  be  cut  up  into  several  pieces  each 
piece  will  live  and  lead  an  independent 
existence  and  develop  into  a  perfect  hydra. 
While,  at  first  sight,  such  a  result  may 
appear  as  a  very  extraordinary  one,  it  be- 
comes a  perfectly  natural  and  intelligible 
one  when  it  is  remembered  that  all  parts 
of  the  body  of  the  hydra  have  essentially 
the  same  function,  and  that  there  is  no  in- 
terdependence between  the  parts  of  which 
it  consists.  Reproduction  by  fission, 
Avhether  produced  artificially  or  naturally, 
is  not  confined,  however,  by  any  means  to 
such  low  forms  of  life  as  the  hydra,  being  observed  as  well  in  quite 
highly  organized  animals,  as  among  the  annelida,  of  which  the  ma- 
rine worms,  such  as  the  clam  worm  (x^ereis  pelagica)  of  our  coasts 
(Fig.  327),  etc.,  are  examples.  The  body  of  a  nereid  worm,  con- 
sisting of  numerous  segments,  is  naturally  very  apt  to  break  up  into 
numerous  pieces  consisting  of  one  or  more  of  the  segments,  as  the 
animal  glides  along  among  the  rocks,  sand,  or  seaweed,  each  piece 
becoming,  under  favorable  circumstances,  a  perfect  animal.     In- 


Clam  worm.    Kereis  pelagica. 


580  THE  NERVOUS  SYSTEM. 

deed,  at  certain  seasons  of  the  year  there  may  be  seen  in  certain 
kinds  of  these  worms  (Protnla)  at  different  portions  of  the  body  con- 
strictions indicating  the  parts  where  the  body  will  break  np,  by 
natural  fission,  into  a  progeny  of  worms.  That  snch  a  mode  of  re- 
production should  take  place  in  an  animal  as  highly  organized  a& 
those  just  mentioned,  having  a  distinct  body  cavity  inclosing  a 
nervous  system,  alimentary  canal,  heart,  may  appear  even  more 
extraordinary  than  the  case  of  the  hydra  just  referred  to.  It  must 
be  borne  in  mind,  however,  that  in  the  worm,  as  in  the  hydra,  there 
is  but  little  interdependence  of  parts,  each  segment  having  its  own 
nervous  ganglion  and  fractional  part,  so  to  speak,  of  the  alimentary 
canal  and  vascular  tubes  running  from  end  to  end  of  the  animal. 
In  fact,  an  annelid  may  be  regarded,  inorphologically,  as  consisting^ 
of  a  chain  of  small  annelids  (the  segments  depending  but  little  upon 
each  other,  linked  together,  as  it  were,  for  only  the  time  being).  A 
glance  now  at  the  organization  of  a  vertebrate  animal,  or  even  one 
of  the  higher  invertebrates,  will  at  once  show  how  profoundly  such 
an  animal  differs  from  any  of  those  hitherto  mentioned.  The  brain, 
as  in  man,  for  example,  situated  in  the  skull,  depending  for  its  ac- 
tivity upon  the  blood  driven  to  it  by  the  heart  in  the  thoracic 
cavity,  the  rhythmical  action  of  the  heart  and  lungs  maintained  by 
nervous  influences  emanating  from  the  base  of  the  brain,  the  ali- 
mentary canal  within  the  abdominal  cavity  supplying  the  materials 
for  the  nourishment  of  the  brain  and  other  organs,  but  dependent 
upon  the  blood  supplied  to  it  by  the  heart  for  the  elaboration  of  the 
alimentary  secretions,  illustrating  sufficiently  how  intimate  is  the 
connection  existing  between  the  cranial,  thoracic,  and  abdominal 
organs,  and  the  impossibility  of  any  one  segment  of  the  body  con- 
taining such,  living  a  life  entirely  independent  of  the  remaining^ 
ones,  as  we  have  just  seen  is  the  case  in  many  of  the  lower  animals. 
This  contrast  between  the  lower  and  higher  animals  with  reference 
to  the  extent  with  which  the  division  of  labor  is  carried  on,  is  well 
illustrated  by  the  difference  between  the  savage  and  civilized  state 
of  society — and,  indeed,  the  difference  is  something  more  than  a 
mere  comparison,  being  of  a  profound  meaning  to  those  who  believe 
that  the  life  of  a  nation  is  developed  according  to  law  as  certainly 
as  that  of  tlie  individuals  of  which  it  is  composed. 

In  the  uncivilized,  savage  state,  each  individual  is  independent 
of  his  neighbors  as  the  one  segment  of  the  worm  may  be  to  that  of 
the  other  ;  his  interest  not  being  usually  their  interest — on  the  con- 
trary, often  antagonistic — he  builds  his  simple  hut,  hunts  his  own 
game,  clothes  himself;  a  birth  among  his  tribe  adds  to,  a  death 
takes  away  nothing,  from  his  daily  life.  Under  such  circumstances 
there  can  be  no  accumulation  of  wealth  and  the  development  inci- 
dental to  it.  In  the  civilized  state,  on  the  contrary,  the  interest  of 
the  one  is  the  interest  of  all,  as  that  of  the  one  organ  in  the  human 
body  is  that  of  the  others  ;  each  individual  confining  himself  to 
one  avocation,  the  latter  is  advanced  to  its  utmost  limits,  de])end- 
ing  upon  others  for  that  which  he  does  not   produce  himself,  the 


DIVISION  OF  LABOR  IN  ANIMALS.  581 

product  of  his  own  industry  reaches  the  highest  perfection  ;  and  so 
with  the  productions  of  others,  and  thus  the  wealth  of  the  nation 
increases  both  in  variety  and  amount.  Just  as  with  the  unciviHzed, 
as  compared  with  tlie  civilized,  so  with  the  lower  animals  as  com- 
pared with  the  higher  ones  ;  just  as  the  development  of  a  nation 
depends,  not  only  upon  the  variety  of  the  interests,  but  upon  the 
mutual  interdependence  of  the  same  ;  so  the  life  of  an  animal  is 
high  in  proportion  to  the  variety  of  its  organs,  and  the  mutual 
harmonious  working  of  the  same.  The  famous  example  of  the 
number  of  persons  engaged  in  the  making  of  nails  or  pins,  and  the 
great  number  that  can,  consequently,  be  so  produced,  as  mentioned 
by  Adam  Smith,^  is  as  applicable  as  illustrating  biological  as  well 
as  politico-economical  laws.  The  life  of  a  man  biologically  as  well 
as  socially,  when  compared  with  that  of  a  sponge,  may  be  summed 
up  in  saying  that  in  the  former  the  division  of  labor  is  carried,  so 
far  as  we  yet  know,  to  its  utmost  limits ;  in  the  latter  but  little,  if 
at  all.  This  division  of  labor,  so  characteristic  of  the  higher  ani- 
mals, and  which  we  have  illustrated  on  account  of  its  importance 
somewhat  in  detail,  is  not  only  well  seen  in  the  general  organiza- 
tion of  the  higher  animals,  but  in  the  extreme  differentiation  ex- 
hibited in  their  alimentary,  vascular,  nervous 
systems,  etc.,  and  as  it  is  the  functions  of  the  Fig.  328. 

latter  that  we  are  now  more  particularly  con- 
sidering, it  will  be  well  to  illustrate  the  general 
structure  of  the  nervous  system  in  animals  by 
a  few  examples  before  taking  up  the  considera- 
tion of  the  subject  of  the  reflex  action  of  the 
spinal  cord  of  man,  the  nature  of  which  it  is 
hoped  will  be  made  clearer  by  the  preceding 
introductory  than  it  would  have  been  without  it. 
Of  the  simplest  form  of  nervous  system  may 
be  mentioned  that  of  the  ascidioida,  as  seen, 
for  example,  in  a  phalusia,  in  which  the  entire 
nervous  system  consists  (Fig.  328)  of  a  single       Nervous  system  of  au 

T  ■  ..  •     •  £o  ji-\  ±     r  ascidiau.    A.  The  mouth. 

ganglion,  receiving  or  giving  otr  nlaments  irom  b  The  vent.  c.  The 
or  to  the  periphery.  On  touching  this  worm-  fl^f,^^',  "•  '^^^  """'' 
like  animal,  and  seeing  it  contract  its  body, 

judging  from  one's  own  feelings  and  actions,  we  would  infer  that 
the  animal  felt  the  touch  and  voluntarily  retracted  its  body,  and 
conclude  that  the  impression  made  upon  the  integument  was  trans- 
mitted by  an  afferent  centripetal,  or  sensory  nerve,  to  the  ganglion, 
and  there  felt,  and  that  the  impulse  emanating  from  the  latter  was 
transmitted  by  an  efferent,  or  centrifugal,  or  motor  nerve  to  the 
muscle,  and  there  resulted  in  voluntary  motion,  the  whole  action 
being  called  a  reflex  one  from  the  fact  of  the  impression  made  upon 
the  periphery  being  first  transmitted  to  the  ganglion  and  thence  re- 
flected back  again.     If  the  ganglion  be  not  endowed  with  sensation 

1  An  Inquiry  into  the  Nature  and  Causes  of  the  Wealth  of  Nations,  Vol.  i.,  p. 
7.     Edinburgh,   1814. 


582  THE  NERVOUS  SYSTEM. 

aucl  volition,  then  the  animal  mnst  be  withont  either,  since  it  pos- 
sesses no  other  structure  of  which  such  qualities  can  be  predicated. 
Further,  if  muscular  action,  in  response  to  stimuli  applied  to  the 
j^eripherv,  is  no  evidence  of  cither  sensation  or  volition,  then  it  is 
impossible  to  say  whether  any  animal  feels,  or  wills,  under  any  cir- 
cumstances. If  now  the  nervous  system  of  a  starfish  be  compared 
"uith  that  of  the  ascidian,  just  mentioned,  the  only  essential  diifer- 
ence  presented  by  the  former  is  that,  instead  of  one  ganglion  there 
are  five  (Fig.  329),  which,  together  with  the  commissural  filaments, 
constitute  a  circum-oral  ring,  from  which  are  given  off  the  nervous 
filaments  supplying  the  rays. 

It  follows,  therefore,  that  if  the  ganglion  of  the  ascidian  be  en- 
dowed with  sensation  and  volition,  then  all  five  ganglia  of  the 
starfish  are  endowed  with  the  same  functions,  the  only  diiference 
between  the  two  being  that,  in  the  one,  whatever  sensation  and  vo- 

FiG.  329.  Fig.  830. 


Nervous  system  of  starfish.     (Daltox.)  Nervous  system  d  ;iiilysia.     (Dalton.) 


lition  the  animal  may  be  possessed  of  is  concentrated  in  the  single 
ganglion,  Avhcreas,  on  the  other,  the  sensation  and  volition  are  dif- 
fused among  the  five  ganglia.  It  is  obvious,  also,  that,  on  ac- 
count of  the  radial  symmetry  presented  by  the  starfish,  it  is  impos- 
sible to  assign  any  special  function  to  any  one  of  the  ganglia  that 
is  not  possessed  by  the  others.  And,  while  even  in  the  mollusca, 
of  which  the  aplysia  (Fig.  330),  or  sea  hare,  is  an  example,  the 
supra-cesophageal  ganglion  (1)  is  regarded,  morphologically,  as  a 
brain,  there  is  little  reason  to  suppose  that  it  possesses,  exclusively, 
any  very  specialized  function  not  shared  by  the  infra-fesophageal 
(2)  one,  or  that  the  latter,  in  turn,  differs  very  much,  functionally, 
from  the  remaining  ganglia  (3,  4)  distributed  through  the  body,  and 
with  Avhich  it  is  connected  by  a  commissural  filament  as  M^ell  as 
with  the  supra-cesophageal  one.  It  is  true  also,  that  the  supra- 
cesophageal  ganglion  (Fig.  331)  of  centipedes,  insects,  etc.,  is  usu- 
ally spoken  of  as  the  brain  of  such  animals,  and  the  ventral  chain 


NERVOUS  SYSTEM  OF  CENTIPEDE. 


583 


Fig.  331. 


of  gauglia  compared  to  the  spinal  cord  of  vertebrates,  but,  as  some 
of  the  nerves  in  insects,  for  example,  supplying  the  head,  are  de- 
rived from  the  supra-cesophageal  ganglion,  and  others  from  the 
infra-cfisophageal  ganglion  and,  as  the  latter  ganglion 
does  not  differ  essentially  from  the  remaining  ones  of 
which  the  ventral  chain  consists,  it  is  difficult  to  see 
why  any  one  ganglion  should  be  designated  as  cere- 
bral and  the  other  as  spinal.  That  there  is  no  such 
essential  diflFerence  between  the  so-called  cerebral 
and  spinal  ganglion  is  shoAvn  from  the  fact  that,  if 
a  worm  breaks  up  into  two,  through  fission,  the 
ganglion  that  was  central  in  the  parent  animal  be- 
comes anterior  in  the  new  individual,  and  goes  to 
form  its  brain.  Further,  in  the  case  of  worms,  in- 
sects, etc.,  it  is  questionable  Avhether  such  animals 
are  comparable  at  all  as  regards  their  nervous  sys- 
tems with  vertebrated  ones,  since,  as  a  glance  at 
Fig.  332  will  show,  while  the  cerebro-spinal  nervous 
centers  of  the  vertebrate  are  dorsal,  the  ganglion 
chain  of  the  articulate  is  ventral,  and,  while  the 
heart  is  dorsal  in  the  articulate,  it  is  intermediate  in 
the  vertebrate  between  the  alimentary  canal  and  the 
nervous  center.  In  other  words,  to  compare  an  ar- 
ticulated wdth  a  vertebrated  animal,  with  reference 
to  homologizing  their  nervous  systems,  one  or  the 
other  must  be  placed  upside  down,  and,  however 
the  vertebrated  animal  lie  placed,  it  is  obvious  that 
no  comparison  can  be  made  at  all  between  its  nerv- 
ous system  and  that  of  the  echinodermatous  or  mol- 
luscous type.  Such  being  the  case,  it  would  be  illogical  to  apply 
the  results  of  investigation  made  upon  the  nervous  system  of  in- 
vertebrates to  that  of  vertebrates,  the  nervous  system  not  being 
comparable  in  the  two  great  divisions  of  the  animal  kingdom. 
For  this  reason,  any  conclusion  as  to  the  functions  of  the  different 
parts  of  the  nervous  system  in  man,  draw^n  from  the  study  of  the 
nervous  system  in  animals,  must  be  based  upon  that  of  the  verte- 
brates only,  more  particularly  of  such  classes  in  which  the  parts 
composing  the  nervous  system  can,  without  doubt  be  homolo- 
gized.  The  amphioxus,  the  low^est  of  vertebrates,  being  practic- 
ally headless,  offers,  in  the  structure  of  its  nervous  system,  little 
or  nothing  comparable  with  the  brain  of  the  remaining  vertebrates. 
Unless  it  be  denied  that  the  amphioxus  can  feel  or  will,  of  which 
there  is  not  the  slightest  evidence,  it  necessarily  follows  that  the 
spinal  cord  of  this  primitive  vertebrate,  at  least,  is  endowed  Avith 
sensation  and  volition.  If  such  be  admitted,  and  it  is  difficult  to 
see  how  the  conclusion  can  be  avoided,  analogy  would  lead  us  to 
suppose  that  the  spinal  cord  of  the  lamprey  and  myxine,  to  a  cer- 
tain extent,  at  least,  would  possess,  also,  similar  qualities,  particu- 
larly as  the  sensation  and  volition  exhibited  by  such  animals  are 


Nervous  system 
of   centipede. 

(IlALTOX.) 


584 


THE  NERVOUS  SYSTEM. 


out  of  all  proportion  to  the  amount  of  brain  present.  Inasmuch, 
however,  as  these  marsipo-branchial  fishes  have  a  brain,  or,  at  least, 
the  basal  ganglia  of  the  brain  of  the  higher  vertebrates,  it  is  to  be 
inferred,  that  with  these  additional  important  structures,  even  if 
little  developed,  there  would  be  exhibited  corresponding  higher  fac- 
ulties than  shown  1)y  the  amphioxus,  and  such  is  found  to  be  the 

Fig.  332. 


N— \>-. 


Diagrammatic  sections  of  an  articulated  invertebrate  and  vertebrate.  1.  Longitudinal  section 
of  invertebrate.  2.  Longitudinal  section  of  vertebrate.  3.  Transverse  section  of  invertebrate. 
4.  Transverse  section  of  vertebrate.  H.  Heart.  A.  Alimentary  canal.  N.  Kervous  system. 
CH.  Chorda  dorsalis. 

case,  and  as  we  pass  from  these  lowly  organized  vertebrates  through 
the  higher  ones,  to  man,  it  will  be  observed  that  the  brain  becomes 
more  and  more  developed  both  relatively  and  absolutely  with  refer- 
ence to  the  sj^inal  cord,  the  extremes  of  the  series  being  represented 
by  man  and  the  amphioxus  respectively. 

Eatio  of  Brain  to  Spinal  Cord  in  Vertebrates. 

Man 33.0      to  1 

Mouse 4.0      to  1 

Pigeon 3.3      to  1 

Triton 0.550  to  1 

Lamprej'          .......  0.001  to  1 

Amphioxus      .         .         .         .         ,         .         .  0.0      to  1 

Now,  as  we  have  seen  in  general  that  the  higher  animals  differ 
from  the  lower  ones  in  the  extent  to  which  the  division  of  labor  is 
carried,  the  higher  grade  of  life  exliibited  by  the  former  depending 
upon  the  greater  differentiation  of  their  organization,  the  develo])- 
ment  of  the  brain  just  alluded  to  miglit  have  been  anticipated,  it 
being  obviously  of  advantage  that  certain  functions  of  tlie  nervous 
system  would  be  restricted  to  the  brain,  others  to  the  spinal  cord, 
and  hence,  as  we  shall  see  presently,  the  great  development  of  the 
intellectual  powers  in  the  higlicr  animals  as  comi^arcd  with  the 
lower  ones.  Further,  it  Avill  1>e  found  that  corresponding  with  this 
idea  of  the  division  of  labor,  that  while  tlic  s])inal  cord  of  the  lower 
vertebrates  may  possess  both  sensation  and  ^•()lition,  that  of  the 


SEAT  OF  SENSATIOX  AXD  VOLITIOX.  58o 

higher  ones  iu  becoming  to  a  considerable  extent  a  conductor  of 
sensory  and  motor  impulses  loses  such  equalities,  the  seat  of  the  sen- 
sorium  and  will  being  transferred  to  a  higher  plane,  being  gradually 
elevated,  so  to  speak,  in  tlie  higher  animals.  Thus,  while  sensation 
and  volition  are  diifused  through  the  spinal  nervous  axis  of  the  low- 
est vertebrates,  it  gradually,  through  the  process  of  development, 
becomes  concentrated  in  the  cranial  expansion  of  that  of  the  higher 
ones.  The  theoretical  considerations  just  oifered  are  fully  borne 
out  by  experiment  as  well  as  by  the  facts  of  comparative  anatomy. 
Thus,  if  a  frog  be  decapitated  and  a  drop  of  acetic  acid  be  placed 
upon  the  skin  near  the  anus  ^  the  animal  keeps  changing  its  posi- 
tion, and  will  endeavor  to  wipe  off  the  acid  by  means  of  the  foot 
of  the  same  side  of  the  body  to  which  the  acid  was  applied,  and,  if 
the  latter  be  amputated,  by  means  of  the  opposite  foot.  Xot  infre- 
quently, also,  the  author  has  seen  the  animal  try  to  remove  the  acid 
by  one  of  the  upper  extremities,  both  legs  having  been  amputated. 
Considerable  difference  of  opinion  still  exists  as  to  whether  such  an 
action  as  that  exhibited  by  a  decapitated  frog  involves  sensation  and 
volition,  or  is  to  be  regarded  as  a  simple  reflex  action — that  is,  of 
an  action  such  that  an  impression  being  made  upon  the  skin  of  an 
animal  and  being  transmitted  by  an  afferent  nerve  to  the  gray 
matter  of  the  cord,  is  thence  reflected  by  an  efferent  nerve  to  a  mus- 
cle without  the  animal  necessarily  feeling  anything  or  making  any 
voluntary  effort.  It  appears  to  us,  however,  that  a  frog  with  its 
head  on  when  stimulated  by  acetic  acid  gives  but  little  more  evi- 
dence of  sensation  and  volition  than  with  its  head  off  when  so  stimu- 
lated, the  difterence  exhibited  between  the  cases  being  rather  one 
of  degree  than  of  Idnd.  Of  course,  the  frog  with  its  head  on  feels 
and  wills  more  than  with  its  head  off,  but  it  does  not  follow,  in  the 
latter  case,  that  the  animal  does  not  feel  or  will  at  all.  Indeed,  if 
it  be  denied  that  the  decapitated  frog  feels  and  wills,  it  becomes 
very  questionable  whether  there  is  any  way  at  all  of  positively  prov- 
ing that  the  frog  with  its  head  on  feels  and  wills.  Further,  if  it  be 
affirmed  that  sensation  and  volition  are  restricted  to  the  brain,  then 
the  amphioxus  must  be  without  either,  and  that  exhibited  l)y  the 
lower  vertebrates,  the  frog  included,  out  of  proportion  to  the  amount 
of  brain  present.  It  is  often  urged  that,  as  we  know  from  cases  in 
which  the  spinal  cord  has  been  injured  in  man,  that  muscular  con- 
tractions resulting  from  the  tickling  of  the  sole  of  the  foot  are  per- 
formed unconsciously,  that  the  muscular  action  just  described  as 
taking  place  in  the  decapitated  frog  is  no  evidence  that  the  animal 
either  feels  or  wills.  It  should  be  borne  in  mind,  however,  that  no 
one  ever  saw  a  man  with  a  fractured  spine,  still  less  with  his  head 
cut  off,  apply  his  hand  or  foot  to  his  anus  and  wipe  away  acetic 
acid  placed  thereupon,  as  done  liy  the  decapitated  frog,  and  until 
this  has  been  observed  it  can  hardly  ]:)c  said  that  the  cases  are  par- 
allel, or  that  conclusions  can  be  drawn  as  to  the  sensation  or  voli- 
tion possessed  by  the  spinal  cord  of  the  decapitated  frog  from  ob- 

iPfliiger,  Die  Sensorisclien  Funktionen  des  Euckeniuarks,  18o3. 


5 8 6  THE  NEB  VO  US  SYSTEM. 

servations  made  upon  human  beings  suffering  from  injuries  of  the 
spine  by  tickling  the  soles  of  the  feet.  Indeed,  the  muscular  con- 
tractions following  the  tickling  of  the  sole  of  the  foot  in  cases  of  in- 
juries of  the  spine  in  human  beings  are  very  simple  in  character, 
similar  to  those  ensuing  when  the  nerve  of  an  amputated  limb  is 
stimulated,  whether  it  be  that  of  a  man  or  frog. 

Such  contractions  are  never  coik'dinated  with  reference  to  the  per- 
formance of  any  definite  object,  and  do  not  suggest  in  any  way  the 
idea  that  the  amputated  limb  either  feels  or  wills,  and  the  case  is 
not  substantially  altered  by  the  limb  being  attached  to  the  body, 
the  only  difference  being  then  that  the  nerve  is  bent  into  an  affe- 
rent and  efferent  arc,  the  gray  matter  of  the  cord  connecting  the 
axis-cylinder  of  the  ascending  and  descending  parts  of  the  same. 
The  question  may  never  be  settled  as  to  whether  the  headless  frog 
feels  and  wills  or  not,  or  to  what  extent  sensation  and  volition  may 
be  properties  of  the  spinal  cord  in  the  lower  vertebrates.  Indeed, 
nothing  short  of  being  a  frog  would  give  us  positive  assurance  that 
such  an  animal  possesses  consciousness  as  Professor  Huxley  ob- 
served in  considering  the  same  point  in  reference  to  the  crayfish.^ 

On  the  supposition,  however,  that  man  has  gradually  developed, 
and  in  harmony  with  the  idea  that  as  we  pass  from  the  lower  to  the 
higher  vertebrates  through  the  division  of  labor,  the  properties  of 
the  spinal  cord  from  being  general,  become  more  and  more  special 
in  character,  it  is  quite  possible  that  many  actions  wdiich  are  now 
performed  unconsciously  in  the  higher  animals  may  have  been 
originally  accompanied  with  both  sensation  and  volition  in  the 
lower  ones,  and  to  a  certain  extent  are  still.  As  a  matter  of  fact, 
many  actions  like  that  of  walking,  playing  upon  musical  instru- 
ments, etc.,  involving  at  first  both  sensation  and  volition,  through 
constant  repetition  are  performed  in  time  unconsciously.  Whether 
this  view  of  all  reflex  action  being  originally  accompanied  with 
consciousness,  but  through  constant  repetition  being  finally  per- 
formed unconsciously,  becoming,  as  it  were,  organized  within  us,  a 
kind  of  second  nature,  be  accepted  or  not,  there  is  no  doubt  that  in 
man,  at  least,  that  the  seat  of  sensation  and  volition  is  limited  to 
the  brain,  and  that  there  are  many  and  varied  actions  going  on  in 
the  body  not  involving  consciousness  at  all,  and  performed  entirely 
by  the  spinal  cord  and  medulla,  to  the  consideration  of  which  let 
us  now  turn. 

A  reflex  action  (Fig.  333)  implies  the  presence  of  an  afferent  or 
centripetal  nerve  (A)  of  the  gray  matter  of  the  cord  ((7),  and  of 
eflFerent  or  centrifugal  ones  (E  E).  We  make  use  of  these  terms  in 
preference  to  those  of  sensory  and  voluntary  motor  nerves,  since 
many  reflex  actions  like  the  rhythmical  action  of  the  heart  and  lungs 
are  performed  entirely  unconsciously  without  our  feeling  or  willing 
in  the  matter  at  all,  while  others,  involving  sensation,  as  the  wink- 
ing of  the  eyelids  on  an  object  being  brought  suddenly  close  to 
the  eyes  is  entirely  involuntary,  as  we  all  know  from  daily  experi- 
1  The  Crayfish,  ISSO,  p.  89. 


REFLEX  ACTION. 


587 


enee.  In  many  instances  of  reflex  action,  as  in  cleglntition,  walking, 
conghing,  sneezing,  tetanns,  vomiting,  etc.,  both  the  aiFerent  and 
efferent  nerves  involved  are  cerebro-spinal  nerves.  In  other  cases, 
as  in  blnshing,  etc.,  while  the  aflPerent  nerves  are  cerebro-spinal, 
the  eflPerent  nerves  belong  to  the  sympathetic  system.  On  the  otlier 
hand,  the  afferent  nerves  may  be  derived  from  the  sympathetic,  the 
efferent  from  the  cerebro-spinal  system,  as  in  convulsions  due  to  the 


Fig.  333. 


Fig. 


Diagram  to  illustrate  reflex  action  of  medulla. 


Diagram  to  illustrate  reflex  action. 

presence  of  intestinal  worms,  not 
uncommon  in  infants.  Finally, 
both  afferent  and  efferent  nerves 
may  be  sympathetic  nerve  fibers, 
as  in  the  production  of  certain  of 
the  intestinal  secretions.  Whether, 

however,  the  afferent  and  efferent  nerves  be  cerebro-spinal  or  sym- 
pathetic in  origin,  or  the  phenomena  be  accompanied  with  sensation, 
but  without  volition,  or  without  either,  in  each  of  the  instances  just 
referred  to,  an  impression  being  made  upon  the  periphery  and  trans- 
mitted bv  an  afferent  nerve  to  the  g-rav  matter  of  the  cord  is  thence 
reflected  outwardly  again  to  the  periphery  by  an  efferent  one.  Fur- 
ther, while  muscular,  glandular,  or  vascular  action  may  follow  an 
afferent  irritation  according  as  the  efferent  nerve  is  distributed  to 
muscle,  gland,  or  vessel,  as  in  the  instances  just  given,  it  is  not  im- 
possible that  all  three  effects  may  be  produced  simultaneously  by  a 
single  impulse,  as  in  the  case  illustrated  by  Fig.  334. 

Many  of  the  examples  just  given  being  rather  illustrations  of  the 
reflex  action  of  the  medulla  than  of  the  spinal  cord,  their  further 
consideration  will  be  deferred  until  the  afferent  and  efferent  nerves 
have  been  described. 

If  the  impression  made  upon  the  periphery  be  not  a  very  strong 
one,  usually  the  reflex  action  resulting  is  unilateral — that  is  to  say, 
is  confined  to  the  same  side  of  the  body  irritated.  If,  however,  the 
impression  be  sufficiently  strong  to  pass  through  the  gray  matter  of 
the  cord  and  be  reflected  outwardly,  then  the  reflex  action  is  sym- 
metrical—  that  is,  the  general  effect  produced  on  the  opposite  side 
of  the  body  is  the  same  as  that  of  the  side  irritated.  As  might  be 
expected,  if  the  impression  be  sufficiently  strong  to  produce  the  same 
effect  on  both  sides  of  the  body,- the  movements  upon  the  opposite 
side  never  surpass  in  extent  those  of  the  side  irritated.  Further, 
w^hile  the  efferent  nerve  excited  is  usually  on  the  same  plane  a& 


588  THE  NERVOUS  SYSTEM. 

that  of  the  aiFerent  one  irritated,  if  the  impression  be  snfficiently 
strong,  the  nerves  excited  are  always  situated  above,  and  never 
below,  that  plane.  It  should  be  mentioned,  however,  in  this  con- 
nection in  the  case  of  the  reflex  action  of  the  encephalon  the  im- 
pression passes  downward  to  the  medulla  oblongata.  It  is  also  well 
known  that  a  single  weak  stimulus,  incapable  in  itself  of  causing 
a  reflex  action,  may  do  so,  however,  if  repeated  sufficiently  often. 
The  piling  up  or  "  summation  of  the  stimuli,"  as  it  is  called,  appears 
to  take  place  in  that  part  of  the  spinal  cord  situated  between  the 
terminal  twigs  of  the  afferent  nerves  and  the  cells.  Some  difference 
of  opinion  exists  as  to  the  number  of  stimuli  necessary  to  elicit  a 
reflex  response.  It  would  seem,  however,  that  while  3  feeble  stimuli 
per  second  will  cause  reflex  action,  16  stimuli  per  second  are  much 
more  effective.  A  certain  period  of  time,  the  so-called  "  period  of 
latent  stimulation,"  elapses  between  the  application  of  a  stimulus 
and  the  reflex  response.  In  the  case  of  a  ])ithed  frog,  dilute  sul- 
phuric acid  being  used  as  the  stimulus,  and  the  latent  period  being 
the  time  elapsing  between  the  application  of  the  stimulus  to  the 
foot  and  the  withdrawal  of  the  latter,  it  has  been  shown  that  the 
latent  period  diminished  as  the  strength  of  the  solution  is  in- 
creased. It  is  also  well  known  that  the  interval  of  time  elapsing 
between  the  application  of  the  stimulus  and  the  response  varies 
within  wide  limits.  Thus  in  making  use  of  electricity  as  a  stim- 
ulus it  has  been  shown  ^  that  the  number  of  stimuli  remaining 
constant,  the  latent  period  may  vary  from  0.05  to  0.4  second.  It 
would  appear,  of  the  time  elapsing  between  the  application  of  the 
stimulus  and  the  reflex  response  in  the  frog,  that  from  0.008  to 
0.015  second  is  applied  to  the  transferring  of  the  impulse  from 
the  afferent  fiber  to  the  cell  in  the  cord  and  from  the  latter  to  the 
efferent  fiber,  the  time  so  consumed  being  known  as  "  reflex  time."  ^ 
Reflex  responses  are  much  more  readily  elicited  when  the  stimulus 
is  applied  to  the  specific  end  organ  of  the  afferent  nerve  than  to  its 
trunk.  Thus  the  reflex  responses  following  the  gentle  tickling  of 
the  skin  are  much  greater  than  those  due  to  the  stimulation  of  an 
exposed  cutaneous  nerve.  It  is  well  known  that  reflex  action  is 
increased  by  certain  substances,  and  diminished  by  others.  Of  the 
former  strychnia  is  the  most  powerful ;  an  animal,  a  frog,  for  ex- 
ample, poisoned  with  strychnia  exliibiting  tetanic  spasms  on  the 
application  of  tlie  slightest  stimulus.  Of  the  latter  may  be  men- 
tioned chloroform,  the  bromides,  etc. 

That  the  different  parts  of  the  body  are  intimately  connected  has 
been  well  known  from  time  immemorial  to  the  physician,  but  it  is 
only  within  comparatively  modern  times  that  it  has  been  recognized 
that  the  sympathy,  as  it  was  called,  undoubtedly  existing  between 
the  various  organs,  depends  upon  reflex  action.  As  the  doctrine  of 
sympathy  is  a  very  important  one  from  a  clinical  as  well  as  from  a 
physiological  standpoint,  it  may  not  appear  superfluous  to  illustrate 

MVard,  Du  Bois  Reyraonrl  Archiv  Phys.  Abthl.,  1880,  s.  72. 
^  Landois,  op.  cit.,  p.  80'.i. 


liEFLEX  ACTION. 


589' 


it  a  little  by  a  few  examples.  Thus,  for  example,  the  oesophagus 
having  been  divided,  if  the  stomach  l)e  irritated,  the  salivary  glands 
Avill  secrete  ;  on  the  other  hand,  if  the  lingual  nerve  be  stimulated  as 
by  the  taking  of  tobacco,  the  stomach  will  secrete.  Evidently  the 
impression  made  upon  the  stomach  in  the  first  case  is  transmitted 
to  the  cord  and  thence  reflected  outwardly  to  the  salivary  glands, 
whereas  in  the  second  case  the  impression,  being  made  upon  the 
tongue,  is  transmitted  to  the  cord  and  thence  reflected  to  the  stomach. 
Similarly,  the  irritation  due  to  hemorrhoids  modifies  the  character  of 
the  gastric  juice  to  such  an  extent  that  digestion  becomes  impossible, 
and  the  ensuing  dyspepsia  only  curable  by  removal  of  the  hemor- 
rhoids or  the  exciting  cause.  The  flow  of  tears  due  to  some  ex- 
ternal irritation  disappears  with  the  loss  of  sensibility,  while  photo- 
phobia, often  attributed  to  irritation  of  the  optical  nerve,  is  in  reality 
due  to  irritation  of  the  fifth  pair  of  nerves.  The  fact  of  disease  in 
one  eye  often  involving  loss  of  the  other  illustrates  the  nervous 
sympathy  existing  between  the  two.  Xeuralgia  of  branches  of  the 
frontal  nerve,  due  to  caries  of  the  teeth,  is  of  frequent  occurrence. 
The  irritation,  and  even  inflammation  of  the  abdominal  viscera 
following  severe  burns  is  well  known  to  the  surgeon.  The  stop- 
page of  the  heart  brought  about  by  blows  on  the  epigastrium,  the 
tetanus  due  to  injuries  of  the  thumb  and  big  toe,  the  paraplegia 
from  disease  of  the  urogenital  organs,  the  development  of  the  mam- 
mary glands  coincident  with  that  of  the  fcetus  are  familiar  example& 
of  reflex  action.^ 

Fig.  335. 


The  knee-jerk. 

The  well-known  "  knee-jerk  "  (Fig.  335)  elicited  by  striking  the 
patellar  tendon  with  the  edge  of  the  hand  or  a  percussion  hammer, 
the  leg  being  semi-flexed,  is  specially  interesting  as  an  example 
of  a  deep  tendon  reflex,  owing  to  the  fact  that  it  is  increased  or 
diminished  by  diseases,  increased,  for  example,  in  lateral  sclerosis, 
diminished  or  lost  in  locomotor  ataxia. 

'Brown  Sequard,  Central  Nervous  System,  p.  lo3.  Philadelphia,  ISfiO.  A.  P. 
Brubaker,  Reflex  Neurose?,  American  System  of  Dentistry. 


590 


THE  NERVOUS  SYSTEM. 


Fig.  336. 


The  above  are  illu.stratious  among  many  that  might  be  offered  of 
the  important  fact  never  to  be  lost  sight  of,  that  the  exciting  causes  of 
many  physiological  and  pathological  phenomena  are  to  be  sought  for, 
not  where  the  latter  are  exhibited,  but  frequently  at  a  remote  portion 
of  the  body,  the  impression  made  upon  one  organ  being  transmitted 
by  an  afferent  nerve  to  the  spinal  cord,  and  thence  reflected  out- 
wardly by  an  efferent  one  to  where  the  phenomena  are  exhibited. 
If  the  various  spinal  nerves  involved  in  the  production  of  reflex 
actions  be  considered  specifically,  it  Avill  be  found  that  just  as  the 
osseous  spinal  column  is  subdivided  into  osseous  segments,  so  the 
spinal  cord  may  be  subdivided  into  nervous  ones  physiologically  at 
least,  the  gray  matter  of  which,  according  to  this  view,  constituting 
so  many  reflex  centers,  and  the  spinal  nerves  the  afferent  and  effe- 
rent nerves  to  and  from  the  same.  A  number  of  such  centers 
appear  to  have  been  satisfactorily  made  out,  among  which  may  be 
mentioned  the  cilio-spinal  center,  by  which  the  dilatation  of  the 
pupil  is  effected,  situated  in  the  lower  part  of  the  cervical  and 
upper  part  of  the  dorsal  regions  of  the  cord  ;  it  will  be  considered 
again  in  connection  with  the  sympathetic.  The  sweat  and  vaso- 
motor centers,  whose  influence  upon  the  secretion  of  sweat  and  the 
blood  vessels  will  be  treated  of  hereafter.  The  ano-spinal  center, 
governing  the  act  of  defecation,  situated  in  the  lumbar  region,  the 
afferent  fibers  being  constituted  by  the  hem- 
orrhoidal and  inferior  mesenteric  nerves, 
the  efferent  by  the  pudendal  plexus,  dis- 
tributed to  the  sphincter  ani  muscle.  The 
vesieo-spinal  center,  both  that  governing 
the  sphincter  vesicae  and  detrusor  urinse, 
being  situated  in  the  lumbar  reo;ion  of  the 
cord. 

Two  centers  are  assumed  to  exist  in  the 
cord,  one,  the  automatic  center  (Fig.  336, 
A  C),  maintaining  the  tonic  activity  of  the 
sphincter  of  the  bladder,  the  other  a  reflex 
center  (/?  C)  exciting  the  fibers  of  the  de- 
trusor uriuffi  muscle,  the  urine-expelling 
fillers.  Such  being  the  disposition,  afferent 
impulses  from  the  sensory  center  (S)  par- 
alyze the  automatic  center  and  excite  the 
reflex  center,  and  so  give  rise  to  micturition. 
If  the  sensory  impulses  reach  the  cerebrum 
voluntary  impulses  descend  which  may  aid 
or  inhibit  micturition,  according  as  the 
automatic  or  reflex  centers  are  stimulated. 

The  center  for  erection  of  the  penis,  lies 
in  the  lumbar  region  of  the  cord,  the  af- 
ferent fibers  being  the  sensory  nerves  of  the  penis,  the  efferent  ones 
the  nervi  erigentcs.     Stimulation  of  the  latter,  as  we  shall  see  here- 


OeO 


Schema  of  micturition.  AC. 
RC,  ('.  Automatic,  reflex,  ami 
cerebral  centers.  B.  liladiler. 
S.  Sensory  center  acted  un  by 
afferent  impulses.     (Lanbois. ) 


BEFLEX  ACTION.  591 

after,  dilates  the  vessels  of  the  penis.  The  center  for  the  emission 
of  semen  is  also  situated  in  the  lumbar  region,  the  afferent  nerves 
being  the  dorsal  sensory  nerves  of  the  penis  ;  the  efferent,  nerve 
fibers  which,  emerging  with  the  fourth  and  fifth  lumbar  nerves, 
pass  into  the  sympathetic,  and  are  distributed  to  the  vesiculje  semi- 
nales  and  vasa  differentia,  and  with  the  third  and  fourth  sacral 
nerves  pass  into  the  perineal  nerves,  and  are  distributed  to  the 
accelerator  muscle.  The  center  for  parturition  lies  in  the  lumbar 
region,  the  afierent  and  efferent  fibers  consisting  of  part  of  the 
uterine  plexus.  From  the  fact  of  the  reflex  actions  being  stronger, 
and  of  less  time  elapsing  between  the  application  of  the  stimulus, 
and  the  resulting  reflex  when  the  spinal  cord  has  been  divided,  it  has 
been  inferred  that  the  encephalic  centers  exercise  a  restraining  or  in- 
hibitory effect  upon  the  reflex  action  of  the  cord.  Thus,  the  spinal 
cord,  being  intact  in  a  frog,  and  the  average  length  of  time 
elapsing  between  the  application  of  the  stimulus  and  the  result- 
ing reflex  effect  being  determined,  it  will  be  observed  that  if  the 
optic  lobes,  for  example,  be  stimulated,  a  greater  length  of  time 
elapses  now  than  before  between  the  stimulus  and  the  reflex.  On 
the  other  hand,  the  spinal  cord  being  divided,  less  time  elapses  be- 
tween the  application  of  the  stimulus  and  the  reflex.  While  such 
experiments  would  lead  one  to  conclude  that  in  the  frog  the  optic 
lobes  contain  a  restraining  or  inhibitory  center,  Setschenow  ^  center, 
it  must  not  l^e  supposed  that  the  inhibitory  influence  of  the  en- 
cephalon  is  limited  to  the  optic  lobes  in  man.  That  there  must  be 
complex  centers  situated  probably  in  the  cortex  of  the  brain  by 
Avhich  the  reflex  action  of  the  cord  is  inhibited,  is  shown  by  the 
manner  in  which  we  are  able  to  restrain,  for  a  time  at  least,  the 
various  functions  performed  by  it,  such,  for  example,  as  keeping 
the  eyelids  open  when  the  eyeball  is  touched,  arrest  of  movement 
when  the  skin  is  tickled,  etc.  It  is  held  by  many  physiologists  that 
the  spinal  cord  not  only  exerts  an  automatic  control  over  certain 
viscera,  such  as  the  rectum,  bladder,  etc.,  as  just  mentioned,  but 
also  over  the  skeletal  muscles  as  well,  maintaining  the  latter  in  a 
state  of  more  or  less  tonic  contraction.  Of  the  facts  offered  among: 
others  as  pro^^ng  the  existence  of  a  muscle  tonus,  it  has  been  urged 
that  when  a  muscle  is  divided  its  ends  retract.  This  effect  appears 
to  be  due,  however,  not  so  much  to  loss  of  spinal  control  as  to 
the  fact  that  all  muscles  are  more  or  less  slightly  stretched  beyond 
their  normal  length.  It  is  also  well  known  that  if  the  muscles  of 
a  decapitated  frog  be  put  on  the  stretch  and  the  sciatic  nerve  di- 
vided the  muscles  do  not  elongate,  a  fact  inconsistent  Avith  the  idea 
of  the  muscles  having  been  previously  maintained  in  a  condition  of 
a  tonus  by  the  spinal  cord.  That  a  condition  of  reflex  tonus  may 
be  brought  about,  however,  is  shown  l)y  the  fiict  that  if  the  decapi- 
tated frog  be  suspended  in  an  abnormal  condition  it  will  be  0I3- 

^Ueber  die  Hemmungsmeclianisnuis  fiir  die  Eeflexth;itio-keit  des  Riifkenmarks, 
1863. 


592  THE  NERVOUS  SYSTEM. 

served  that  while  the  leg  in  whicli  the  sciatic  nerve  has  been  di- 
vided hangs  limp,  the  sound  one  is  slightly  retracted,  the  weight  of 
tlie  limb  acting  then  as  a  stimulus.  It  should  be  mentioned  in  this 
connection  that  while  there  is  no  doubt  tliat  the  spinal  cord  exerts 
automatic  control  over  certain  viscera  and  blood  vessels  (vascular 
tonus),  the  expression  "  automatic  center  "  is  a  misleading  one,  as 
the  so-called  automatic  centers  differ  only  from  other  reflex  centers 
in  being  stimulated  at  all  times  by  blood  or  other  stimulus,  the  or- 
dinary reflex  centers  only  temporarily.  The  spinal  cord  appears 
also  as  already  mentioned  to  influence  the  nutrition  of  the  tissues  to 
which  its  nerves  are  distributed,  the  nutrition  of  the  muscles  being 
controlled  by  the  anterior  gray  matter,  and  probably  by  the  motor 
cells,  that  of  the  bones  and  joints  being  excited  probably  through 
the  posterior  roots.^ 

Kiowei-'s  Diseases  of  the  Nervous  System,  Vol.  i.,  1892,  p.  206. 


CHAPTER    XXXII. 

THE  XERYOUS  ^YSTE'SL—(Contini'ed.) 
THE  MEDULLARY  NERVES. 

The  medulla  ohloiiuata,  regarded  as  a  center  of  reflex  action,  is 
€ven  more  important  than  the  spinal  cord,  on  account  of  its  giving 
origin  to  ten  of  the  so-called  cranial  nerves — that  is,  of  the  nerves 
involved  in  the  performance  of  mastication,  insalivation,  deglutition, 
of  gastric  and  intestional  digestion,  circulation,  and  respiration — in 
a  word,  of  the  functions  of  nutrition.  In  order,  however,  to  appre- 
ciate the  manner  in  which  these  nerves  conduct  afferent  and  efferent 
impressions  to  and  from  the  medulla,  the  latter  acting  as  a  reflex 
center,  it  will  first  be  necessary  to  describe  their  origin,  distribu- 
tion, and  function.  From  the  fact  of  the  medulla  being  simply  the 
upper  expanded  portion  of  the  spinal  cord  one  would  be  led  to  sup- 
pose that  the  ten  nerves  originating  in  it  would  be  either  motor  or 
sensory  in  function,  and  that  taken  together  in  pairs  from  below 
upward  each  pair  would  be  comparable  to  the  anterior  or  motor  and 
posterior  or  sensory  roots  of  one  of  the  true  spinal  nerves.  As  a 
matter  of  fact,  the  roots  of  the  two  nerves  of  any  one  of  the  medul- 
lary pairs,  supposing  such  to  exist,  do  not  unite  together  into  a 
single  nerve  as  in  the  case  of  a  spinal  nerve,  but  pass  on  separately 
to  their  ultimate  distribution  as  two  distinct  nerves  ;  and  further, 
the  reflex  centers  of  the  medulla  oblongata,  of  which  these  nerves 
are  the  afferent  and  efferent  fibers,  are  so  fused  together  in  man  and 
the  higher  vertebrates  that  the  primitive  disposition  of  these  centers 
and  the  relation  of  the  nerves  originating  m  them  are  no  longer  ap- 
parent. In  fact,  the  union  is  so  intimate  that  it  is  impossible  to 
say  now  how  many  such  nerves  or  roots  there  were  originally,  and 
until  that  is  determined  it  ^\ill  l)e  impossible  to  homologize  the 
medullary  ^nth  the  true  spinal  nerves.  Indeed,  until  the  develop- 
ment of  the  cranial  nerves  in  the  mammalia  has  been  thorouffhlv 
worked  out  by  the  embryologist,  and  the  relations  between  the 
cranial  and  spinal  nerves  in  some  of  the  lower  vertebrates  been 
established  by  the  comparative  anatomist,  any  view  yet  offered  may 
be  considered  as  based  upon  little  more  than  speculation.^ 

Twelve  pairs  of  nerves  are  given  off  from  the  base  of  the  brain. 
The  first  two  pairs,  the  olfactory  and  optic,  the  special  nerves 
of  the  sense  of  smell  and  sight,  are,  as  we  shall  see  hereafter, 
morphologically  outgrowths   of  the  anterior  cerebral  vesicle ;  the 

1  Gegenbaur,  Elements  of  Comparative  Anatomy,  transl.  ]>y  F.  J.  Bell,  1878,  p. 
515,  Gaskell,  Journal  of  Physiology,  Vol.  x.,  1889,  p.  153. 

38 


594 


THE  NERVOUS  SYSTEM. 


remaiuing  ten  pairs,  however,  while  apparently  arising  like  the 
first  two  pairs  from  the  base  of  the  brain,  in  reality  originate,  as 
already  mentioned,  from  nnclei  in  the  medulla  (Fig.  337),  hence 
our  reference  to  them  as  medullary  nerves.  Taking  them  in  the 
order  in  which  they  succeed  the  olfactory  and  optic  nerves,  they 
are  as  follows  (Figs.  338,  339)  :  The  third  pair,  or  motor  oculi 
communis ;  fourth  pair,  or  patheticus  ;  fifth  pair,  or  trigeminal  or 


View  of  the  posterior  surface  of  the  medulla,  the  roof  of 
the  fourth  ventricle  being  removed  to  show  the  rhomboid 
sinus  clearly.  The  left  lialf  uf  the  fiKure  rcjjresents  :  On. 
Funiculus  cuneatus,  and //,  funiculus  grmilis.  O.  Obex. 
■y).  Nucleus  of  the  spinalaceessorv.  ji.  Nucleus  of  pneu- 
niogastric.  p  +  xp.  Ala  cinera. "  H.  Ite.stiforni  body. 
A'lr.  Nucleus  of  the  hypoglossal.  /.  Ininiculus  teres. 
(/.  Nucleus  of  the  acousticus.  m.  Striae  niedullares.  1,2 
and  3.  Middle,  superior,  and  inferior  cerebellar  i>caunc]es 
respectively.  /.  Fovea  anterior.  4.  Eminentia  teres  (genu 
nervi  facialis).  5.  Locus  ca^ruleus.  The  right  half  of  the 
figure  rciiresents  t lie  nerve  nuclei  diagrammatically  :  I'. 
Motor  trigeminal  nucleus.  V.  Median  and  V",  inferior 
sensory  and  trigeminal  nuclei.  I'/.  Nucleus  of  abducens. 
r//.  Facial  nucleus.  IT//.  Posterior  median  acoustic 
nucleus.  I'///'.  Anterior  median.  VIII".  Posterior 
lateral.  VIII'".  Anterior  lateral  acoustic  nuclei.  IX. 
Glosso-pharyngeal  nucleus.  X,  XI,  and  XII.  Nuclei  of 
vagus,  spinal  accessdry,  and  hyjKj-glossal  nerves  respect- 
ively. The  Honjan  inimerals  at  the  side  of  the  figure, 
from  F to  A'//,  represent  the  corresponding  nerve  roots. 
(Erb.) 


View  from  below  of  the  connection 
of  the  principal  nerves  with  the 
brain.  I'.  The  right  olfactorv  tract. 
II.  The  left  optic  nerve.  IP.  The 
right  optic  tract ;  the  left  tract  is 
seen  passing  back  into  ('  and  e,  the 
internal  and  external  corjtora  geu- 
ieulata.  III.  The  left  oculomotor 
nerve.  IV.  The  trochlear.  V,  V. 
The  large  roots  of  the  trifacial 
nerves.  +  +.  The  lesser  roots,  the 
+  of  the  right  side  is  placed  on  the 
Gasserian  ganglion.  1,  the  oplithal- 
mic  ;  2,  the  superior  maxillary;  and 
3,  the  inferior  maxillary  nerves. 
VI.  The  left  abducent  nerve.  VII, 
a,  b.  The  facial  and  auditory  nerves. 
a,  VIII,  b.  The  glosscj-phiiryiigeal, 
pneumogastric,  and  spinal  accessory 
nerves.  IX.  The  right  liy)Mi-Klossal 
nerve.  C  I.  The  left  sulxiccipital  or 
first  cervical  nerve. 


trifacial ;  sixth  pair,  or  abducens ;  seventh  pair,  or  facial ;  eighth 
pair,  or  auditory,  the  special  nerve  of  the  sense  of  hearing ;  ninth 
pair,  glosso-pharyngeal ;  tenth  pair,  pneumogastric  ;  eleventh  pair, 
spinal  accessory ;  twelfth  pair,  hypo-glossal.  The  third  nerve,  or 
motor  oculi  communis  (Figs.  338  and  339,  III),  consisting  of  about 
15,000  fibers,^  arises  from  a  series  of  nuclei  (Fig.  340)  situated 
'Eosenthal,  De  Numero  atqne  Mensura  Microscop  Filn-illarum.     Breslaii,  1845. 


NUCLEI  OF  THE  MEDULLARY  NERVES. 


595 


upon  both  sides  of  the  middle  line  of  the  aqueduct  of  Sylvius  be- 
neath the  corpora  quadrigemina,  those  of  the  fibers  crossing  the 
middle  line  decussating  with  those  of  the  opposite  side.  The 
nuclei  of  the  third  nerve,  and  those  of  the  fourth  and  sixth  as 
"well,  it  may  be  here  mentioned,  to  avoid  repetition,  are  in  rela- 


FiG.  339. 


Fig.  3-40. 


Roots  of  the  cranial  nerves.  I.  First  pair ;  olfac- 
tory. II.  Second  pair ;  optic.  III.  Third  pair  ;  motor 
ociili  communis.  IV.  Fourth  pair;  patheticus.  V. 
Fifth  pair;  nerve  of  mastication  and  trifacial.  VI. 
Sixth  pair  ;  motor  oculi  externus.  VII.  Facial.  VIII. 
Auditory — Seventh  pair.  IX.  Glosso-pharyngeal.  X. 
Pneumogastric.  XI.  Spinal  accessory — Eighth  pair. 
XII.  Xinth  pair;  sublingual.  The  numbers  1  to  lij 
refer  to  branches  which  will  be  described  hereafter. 

(HiRSCHFELD.) 


A  partly  diagrammatic  view  of  the 
floor  of  the  aqueduct,  looking  upward 
(dorsally ) ,  nuclei  of  the  third  and  fourth 
nerves,  and  the  decussating  libers  of  the 
latter  all  shown  ;  the  third  nerve  nuclei 
are  subdivided  into  an  anterior  nucleus, 
the  Edinger-Westphal  nucleus  (a  and  6), 
and  a  posterior  nucleus  ;  the  posterior 
nucleus  has  a  dorsal,  a  ventral,  and  a 
mesal  portion  ;  the  decussation  of  the 
fibers  from  the  dorsal  portion  of  the 
posterior  nucleus  of  the  third  nerve  is 
shown.     (Edixger.) 


tion,   functionally   on   the   one  hand 

"with  axis-cylinders,  "svhich  arising  in 

the  cells  of  the  motor  or  visual  cortex,  descend  about  the  knee  of 

the  internal  capsule,  and  on  the  other  by  the  axis-cylinders,  which 

they  give  rise  to,  "v\ith  the  tissues  supplied  by  the  ocular  nerves. 

While  some  difference  of  opinion  still  prevails  as  regards  the 
relative  position  occupied  by  the  nuclei  giving  origin  to  the  differ- 
ent fibers  of  the  third  nerve,  recent  researches  ^  render  it  probable 
that  they  are  situated  from  before  backwards  somewhat  in  the  fol- 
lowing order  (Fig.  341)  : 


J  C.  K.  Mills,  The  Xervous  System  and  its  Diseases,  1898,  j). 


596 


THE  NERVOUS  SYSTEM. 


Sphincter  iridis, 

Musciiliis  ciliaris, 

Convergence  center, 

Rectus  superior, 

Rectus  internus. 

Levator  palpebra?  superioris, 

Obliquus  inferior. 

Rectus  inferior, 

Obliquus  superior, 

Rectus  externus. 


Fig.  341. 


'SV'/i  in cter  iridis. 

MhscuIus  ciliaris. 

^Xr^   r\.(l("iyei-aeiice  centre. 
T\t  1  \J  Hnctus  superior 
U.>^::::'- Rectus  inlemus'. 

0^^~T\   "{■,";9''"' P^'pcbrce  superioris 
KJ^     OblKjuHs  inferior. 
_  Meet  us  inferior. 

Obliquus  superior. 

licet  us  externus 


Schema  of  the  luielei  of  the  nerves  of  ocular  movemcDt  ami  of  their  central  and  perii)lieral 
tracts.  A'.  Right  eye.  L.  Left  eye.  ('.  Chia.sm.  Ore.  Optic  nerve.  Of.  Optic  tract.  Q.  Pre^eni- 
inum  (anterior  quadrigeiuinal  body).  P.  Cortical  center  for  the  movement  of  elevation  ot  the 
upper  eyelid.  M.  Cortical  center  for  ocular  movement.s.  Tii.  Course  of  all  the  ocular  nerves  in 
the  cavernous  sinus.  The  names  of  the  different  nuclei  are  printed  on  the  diagram,  and  the  nerve 
tracts  going  from  these  nuclei  can  be  readily  traced  to  where  they  converge  in  their  course  in  the 
cavernous  sinus  and  where  they  diverge  to  pass  to  the  various  muscles  of  the  eye.  The  dotted 
line  represents  associating  and  commissural  tracts.     (Mills.) 

From  this  nucleus  the  fibers  pass  forward  through  the  cms, 
emerging  at  tlie  l^ase  of  the  brain  from  the  inner  surface  of  the 
crura  cercl^ri  immediately  in  front  of  the  jions.  As  the  nerve 
passes  through  the  sphenoidal  fissure  into  the  orbit  (Fig.  342)  it 
divides  into  two  branches,  the  superior  and  smaller  branches  sup- 
plying the  superior  rectus  and  levator  palpebrje  superioris  muscles, 
the  inferior  and  larger  brancii  the  internal  and  inferior  recti  and 


THE  THIRD  XERVE. 


597 


the  superior  oblique  muscles.  The  latter  or  inferior  branch  gives 
off  also  a  short,  thick  filament,  which  passing  into  the  ophthalmic 
ganglion  of  the  sympathetic  is  supposed,  as  Ave  shall  see,  to  pass 
thence  as  the  short  ciliary  nerves 

into  the  iris,  innervating  the  eir-  F^f'-  3-12. 

cular  muscular  fibers  of  the  latter. 
During  its  course  the  fibers  of 
the  third  pair  run  in  common  or 
in  juxtaposition  witli  fibers  de- 
rived from  the  ophthalmic  divis- 
ion of  the  fifth  pair,  and  from  the 
cavernous  plexus  of  the  sympa- 
thetic.    AVe  make  use  of  the  ex- 


pression running  in  company 
with,  or  in  juxtaposition  with,  in 
preference  to  that  of  anastomosis, 
etc.,  since  the  various  medullary 
nerves  do  not  actually  receive 
fibers  from  or  anastomose  with 
each  other  in  the  sense  that 
arteries  and  veins  anastomose. 
The  nerves,  in  fiict,  never  lose 
their  individuality,  but  undoubt- 
edly preserve  through  the  whole 
extent  of  their  course  the  char- 
acteristic functions  obtaining  at 
their  roots,  as  in  the  case  of  the 
spinal  nerves. 


Distribun  11  ■!  tin'  motor  oculi  communis. 
1.  Trunk  ui  Uu-  imitur  oculi  communis.  2. 
Superior  branch.  3.  Filaments  which  this 
branch  sends  to  the  superior  rectus  and  the 
levator  palpebrse  superioris.  4.  Branch  to  the 
internal  rectus.  5.  Branch  to  the  inferior 
rectus.  6.  Branch  to  the  inferior  oblique 
muscle.  7.  Branch  to  the  lenticular  ganglion. 
8.  Motor  oculi  externus.  9.  Filaments  of  the 
motor  oculi  externus  anastomosing  with  the 
sympathetic.    10.  Ciliary  nerves.      (Hirsch- 

FELD.) 


This  distinction  mu.st  be  continually  borne  in  mind,  for,  as  we 
shall  see  presently,  while  each  of  these  nerves,  at  its  origin,  has  a 
definite  function — motor,  or  sensory — they  become,  sooner  or  later, 
apparently  mixed  nerves,  from  the  fact  of  being  accompanied  by 
the  fibers  of  the  adjacent  cranio-medullary  nerves.  It  is  in  this 
sense  that  the  third  nerve  is  to  be  understood  as  being  a  motor 
nerve,  any  evidences  of  sensibility  being  due,  not  to  its  intrinsic 
fibers,  but  to  the  extrinsic  ones  of  the  fifth  pair.  That  the  third 
nerve  is  exclusively  a  motor  nerve  is  shown  by  the  fact  of  irritation 
of  the  root  causing  contractions  of  the  muscles  to  which  it  is  dis- 
tributed, but  no  pain,  while  division  of  the  nerve  is  followed  by 
paralysis  of  the  same.^  Pathological  fiicts,  like  the  falling  of  the 
upper  eyelid,  or  blepharoptosis,  external  strabi.smus,  immobility  of 
the  eye,  except  outwardly  ;  inability  to  rotate  the  eye  on  its  antero- 
posterior axis  in  certain  directions  ;  slight  protrusion  of  the  eye- 
ball ;  dilation  of  the  pupil,  with  some  interference  with  the  move- 
ments of  the  iris,  following  disease  of  the  third  pair  in  man,  are 

1  Mayo,  Anatomical  and  Physiological  Commentaries,  p.  5.  London,  1823.  Out- 
lines of  Human  Physiology',  p.  294.  London,  1827.  Bernard,  Systeme  nerveux, 
Tomeii.,  p.  204.  Paris,  18-58.  Chauveau,  Journal  de  phvsiologie,  Tome  v.,  p. 
274.     Paris,  1862.     Longet,  Phvsiologie,  Toraeiii.,  p.  554."    Paris,  1869. 


598 


THE  NERVOUS  SYSTEM. 


Fig.  343. 


among  the  proofs  that  may  be  offered  that  the  third  pair  of  nerves 
is  in  man  motor,  as  we  woukl  be  hxl  to  snppose  it  wonkl  be,  both 
from  its  anatomical  distribution  as  well  as  from  the  results  obtained 
by  vivisection. 

The  Fourth  Nerve. 
The  fourth  nerve,  or  patheticus,  consisting  of  about  1200  fibers, 
arises  from  a  nucleus  situated  immediately  posterior  to  the  nucleus  of 

the  third  nerve  (Fig.  340)  and 
gives  origin  to  the  fibers  sup- 
plying the  rectus  inferior  muscle. 
The  fibers  so  originating  cross 
the  middle  line  of  the  fourth 
ventricle  and,  decussating  with 
those  of  the  opposite  side,  emerge 
from  the  valve  of  Vieusseus  at 
the  base  of  the  brain  (Figs.  338 
and  339,  IV),  as  comparatively 
slender  filaments  at  the  sides  of 
the  pons,  and,  Avinding  around 
the  crura,  pass  through  the 
sphenoidal  fissure  (Fig.  343) 
into  the  orbit,  and  supply  the 
superior  oblique  muscle.  Irri- 
tation of  the  nerve  in  a  liviuij: 
animal,  at  its  origin,  causes  con- 
traction of  the  superior  oblique 
muscle,  and  division  of  the  nerve 
paralysis  of  the  same.^  In  cases 
where  the  nerve  is  diseased  in 
man,  paralysis  of  the  superior 
oblique  muscle  is  observed  as  well  as  immobility  of  the  eyeball,  so 
far  as  rotation  is  concerned,  and,  when  the  eye  is  moved  toward  the 
shoulder,  we  have  double  vision,  the  eye  not  rotating  to  maintain  the 
globe  in  the  same  relative  position.  The  pathological  facts  observed 
in  man,  as  well  as  the  anatomical  distribution,  confirm  the  view 
based  upon  vivisections,  that  the  fourth  nerve  is  exclusively  motor 
at  its  origin,  any  sensibility  it  may  possess  further  on  in  its  course 
being  due  to  adjacent  filaments  from  the  ophthalmic  branches  of  the 
fifth  pair,  or  the  sympathetic. 

The  Sixth  Nerve. 
The  sixth  nerve,  the  abducens,  or  motor  oculi  externus,  being, 
like  the  fourth  nerve,  distributed  to  a  single  muscle,  the  external 
rectus,  and,  therefore,  exclusively  motor  in  function,  will  be  consid- 
ered now,  before  the  fifth  nerve,  which  would,  otherwise,  be  the 
next  in  order.  The  sixth  nerve,  consisting  of  about  3000  fibers, 
arises  from  a  nucleus,  situated  beneath  the  eminentia  teres,  in  the 
middle  of  the  floor  of  the  fourth  ventricle  (Fig.  337,  VI)  just  pos- 
'  Longet,  op.  cit.,  Tome  iii.,  p.  557.     Chauvcau,  op.  cit.,  Tome  v.,  p.  275. 


Bistribnti  n  ol  tlu  )i  itlit  tic  ii^  /  Olfiftory 
nerve  //  Ojticii  mcn  ///  "NT  t  i  iilicum- 
munib  71  PitlatRUN  li}  the '^l<U  nt  the  oph- 
thalmic l)ianch  oi  the  fafth,  aud  passing  to  the 
superioi  obliiiue  muscle  1 1  Motor  oculi  ex- 
teruiis.  1.  (iangllon  of  Gasser.  2,  3,  4,  5,  6,  7, 
8,  9,  10.  Ophthalmic  division  of  the  fifth  nerve, 
with  its  branches.     (Hirschfeld.) 


THE  SIXTH  NEEVE.  599 

terior  to  the  nucleus,  giving  origin  to  the  fourth  nerve.  Unlike  the 
iibers  of  the  third  and  fourth  pairs,  it  has  not  yet  been  shown  that 
the  fibers  of  the  sixth  nerve  decussate  at  their  origin  in  the  floor  of 
the  fourth  ventricle.  The  sixth  nerve  appears  at  the  base  of  the 
brain  in  the  groove  separating  the  anterior  pyramid  of  the  medulla 
from  the  pons  (Fig.  o->8),  and  passes  thence  through  the  sphenoidal 
fissure  into  the  orbit.  While  in  its  course  the  sixth  nerve  runs  in 
juxtaposition  with  the  filaments  derived  from  the  sensitive  ophthal- 
mic branch  of  the  fifth  pair,  and  from  the  sympathetic  through  the 
carotid  plexus,  and  Meckel's  ganglion.  It  is  undoubtedly  exclu- 
sively a  motor  nerve,  supplying  only  the  external  rectus  muscle  (Fig. 
342,  8).  Irritation  of  the  nerve  at  the  root  in  a  living  animal  causes 
the  latter  muscle  to  contract,  but  no  pain,  while  division  of  the  nerve 
is  followed  bv  paralysis  of  the  external  rectus  and  internal  strabis- 
mus,^ the  latter  lieing  also  observed  in  man  in  cases  of  disease  of 
the  sixth  nerve.  The  third,  fourth,  and  sixth  pairs  of  nerves,  taken 
tosrether,  constitute  the  eiferent  or  motor  nerves  in  the  reflex  actions 
involved  in  the  movements  of  the  pupil  and  the  eyeball  in  ^^sion, 
and  which  will  be  considered  hereafter,  the  optic  nerve  and  the 
ophthalmic  division  of  the  fifth  nerve  constituting  the  afferent  or 
sensory  nerves. 

The  Fifth  Nerve. 

The  fifth  nerve,  trifacial,  or  trigeminus,  in  arising  from  the  base 
of  the  brain  by  two  roots  (Fig.  3o8,  V  -f ),  the  posterior  large  and 
sensory,  with  ganglion  attached,  and  the  anterior  small  and  motor, 
is  usually  regarded  as  especially  comparable  with  a  spinal  ners-e. 
For  the  reasons  already  given,  it  is  quite  as  possible,  however,  that 
the  fibers  of  the  third,  fourth,  and  even  of  the  sixtli  nerves  may 
constitute  the  true  motor  fibers  corresponding  to  the  sensory  fibers 
of  the  fifth  (ophthalmic  and  superior  maxillary)  as  that  the  fibers 
of  its  small  motor  root  should  be  so  especially  regarded,  particularly 
as  the  latter,  as  we  shall  see  presently,  are  distriljuted  exclusively 
in  company  -s^-ith  the  fibers  of  the  inferior  maxillary  branch  of  the 
fifth.  Of  the  two  roots  of  which  the  fifth  nerve  consists  (Fig.  344, 
J,  (r),  the  larger  or  sensory  root  appears,  from  recent  researches," 
to  arise  in  the  Gasserian  or  semilunar  ganglion,  situated  in  the  de- 
pression on  the  internal  portion  of  the  anterior  face  of  the  petrous 
portion  of  the  temporal  bone  rather  than  to  pass  into  it,  as  usually 
stated.  The  axis-cvlinders  of  the  cells  of  the  ganglion  divide  into 
two  branches,  of  which  one  set  pass  towards  the  brain,  decussating 
with  the  fibers  of  the  opposite  side,  as  the  long  root  (.7),  the  other 
set  peripherally  as  the  ophthalmic  (*!/),  the  superior  maxillary  (X), 
and  the  inferior  maxillary  (i/)  nerves.  Of  the  30,000  fibers  pass- 
ing as  the  long  root  (J)  towards  the  brain,  some  ascending  cross 
the  middle  line  and  terminate  in  the  thalamus  opticus  (C)  and  sen- 
sory areas  of  the  cortex  (i>)  of  the  opposite  hemisphere,  others  de- 
scending (i)  pass  into  the  cervical  region  of  the  spinal  cord.     The 

'Longet,  op.  cit.,  Tome  iii.,  p.  560.     Cliauvean,  op.  cit..  Tome  v.,  p.  275. 
^S.  Eamon  y  Cayal,  Beitrag  Zum  Studium  Der  Medulla  Oblongata,  1896,  s.  1. 


600 


THE  NERVOUS  SYSTEM. 


fibers  of  the  small  or  motor  root  ((t)  arise  from  the  cells  of  Uvo 
centers,  a  chief  motor  center  (F)  situated  in  the  floor  of  the  fourth 
ventricle  and  an  accessory  motor  one  (TJ)  beneath  the  corpora  quad- 
rigemina,  and  which  are  in  relation  with  the  cells  of  the  cortex  (A, 
A)  of  the  lower  part  of  the  central  convolutions  of  the  opposite 
hemisphere  and  decussating  with  those  of  the  opposite  side.  The 
two  sets  of  fibers  so  arising  pass  together  peripherally  (G),  and, 
running  juxtaposed  with  the  most  inferior  of  the  sensory  fibers  of 
the  long  root,  constitute  the  inferior  maxillary  nerve  (ii).     The  an- 

FiG.  344. 


Schema  of  trigeminal  apparatus.  A  A.  Cortical  centers  for  trigeminal  motor  tracts.  B.  Cort- 
ical terminus  of  the  trigeminal  sensory  tract.  ('.  Thalamus  to  which  the  central  trigeminal  sen- 
sory tract  may  be  in  large  part  distributed.  I).  Accessory  (motor)  nucleus.  £.  Descending 
(mesencephalic)  root.  F.  Chief  motor  nucleus.  G.  ]Motor  roots.  J/.  Inferior  maxillary  nerve. 
/.  Gasserian  ganglion.  ./.  Sensory  roots  between  the  (iasserian  ganglion  and  the  pons.  /»'. 
Ascending  .sensory  root.  L.  Descending  (spinal)  root.  jif.  First  or  ophthalmic  division  of  the 
trigeminus.    JV.  Second  or  superior  maxillary  division.     (Mills.) 

terior  small  or  motor  root,  consisting  of  about  10,000  fibers,  passes 
underneath  the  ganglion  of  Gasser,  from  which  it  occasionally  re- 
ceives a  few  filaments,  and  lying  behind  the  inferior  maxillary 
branch  of  the  large  root,  passes  through  the  foramen  ovale  in  com- 
pany with  the  latter,  with  which  it  is  finally  distributed.  It  will 
be  observed  that  while  the  ophthalmic  and  superior  maxillary 
branches  of  the  fifth  are  purely  sensory,  being  derived  solely  from 
the  large  root  through  the  (jasserian  ganglion,  the  inferior  maxil- 
lary branch  is  both  motor  and  sensory,  being  derived  not  only  from 
the  ganglion  but  from  the  small  or  motor  root  as  well. 


THE  FIFTH  yEEVE.  601 

In  division  of  the  nerve  in  a  living  animal  witli  the  view  of  de- 
terminins:  its  function  '  both  roots  are  necessarilv  divided,  and  with 
the  complete  loss  of  sensibility  ensuing  under  such  circumstances, 
there  is  also  observed  paralysis  of  the  temporal,  masseter,  internal 
and  external  pterygoid,  mylo-hyoid,  and  anterior  belly  of  the  digas- 
tric muscles,  or  the  muscles  of  mastication  supplied  by  the  fibers 
of  the  small  root  running  in  the  inferior  maxillary  division  of  the 
fifth  nerve  and  of  the  tensor  muscles  of  the  velum  palati,  and  prob- 
ably of  the  tensor  tympani  also.  The  effect  of  division  of  the  fifth 
nerve  is  very  striking  in  the  case  of  the  rabbit,  in  ^vhich,  through 
the  consequent  paralysis  of  the  muscles  of  mastication,  the  line  of 
contact  between  the  incisor  teeth  becomes  oblique  instead  of  hori- 
zontal, the  incisor  teeth  being  worn  away  unevenly  through  the  jaw 
being;  drawn  to  one  side  bv  the  action  of  the  active  muscles. 

While  it  is  an  extremely  difficult  operation,  if  not  impossible,  to 
stimulate  the  small  root  of  the  fifth  nerve  in  a  living  animal,  never- 
theless, there  can  be  little  doubt  that  it  is  a  purely  motor  nerve  in 
function,  since  if  it  be  stimulated  in  an  animal  just  dead,  in  which 
the  cerebral  lobes  have  been  removed,  such  of  the  muscles  of  masti- 
cation as  are  supplied  by  the  nerves  of  the  small  root  (running  in  the 
inferior  maxillary  division  of  the  fifth)  at  once  contract,^  and  in  the 
case  of  old  horses,  for  example,  with  such  force  as  to  break  off  pieces 
of  the  teeth,'^  no  such  result  following  stimulation  of  the  large  root. 

The  cases  of  paralysis  of  the  fifth  nerve  that  have  been  noted  in 
man  confirm  in  the  main  the  results  of  experiments  made  upon  ani- 
mals. In  all  instances  where  both  the  large  and  small  roots  were 
involved  by  the  disease,  entire  loss  of  sensibility  and  paralysis  of 
the  muscles  supplied  by  the  fifth  were  observed  *  the  only  cases  in 
which  there  was  no  paralysis  of  the  muscles  of  mastication,  etc., 
being  those  in  which  the  small  root  was  unatiected,  loss  of  sensi- 
bility on  the  side  affected  being  then  only  noted. 

In  order  to  appreciate  the  results  following  division  of  the  large 
root  of  the  fifth  nerve  in  a  living  animal  or  disease  in  man,  it  will 
be  first  necessary  to  describe  briefly  the  distribution  of  its  principal 
branches.  It  has  already  been  mentioned  that  the  large  root  arising 
in  the  ganglion  of  Gasser  passes  thence  peripherally  as  the  ophthal- 
mic superior  and  inferior  maxillary  nerves. 

The  ophthalmic,  the  smallest  of  the  three  branches  of  the  large 
root  ( Fig.  345,  below  3  ),  passes  through  the  sphenoidal  fissure 
into  the  orbit,  subdividing  into  the  lachrymal,  frontal,  and  nasal 
nerves,  and  gives  off  during  its  course  to  the  orbit,  fibers  to  the 
third,  fourth,  and  sixth  nerves,  to  the  tentorium  and  to  the  sympa- 
thetic. The  lachrymal  nerve  supplies  the  lachrymal  gland,  con- 
junctiva, integument  of  the  upper  eyelid,  and  gives  off  fibers 
to  the  orbital  branch  of   the  superior    maxillary.       The    frontal 

^Bernard,  Systeme  nerveux,  Tome  ii. ,  p.  100.     Paris,  lSo8. 

^Longet,  Anat.  et  Phys.  du  systeme  nerveux,  Tome  ii.,  p.  lUO.     Paris,  1842. 

^Chauveau,  op.  cit.,  p.  -76. 

*Langet,  op.  cit.,  p.  191  ;  MilU,  op.  cit.,  pp.  890-895. 


602 


THE  NERVOUS  SYSTEM. 


branch  divides  into  the  supratrochlear  and  supraorbital  nerves,  the 
former  nerve  supplies  the  integument  of  the  forehead  and  gives  oif 
a  long,  delicate  hlament  to  the  nasal  nerve  ;  the  latter,  or  supra- 
orbital nerve,  passing  through  the  supraorbital  foramen,  supplies,  to 
a  certain  extent,  the  upper  eyelid  and  forehead,  the  anterior  and 
median  portions  of  the  scalp,  the  mucous  membrane  of  the  frontal 
sinus,  and  the  pericranium  covering  the  frontal  and  parietal  bones. 

Fig.  345. 


General  plan  of  the  branches  of  the  fifth  pair.  1.  Lesser  root  of  the  fifth  pair.  2.  Greater  root 
passing  forward  into  the  Gasserian  ganglion.  ;i  Placed  on  the  bone  above  the  ophthalmic  nerve, 
■which  is  seen  dividing  into  the  suin'aorbital,  laelirymal,  and  nasal  branches,  the  latter  connected 
witli  tlie  u|ilitlKilniic  ganglion.  4.  I'laced  on  tlic  bone  close  to  the  foramen  rotundiim,  marks  the 
superior  maxillary  division.  5.  Placed  on  the  bone  over  the  foramen  ovale,  marks  the  submaxil- 
lary nerve.     (After  a  sketch  by  Cuarles  Bell.  )    %. 

The  nasal  branch,  before  entering  the  orbit,  gives  oflP  a  long  fila- 
ment to  the  ophthalmic  ganglion,  and  then  the  long  ciliary  nerves 
supplying  the  ciliary  muscle,  iris,  and  cornea ;  it  then  divides  into 
the  external  nasal,  or  infra-trochlearis,  and  the  internal  nasal,  or 
ethmoidal  nerves.  The  infra-trochlearis  nerve  supplies  the  integu- 
ment of  the  forehead  and  nose,  the  internal  surface  of  the  lower 
eyelid,  the  lachrymal  sac,  and  caruncula.  The  internal  nasal,  or 
ethmoidal  nerve,  supplies  the  mucous  membrane  of  the  nose,  and 
partly  its  integument.  The  second  l)ranch  of  the  fifth  nerve,  the 
superior  maxillary  nerve  (Fig.  34(3,  1),  passes  out  of  the  cranium  by 
the  foramen  rotundum,  and  traversing  the  infraorbital  canal  emerges 
by  the  infraorbital  foramen  upon  the  face,  giving  off  palpebral 
branches  to  the  lower  eyelid,  nasal  branches  to  the  side  of  the  nose, 
the  latter  running  in  common  with  the  nasal  branch  of  the  ophthal- 


SUPERIOR  MAXILLARY  NERVES.  603 

mic  and  lal)ial  Ijranehes  to  the  iutegument  and  mucous  membrane 
of  the  upper  lip.  During  its  course  through  the  spheno-maxillary 
fossa  the  superior  maxillary  nerve  gives  off  several  branches ;  the 
orbital,  which,  passing  into  the  orbit,  gives  off,  in  turn,  the  temporal 
and  malar  nerves,  which,  emerging  by  foramina  in  the  malar  bones, 
are  distributed  to  the  integument  of  the  temple  and  side  of  the 
forehead,  and  the  integument  covering  the  malar  bone  respectively, 
the  two  posterior  dental  nerves  (Fig.  346),  the  latter  supplying  the 

Fig.  346. 


/         i 


^  r-^ .         V        .  -^    "'    ^  ^      l?  -       ^>    --Cj    ^  - 


^*^ 


Dissection  of  the  superior  maxillary  nerve  and  Meckel's  ganglion.  1.  Superior  maxillary  nerve. 
2.  Posterior  dental  nerves.  3.  Inner  wall  of  orbit.  4.  Orbital  branch  (cut).  5.  Anterior  dental 
nerve.  6.  Meckel's  ganglion.  7.  Vidian  nerve.  8.  Sixth  nerve.  9.  Carotid  branch  of  Vidian. 
10.  Greater  superficial  petrosal  nerve.  11.  Carotid  plexus  of  sympathetic.  12.  Lesser  superficial 
petrosal  nerve.  13.  Superior  cervical  ganglion  of  sympathetic.  14.  Facial  nerve.  15.  Interr.al 
jugular  vein.  16.  Chorda  tympani  nerve.  17.  Glos.so-pharyngeal  nerve.  19.  Jacobson's  nerve. 
(From  HiRSCHFELD  and  Le'veille.  ) 

molar  and  bicuspid  teeth,  the  mucous  membrane  of  the  alveolar 
processes  and  of  the  antrum.  In  the  infraorbital  canal  the  anterior 
dental  is  given  off,  constituting,  together  with  the  posterior  dental, 
the  dental  arcade,  the  anterior  dental  supplying  the  canine  and 
incisor  teeth,  and  the  mucous  membrane  of  the  alveolar  processes. 
The  third  branch  of  the  fifth  nerve,  or  the  inferior  maxillary  (Fig. 
345,  5),  passes  out  of  the  cranial  cavity  by  the  foramen  ovale,  and 
after  uniting  Mith  the  small  or  motor  root  of  the  fifth,  divides  into 
anterior  and  posterior  branches,  the  anterior  branch  containing  the 
motor  fibers  supplying  the  principal  muscles  of  mastication,  and  the 
tensor  muscles  of  the  velum  palati  through  the  otic  ganglion,  and 
derived,  as  already  mentioned,  from  the  small  or  motor  root,  the 
posterior  branch  containing  principally  sensory  fibers.  Among  the 
most  important  of  these  may  be  mentioned  the  auriculo-temporal, 
the  lingual,  and  the  inferior  dental  nerves.  The  auriculo-temporal 
nerve  supplies  the  integument  of  the  temporal  region  of  the  ear,  the 
auditory  meatus,  the  temporo-maxillary  articulation,  and  the  parotid 
gland  ;  it  gives  off,  also,  filaments'  that  run  in  common  with  those  of 
the  seventh  nerve,  or  facial.  The  lingual  nerve,  distributed  to  the 
mucous  membrane  of  the  point  of  the  tongue,  mouth,  gums,  sub- 


604  THE  NERVOUS  SYSTEM. 

lingual  gland,  submaxillary  ganglion,  consists,  as  we  shall  see^ 
through  a  considerable  extent  of  its  course,  of  two  distinct  nerves, 
the  lingual  proper  and  the  chorda  tympani,  and  whose  relations 
will  l)e  considered  presently.  The  inferior  dental  nerve,  after  giv- 
ing oif  the  mylo-hyoid  nerve,  passes  through  the  dental  canal  in  the 
inferior  maxillary  bone,  and  supplying  the  lower  teeth,  emerges  upon 
the  face  at  the  mental  foramen,  and,  as  the  mental  nerve,  supplies 
the  integument  of  the  chin,  the  lower  part  of  the  face,  and  lower 
lip,  and  partly  the  mucous  membrane  of  the  mouth.  While,  as 
already  mentioned,  it  is  impossible  to  stimulate  directly  the  large 
root  of  the  fifth  nerve  in  a  living  animal,  yet,  since  all  of  its  acces- 
sible branches,  both  in  man  and  animals,  have  been  shown  to  be 
very  sensitive,  it  might  reasonably  be  inferred  that  the  large  root 
from  which  all  these  branches  arise  is  sensory  in  function,  especially 
W'hen  it  is  remembered  that  its  stimulation  in  an  animal  just  dead 
is  followed  by  no  contractions  of  the  muscles  to  which  the  fifth 
nerve  is  distributed.  Further,  as  well  known, ^  if  the  large  root  be 
divided  in  a  living  animal,  entire  loss  of  sensibility  on  the  side  of 
the  head  affected  at  once  follows,  any  muscular  paralysis  ensuing 
being  limited  to  the  parts  supplied  by  the  fibers  of  the  small  or 
motor  root.  The  immediate  effect  of  division  of  the  large  root  is 
very  striking,  the  cornea,  integument,  and  nuicous  meml)rane  of  the 
side  affected  are  at  once  deprived  of  sensibility,  and  may  be  burned, 
lacerated,  or  .])ricked  without  the  animal  evincing  any  pain.  Loss  of 
general  sensibility  in  the  tongue  is  also  observed,  though  no  loss  of 
taste,^  since,  as  we  shall  see  hereafter,  the  gustatory  properties  of 
the  anterior  part  of  the  tongue  are  due  to  the  chorda  tympanic 
fibers  of  the  lingual  nerve,  and  not  to  those  fibers  of  the  lingual 
proper  derived  from  the  inferior  maxillary  branch  of  the  fifth  nerve. 
The  loss  of  general  sensibility,  etc.,  are  also  observed  in  paralysis 
of  the  fifth  nerve  occurriup;  in  human  being's.  In  one  of  these 
cases,^  it  may  be  mentioned  as  a  proof  of  the  sensory  properties  of 
the  large  root  of  the  fifth  nerve,  that  an  operation  was  performed 
Avithout  the  slightest  evidence  of  pain  on  the  part  of  the  patient. 
In  addition  to  the  loss  of  sensibility,  etc.,  following  division  of  the 
large  root  of  tlie  fifth  nerve,  in  certain  cases  inflammation  of  the 
eye,  ear,  and  nose  have  also  been  observed,  the  eye  on  the  side  af- 
fected becoming  the  seat  of  purulent  inflammation  ;  the  cornea,  after 
becoming  opacpie,  ulcerating,  the  humors  of  the  eye  discharging, 
and  the  organ  destroyed.  Ulcers  also  appear  upon  the  tongue  and 
lips,  and  there  is  a  discharge  from  the  mucous  membrane  of  the 
nose  and  mouth,  and  the  hearing  appears  to  be  affected.  The  im- 
pairment in  the  nutrition  of  the  eye,  mouth,  etc.,  following  division 
of  the  fifth  nerve,  ai)pears  to  be  due  rather  to  inflannuatory  irritation 

^Magendie,  Journal  de  Pliy.siologie,  Tome  iv.,  pp.  176,  302.  Paris,  1824.  Ber- 
nard. Leyons  sur  la  i)livsiologie  et  la  pathologie  du  Svsteme  nerveux,  Tome  ii.,  p. 
53.     Paris,  1.S58. 

^SchiftJ  Leyons  sur  la  physiologie  de  la  digestion.  Tome  i.,  p.  103.  Florence, 
18()7.     Lusanna,  Arelii\es  de  Pliys.,  Tome  ii.,  p.  27.     Paris,  1869. 

''Noyes,  New  York  Med.  Journal,  1871,  Vol.  xiv.,  ]>.  163. 


THE  SEVENTH  NERVE. 


605 


of  the  nerve  than  to  division  of  the  fiber?^  of  the  sym]>athetic  passing 
into  the  Gasserian  ganglion  Avith  eonseqnent  vasomotor  distnrbance 
as  was  formerly  snpposed.  That  the  })aralysis  of  tlie  mnscles  of 
mastication  incidental  to  the  division  of  the  fifth  nerve  which  inter- 
feres seriously  with  the  digestion  of  food  may  account  to  some  ex- 
tent for  the  disturbances  of  nutrition  just  mentioned  appears  to  be 
shoM'n  from  the  fact  that  the  inflammation  of  the  eye,  etc.,  can  be 
j)revented,  for  some  weeks  at  least,  if  the  animal  be  artificially  fed 
with  good  nutritive  food.  It  need  hardly  be  mentioned  that  the 
nervous  fibers  transmitting  gustatory,  olfactory,  and  auditory  im- 
pressions are  not  in  any  way  derived  from  the  large  root  of  the  fifth 
nerve,  as  once  thought,  the  large  root  being  only  a  nerve  of  general 
sensibility,  the  small  root  of  motion. 

The  Seventh  Nerve. 
The  seventh  nerve,  the  nerve  of  expression,  the  facial,  or  the 
portio  dura  of  the  seventh  pair,  supposing  the  latter  to  include,  as 
in  the  arrangement  of  Willis,  not  only  the  fibers  of  the  facial  pro])er, 
but  those  of  the  auditory,  or  porto  mollis,  containing  about  4,500 
fibers,  arises  in  a  fan-shaped  manner  from  a  group  of  cells  situated 
in  the  grav  matter  of  the  floor  of  the  fourth  ventricle  (Figs.  337, 
VII;   347;  A). 

Fig.  347. 

C 


Schema  of  the  apparatus  of  the  facial  nerve.  P.  Pons.  A.  Facial  nucleus.  B.  Facial  cortico- 
bulbar  tract.  C.  Cortical  center  for  facial  movements.  D.  Nucleus  of  the  pars  intermedia  of 
Wrisberg.  E.  Descending  glossn-pluiryngeal  roots.  H.  Nucleus  of  the  hvpo-glossal  nerve.  FF. 
Trunk  of  the  facial  nerve,  a.  (ii'iiiculate  ganglion.  TTT.  Pars  interuiedia  of  Wrisberg  and 
chorda  tympaui  nerve.  M.  IMcckel's  sphcuo-palatiuc  ganglion.  O.  Otic  ganglion,  a.  Great  super- 
ficial petrosal  and  Vidian  nerves,  b.  Lesser  siq)er<i(ial  petrosal  nerve,  c.  External  superficial 
petrosal  nerve  ;  branch  of  the  facial  nerve  to  the  stajifdius  muscle,  e.  Branch  of  the  facial  to  the 
auricular  branch  of  the  vagus.  /.  Posterior  auricular  branch,  g.  Digastric  branch,  h.  Stylo- 
hyoid branch,  i.  Temporalbrauch.  j.  Malar  branch,  k.  Intraorbital  branch.  /.  Buccal  branch. 
m.  Supramaxillary  branch,    n.  Inframaxillary  branch.     (Mills.) 


606 


THE  NERVOUS  SYSTEM. 


Fig.  348. 


The  fibers  so  arising  pass  from  the  fioor  of  the  fourth  ventricle  as 
a  compact  bundle  which,  curving  over  the  nucleus  of  the  sixth  nerve 
horseshoe  like  (Fig.  347,  T),  turns  obliquely  outward  and  emerges, 
together  with  the  pars  intermedia  or  nerve  of  Wrisberg,  from  the 
transverse  fil)ers  of  the  pons  P  between  the  abducens  and  acoustic 
nerves.  The  facial  nucleus  is  in  relation  with  axis-cylinders  which, 
crossing  the  middle  line  of  the  floor  of  the  fourth  ventricle  and  de- 
cussating with  the  fibers  of  the  opposite  nerve,  pass  through  the 
knee  of  the  internal  capsule,  and  the  corona  radiata  into  the 
motor  cells  of  the  lower  extremity  of  the  central  convolution  C  of 
the  opposite  hemisphere.  According  to  some  observers  the  facial 
nucleus  is  also  connected  by  axis-cylinders  from  the  substantia 
gelatinosa  of  the  cord  with  the  descending  spinal  root  of  the  fifth 

nerve.  That  the  fibers  of  the  ftu'ial  nerve 
decussate  in  the  pons  as  just  described  is 
shown  by  the  fact  of  what  is  known  as 
"alternate  paralysis,"  it  l)eiug  well  known 
that  if  a  lesion  be  situated  in  tlie  pons. 
Fig.  348,  L,  the  facial  paralysis  and  that 
of  motion  and  sensation  will  be  on  opposite 
sides  of  the  body,  whereas  if  the  lesions 
be  situated  anterior  to  the  pons,  the  facial 
paralysis  and  that  of  motion  and  sensation 
will  be  on  the  same  side  of  the  body. 

The  facial,  pars  intermedia,  and  audi- 
tory nerves,  after  leaving  the  base  of  the 
brain,  pass  thence  into  the  internal  audi- 
tory meatus,  the  pars  intermedia  being 
connected  in  this  part  of  its  course  with 
the  auditory  nerve,  a  relation  the  func- 
tional significance  of  which  it  may  be 
stated  has  not  yet  been  shown.  Leaving 
for  the  present  the  further  consideration 
of  the  auditory  nerve,  the  facial  and  the 
pars  intermedia  will  be  found  to  enter  the 
Fallopian  canal,  the  pars  intermedia  pre- 
senting a  gangliform  enlargement,  the  gen- 
iculate ganglion,  and  passing  by  this  route 
through  the  jietrous  portion  of  tlie  temporal  bone  the  two  nerves 
unite  and  emerge  as  a  common  trunk  by  the  stylo-mastoid  foramen. 
Consideral)l('  difference  of  opinion  still  ])revails  as  to  the  exact 
origin  and  distribution  of  the  pars  intermedia  which  we  have  just 
seen  emerges  from  the  base  of  the  brain  between  the  facial  and 
auditory  nerves.  According  to  i-ccent  observations  the  pars  inter- 
media, regarded  by  some  histologists  as  a  root  or  branch  of  the 
facial,  by  others  as  a  distinct  nerve,  arises  or  rather  terminates  in 
the  nucleus  of  the  glosso-pharyngeal  nerve  (Fig.  349,  A)  from 
the  cells  of  which  fibers  run  for  a  time  juxtaposed  with  those  of 
the  facial  projjer  and  thence  pass  peripherally  as  the  chorda  by 


To  illustrate  alternate  para 
vsis.  C.  Cerebrum.  /'.  Pou 
ll/.  Medulla.  /•'.  Facial. 
Lesion.    (S'.  Spinal  cord. 


L. 


THE  SEVENTH  NERVE. 


607 


certain  nerves.     On  the  other  hand,  there  are  gMxxl  reasons,  as  we 
shall  see  presently,  for  snpposing-  that  the  ehorda  tympani  nerve 


Fig.  .349. 


Ociiiciila/e 


Jiujiilar  ganr/Iion 


jS Petrous  ganglion 


Peripheral  gustatory  apparatus.  .^I.  Portion  of  the  sensory  glosso-pharyngeal  nucleus  in  which 
the  pars  intermedia  terminates.  B.  Main  portion  of  the  sensory  glosso-pharyngeal  nucleus.  C. 
Commissural  nucleus  of  Ramon  y  Cajal.  V.  Nucleus  amhiguus.  O.  Olive.  P.  Pyramid.  JR. 
Restis.     V.  Spinal  root  of  the  fifth  nerve.     (Mills.) 

is  the  continuation  of  the  great  petrosal  nerve,  the  two  nerves  be- 
ing connected  in  the  geniculate  ganglia.     The  significance  of  these 
relations  will  be  better  ap- 
preciated,  however,   w  h  e  n  Fig.  350. 
the    peripheral    distribution 
of  the  facial  has  been   de- 
scribed. 

The  most  i  m  p  o  r  t  a  n  t 
branches  of  the  facial  are 
briefly  as  follows  :  The  large 
and  small  petrosal  nerves 
p  a  s  s  i  n  g,  respectively,  to 
Meckel's  and  the  otic  gan- 
glia (Fig.  349),  the  external 
petrosal  to  the  sympathetic 
fibers  of  the  middle  menin- 
geal artery,  tlie  tympanic 
branch  distril)uted  to  the 
stapedius  muscle,  the  chorda 
tympani  nerve  (Figs.  349, 
350)  passing  through  the 
tympanum  to  join  the  lin- 
gual branch  of  the  inferior  maxillary,  the  branch  to  the  pneumo- 
gastric. 


1,  2, 3,  4.  Facial  nerve  passing  tlirough  the  aqujeduc- 
tus  Fallopii.  5.  (lantjliform  cnhirgeraent.  6.  Great 
petrosal  nerve.  7.  Spluud-pahitine  ganglion.  S.  Small 
petrosal  nerve,  it.  Chdrda  tympani.  10,  11,  12,  13. 
Various  branches  of  the  facial.  14,  14,  15.  Glosso- 
pharyngeal nerve.     (Hirsihfklu.) 


608 


THE  NERVOUS  SYSTEM. 


The  six  brauches  just  mentioned  are  given  off  h\  the  facial  dur- 
ing its  course  through  the  aqueduct  of  Fallopius.  The  remaining 
branches  still  to  be  mentioned  are  given  off  after  the  nerve  has 
emerged  from  the  stylo-mastoid  foramen,  tlie  branch  to  the  glosso- 
pharyngeal nerve,  the  posterior  auricular  connected  ^vith  the  cer- 
vical plexus  by  the  auricularis  magnus  and  distributed  to  the 
retrahens  and  attolens  aurem,  the  occipital  portion  of  the  occipito- 
frontalis  muscle,  and  the  integument,  the  digastric  l)ranch  receiv- 
ing filaments  from  the  glosso-pharyngeal  supplying  the  posterior 
belly  of  the  muscle  of  the  same  name  and  the  stylo-hyoid,  a  distinct 
branch  also  to  the  stylo-hyoid  muscle,  the  lingual  branch — ^that  is, 
the  branch  passing  behind  the  stylo-pharyngeus  muscle  and  re- 
ceiving filaments  from  the  glosso-pharyngeal  nerve  to  be  distrib- 
uted to  the  mucous  membrane,  tongue,  stylo-glossus,  and  palato- 
glossus muscles,  and  finally,  the  temporo-facial  and  cervico-facial 
branches  (Fig.  351)  into  which  the  main  trunk  divides  as  it  passes 
through  the  parotid  gland. 

Fig.  ;].")1. 


Superficial  branches  of  till  i    i        iili      1     1 1  iink  of  the  facial.    2.  Po.sterior  auricular 

iKTve.  3.  Branch  which  It  icccnc  Iroin  till  cciMcal  pit  \ii'»  4.  Occipital  branch.  5,6.  Branches 
to  the  muscles  ol  the  c  ir  7  Itigi^trii  liraiuhc^  H  Kr  iiidi  to  the  stylo-hyoid  muscle.  9.  Supe- 
rior terminal  branch  W  lonporil  biandic^  11  1  lontal  Ijranches.  12.  Branches  to  the 
orbicularis  palpebrarum.  l:s.  Nasal,  or  suborbital  branches.  14.  Buccal  brauches.  15.  Inferior 
terminal  branch.  Ki.  Mental  branches.  17.  Cervical  branches.  18.  Superficial  temporal  nerve 
(branch  of  the  fifth).  19,  20.  Frontal  nerve  (branches  of  the  fifth).  21,  22,  23,  24,  25,  26,  27. 
Branches  of  the  fifth.    28,  29,  30,  31,  32.  Branches  of  the  cervical  nerves.     (Hirschfeld.) 


THE  SEVENTH  NERVE.  609 

The  tenijjoro-faeial  branch  passing  u})war(l  and  forward  is  dis- 
tril^nted  to  the  attrahens  anreni,  the  frontal  portion  of  the  occipito- 
frontalis,  the  orbicuhiris  ])alpel)raruni,  corrngator  snpereilii,  pyra- 
midalis  nasi,  levator  lal)ii  snperioris,  alseqne  nasi,  tlie  dilator  and 
compressor  nasi,  part  of  the  bnceinator,  the  levator  anguli  oris,  and 
the  zygomatic  muscles.  During  its  course  the  tem]X)ro-facial  branch 
receives  filaments  from  the  auriculo-temporal  l)ranch  of  the  inferior 
maxillarv  nerve,  from  tlic  temj)()ral  branch  of  the  su])eri<)r  maxillary, 
and  from  the  ophthalmic  ;  it  becomes,  therefore,  a  mixed  nerve  in 
function.  The  cervico-facial  nerve,  passing  downward,  supplies  the 
buccinator,  orbicularis  oris,  risorius,  levator  labii  inferioris,  depressor 
hil)ii  inferioris,  depressor  anguli  oris,  and  platysma  myoides.  From 
the  fact  that  division  of  the  fifth  nerve  is  at  once  followed  by  entire 
loss  of  sensibility  in  the  parts  supplied  by  that  nerve,  it  is  evident 
that  the  facial,  supplying  to  a  considerable  extent  identical  regions, 
cannot  be  a  sensory  nerve,  otherwise  sensibility,  though  weakened, 
should  nevertheless  persist  in  the  face,  etc.,  even  after  division  of  the 
fifth  nerve.  Direct  evidence,  however,  as  well  as  indirect,  proves 
conclusively  that  the  seventh  nerve,  at  its  origin  at  least,  is  a  purely 
motor  nerve.  Thus,  division  of  the  nerve  in  a  living  animal  or 
disease  in  man  is  at  once  followed  by  paralysis  of  the  facial  and 
other  muscles  that  we  have  just  seen  are  supplied  by  the  nerve, 
while  stimulation  of  the  nerve  at  its  root  in  a  living  animal  or  in 
one  recently  dead,  causes  contraction  of  the  muscles,  but  in  the  case 
of  the  living  animal  no  pain.  Any  sensibility  then  exhibited  by 
the  facial  nerve  beyond  its  root  must  be  attributed  to  tlie  fillers  de- 
rived from  the  fifth  nerve,  glosso-pharyngeal,  and  pueumogastric, 
that  we  have  seen  run  in  juxtaposition  with  it.  In  order  to  appre- 
ciate the  varied  and  important  functions  of  the  facial  nerve,  it  will  be 
best  to  consider  those  of  its  Ijranches  seriatim.  In  the  considera- 
tion of  the  sympathetic,  to  be  taken  up  hereafter,  it  will  l)e  then 
shown  that  the  nerve  fibers  supplying  the  levator  palati,  azygos 
uvulae,  palato-pharyngeus,  and  palato-glossus  are  derived  from  the 
ganglion  of  ^Meckel,  and  those  sup})lying  the  tensor  palati  and  tensor 
tympani  from  the  otic  ganglion  ;  and  on  the  supposition  that  the 
great  and  small  petrosal  nerves  pass  respectively  through  the  two 
ganglia  to  the  muscles  just  mentioned,  supplied  by  the  latter,  it 
might  be  inferred  that  paralysis  of  the  facial  nerve  would  be  ac- 
companied with  difficulty  in  deglutition  and  an  increased  sensi- 
tiveness to  sound,  the  tympanic  membrane  being  relaxed  through 
the  paralysis  of  the  tensor-tympani  muscle,  it  being  well  known 
that  the  tympanic  membrane'  vibrates  more  intensely  when  relaxed 
than  when  tensed.  Clinical  cases  of  facial  paralysis  occurring  in 
man  fully  confirm  this  view,  since  in  such  cases  both  difficulty  in  deg- 
lutition and  increased  susceptil)ility  to  sounds,  etc.,  are  observed.^ 

'  Mnller's  Elements  of  Physiology,  Vol.  ii.,  ]).  1256.     London,  1843. 

^Montaiit,  Dessertation  sur  riieniiplegie  i'iiciale  these  300,  Paris  1S31.  Pell,  The 
Nervous  System,  London  1844,  p.  329.  Pernard,  Leyons  sur  la  jiliysiologie  et  la  j)a- 
thologiedusvstemenervenx.  Paris,  1858,Tome  xi.,pp.  114, 113.  Mills,  oj).  cit.  p.  907. 
39 


610  THE  NERVOUS  SYSTEM. 

Further,  as  confirming  the  view  that  the  muscles  of  deghitition  are 
supplied  by  the  facial,  may  be  mentioned  the  fact  of  the  facial  nerve 
giving-  oif  the  branch  already  alluded  to  supplying  the  stylo-glossus 
and  palato-glossus  muscles,  and  occasionally  of  the  branch  dis- 
tributed to  the  palato-glossus  and  palato-pharyngeus  muscles  pass- 
ing directly  to  the  latter  without  being  connected  with  the  glosso- 
pharyngeal, as  is  usually  the  case.^ 

It  must  be  mentioned,  however,  that  according  to  Gowers  ^  in 
more  than  one  hundred  cases  of  facial  paralysis  due  to  disease  of 
the  nerve  in  various  situations  no  defect  of  movement  in  the  palate 
was  ever  observed.  Such  Ijeing  the  case  it  is  obvious  that  the 
motor  fibers  innervating  the  palate  must  be  derived,  in  some  cases 
at  least,  perhaps  in  all,  not  only  from  the  facial,  but  from  other 
nerves  as  well.  From  the  fact  that  the  motor  fillers  innervating 
the  tensor  palate  are  derived  from  the  otic  ganglion  and  that  in 
certain  cases,  at  least,  of  disease  of  the  fifth  nerve  deglutition  is  in- 
terfered with  or  rendered  impossible,  it  has  been  inferred  by  some 
physiologists  ^  that  the  motor  fibers  innervating  the  tensor  palate 
are  derived  from  these  fibers  of  the  small  or  motor  root  of  the  fifth 
nerve  that  pass  into  the  otic  ganglion.  On  the  other  hand,  it  has 
been  shown  that  stimulation  of  the  spinal  accessory  nerve  in  cer- 
tain animals  causes  contractions  of  the  palate,*  the  impidses  pass- 
ing to  the  latter  either  by  the  branch  that  the  pueumogastric 
gives  to  the  pharyngeal  plexus  or  possibly  by  the  tympanic 
branch  of  the  glosso-pharyngeal,  some  of  the  fibers  of  which 
pass  to  the  otic  ganglion.  Further,  it  is  well  known  that  in 
disease  of  the  spinal  accessory  nerve,  movement  of  the  palate  on 
the  same  side  is  lost.'  The  facts  of  experiment  and  clinical 
medicine  render  it  highly  probable,  therefore,  that  the  spinal  ac- 
cessory nerve  is  the  motor  nerve  of  the  palate.  With  such  dis- 
cordant views  still  prevailing  it  must  l)e  admitted  that  the  nerve 
fibers  innervating  the  muscles  of  the  palate  have  not  yet  been 
positively  determined. 

The  chorda  tympani  nerve  (Fig.  350),  one  of  the  most  remarkable 
nerves  in  the  V)ody,  both  on  account  of  its  origin  and  distribution  as 
well  as  of  its  properties,  is  usually  said  to  arise  from  the  facial  in  the 
a(iueduct  of  Fallopius  and  passing  by  a  special  canal  into  the  tym- 
panum crosses  the  latter  cavity  between  the  incus  and  malleus  and 
emerges  by  the  canal  of  Hugier  to  join  the  lingual  nerve  at  an 
acute  angle. 

In  the  horse  and  calf,  however,  as  shown  by  Owen,"  the  chorda 
tympani  nerve  (Fig.  '352),  while  apparently  arising  from  the  facial,  as 

1  Lonj^et,  op.  cit.,  Tome  iii.,  p.  o81. 
2 Gowers,  op.  eit.,  Vol.  ii.,  ]>.  236. 
"MilLs,  op.  cit.,  pp.  890,  895. 

*\Y.  A.  Turner,  Journal  of  Anat.  ami  Pliys.,  1889.  Beaver  and  Ilorsley,  Proc. 
Koyal  Society. 

5 Gowers,  op.  cit.,  Vol.  ii.,  p.  307. 

^ The  Anatomy  of  Vertebrates,  Vol.  iii.,  p.  150.     London,  1868. 


THE  CHORDA    TYMPAXI  XERVE. 


611 


Fig.  352. 


Ill 


Piagram  to  illustrate  suj>- 
posed  connection  of  chorda 
tympani  with  superior  max- 
illary through  facial,  great 
petrosal,  and  ganglion  of 
Meckel. 


in  man,  in  reality  can  be  traced  through  the  fibers  of  the  facial 
as  a  continuation  of  the  large  petrosal,  and  as  the  latter  nerve  is 
connected  through  the  ganglion  of  Meckel  with  the  superior  max- 
illarv  nerve  a  pathway  evidently  exists  in  these  animals  by  which 
the  impressions  made  upon  the  tongue  can  be  transmitted  to  the 
latter  nerve,  and  while  the  chorda  tympani  nerve  has  not  ])een 
actually  demonstrated  in  man  to  be  a  continu- 
ation of  the  large  petrosal,  as  in  Fig.  352, 
both  experiments  upon  animals  and  patho- 
logical cases  in  man  lead  one,  as  we  shall  see, 
to  suppose  that  such  is  substantially  the 
case.^  On  the  other  hand,  apart  from  the 
fact  of  nerve  fibers  not  anastomosing,  there 
is  direct  experimental  evidence  to  show  that 
the  chorda  tympanic  fibers  do  not  lose  their 
individuality  after  joining  those  of  the  lingual 
branch  of  the  inferior  maxillary,  but  pre- 
serve their  functional  activity  entirely  inde- 
pendent of  those  of  the  latter.  Thus,  if  the 
lingual  branch  of  the  inferior  maxillarv  be 
divided  before  it  is  joined  by  the  chorda 
tympani,  its  fibers  alone  atrophy,  with  ensu- 
ing loss  of  general  sensibility  of  the  anterior  part  of  the  tongue, 
whereas,  if  the  chorda  tympani  nerve  be  divided  before  it  reaches 
the  lingual  its  terminal  fibers  alone  atrophy,  loss  of  taste  en- 
suing. 

Experiment  not  only  shows,  however,  that  the  terminal  portion 
of  the  lingual  nerve  consists  of  fibers  derived  from  both  the  lingual 
branch  of  the  inferior  maxillary,  and  from  the  chorda  tympani, 
but  that  the  latter  consists  of  three  distinct  sets  of  fibers  ;  1st, 
those  endowing  the  anterior  two-thirds  of  the  tono;ue  with  the 
sense  of  taste  ;  2d,  those  modifying  the  blood  vessels  of  the  tongue, 
vasa  dilator  nerves  ;  3d,  those  stimulating  through  the  submaxil- 
lary ganglion  the  submaxillary  and  sublingual  glands.  The  chorda 
tympani  nerve,  consisting,  as  it  undoubtedly  does,  then,  of  sensory, 
motor,  and  secretory  filjers,  it  is  to  be  expected  that  it  should  have 
specially  different  centers  of  origin,  which  is  in  harmony  with  the 
view  just  offered  of  its  motor  fibers  being  derived  from  the  facial, 
and  its  sensory  fibers  from  the  superior  maxillarv  nerve  through 
the  large  petrosal  and  the  ganglion  of  Meckel.  That  the  chorda 
tympani  nerve  does  contain  at  least  some  fibers  derived  from  the 
superior  maxillary  nerve  is  further  shown  from  the  fact  that  disease 
of  the  fifth  nerve,  removal  of  the  ganglia  of  Gasser  and  Meckel  in 
man,  is  folloMed  by  the  loss  of  the  sense  of  taste  in  the  anterior 
two-thirds  of  the  tongue."     It  must  be  admitted,  however,  that  it 


'  Goweis,  op.  cit.,  Vol.  ii.,  p.  214 


^Schitt;  Leyons  sur  la  Physiologie  de  Digestion,  Tome  premier,  p.  100. 
and  Turin.     Gowers,   op.   tit..  Vol.  ii.,  p.  21G.      Mills,   op.   cit.,   p.   094. 


Florence 


612 


THE  NERVOUS  SYSTEM. 


is  held  by  many  physiologists  at  the  present  day  that  the  chorda 
tympani  ministers  to  the  sense  of  taste  of  the  supposition  that  its 
fibers  are  continuous  with  those  of  the  pars  intermedia  and  that 
the  latter  nerye  is  endowed  with  gustatory  properties  because  de- 
rived from  the  glosso-pharyngeal/  The  well-known  fact  that  dis- 
ease of  the  facial  nerve  situated  between  the  origin  of  the  chorda 
tympani  and  the  geniculate  ganglion  is  accompanied  with  loss  of 
taste  in  the  anterior  part  of  the  tongue  -  has  been  cited  as  a  proof 
that  the  chorda  tympani  is  continuous  with  the  great  petrosal.  It 
is  obvious,  however,  from  what  has  just  been  said  that  the  fact  of 
disease  of  the  facial  involving  the  sense  of  taste  might  be  offered 
equally  well  as  a  proof  that  the  chorda  tympani  is  continuous  with 
the  pars  intermedia. 

It  may  be  mentioned  in  this  connection  that,  even  if  the  view- 
that  the  chorda  tympani  is  derived  from  the  pars  intermedia  is  not 
admitted,  the  fact  that  the  latter  unites  with  the  facial  in  the  Fal- 
lopian canal  is  not  without  functional  significance,  since  it  is  well 

Fig.  358. 


Schema  of  the  iiervt'S  of  the  salivary  glands.  P.  Pons.  MO.  Medulla  oblongata.  XV.  Nerve  of 
Jaeobson.  O,  SM,  IM.  Ophthalmic,  superior,  and  inferior  maxillary  division.s  of  I',  tifth  nerve. 
VII.  Seventh  nerve.  S.iji.  Small  superticial  i)etrosal  nerve.  I«(/.  Vagus.  Si/m.  Sympathetic. 
OG.  otic,  and  SO.  Submaxillary  ganglia.  P,  >S,  L.  Parotid,  sub-maxillary  and  sub-lingual 
glands.     T.  Tongue.     (Laxdois.) 


known  that  the  facial,  after  emerging  from  the  stylo-mastoid  fora- 
men, contains  sensory  fibers,  which  may  account  for  sensation  being 
more  or  less  restored  in  certain  cases  of  removal  of  the  Gasserian 
o-ano-lion.  Leaving  the  further  account  of  the  gustatory  fibers  of 
the  chorda  tympani  for  the  present,  let  us  turn  now  to  the  consider- 
ation of  those  of  its  fibers  that,  passing  to  the  submaxillary  gang- 
lion (Fig.  353,  SG),  constitute,  together  with  the  sympathetic  fibers 

1  Mills,  op.  cit.,  p.  G86. 

^Bernard,  Systeme  Ncrveux,  1858,  Tome  ii.,  p.  122.  Sdiiff,  op.  eit.,  Tome  i., 
p.  183.  Lusanna,-  Airhivcs  de  Physiologie,  Tome  ii.,  p.  201.  Paris,  1869. 
Gowers,  op.  cit.,  Vol.  ii.,  p.  237. 


NEEJ^ES  OF  THE  SALIl'ARY  GLANDS.  613 

accompanying  the  blood  vessels,  the  efferent  fibers  involved  in 
the  reflex  production  of  saliva  by  the  submaxillary  and  sub- 
lingual glands,  the  lingual  glosso-pharyngeal  and  pnenmogastric 
nerves,  the  afferent  fibers,  the  center  of  the  reflex  arc  being 
situated  in  the  medulla  at  the  origin  of  the  seventh  and  ninth 
cervical  nerve.  It  may  be  mentioned,  in  this  connection  as  ap- 
propriately as  elsewhere,  that  while  in  the  reflex  production  of 
saliva  by  the  parotid  gland  the  afferent  nerves  are  the  same  as 
in  the  case  of  the  submaxillary  and  sublingual  nerves ;  the  ef- 
ferent nerves  involved,  in  addition  to  sympathetic  fibers,  are 
derived  from  the  otic  ganglion,  from  the  facial  by  the  small 
petrosal,  and  from  the  glosso-pharyngeal  nerve  by  the  tympani 
branch  of  the  glosso-pharyngeal  or  Jacobson's  nerve. 

Fk;.  35-t. 

3Incous  Mejiibrnne 


jServe         ^  ■^  '"'^ 


Secretory  N 


Xervi 

Ceutre\^4-„      ,'X,  jQ^        "~(!^^\_Secretijig 

CeUs 


Bloodvessels 
of  Gland 


Diagram  of  a  salivary  gland  aud  nerves.     (La>'dois.) 

If  the  submaxillary  and  sublingual  glands  be  cleanly  dissected 
out,  as  in  a  living  dog,  for  example,  in  which  the  glands  are  very 
accessible,  they  will  be  seen  to  be  comparatively  at  rest,  secreting 
little  or  no  saliva,  and  their  venous  blood  of  a  dark  hue.  If  now 
a  drop  of  vinegar  be  placed  upon  the  tongue  of  the  animal,  at  once 
the  arterial  twigs  enlarge,  the  blood  flows  more  rapidly,  the  veins 
pulsate,  the  color  of  their  blood  becomes  scarlet,  and  the  pressure 
increases,  followed  by  an  abundant  discharge  of  limpid,  very  alka- 
line saliva,  the  so-called  chorda  tympani  saliva,  containing  small 
quantities  of  albumin,  globulin,  mucin.  That  the  phenomena  just 
described  are  due  to  impressions  transmitted  to  the  medulla  by  the 
aflerent  sensory  fibers  of  the  lingual  branch  of  the  inferior  maxil- 
lary and  glosso-pharyngeal  nerves,  and  thence  reflected  back  to  the 
submaxillary  aud  sublingual  glands  by  the  efferent  secreto-motor 
fibers  of  the  chorda  tympani  (Fig.  o54),  is  shown  by  such  fiicts  as 
that,  after  division  of  the  lingual  branch,  the  secretion  of  saliva,  etc., 
ceases,  but  recommences  if  the  central  end  of  the  divided  nerve  be 
stimulated.     On  the  other  hand,  if  the  chorda  tympani  be  divided, 


614  THE  NEB  VO  US  S  YSTEM. 

tlie  vessels  supplying  the  submaxillary  and  sublingual  glands  con- 
tract ;  owing  to  the  unopposed  action  of  the  sympathetic  vaso-con- 
stricting  fibers,  the  blood  flows  slowly,  is  diminished  in  quantity, 
and  becomes  dark,  the  secretion  of  saliya  diminishes  ;  the  applica- 
tion of  vinegar  no  longer  excites  the  secretion.  That  the  secretion 
does  not  altogether  cease  after  division  of  the  chorda  tympani  ap- 
pears to  be  due  to  the  independent  reflex  action  of  the  submaxillary 
ganglion.  If  now,  however,  tlie  divided  chorda  tympani  be  stimu- 
lated at  its  distal  end,  all  the  former  phenomena  recur.  It  may  be 
mentioned,  in  this  connection,  though  anticipated  somewhat,  that  if 
the  sympathetic  plexus  surrounding  the  facial  artery  be  stimulated, 
the  blood  vessels  of  the  glands  become  very  much  contracted,  the 
lilood  flowing  more  slowly,  and  darker  in  color  in  the  veins,  and 
that  the  saliya  then  secreted — the  so-called  sympathetic  saliva — is 
not  only  diminished  in  quantity,  but  contains,  in  addition  to  albu- 
min and  mucin,  sarcode-like  bodies.  With  division  of  the  sympa- 
thetic fibers,  the  secretion  of  saliva  does  not  altogether  cease,  a  small 
quantity  of  the  so-called  paralytic  saliva  being  secreted,  if  the  tongue 
be  stimulated  with  induced  electricity. 

The  fact  that  an  abundant  supply  of  chorda  saliva  accompanies 
increased  blood  flow,  a  scanty  supply  of  sympathetic  saliva  or  di- 
minished one  would  naturally  suggest  the  idea  that  the  secretion  of 
saliva  was  simply  a  vasomotor  effect,  dependent  upon  the  quantity 
and  pressure  of  the  blood.  That  such  is  not  the  case,  however, 
that  the  phenomenon  depends  upon  the  stimulation  of  the  salivary 
glands  by  secretory  nerves  is  shown  by  the  following  considerations  : 
That  the  pressure  in  the  duct  is  greater  than  in  the  artery  supply- 
ing the  gland ;  that  the  temperature  of  the  gland  rises ;  that  the 
amount  of  carbon  dioxide  is  increased ;  that,  after  the  injection  of 
atro[)ine  into  the  gland,  stimulation  of  the  chorda  tympani  will 
still  cause  vascular  dilatation,  though  no  secretion.  Just  as  there 
are  involved  in  the  production  of  saliva  t\yo  sets  of  nerve  fibers, 
secretory  and  vaso-dilator,  so  it  is  held  by  many  physiologists 
that  there  are  two  kinds  of  secretory  fibers,  the  secretory  fibers 
proper,  whose  function  it  is  to  regulate  the  production  of  water 
and  inorganic  salts,  and  trophic  fibers,  which  cause  the  forma- 
tion of  the  organic  constituents  of  the  saliva.  While  it  is  pos- 
sible that  such  a  distinction  exists  as  that  of  secretory  and 
trophic  fibers  it  cannot  be  said  as  yet  to  have  been  positively 
established. 

In  concluding  our  account  of  the  functions  of  the  facial  nerve  it 
remains  for  us  now  briefly  to  call  attention  to  its  external  branches. 
Immediately  after  the  nerve  passes  out  of  the  stylo-mastoid  fora- 
men, as  already  mentioned,  it  sends  a  branch  to  the  glosso-pharyn- 
geal,  upon  which,  as  we  shall  see,  the  motor  properties  of  the  latter 
nerve  depend.  The  posterior  auricular  branch  receiving  sensory 
filaments  from  the  cervical  plexus  supplies  the  attolens  and  retra- 
hens  aurem  and  the  posterior  portion  of  the  occipito-frontalis  muscle 


THE  XIXTH  XER  VE.  6 1 5 

and  the  adjacent  integument.  The  branches  supplying  the  pos- 
terior belly  of  the  digastric,  stylo-hyoid,  and  stylo-glossus  muscles 
are  important,  as  these  muscles  are  involved  in  mastication  and 
deglutition.  The  temporo-facial  branch,  as  Ave  have  seen,  supplies 
all  the  muscles  of  the  upper  part  of  the  face.  If  this  branch  be 
paralyzed,  the  eye  remains  therefore  constantly  open,  through 
paralysis  of  the  orbicularis  palpebrarum  muscle,  and  may  become 
inflamed  in  consequence  from  constant  exposure.  The  frontal  por- 
tion of  the  occipito-frontalis,  attrahens  aurem,  and  the  corrugator 
supercilii  are  also  paralyzed.  A  striking  symptom  of  paralysis  of 
the  facial  nerve  if  these  filaments  be  affected,  is  inability  to  corru- 
gate the  brow  upon  one  side,  as  in  frowning.  Through  paralysis 
of  the  muscles  that  dilate  the  nostrils  olfaction  and  inspiration  are 
also  somewhat  interfered  with.  To  appreciate  the  influence  exerted 
by  the  facial  nerve  upon  inspiration  it  may  be  mentioned  that  in 
the  horse,  where  the  breathing  is  entirely  nasal,  death  from  suffo- 
cation very  soon  takes  place  if  both  facial  nerves  be  divided,  both 
nostrils  then  collapsing  and  becoming  closed  with  each  inspiratory 
effort.^  The  effect  of  paralysis  of  the  facial  nerve  is  well  seen  in 
cases  of  facial  palsy  affecting  one  side,  the  distortion  of  the  features 
being  due  in  such  cases  to  the  unopposed  action  of  the  muscles 
upon  the  unaffected  side.  ^Vhen  the  paralysis  is  complete  the 
angle  of  the  mouth  is  drawn  to  the  sound  side,  the  eye  on  the 
affected  side  is  widely  opened,  even  during  sleep,  the  lips  are  par- 
alyzed upon  one  side,  the  saliva  frequently  flowing  from  the  corner 
of  the  mouth  while  the  food  tends  to  accumulate  between  the  teeth 
and  cheek  through  paralysis  of  the  buccinator,  mastication  in  con- 
sequence being  materially  interfered  with.  If  both  facial  nerves 
be  paralyzed,  mastication  becomes  very  difficult,  and  the  face  ex- 
hibits a  peculiarly  expressionless  appearance. 

The  Ninth  Nerve. 

The  next  nerve  in  order,  the  ninth  or  glosso-pharyngeal,  the  con- 
sideration of  the  eighth  nerve  or  auditory  being  deferred  for  the 
present,  arises  in  common  with  the  nucleus  of  the  pneumogastric 
from  a  column  of  cells  (Fig.  337,  IX)  deeply  situated  beneath  the 
lower  and  outer  part  of  the  floor  of  the  fourth  ventricle. 

The  nucleus  appears  to  be  in  relation  with  axis-cylinders  that 
are  supposed  to  descend  from  motor  cells  of  the  opposite  hemisphere, 
the  locality  of  which  is  as  yet  ill-defined,  and  passing  probably  near 
the  pyramidal  tract  cross  the  middle  line  to  terminate  in  the  medulla. 
After  emerging  from  the  medulla,  the  fibers  of  the  glosso-pharyngeal 
proceed  forward  and  outward  by  a  series  of  five  or  six  roots,  contain- 
ing about  9000  fibers,  attached  to  the  surface  of  the  restiform 
body,  the  highest  being  close  to  the  auditory  nerve  and  passes  out 

1  Bernard,  Le^-ons  sur  la  phvsiologie  et'  la  patholuirie  du  Svstcme  Xerveux,  Tome 
ii.,   p.   308.     Paris,  1858. 


616 


THE  NERVOUS  SYSTEM. 


Fir; 


of  the  cranial  cavity  through  the  jugular  forameu  (Fig.  355),  in 
company  with  the  pneumogastric  and  spinal  accessory  nerves. 
As  the  glosso-pharyngeal  nerve  passes  out  of  the  jugular  foramen, 
it  expands  into  the   petrous    ganglion    or    ganglion    of  Audersch 

from  which  fine  filaments  are 
given  oif  to  the  pneumogastric 
and  sympathetic  nerves.  The 
o:ano;lion  ffives  orip^in  also  to 
the  tympanic  or  Jacobson's 
nerve ;  the  latter,  ascending 
through  the  canal  of  the  same 
name  in  the  petrous  portion  of 
the  temporal  bone,  expands 
upon  the  promontory  of  the 
tympanum  into  a  number  of 
Ijranchcs  which  supply  the  lin- 
ing membrane  of  the  tym- 
panum, the  round  and  oval 
windows,  and  tlie  Eustachian 
tube.  The  tympanic  nerve 
o-ives  off  also  two  small 
branches  which  pass  respec- 
tively to  the  large  and  small 
])etrosal  nerves  and  filaments 
to  the  sympathetic  plexus  of 
the  internal  carotid  artery. 
From  tlie  ganglion  of  Andersch 
the  glosso-pharyngeal  nerve 
descends  between  the  jugular 
vein  and  the  internal  carotid 
artery  to  the  root  of  the  tongue 
on  the  inner  side  of  the  stylo- 
pharyngeus  muscle  terminating 
in  the  muscles  and  mucous 
membrane  of  the  pharynx,  soft 
palate,  tonsils,  the  root  and 
m  u  c  o  u  s  membrane  of  the 
tongue,  including  the  circum- 
vallate  papillae. 

During  its  course  the  glosso- 
pharyngeal sends  off  filaments 
to  the  pneumogastric  and  sym- 
pathetic, and  as  already  men- 
tioned, receives  filaments  from 
the  facial. 
The  glosso-pharyngeal  nerve  appears  from  recent  researches  to 
consist  of  three  sets  of  fibers,  sensory,  gustatory,  and  motor,^  origi- 
'  Obei-steiner,  op.  cit.,  s.  294,  s.  -123. 


The  last  four  cerebral  uerves  :  the  facial  nerve, 
the  sympathetic  and  the  upper  two  cervical 
nerves.  1.  Facial  nerve.  2.  (Jlosso-pharyngeal. 
2'.  Anastomosis  between  a  branch  of  the  facial 
and  the  glosso-pharyngeal.  .3.  Vagus.  4.  Ac- 
cessory. .5.  Hypo-glossal.  6.  First  cervical 
ganglion  of  the  sympathetic.  7.  First  and  second 
cervical  nerves.  8.  Cavernous  jjlexus  of  the  sym- 
pathetic on  the  internal  carotid  artery.  9. 
Tympanic  nerve  from  the  petrous  ganglion  of 
the  glosso-pharyngeal.  10.  Its  c  o  u  n  e  c  t  i  o  n 
with  the  carotid  plexus.  11.  Branch  to  the 
Eustachian  tube.  12,  VA.  Branches  to  the  oval 
and  round  windows  of  the  ear.  14,1.^.  Branches 
joining  the  small  and  superficial  petrosal  nerves. 
16.  Otic  ganglion.  17.  Auricular  branch  from 
the  jugular  ganglion  and  the  facial  nerve.  18. 
Anastomosis  (if  the  acii'.-sory  with  the  vagus. 
19.  AiKistimiosis  ol'  tlir  first  cervical  nerve  with 
the  liypo-glos-ai.  -U.  Anastomosis  of  the  second 
cervical  nerve  with  a  branch  of  the  accessory. 
21.  Pharyngeal  plexus.  22.  Su|ierior  laryngeal 
nerve.  23.  Its  external  branch.  24.  .Second 
cervical  ganglion  of  the  sympathetic.  (IIirsch- 
fkld-Sappey.) 


THE  NINTH  NERVE. 


617 


nating  in  distinct  parts  of  the  nucleus  of  origin  in  the  medulla, 
some  of  the  motor  fibers  being  derived,  however,  from  the  branch 
of  the  facial  that  joins  the  glosso-pharyngeal  nerve  at  the  petrous 
ganglion. 

That  the  glosso-pharyngeal  nerve  is  a  sensory  nerve,  at  least  at 
its  origin,  is  shown  by  the  loss  of  sensibility  in  the  parts  to  which 
it  is  distributed  and  loss  of  the  sense  of  taste  in  the  posterior  third 
of  the  tongue  following  its  division  in  a  living  animal  or  paralysis 
in  man,  and  that  stimulation  at  the  root  in  a  living  animal  fails  to 
produce  muscular  contractions.  Owing,  however,  to  it  containing 
motor  fibers  derived  as  already  mentioned  from  its  nucleus,  as  well 
as  to  its  connections  with  the  facial,  the  glosso-pharyngeal  un- 
doubtedly receives  motor 

fibers,  to   which   are   due  ^ig.  3o6. 

the  muscular  contractions 
following  irritation  of  the 
glosso-pharyngeal  av  hen 
stimulated  outside  of  the 
cranium,  and  the  difficulty 
experienced  in  degluti- 
tion, if  the  nerve  be 
divided  in  an  animal, 
or  be  paralyzed  in  man. 
It  has  already  been  men- 
tioned that  the  contrac- 
tions of  the  muscles  in- 
volved in  deglutition  fol- 
lowing; stimulation  of  the 
glosso-pharyngeal  are  re- 
flex in  character,  the  im- 
pressions made  upon  the 
latter  nerve,  like  those 
made  upon  the  pala- 
tine branches  of  the  fifth 
nerve,  being  transmitted 
to  the  deglutition  center 
in  the  medulla  (Fig.  3o()) 
and  thence  reflected  through  the  petrosal  nerves  to  the  ganglion 
of  Meckel,  and  the  otic  ganglion  to  the  muscles  supplied  by  the 
latter. 

It  will  be  seen  from  the  above  description  that  the  glosso-pharyn- 
geal nerve  is  a  sensory  nerve,  endowing  the  tongue  and  pharynx 
with  sensibility,  and  the  posterior  third  of  the  tongue,  and  the  an- 
terior two-thirds  as  well,  with  the  sense  of  taste,  if  the  chorda  tym- 
pani  be  regarded,  as  already  mentioned,  as  a  continuation  of  the 
pars  intermedia,  and  the  latter  a  branch  of  the  glosso-pharyngeal. 
If  it  be  admitted  that  the  glosso-pharyngeal  nerve  contains  specific 
motor  fibers  it  must  be  regarded  then  as  a  motor  as  well  as  a  sen- 


Pecjlufition 
Centre 


&ypucj\o^* 


«chema  of  the  afterent  and  efferent  nerves  concerned  in 
deglutition.     (Stirling.) 


618  THE  NERVOUS  SYSTEM. 

soiy  nerve,  iiidepeudeutly  of  its  connections  with  the  faciah  In 
conclusion  it  may  be  mentioned  that  the  glosso-pharyngeal  nerve 
possesses  also  inhibitory  functions,  diminisliing  or  arresting  the  ac- 
tion of  the  cardio-motor,  respiratory,  and  vasomotor  centers  of  the 
medulla. 

The  Tenth  Nerve. 

The  tenth  nerve,  the  pneumogastric,  par  vagum,  or  vagus,  arises 
as  already  mentioned,  in  common  Avith  the  glosso-pharyngeal  from 
a  group  of  nerve  cells  situated  beneath  the  lowest  part  of  the  floor 
of  the  fourth  ventricle,  giving  rise  to  a  promontory  on  the  surface 
of  the  latter  (Fig.  337,  A').  At  the  point  of  the  calamus  scripto- 
rius,  the  symmetrically  disposed  nuclei  are  in  contact  at  the  middle 
line,  but  a  little  higher  up  are  separated  by  the  nuclei,  giving  origin 
to  the  hypo-glossal  nerves.  From  this  origin  the  fibers  pass  for- 
ward through  the  medulla,  emerging  by  twelve  or  more  roots  con- 
taining about  9000  fibers  attached  to  the  restiform  body  in  a  line 
below  those  of  the  glosso-pharyngeal  nerve,  and  leave  the  cranial 
cavity,  as  already  mentioned,  in  company  with  the  glosso-pharyn- 
geal, spinal  accessory  nerves,  and  the  internal  jugular  vein.  In 
the  jugular  foramen  the  pneumogastric  nerve  presents  a  well- 
marked  enlargement  from  one-sixth  to  one-fourth  of  an  inch  in 
lenp-th,  the  2:ang;lion  of  the  root  or  the  iuoular  ranolion,  from 
which  pass  filaments  to  the  facial,  and  the  ganglion  of  the  glosso- 
pliaryngeal  and  superior  cervical  ganglion  of  the  sympathetic. 
After  leaving  the  cranial  cavity  the  pneumogastric  nerve  presents 
another  enlargement  from  half  an  inch  to  an  inch  in  length,  the 
ganglion  of  the  trunk,  from  which  filaments  pass  to  the  hypo-glossal 
nerve  and  occasionally  to  the  arcade  formed  by  the  first  two  cer- 
vical nerves.  Immediately  after  leaving  the  cranial  cavity  the  pneu- 
mogastric nerve  receives  an  important  branch  from  the  spinal  ac- 
cessory, and  during  its  course  filaments  from  the  first  two  cervical 
nerves,  and  together  M'ith  fibers  from  the  glosso-pharyngeal,  spinal 
accessory,  and  sympathetic  forms  the  pharyngeal  plexus.  That 
the  pneumogastric  is  exclusively  sensory  at  its  origin,  whatever 
may  be  the  functions  of  its  branches,  appears  to  be  satisfactorily 
shown,  even  though  indirectly,  by  experiments  like  those  of 
Longet^  made  upon  horses  and  dogs  just  dead,  in  which  stimu- 
lation of  the  nerve  at  its  root  failed  to  produce  muscular  contrac- 
tions if  the  nerve  was  carefully  insulated  and  all  its  motor  con- 
nections divided.  That  irritation  should  be  followed  by  muscular 
contractions  if  the  latter  precaution  be  not  observed,  should  not  ex- 
cite surprise  when  it  is  remembered  that  the  pneumogastric  receives 
motor  filaments  from  at  least  five  sources,  viz.,  the  facial,  spinal 
accessory,  hypoglossal,  and  first  and  second  cervical  nerves,  not  to 
speak  of  the  motor  fibers  derived  from  the  sympathetic.  Any  mus- 
cular  contractions   ensuing  upon   irritation  of  the   pneumogastric 

'  Physiologie,  Tomoiii.,  p.  508.     Paris,  1869. 


THE  TEXTH  NERVE. 


619 


must  therefore  be  either  reflex  in  character  like  many  of  those  of  the 
glosso-pliarvngeal  ah-eady  referred  to,  or  be  attrilnited  to  the  stimu- 
lation of  fibers  derived  from  the  motor  sources  just  metitioned. 


Fig.  357. 


.  'C 


f.im\'-.  ^^F^' 


mmw^-^W" 


i 

i  / 


>^^y^j^i 


.1 


V:  JC^^f, 


.I^A-/:^'    /  (U. 


Distribution  of  the  pneumogastric.  1.  Trunk  of  the  left  pneumogastric.  2.  Ganglion  of  the 
trunk.  3.  Anastomosis  with  the  spinal  accessor}-.  4.  Anastomosis  with  the  sublingual.  5. 
Pharyngeal  branch  (the  auricular  branch  is  not  shown  in  the  figure).  6.  Superior  laryngeal 
branch.  7.  ICxternal  laryngeal  nerye.  8.  Laryngeal  plexus.  9,  9.  Inferior  laryngeal  branch. 
10.  Ceryical  cardiac  branch.  11.  Thoracic  cardiac  branch.  12,  13.  Pulmonary  branches.  14. 
Lingual  branch  of  the  fifth,  lo.  Lower  portion  of  the  sublingual.  16.  Glosso-pharyugeal.  17. 
Spinal  accessory.  18, 19. 20.  Spinal  neryes.  21.  Phrenic  nerye.  22,  23.  Spinal  ueryes.  24,  25,  26, 
27,28,29,30.  Sympathetic  ganglia.     (Hirschfeld.) 

The  most  important  branches  given  off  by  the  pneumogastric 
(Fig.  ooT),  whose  functions  Ave  shall  study  seriatim,  are  as  follows  : 
the  meningeal,  auricular,  pharyngeal,  superior  and  inferior  laryn- 
geal, cervical  and  thoracic,  cardiac,  anterior  and  posterior  pulmo- 
nary, oesophageal,  and  abdominal. 


(320  THE  NEE  \  '0  US  S  \  'S  TEM. 

The  first  or  mening-eal  branch  of  the  pneumogastric  uerve  is 
given  off  from  the  juguhir  ganglion  and  passes  with  the  vasomotor 
fibers  of  the  sympatlietic  supplying  the  middle  meningeal  artery  to 
the  occipital  and  transverse  sinnses.  It  is  nsnally  regarded  as  con- 
sisting of  sensory  fibers. 

The  auricular,  or  Arnold's  nerve,  though  containing  fibers  derived 
from  the  facial  and  glosso-pharyngeal  nerves,  is  usually  described  as 
being  a  In-anch  of  the  pneumogastric  nerve,  being  given  off  from  the 
ganglion  of  its  trunk.  Passing  through  the  temporal  bone  by  the 
canal  of  the  same  name,  it  is  distributed  to  the  external  auditory 
meatus  and  the  mend)rana  tympani,  endowing  those  parts  with  sensi- 
bility. The  jjharyngeal  branches  are  given  off  from  the  superior  por- 
tion of  the  ganglion  of  the  trunk  of  the  pneumogastric  nerve,  but  con- 
sist largely  of  filaments  derived  from  the  spinal  accessory,  reinforced, 
further,  during  their  course,  by  filaments  from  the  glosso-pharyngeal 
and  superior  cervical  ganglion  of  the  sympathetic  to  form  the 
pharyngeal  plexus,  which  supj)lies  the  nuiscles  and  mucous  mem- 
brane of  the  ])harvnx,  the  motor  filaments  l)eing  derived,  as  we  shall 
see,  from  the  spinal  accessory,  and  the  sensibility  being  due  to  the 
filaments  of  the  pneumogastric  proper,  and  also  to  those  of  the 
pharvngeaH)ranches  of  the  fifth,  and  of  the  glosso-pharyngeal. 

The  superior  laryngeal  nerve  arising  from  the  ganglion  of  the  trunk 
divides  into  the  external  and  internal  branches,  the  external  branch 
receiving  filaments  from  the  inferior  laryngeal,  and  the  sympathetic 
supplies  the  mucous  membrane  of  the  ventricle  and  crico-thyroid 
muscles  of  the  larynx,  and  the  inferior  constrictor  of  the  pharynx. 
The  internal  branch,  also  receiving  filaments  from  the  inferior 
laryngeal,  supplies,  like  the  external  branch,  the  crico-thyroid 
muscles,  and  is  distributed  to  the  mucous  membrane  of  the  epi- 
glottis, the  base  of  the  tongue,  the  aryteno-epiglottidcan  folds,  and 
the  mucous  mend)rane  of  the  larynx  as  far  down  as  the  true  vocal 
membranes.  From  the  anatomical  disposition  it  might  be  inferred 
that  the  general  sensibility  of  the  upper  })art  of  the  larynx  and  the 
surrounding  mucous  membrane,  as  well  as  the  innervation  of  the 
crico-thyroid  muscle,  was  due  to  the  superior  laryngeal  nerve,  and 
experiment  shows  that  such  is  the  case.  Thus,  stimulation  of  the 
suj)erior  laryngeal  nerves  in  a  living  animal  gives  rise  to  intense 
pain,  and  causes  contraction  of  the  crico-thyroid  muscle.  It  is 
through  the  exquisite  sensil)ility  of  the  upper  part  of  the  mucous 
membrane  of  the  larynx  that  foreign  Ixxlies  are  prevented  from  en- 
tering the  air  passages  ;  impressions  made  by  such,  being  trans- 
mitted to  the  medulla,  are  thence  reflected  through  the  inferior 
larvngeals  back  to  the  larynx,  bringing  al)out  a  closure  of  the 
glottis.  Every  one  is  familiar  with  the  fact  that  if  a  crund)  of 
bread,  etc.,  fall  upon  the  aryteno-epiglottidcan  folds  or  the  edge  of 
the  vocal  membranes,  the  sensibility  of  the  parts  is  such  as  to  ex- 
cite a  convulsive  cough,  by  which  the  foreign  body  is  dislodged  and 
expelled.      The    impression    conveyed  by   the    superior    laryngeal 


THE  INFERIOR  LARYNGEAL  NERVES.  621 

nerve  to  the  cough  center  of  the  medulki  being  reflected  thence 
through  the  nerves  supplying  the  expiratory  muscles  of  the  chest 
and  abdomen,  l)y  which  the  coughing  is  accomplished.  That  this 
reflex  action  is  due  to  the  sensibility  of  the  laryngeal  mucous  mem- 
brane is  shown  by  the  fact  that,  after  division  of  the  superior 
laryngeal  nerve,  iun)ressions  made  upon  tlie  mucous  membrane  fail 
to  bring  about  such  action.  The  superior  laryngeals,  also,  consti- 
tute the  afierent  nerves  in  the  reflex  mechanism  by  which,  through 
contraction  of  the  constrictors  of  the  pharynx,  the  act  of  deglutition 
is  completed.  It  is  interesting  to  observe  that  the  impressions 
made  upon  the  mucous  membrane  of  the  larynx,  and  the  surround- 
ing membrane,  and  l)y  which,  through  reflex  action,  deglutition  is 
brought  about,  cause,  at  the  same  time,  closure  of  the  glottis,  and 
arrest  of  respiration,  thereby  protecting  the  air-passages  against  the 
entrance  of  food  or  other  foreign  bodies. 

The  two  inferior  or  recurrent  laryngeal  nerves,  so  called  from 
reascending  to  the  larynx  after  descending  from  the  pneumogas- 
tric,  diifer  slightly  in  their  course  on  the  two  sides,  that  of  the 
left  side  passing  beneath  the  aorta,  that  of  the  right  side  winding 
from  before  backward  around  the  subclavian  artery  before  they  as- 
cend in  the  groove  between  the  trachea  and  the  oesophagus  to  the 
larynx.  In  other  respects,  the  course  and  distribution  of  the  two 
nerves  are  the  same.  The  curious  course  taken  by  the  inferior  lar- 
yngeal nerve,  Avhether  of  the  right  or  left  side,  is  due  to  the  fact 
that,  while  in  the  embryonic  condition,  the  larynx  and  heart  are  in 
close  proximity ;  through  the  elongation  of  the  neck,  incidental  to 
development,  the  heart  and  great  blood  vessels  recede  from  the  lar- 
ynx, and,  in  so  doing,  drag  down  with  them  the  inferior  laryngeal 
nerves,  which  ])ass,  loo])-like,  around  them.  It  may  be  mentioned 
in  this  connection,  as  observed  by  Owen,'  and  by  the  author,-  in 
the  individuals  dissected  by  the  latter,  that  in  the  giraife  the  infe- 
rior laryngeal  nerves  pass  directly  from  the  pneumogastric  to  the 
larynx,  like  the  superior  laryngeals.  The  significance  of  this  is 
very  evident,  for,  were  the  course  of  the  inferior  laryngeals  in  the 
girafie  the  same  as  in  man,  the  nerve,  in  descending  and  ascending 
through  so  many  feet,  would,  in  all  probability,  be  so  stretched  and 
tensed  as  to  render  it  incapable  of  performing  its  functions.  As 
the  inferior  laryngeal  nerves  ascend  they  give  olf  filaments,  which 
join  those  of  the  cardiac  branches  of  the  pneumogastric  filaments 
to  the  muscular  tissue,  and  mucous  membrane  of  the  upper  jiart  of 
the  oesophagus,  to  the  mucous  membrane  and  inter-cartilaginous 
muscular  tissue  of  the  trachea,  to  the  inferior  constrictor  of  the 
pharynx,  and,  as  already  mentioned,  a  branch  which  joins  the  su- 
perior laryngeal,  terminating,  finally,  after  penetrating  the  larynx 
behind  the  ])osterior  articulation  of  the  cricoid,  Avith  the  thyroid 
cartilage,  in  all  of  the  intrinsic  muscles  of  the  larynx,  except  the 

iQp.  cit.  Vol.  iii.,  p.  100. 

^H.  C.  Chapman,  Proc.  Acad.  Nat.  Sciences,  Phil.,  1887,  p.  37. 


622  THE  NERVOUS  SYSTEM. 

crico-thyroid,  which,  it  Avill  be  remenil)cred,  is  supplied  by  the  su- 
perior larvng-eal  nerve.  Direct  stimidation  of  the  inferior  hirvn- 
geal  nerves  proves  what  one  wonkl  lie  led  to  expect  from  their  dis- 
tribution, that  thev  are  principally  motor  in  function,  and  from  the 
fact,  as  we  shall  see  hereafter,  of  division  of  the  spinal  accessory 
being;  followed  by  loss  of  voice,  the  respiratory  movements  of  the 
glottis  being,  however,  unaffected,  but  that  division  of  the  inferior 
laryngeal  nerves  not  only  involves  loss  of  voice,  but  paralysis  of 
the  respiratory  movements  of  the  larynx  as  well — that  their 
motor  filaments  are  derived  at  least  from  two  different  sources,  if 
not  more.  To  anticipate  what  we  shall  see  more  particularly  here- 
after, the  muscles  of  the  larynx  involved  in  the  production  of  the 
voice  are  the  arytenoid,  the  thyro-arytenoid,  and  the  lateral  crico- 
arytenoid, supplied  by  the  inferior  laryngeal  nerves  and  the  crico- 
thyroid, supplied  by  the  superior  laryngeal  nerves.  The  pos- 
terior crico-arytenoid  muscles  supplied  by  the  inferior  laryngeal 
nerves  opening  the  glottis,  are,  however,  respiratory  in  function. 
Now,  while  in  an  animal  the  voice  is  lost  after  division  of  the  in- 
ternal branch  of  the  spinal  accessory,  nevertheless,  the  glottis, 
though  not  closing  on  irritation,  being  still  capable  of  dilatation, 
respiration  is  not  interfered  with.  Such  being  the  case,  if  the  in- 
ferior laryngeal,  however,  be  divided,  the  glottis  is  at  once  mechan- 
ically closed  with  each  inspiratory  effort,  and  the  animal,  if  young, 
dies  of  suffocation.  In  adults,  however,  the  cartilages  of  the  lar- 
ynx, being  rigid,  permit  of  respiration  even  after  the  larynx  is  para- 
lyzed. The  only  inference  from  these  facts  is  that  the  libers  of  the 
inferior  laryngeal  that  innervate  the  muscles  of  phonation  are  de- 
rived from  the  spinal  accessory,  but  that  those  innervating  the  res- 
piratory movements  of  the  glottis  are  derived  from  some  other 
source — from  the  facial,  in  all  probability,  or,  possibly,  from  the 
hypo-glossal,  or  the  cervical  nerves  that  we  have  seen  give  off 
branches  to  the  pneumogastric  nerve.  Inasmuch,  also,  as  the  crico- 
thyroid muscle  is  involved  in  phonation,  and  as  we  have  seen  that 
the  superior  laryngeal  nerve  sup])lying  it  receives  fibers  from  the 
inferior  laryngeal,  in  all  probability  it  is  the  fibers  of  the  latter 
nerve  that  influence  the  crico-thyroid  muscle  in  phonation,  other- 
wise it  is  difficult  to  see  wdiy  the  paralysis  of  the  voice  following 
division  of  the  inferior  laryngeal  nerve  should  be  so  complete. 

It  must  be  admitted,  however,  that  the  view  just  offered  of  the 
functions  of  the  laryngeal  nerves  is  not  universally  accepted.  In- 
deed, considerable  difference  of  opinion  still  ])revails  among  phys- 
iologists as  to  exactly  how  the  different  ])arts  of  the  larynx  are 
innervated. 

The  cervical  cardiac  branches,  two  or  three  in  number,  arising 
from  the  })neumogastric,  consist  princi])ally,  as  we  shall  see,  of 
fibers  derived  from  the  sympathetic.  The  thoracic  cardiac  branches 
given  off  Ixlow  the  origin  of  the  iuferior  laryngeal  nerves  pass  to 
the  cardiac  plexus. 


THE  IXNERVATIOX  OF  THE  HEART.  623 

The  Innervation  of  the  Heart.     Intracardiac  Centers  and  Nerves. 

It  is  well  known  that  the  heart  of  the  lower  verteljrates,  like  the 
shark,  sturgeon,  etc.,  will  eontinue  beating  for  many  hours  after  re- 
moval from  the  body.  The  same  has  been  shown  to  be  true  also 
of  the  heart  of  rabbits,  cats,  clogs  Avheu  proper  precautions  are 
taken.^  Such  facts  show  conclusively  that  the  cause  of  the  rhyth- 
mical beat  of  the  heart,  being  independent  of  the  central  nervous 
system,  must  lie  within  the  heart  itself.  Difference  of  opinion  still 
prevails,  however,  as  to  whether  the  beat  of  the  heart  is  due  to  the 
heart  muscle  possessing  the  power  of  rhythmical  contraction  in  it- 
self, or  to  the  heart  muscle  being  periodically  stimulated  by  im- 
pulses from  the  intracardiac  cells.  That  the  latter  is  the  cause  of 
the  rhvthmical  beat  of  the  heart  appears  to  be  shown  from  the  fact 
that  the  contractions  are  more  powerful  in  those  parts  of  the  heart 
in  which  the  nerve  supply  is  richest.  Thus  the  contractions  of  the 
auricle  are  more  powerful  than  those  of  the  ventricle,  those  of  the 
base  of  the  ventricle  more  so  than  those  of  the  apex,  the  num- 
ber of  nerve  cells  being  greatest  in  the  auricle,  smallest  in  the  ven- 
tricle. Indeed,  in  the  apex  of  the  ventricle  ganglion  cells  are 
entirelv  absent  according  to  most  histologists.  It  may  be  also 
mentioned  as  confirmatory  of  the  view  that  the  cause  of  the  heart 
beat  is  nervous  in  origin,  that  while  muscarin  arrests  the  contrac- 
tions of  the  muscular  fibers  of  the  heart  it  does  not  exert  the  same 
influence  upon  otlier  kinds  of  either  striped  or  smooth  muscle.  On 
the  other  hand,  there  can  be  no  doubt  that  the  muscular  fibers  of 
the  heart  respond  to  stimuli  other  than  nervous,  since  a  slip  cut 
from  the  ventricle  of  the  heart  of  a  tortoise,  when  suspended  in 
a  moist  chamber,  will  begin  beating  in  a  few  minutes  and  continue 
to  beat  for  more  than  twenty-four  hours.  The  nerve  fibers  that 
are  supposed  to  convey  the  impulses  stimulating  the  muscular 
fibers  to  contract,  appear  to  arise  in  ganglia  situated  near  the 
orifice  of  the  superior  vena  cava,  in  the  septum  of  the  auricles  and 
in  the  auriculo-ventricular  grooves,  whence  they  pass  as  fine  non- 
medullated  fibers  to  penetrate  the  walls  of  the  auricles  and  ventri- 
cles. The  ganglia  of  the  heart,  at  least  in  the  case  of  the  frog, 
appear  to  have  antagonistic  functions,  some  of  the  ganglia,  for 
example,  inhibiting  the  functions  of  the  other.  The  presence  of 
cardiac  ganglia  can  be  readily  demonstrated  in  the  heart  of  the 
frog,  and  their  functional  significance  shown  by  the  well-known 
experiment  of  Stannius.^  In  the  frog,  as  is  well  known,  the  two 
superior  venre  cava?  ('S'lT',  Fig.  358)  unite  before  entering  the 
right  auricle  to  form  a  dilatation — the  sinus  venosus  ('S'T").  It  is 
in  the  wall  of  the  latter,  near  the  opening  of  the  inferior  vena  cava, 
that  the  first  of  these  ganglia,  the  ganglion  of  Remak  {R),  is  situ- 
ated, the  second  or  the  ganglion  of  Bidder  [E),  bemg  found  in  the 

'  Stolnikow,  Pawlow,  Langendorff  in  Tlgei-stedt,  Lehrbuch  Der  Physiologie  Des 
Kreblaufes,  1893.  ^  Zwei  Reilien,  Physiologische,  Vei-suche,  1851. 


624 


THE  NERVOUS  SYSTEM. 


left  auri(•ulo-^'c'ntricular  groove,  the  third  ganglion  or  that  of  Lud- 
wig,  in  the  septum  between  the  aurieles. 

If  a  ligature  be  applied  between  the  sinus  venosus  (aS'T^)  and  the 
right  auricle  (.4,  Fig.  359,  1),  the  heart  stops  beating  and  remains 
in  a  state  of  diastole. 


B.A 


Fig.  359. 


I.V.C. 


Schema  of  nerve.s  of  frog's  heart.  R, 
Remak's,  and  B,  Bidder's  ganglia. 
.ST.  Sinus  venosus.  A.  Auricles.  V. 
Ventricle.  BA.  Bulbus  arteriosus. 
Vag.  Vagi.  <S  IT',  superior  vense  ca- 
Tse.     (Landois.  ) 


Stannius'  experiment.  A.  Auricle. 
T'.  Ventricle.  .ST.  Sinus  venosus. 
The  zig-zag  lines  indicate  which  parts 
continue  to  beat ;  in  2  the  ventricle 
beats  at  a  different  rate.     (Landois.) 


Fig.  360. 


The  sinus  venosus,  however,  continues  beating,  and  the  auricles 
or  the  ventricle  will  made  a  few  movements  in  response  to  direct 
stimulation.  If  now  a  second  ligature  be  applied  between  the  auri- 
cle {A),  and  ventricle  ( T",  Fig.  359,  2),  the  ventricle  will  begin 
beating  again,  the  auricles,  however,  still  remaining  quiet.  Many 
explanations  have  been  offered  of  the  phenomenon  just  described, 
one  of  the  simplest  and  most  plausible  being  that  which  regards 
the  ganglion  of  Ludwig  as  inhibitorv  in  function  and  exerting 
greater  influence  than  that  of  Remak  or  Bid- 
der, when  either  of  these  ganglia  is  exerted 
alone.  If  such  be  the  case,  it  follows  that  a 
ligature  being  applied  to  the  sinus  venosus 
(Fig.  359,  1),  the  inhibitorv  action  of  the 
ganglion  of  Ludwig  being  only  opposed  to  the 
exciting  action  of  that  of  Bidder,  the  heart 
stops,  and  that  after  a  ligature  is  applied  be- 
tween the  auricles  and  the  ventricle  (Fig. 
.'>59,  2),  tlien  the  inhibitory  action  of  the 
ganglion  of  J^udwig  being  cut  off,  and  there 
being  nothing  to  counteract  the  action  of  the 
ganglion  of  Bidder,  the  ventricle  begins  to 
l)eat  again.  AVhatever  the  explanation  may  be 
of  the  facts  just  described,  it  is  evident  that  the 
heart  possesses  an  intrinsic  nervous  mechanism 
by  ^vhich,  in  response  to  the  stimulus,  its  fibers 
arc  excited  to  contract. 

It  may  be  mentioned  in  this  connection  that 
many  of  the  ganglionic  nerve  cells  of  the 
heart  of  the  frog  present  not  only  an  axis- 
cylinder,  l)ut  a  s])iral  process  as  well  (Fig.  360,  o),  of  functional 
interest  since  the  process  appears  to  be  derived  from  the  pneumo- 
gastric  nerve  and  to  convey  impulses  to  the  nerve  cell. 


Pyriform  ganglionic  bi- 
polar nervf-uell  from  the 
heart  of  a  frog.  m.  Sheath. 
11.  Straight  process,  o.  spi- 
ral process. 


CURRENT  OF  ACTION  OF  HEART.  625 

If  non-polarizable  electrodes  be  applied  to  the  surface  of  the  ven- 
tricle of  a  frog's  heart  and  connected  with  a  delicate  galvanometer, 
it  will  be  observed  that  with  each  ventricular  systole  the  needle  of 
the  galvanometer  is  deflected,  returning  to  rest  with  each  diastole, 
showing  that  a  change  in  electrical  potential  precedes  or  more  prob- 
ably accompanies  the  change  in  form  that  has  l)een  described  as  a  car- 
diac contraction.  Further,  if  one  electrode  be  applied  to  the  base  of 
the  heart  and  the  other  to  the  apex  it  will  be  foimd  that  this 
change  in  electrical  potential,  "  the  current  of  action,"  the  excita- 
tion wave  travels  from  base  to  apex  at  the  rate  of  from  50  to  150 
millimeters  per  second  and  preceded  according  to  some  observers 
by  a  latent  period  of  about  0.08  sec.^  Some  difference  of  opinion 
still  exists  as  to  whether  the  excitation  wave  passes  along  the  mus- 
cular or  nervous  tissues  of  the  heart.  From  the  fact  that  the 
wave  travels  comparatively  slowly,  about  90  millimeters  per  sec- 
ond or  300  times "  less  than  at  the  rate  at  which  it  would  travel 
if  it  were  transmitted  by  nervous  tissue,  it  is  generally  supposed 
that  the  wave  travels  along;  the  muscular  rather  than  alono-  the 
nervous  tissue.  That  the  excitation  wave  travels  along  the  mus- 
cular liber  is  still  further  shown  by  the  fact  that  the  "block,"^  or 
the  delay  that  the  wave  experiences  in  passing  from  the  auricle  to 
the  ventricle,  appears  to  depend  upon  the  relatively  few  fibers  pres- 
ent in  that  situation,  and  that  the  duration  of  the  "block"  is  about 
what  it  ought  to  be  on  the  supposition  that  the  wave  passes  along 
the  muscular  fibers  connecting  the  auricles  and  ventricle. 

It  is  well  known  that,  while  the  heart  will  contract  in  response 
to  mechanical  and  electrical  stimuli  when  sloAvly  repeated,  it  will 
not  contract  when  the  stimuli  follow  each  other  too  rapidly.  Tliis 
appears  to  be  due  to  the  fact  that  the  heart  will  not  contract 
secondarily  in  response  to  an  extra  stimulus  when  applied  during 
the  period  intervening  between  the  beginning  and  maximum  of  its 
systole,  whereas  it  will  contract  secondarily  when  the  stimulus  is 
applied  during  the  period  intervening  between  the  maximum  of 
one  systole  and  the  beginning  of  the  next.^  The  period  of  the 
cardiac  cycle  during  which  the  heart  refuses  to  contract  in  response 
to  a  stimulus  is  called  the  "  refractory  period."  Since  a  period 
exists  however  in  which  the  heart  will  contract  in  response  to  a 
stimulus  it  might  be  supposed  that  if  the  stimulus  be  rapidly  ap- 
plied during  that  period,  that  is  during  the  "  non-refractory 
period,"  on  account  of  the  extra  contraction  produced  with  each 
stimulus,  the  total  number  of  contractions  would  be  increased.  As 
a  matter  of  fact,  however,  such  is  not  the  ease,  as  the  extra  con- 

1  Engelmann,  1874,  p.  6. 

^  The  author  takes  occasion  to  say  that  by  throwins  a  beam  of  light  upon  the 
mirror  of  the  galvanometer  and  reflecting  the  same  upon  a  screen  he  has  been 
able  to  demonstrate  the  "current  of  action  "  of  the  frog's  heart  to  a  large  autlience, 
the  ball  of  light  moving  pendulum-like  with  the  systole  and  diastole  of  the  heart. 

^Gaskell,  Journal  of  Physiology,  ^'ol.  iv.,  p.  95. 

*Marey,  1876,  p.  73.     Engelmann,  1895,  p.  313. 

40 


626 


THE  NERVOUS  SYSTEM. 


traction  is  followed  by  a  pause,  the  duration  of  which,  being  that  of 
the  normal  pause  plus  the  interval  between  the  appearance  of  the 
extra  contraction  and  what  would  have  been  the  end  of  the  cardiac 
cycle  in  which  the  extra  contraction  occurred,  the  normal  number  of 
contractions  is  maintained.  The  pause  following  the  extra  con- 
traction induced  during  the  "  non-refractory  period"  is  appropri- 
ately called  therefore  the  "  compensatory  pause."      It  follows  from 

Fig.  361. 


The  refractory  period  and  compensatory  pause.  Curves  to  be  read  from  left  to  right.  The 
interruption  on  the  abscissa  below  each  curve  indicates  the  moment  at  which  the  ventricle  was 
stimulated.  In  the  curves  1,  2,  :!,  the  ventricle  was  refractory  to  the  stimulus,  the  latter  being 
applied  during  the  refractory  i)eriod.  In  the  remaining  curves  an  extra  contraction  and  com- 
pensatory pause  are  seen,  the  stimulus  having  been  applied  after  the  refractory  period.   (Marey.  ) 


what  has  just  been  said  that  a  continuous  stimulus  may  produce  a 
rhythmical  heart  beat,  since,  the  heart  contracting  only  during  the 
*'  non-refractory  period,"  each  contraction  will  be  followed  by  a 
compensatory  pause.  That  the  refractory  period  and  compensatory 
pause  are  produced  inde])endently  of  the  cardiac  nerve  centers  ap- 
pears to  be  shown  from  the  fact  that  both  can  be  obtained  when  the 


EXTRA  CA  RDIA  C  INHIBITOB  Y  CENTERS.  627 

apex  of  the  ventricle  is  used  in  which  it  is  generally  supposed,  as 
already  mentioned,  that  nerve  centers  arc  absent. 

Extracardiac  Inhibitory  Centers  and  Nerves. 

Contrary  to  what  might  have  been  naturally  expected  from  what 
we  have  hitherto  learned  as  to  the  effect  of  division  and  stimulation 
of  nerves,  division  of  the  pneumogastric  nerve  in  a  living  animal, 
so  far  from  arresting  the  action  of  the  heart,  actually  increases  the 
rapidity  of  its  pulsations,  while  electrical  stimulation  of  the  pneumo- 
gastric nerve  arrests  the  heart's  action  in  diastole  (Fig.  '362),  and 
causes  a  fall  in  the  blood  pressure  (Fig.  363). 

Fig.   'M;± 

l/\/lAA/W\/l__.../vAAAA. 

Etfect  ol'stimulatii)U  of  jmk  iimogastric  nerve  upon  action  of  heart  in  frog. 
Ill  be  read  from  riglit  to  left. 

The  effect  of  division  of  one  pneumogastric  nerve,  however,  in  a 
frog  or  a  rabbit,  for  example,  is  not  by  any  means  as  marked  as 
when  both  nerves  have  been  divided.  In  the  latter  case  the  action 
of  the  heart  is  tremulous, 

the    number    of    its    beats  Fig.  363. 

may  be  doubled,  while  the  /vA^^'MA/i 

respiration,    from    being  ^         -^^ .  ~^ 

momentarily  accelerated, 
becomes  calm  and  pro- 
found, but  diminished  in 
frequency.  It  might  natu- 
rally be  supposed  that  the 

inhibitory   influence    of   the  Effect    of     cardiac    inliibition    in    rabbit    on    blood 

T.         f.!  n    ,1  pressure.     Current  sent  into  pneumogastric  nerve  at  a, 

cardiac  nbers  Ot    tne    pneu-      shut  off  at  6.    First,  there  is  a  rapid  fail,  and  when  the 

mogastric  is  directly  ex-  H^a'^to'thenoS.'  ''''  "'''"'''  "'''  ''^  '"'"'''"' 
erted  upon  the  heart.    That 

such,  liowever,  is  not  the  case,  appears  from  the  fact  of  the  latent 
period — that  is,  the  time  elapsing  between  the  application  of  the 
stimulus  and  the  inhibitory  effect — being  very  long,  nearly  one-fifth 
of  a  second,  instead  of  one-hundredth  of  a  second,  in  some  cases 
even  two  entire  beats  of  the  heart  intervening  before  its  arrest  occur- 
red, indicating  that  some  resistance  must  be  overcome,  the  inhibi- 
tory fibers  of  the  pneumogastric  acting  upon  inhibitory  centers  in 
the  heart  itself.  That  such  is  the  case  is  shown  by  the  fact  that  the 
action  of  the  heart  in  the  eel  and  the  frog  can  be  arrested  by  direct 
stimulation,  and  that  in  the  mollusca,  although  no  pneumogastric 
nerve  is  present,  the  heart  can  be-  stopped  in  diastole  by  direct 
irritation.     Again,  if  nicotin  or  curara  be  subcutaneously  injected 


628 


THE  NERVOUS  SYSTEM. 


in  small  doses  into  a  living  animal  the  heart  beats  first  slower  then 
faster,  possibly  on  acconnt  of  the  extracartliac  inhibitory  centers  of 
the  pnenraogastric  (Fig.  364)  becoming  paralyzed  ;  if  now  muscarin 
or  jaborandi   be  then  administered,  the   heart  will  be  arrested  in 

diastole,  the   latter  sub- 


Fifi.  364. 


VaaaJ  o 
extrc-card.  inMi. 


OrsAccelt 


cceZer.cent.  of 
■'   '  Olil. 


stances  appeanng  to  act 
directly  npon  intracardiac 
inhibitory  centers.  On 
the  other  hand,  if  atropia 
be  injected,  then  neither 
muscarin  nor  jaborandi 
will  have  any  inhibitory 
effect  upon  the  heart, 
atropia  appearing  to  par- 
alyze both  the  extra-  and 
intracardiac  inhibi  t  o  r  y 
centers. 

Stimulation  of  t  h  e 
])ncumogastric  nerve  not 
only  inhibits  the  heart's 
action  but  modifies  the 
latter  in  many  ways. 
Thus  the  duration  of  both 
tlie  systole  and  diastole 
are  lengthened.  The  force 
of  the  contraction,  the 
input  and  output  of  the 
ventricle  are  diminished, 
the  diastolic  pressure  and 
volume  of  the  blood  in 
the  ventricle  are  in- 
creased. Tlie  contrac- 
tions of  the  ventricle  do 
not  correspond  in  number 
to  those  of  the  auricle, 
the  latter  being  often 
twice  as  numerous  as  the 
former.  A  change  in  elec- 
trical potential  occurs 
also,  the  current  of  rest  of  the  injured  auricle  of  a  tortoise  heart  lead 
off  to  a  galvanometer  exhibiting  a  marked  increase.  It  may  be 
mentioned  in  this  connection  that  the  act  of  swallowing  temporarily 
al)olishes  the  inhibitory  action  of  tlie  vagus,  the  pulse  rate  l)eing 
accelerated  often  -'30  per  cent.  l)y  merely  sipping  a  wineglassful  of 
water.  That  the  influence  exerted  by  the  fibers  of  the  pneumogas- 
tric  nerve  upon  the  heart  is  transmitted  centrifugally  and  is  de- 
pendent upon  its  motor  fi])ers  is  shown  by  the  fact  that  if  the 
pneumogastric  nerve  be  divided  in  a  living  animal   and  stimulated 


Diagrammatic  view  of  tlie  nerves  influencing  tlic  action 
of  the  lieart.  Tlie  right  half  represents  the  course  of  tlie 
inhibitory,  and  the  left  the  course  of  the  accelerating 
nerves  of  the  heart ;  the  arrows  showiug  the  direction  in 
which  impressions  are  conveyed.  The  ellipse  at  the  up- 
per extremity  of  the  vagus  looking  like  the  section  of  the 
nerve  is  inteiulccl  ti>  rrprt'sent  the  vagal  nucleus  or  center. 
In  this  diagram  tlic  iirrves  are  incorrectly  made  to  cross, 
instead  of  i)a,ssiiig  lii-hiiid,  the  aorta. 


INHIBITORY  FIBERS  OF  VAGUS.  621> 

at  its  central  end  none  (if  tlie  effects  such  as  those  just  descriljed 
ensue;  stimuhithm  of  the  (Hstal  end  only  slowino;  up  the  action  of 
the  heart  and  causing-  a  fall  in  blood  pressure  ;  and  that  if  the  stim- 
ulation be  continued  too  long,  so  as  to  exhaust  the  irritability  of  the 
motor  fibers,  the  heart  begins  to  beat  again,  their  inhibitory  effect 
being  lost.^  Further,  in  animals  poisoned  ^vith  curara,  which,  as  is 
well  known,  paralyzes  the  motor  nerves,  stimulation  of  the  pneu- 
mogastrie  nerve  fails  to  arrest  the  action  of  the  heart.  That  the 
motor  fibers  of  the  pneumogastric  nerve  influencing  the  heart's  ac- 
tion are  derived  from  the  s])inal  accessory  can  be  shown  by  experi- 
ments like  those  of  Waller,"  in  which  after  division  of  the  spinal 
accessory  of  one  side  in  a  living  animal,  allowing  sufficient  time  to 
insure  disorganization  of  its  fibers,  stimulation  of  the  pneumogastric 
nerve  of  the  corresponding  side  failed  to  arrest  the  action  of  the 
heart,  the  usual  effect,  however,  being  observed  when  the  pneumo- 
gastric nerve  was  stimulated  on  the  one  side  in  which  the  s])inal  acces- 
sorv  nerve  was  still  intact.  It  must  be  mentioned,  however,  that 
according  to  some  experimenters,  stimulation  of  the  spinal  acces- 
sorv  before  its  union  with  the  pneumogastric  nerve,  or  of  its  bulbar 
roots  does  not  inhibit  the  heart's  action  and  that  the  method  employed 
l)v  AValler  just  mentioned  involves  the  pulling  out  of  some  of  the 
fibers  of  the  pneumogastric  nerve.  If  such  be  the  case  it  must  be 
admitted  that  the  origin  of  the  inhilMtorv  fibers  of  the  vagus  are 
still  unknown.  The  fillers  ])assing  along  the  pneumogastric  nerve 
and  conveying  inhibitory  impulses  to  the  heart  are  usually  re- 
garded as  arising  from  a  cardio-inhibitory  center  (Fig.  364),  situ- 
uated  in  the  medulla  oblongata  near  the  nucleus  of  the  hypo-glossal 
nerve.  The  cardio-inhibitory  center  appears  to  be  a  tonic  center, 
tiiat  is,  always  acting,  division  of  the  pneumogastric  nerve  being 
followed  as  we  have  seen  by  quickening  of  the  heart's  action.  The 
center  seems  to  be  maintained  in  this  state  of  constant  activity  re- 
fiexly  through  impressions  conveyed  to  it  by  afferent  nerves,  since 
the  heart  beat  is  not  quickened  by  division  of  the  pneumogastric 
if  many  afferent  impulses  are  cut  off,  as  is  the  case  after  division 
of  the  spinal  cord.  It  is  impossible  in  the  present  state  of  our 
Icnowledge  to  offer  an  entirely  satisfactory  explanation  of  the  in- 
hibitory effect  of  the  ]meumogastric  nerve  upon  the  heart  and  of  the 
accompanying  fall  in  blood  pressure.  A  plausible  explanation  that 
has  been  offered  is  as  follows  : 

A  stimulus  being  applied  to  the  central  end  of  the  vaso-inhibitory 
or  depressor  fibers  of  the  vagus  (Fig.  364),  the  impulse  generated, 
as  already  mentioned,  is  not  only  transmitted  to  the  extracardiac 
inhibitory  centers,  whence  it  is  reflected  through  the  cardio-inhibi- 
tory fibers  of  the  pneumogastric  nerve  to  the  heart,  slowing  or  ar- 
resting the  latter,  but  also  which  exerts  a  restraining  or  inhibitory 
influence  upon  the  vasomotor  center  of  the  medulla,  the  result  of 


'  Weber,  Arcliiv  d'Anat.  Gen.  et  cle  Physiologie,  1846 
^Gazette  Medicate,  Sieme  serie,  Tome  xi.,  p.  420.     Pt 


Paris,  1856. 


B30  THE  NERVOUS  SYSTEM. 

which  is  that  the  bh^od  pressure  sinks  through  the  inhi])ition  of  the 
vasomotor  nerve  fibers  supplying  the  bh>od  vessels,  and  which  ema- 
nate from  tliis  center.  To  anticipate  a  little  what  will  be  described 
more  in  detail  in  our  consideration  of  the  sympathetic,  it  maybe  men- 
tioned, with  reference  to  the  explanation  just  offered  of  the  fall  in 
blood  pressure,  that,  under  ordinary  circumstances,  a  nervous  influ- 
ence emanates  from  the  vasomotor  center  in  the  medulla,  and  which, 
being  transmitted  through  the  spinal  cord,  spinal  and  splanchnic 
nerves,  maintains  the  l:>lood  vessels  to  which  these  nerves  are  dis- 
tributed in  a  state  of  tonic  contraction,  which  keeps  up  the  blood  pres- 
sure. If,  however,  the  vasomotor  center  of  the  medulla  be  paralyzed 
through  the  stimulation  of  the  dej^ressor  nerve,  no  such  nervous  in- 
fluence being  tlien  exerted  upon  the  l)lood  vessels,  the  latter  dilate, 
and  the  blood  pressure  falls.  The  result  of  this  is,  hoMCver,  that  the 
medulla  receives  less  blood,  so  much  passing  into  the  abdominal  ves- 
sels, etc.,  the  consequence  of  which  is,  that  the  extracardiac  inhibitory 
centers  of  the  pneumogastric  become  less  active,  and  the  heart  re- 
sumes its  usual  activity.  That  it  is  to  the  paralysis  of  the  splanchnic 
nerve,  and  consequent  dilatation  of  the  great  abdominal  vessels,  that 
the  ftdl  in  blood  pressure  induced  by  stimulation  of  the  depressor 
nerve  is  princi])ally  due,  is  shown  l)y  the  fact  that  if  the  splanchnic 
nerves  be  first  divided,  and  then  tlie  depressor  nerve  l)e  stimulated, 
the  blood  pressure  sinks  l)ut  little  more  than  when  the  splanchnics 
are  alone  divided. 

That  the  cardiac  branches  of  the  pneumogastric  nerves  have  the 
same  inhil)itory  influence  upon  the  heart  in  man  as  they  have  been 
shown  experimentally  to  have  in  animals,  may  be  inferred  from 
such  pathological  ^  cases  as  those  in  which  the  number  of  heart 
beats  have  been  knoAvn  to  be  reduced  to  three  or  four  per  minute 
from  the  compression  exerted  upon  the  nerve  by  pressing  upon 
glands,  tumors,  etc.  That  the  inhibitory  action  of  the  pneumo- 
gastric upon  the  heart  can  also  be  exerted  in  a  reflex  as  well  as  di- 
rect manner,  is  shown  by  those  cases  in  which  there  is  a  sudden 
stojipage  of  the  heart  following  blows  u})on  the  epigastrium,  es- 
j)ecially  after  full  meals,  draughts  of  cold  water,  tlie  body  being 
overheated,  great  emotional  excitement,  etc.,  the  impression  in  such 
cases  being  transmitted  from  the  general  sensory  surface  to  the 
medulla  and  thence  reflected  through  the  inhibitory  fibers  of  the 
pneumogastric  to  the  heart.  That  the  ])neumogastric  nerve  in  man 
contains  also  special  afferent  fibers  passing  from  tlie  heart  as  well 
as  efferent  ones  to  it,  by  which  impressions  are  transmitted  to  the 
medulla  and  thence  reflected  back  to  the  heart  by  the  inhibitory 
fibers,  appears  very  probable  from  what  has  been  shown  to  be  ex- 
p  'rimentally  the  case  in  the  rabljit  and  other  animals.  Thus,  if  in 
the  rabbit,  the  so-called  depressor  nerve  (Fig.  3G4) — that  is,  the 
nerve  arising  partly  from  the  jjueumogastric  and  partly  from  the 
superior  laryngeal  nerve,  be  divided  and  its  distal  end  stimulated, 
1  AluUer's  Arcliiv,  1841,  Heft  3.     Jentesche  Zeits.,  165,  s.  384. 


ACCELERATING  FIBERS  OF  VAGUS.  631 

no  effect  upou  the  heart  is  observed ;  if,  however,  the  central  end 
of  the  nerve  be  stiniuhited,  the  action  of  the  heart  is  arrested  and 
the  blood  ])ressure  falls  just  as  if  tlie  pnenmogastric  nerve  or  the 
cardio-inhil>itory  fibers  of  the  same  (corresponding  in  man  to  the 
superior  cardiac  nerve)  be  stimulated,  the  action  being  evidently  a 
reflex  one  ;  the  impression  made  upon  the  central  end  of  the  de- 
pressor nerve  is  transmitted  to  the  medulla  and  thence  reflected 
back  through  the  cardiac  inhibitory  fibers  of  the  pneumogastric  to 
the  lieart. 

Extracardiac  Accelerator  Centers  and  Nerves. 

The  cardiac  fibers  of  the  pneumogastric  nerve  not  only  consist 
of  inhibitory  or  restraining  fibers,  but  also  augmentor  or  acceler- 
ating ones  (Fig.  364).  The  latter  are,  however,  derived,  to  a  con- 
siderable extent,  also,  from  fibers,  which,  descending  from  the 
medulla  througli  the  spinal  cord,  emerge  opposite  the  last  cervical 
and  first  dorsal  ganglia  of  the  sympathetic,  which  they  pass  before 
terminating  in  the  heart. 

Stimulation  of  the  augmentor  nerves  not  only  accelerates  the 
heart's  action  (Fig.  365),  but  increases  the  force  of  the  beat,  the 

Fig.  365. 


Effect  produced  by  stimulation  of  peripheral  end  of  the  accelerating  nerve  of  the  heart.    The 
heart  beats  quicker.    Stimulation  begun  at  5.     (Landois.) 

output,  and  the  speed  of  the  excitation  wave.  The  accelerating 
nerves  appear  to  act  less  powerfully  than  the  inhibitory  ones,  at 
least  the  effect  of  simultaneous  stimulation  is  inhibition,  the 
amount  of  the  latter  being  less,  however,  than  when  the  inhibitory 
nerves  are  stimulated  alone.  Analogy  would  lead  us  to  suppose 
that  there  exists  an  extracardiac  accelerating  center,  situated 
probably  in  the  medulla  (Fig.  364),  which  acts  upon  the  heart  in 
a  similar  manner  to  that  of  the  extracardiac  inhil)itory  one.  That 
such  a  center  exists  and  is  tonic  in  nature,  ever  acting,  appears  to 
be  shown  by  the  fact  that  the  pulse  rate  is  lowered  by  division  of 
the  vagi  and  subsequent  bilateral  extir]iation  of  the  inferior  cer- 
vical and  first  thoracic  ganglia.  It  is  Mell  known  that  stimulation 
of  the  intracardiac  nerves  by  the  application  of  acids  to  the  sur- 
face of  the  heart  gives  rise  to  reflex  actions,  such  as  movements  of 
the  limbs,  etc.  That  the  impulses  are  conveyed  by  the  vagi  ap- 
pears to  be  shown  from  the  fact  that  such  reflexes  do  not  occur  if 
the  vagi  are  divided.     The  vagi  are  also  supposed  by  some  physi- 


632  THE  NERVOUS  SYSTEM. 

ologists  to  convey  sensory  impnlses  to  the  brain.  If  snch  be  the 
case  the  sensations  cannot  be  very  acnte  since  in  cases  like  those  of 
the  Viscount  Montgomery  described  by  Harvey/  where  the  oppor- 
tunity was  aiforded  of  feeling  directly  the  heart  the  individual  was 
entirely  unconscious  when  his  heart  was  touched. 

Innervation  of  the  Lungs. 

The  pulmonary  branches  of  the  pneumogastric  nerve  are  given 
off  as  the  anterior  and  posterior  branches.  The  anterior  pulmo- 
nary branches,  after  sending  a  few  filaments  to  the  trachea,  form  a 
plexus  wdiich,  surrounding  the  bronchial  tubes,  is  continued  to  the 
termination  of  the  latter  in  the  pulmonary  air  cells.  The  posterior 
pulmonary  branches,  larger  and  more  numerous  than  the  anterior 
ones,  together  with  fibers  derived  from  the  upper  three  or  four 
thoracic  ganglia  of  the  sympathetic,  constitute  the  posterior  pul- 
monary plexus.  After  giving  off  fibers  to  the  inferior  and  pos- 
terior portion  of  the  trachea,  to  the  muscular  tissue  and  mucous 
membrane  of  the  middle  portion  of  the  oesophagus,  to  the  pos- 
terior and  superior  portion  of  the  pericardium,  the  posterior  pul- 
monary plexus  surrounds  the  bronchial  tubes,  and,  like  the  anterior 
one,  is  continued  with  the  latter  to  the  air  cells.  The  pulmonary 
branches  of  the  pneumogastric  nerve  supply  the  lower  part  of  the 
trachea,  the  bronchi,  and  the  lungs,  with  both  sensory  and  motor 
fibers,  as  shown  by  experiments  like  those  of  Longet,^  in  which, 
after  division  of  the  pneumogastric  nerve  in  the  neck,  the  mucous 
membrane  of  the  trachea  and  bronchus  became  insensible,  while 
stimulation  of  its  branches  caused  the  muscular  fibers  of  the  bron- 
chus to  contract. 

Respiratory  Center  and  Nerves. 

The  phenomenon  of  respiration,  the  principal  features  of  which 
have  been  already  described,  is  essentially  an  involuntary  reflex 
one,  involving  the  nice  co5rdination  of  very  complex  muscular  ac- 
tion, and  depending  upon  the  presence  of  a  respiratory  center  in 
relation  with  afferent  and  efferent  nerves.  From  the  fact  that  res- 
piration may  continue  after  removal  of  all  parts  of  the  brain  above 
the  level  of  the  bulb,  but  immediately  ceases  after  the  destruction 
of  an  area  about  5  millimeters  wide  lying  between  the  nuclei  of  the 
pneumogastric  and  hypo-glossal  nerves,  in  the  lower  part  of  the 
calamus  scriptorius  it  is  supposed  that  the  respiratory  center,  the 
"  u(eud-vital "  of  Flourens,  is  situated  in  the  medulla.  The  res- 
piratory center  appears  to  consist  of  two  halves  symmetrically 
situated  on  either  side  of  the  middle  line,  but  so  intimately  con- 
nected by  commissural  fibers  that  the  two  halves  constitute  physio- 
logically but  one  center.  That  this  is  the  case  is  shown  by  such 
facts  as  that  the  change  in  the  character  of  the  respiration  follow- 

'  Exerc'itationes  De  (ieneratione  Aninmliam,  Londini,  lO^l,  Exer.  lii. 
^Traite  de  Pliysiologie,  Tome  iii.,  p.  535. 


AFFERENT  BESPIBATORY  NERVES.  633 

ing  division  of  one  pneumogastric  nerve,  or  stimulation  of  its 
central  end  is  manifested  upon  the  opposite  as  well  as  upon  the 
injured  side  of  the  body.  On  the  other  hand,  if  the  commissural 
fibers  connecting  the  two  halves  of  the  respiratory  center  be  di- 
vided, the  two  halves  act  separately  independently  of  each  other, 
yet  synchronously.  Each  half  of  the  respiratory  center  is  further 
supposed  by  many  physiologists  to  consist  physiologically  of  two 
centers,  inspiratory  and  expiratory,  influencing  the  inspiratory 
and  expiratory  muscles  respectively.  As  the  inspiratory  center 
increases  the  rate  of  respiration  and  the  expiratory  center  dimin- 
ishes it,  the  inspiratory  center  is  regarded  as  being  acceleratory 
the  expiratory  as  inhibitory,  in  nature.  Both  centers,  however, 
arrest  the  respiratory  movements  in  the  inspiratory  and  expira- 
tory phases  respectively,  if  the  stimulus  be  sufficiently  power- 
ful. Of  the  two  centers  the  accelerating  center  appears  to  be 
the  more  irrital)le,  hence  if  both  centers  be  stimulated  simultane- 
ously, the  effect  will  be  accelerating.  While  there  is  no  doubt 
that  the  respiratory  movements  are  due  to  impulses  arising  in  the 
respiratory  center  and  transmitted  periodically  by  efferent  nerves 
to  the  respiratory  muscles,  difference  of  opinion  still  prevails  as  to 
what  constitutes  exactly  the  stimulus  exciting  the  respiratory  center 
to  action.  From  the  fact  that  rhythmical  respiratory  movements 
still  persist  even  with  removal  of  all  parts  of  the  brain  above  the 
bulb  and  after  division  of  the  vagi  and  glosso-pharyngeal  nerves,  of 
the  spinal  cord  in  the  lower  cervical  region,  and  posterior  roots,  it 
is  obvious  that  the  respiratory  center  is  susceptible  of  being  ex- 
cited by  other  stimuli  than  impulses  transmitted  by  afferent  nerves. 
In  such  exceptional  cases  and  probably  in  all  cases,  the  stimulus 
exciting  primarily  the  respiratory  center  appears  to  be  the  blood, ^ 
the  respiratory  rhythm  being,  however,  much  modified  by  the  influ- 
ence exerted  by  the  will,  the  emotions,  and  various  afferent  impulses. 
That  the  respiratory  movements  are  greatly  influenced,  if  not  en- 
tirely due  to  the  stimulus  exerted  by  the  blood  is  shown  by  the  fact 
that  the  number  of  respirations  are  increased  or  diminished,  and 
the  rhythm  modified  in  proportion  as  the  blood  is  freely  supplied  or 
cut  off,  and  according  to  its  temperature,  and  the  relative  amounts 
of  oxygen  or  carbon  dioxide  and  products  of  muscular  activity 
that  it  contains.  That  we  can  voluntarily  modify  to  some  extent, 
at  least,  our  respiratory  movements  and  that  the  latter  are  greatly 
affected  by  the  emotions  is  familiar  to  all. 

Afferent  Respiratory  Nerves. 

The  afferent  respiratory  nerves  are  the  pneumogastric  and  its 
laryngeal  branches,  the  glosso-pharyngeal,  the  trigeminus,  and  the 
cutaneous  nerves  generally.  AVhile  division  of  the  pneumogastric 
nerve  on  one  side  may  not  afl'ect  the  respiration,  as  a  general  rule 

iLoewy,  Pfluger's  Aroliiv,  Band  xliii.,  1889,  s.  245,  281. 


(334 


THE  NERVOUS  SYSTEM. 


the  respiratory  movements  become  slower,  deeper,  and  longer  ;  these 
effects  being,  however,  only  transient,  the  respiration  soon  becomes 
normal  again.  If  the  central  end  of  the  divided  pnenmogastric  be 
stimulated,  the  effects  following  will  depend  upon  the  nature  of  the 


Fig.  36e 


a/ Tracing  of  the  respiratory  movemeuts  of  the  cat.     a.  Before,     b.  After  division  of  both  vagi. 

stimulus.  Thus,  chemical  stimuli  excite  expiration,  mechanical 
stimuli  inspiration,  electrical  stimuli  expiration  or  inspiration,  or 
both,  according  to  the  strength  of  the  current.  After  section  of 
both  pnenmogastric  nerves,  the  respiratory  movements  become 
slower,  deeper,  more   powerful  (Fig.  '](U),  6),  the  amount  of  air 

inspired    being,    however,    the 
Fig.  367.  same,  expiration  active,  with  a 

pause  following  expiration. 
Ex])i ration  appears  to  be  more 
readily  produced  by  weak  elec- 
trical stimuli  than  inspiration, 
a  weak  current  when  applied  to 
the  central  end  of  the  pnenmo- 
gastric nerve,  both  nerves  hav- 
ing been  divided,  exciting 
expiration,  a  strong  current  in- 
spiration. 

tSuch  facts  as  those  just  men- 
tioned apj)ear  to  show  that  the 
pneumogastric  nerve  contains 
two  sets  of  afferent  fibers,  one 
set  (CX,  Fig.  367)  conveying 
impulses  that  excite  the  inspira- 
tory center  [INS),  the  other  set 
(CX'),  conveying  impulses  that 
excite  the  expiratory  center 
(EXP),  both  sets  of  fibers  origi- 
nating in  the  lungs  at  the  pe- 
riphery of  the  pneumogastric 
nerves.  From  the  fact  that  in- 
fllation  of  the  lungs  appears  to 
cause  expiration  and  collapse 
inspiration,  and  that  the  effects 
of  opening  the  j)l('Mral  cavity  or  of  occluding  the  bronchus  on  one 
side  are  the  same  as  the  following  division  of  one  pneumogastric 
nerve,  it  is  usually  held  at  the  present  day  that  the  mechanical 


Schema  of  the  chief  respiratory  nerves.  INS, 
Inspiratory,  and  EXP,  Expiratory  center — 
motor  nerves  are  in  smooth  lines.  Expiratory 
motor  nerves  to  abdominal  muscles,  AB ;  to 
muscles  of  back,  J)(>.  Ins])iratory  motor  nerves. 
PH.  Phrenic  to  diaphragm,  I).  INT.  Inter- 
costal nerves.  liL.  Kccurrent  laryngeal.  f'X. 
Pulmonary  fibers  of  vagus  that  excite  inspira- 
tory center.  CX'.  Pulmonary  fibers  that  excite 
expiratory  center.  CX".  I'ibcis  ot  sii|).  laryn- 
geal thatexcite  expiratory  (■enter.  J.XIf.  Fibers 
of  sup.  laryngeal  that  inhiltil  the  iiisjiiratory 
center.     (Lani)OIS.) 


COUGH  CENTER. 


635 


Fig.  368. 


conditions  existinf^  at  the  end  of  inspiration  and  expiration  consti- 
tute the  stimuli  to  the  same,  tlie  impulses  then  generated  l)eing 
transmitted  h\  the  afferent  fibers  to  the  expiratory  and  inspiratory 
centers  respectively.  It  should  be  mentioned,  however,  that  ac- 
cording to  some  physiologists  at  the  end  of  expiration  the  accumu- 
lation of  carbon  dioxide  in  the  air  cells  excites  the  afferent  fibers 
that  convey  impulses  to  the  inspiratory  center  and  so  causes  in- 
spiration. 

It  is  doubtful,  however,  whether  the  carbon  dicjxide  present  in 
the  lungs  at  the  end  of  expiration  exists  in  sufficient  quantity  to  ex- 
cite the  fibers  conveying  impulses  to  the  inspiratory  center.  That 
the  pneumogastric  nerves  are  essential  to  the  proper  performance 
of  respiration  is  shown  by  the  fact 
that  death  usually  takes  place 
after  their  division  in  an  animal 
within  from  one  to  six  days — re- 
covery taking  place  occasionally 
however  through  reunion  of  the 
divided  ends.  Stimulation  of  the 
central  ends  of  the  superior  and 
inferior  laryngeal  branches  of  the 
pneumogastric  nerve  diminishes 
or  even  arrests  altogether  respira- 
tion in  the  expiratory  phase.  The 
fibers  of  the  superior  laryngeal 
nerve  are  exquisitely  sensitive,  the 
functional  significance  of  which  is 
well  illustrated  by  those  cases  in 
which  foreign  bodies  entering  the 
larynx  during  deglutition  not  (jnly 
arrest  inspiration  but  excite  expi- 
ration and  are  coughed  out.  The 
impulses  generated  by  the  pres- 
ence of  foreign  bodies  in  the 
larynx  are  conveyed  to  "a  cough 
center"  which  appears  to  be  situ- 
ated in  the  medulla  (Fig.  3(58) 
whence  efferent  impulses  are 
transmitted  to  the  expiratory 
muscles.      It  may  be  mentioned 

in  this  connection  that  the  cough  center  receives  impulses  not  only 
from  the  larynx,  but  also  from  the  nose,  ear,  pharynx,  cesophagus, 
and  stomach. 

The  fibers  of  the  glosso -pharyngeal  nerve  also  arrest  inspiration, 
the  respiratory  center  being  inhibited  through  impulses  generated 
by  the  passage  of  food  during  deglutition.  That  breathing  should 
be  suspended  during  an  interval. equal  to  about  that  of  the  three 
preceding  respirations  is  obviously  of  great  advantage,  otherwise  the 


i< 


Abdom. 
Muscles  J 


Schema  of  the  aflferent  nerves  through  which 
coughing  may  be  excited  reflexly.  The  effe- 
rent nerves  are  dotted.     (Laxdois.) 


630  THE  NERVOUS  SYSTEM. 

solid  and  liquid  food  would  be  constantly  sucked  into  the  larynx 
when  swallowed. 

Respiration  may  also  be  arrested  through  excitation  of  the  sen- 
sory fibers  of  the  olfiictory,  of  the  nasal  branch  of  the  fifth  pair,  of 
the  laryngeal  and  pulmonary  branches  of  the  pncumogastric,  of  the 
splanchnic,  and  under  certain  circumstances  of  the  sciatic  and  sen- 
sory nerves  in  general,  though  the  effect  of  stimulation  of  the  latter 
is  usually  to  excite  inspiration.  On  the  other  hand,  stimulation  of 
the  cutaneous  nerves  increases  primarily  the  number  and  depth  of 
the  respirations,  though  finally  arresting  respiration  in  the  expira- 
tory phase. 

Every  one  is  familiar  with  the  fact  that  the  dashing  of  cold  water 
in  the  face,  or  the  first  plunge  into  a  cold  bath,  and  the  application 
of  a  pungent  vapor  to  the  nostrils,  cause  involuntary  respiratory 
efforts.  It  is  well  known,  also,  that  the  first  inspiratory  efforts  of 
the  newborn  child  are  usually  made  in  response  to  the  stimulation 
of  the  cool  external  air  coming  in  contact  with  the  face,  and  that 
impressions  on  the  general  surface,  such  as  a  slap  on  the  face  or 
upon  the  buttocks,  will  frequently  excite  the  child  to  breathe  when 
otherwise  it  would  not  do  so.  It  would  appear,  therefore,  that  im- 
pressions made  upon  the  general  sensory  surface  when  transmitted 
to  the  medulla  will  cause,  through  stimulation  of  the  respiratory 
center  reflexly,  inspiratory  movements,  as  well  as  stimuli  trans- 
mitted through  the  pneumogastrics. 

Efferent  Respiratory  Nerves. 

The  efferent  nerves  involved  in  easy  breathing  are  the  phrenics, 
spinal,  and  pncumogastric  nerves.  The  importance  of  the  phrenic 
nerves  in  respiration  is  shown  by  the  fact  tliat  after  their  division, 
the  diaphragm,  being  paralyzed,  is  so  relaxed,  that  it  is  drawn  up 
into  the  thorax  with  each  ins})iration,  and  which  interferes  so 
with  the  proper  expansion  of  the  lungs  that  death  follows  from 
asphyxia  within  a  few  hours.  On  the  other  hand,  if  the  spinal  cord 
be  divided  at  the  level  of  the  fifth  cervical  nerve,  that  is  below  the 
origin  of  the  roots  of  the  phrenics,  though  diaphragmatic  breathing 
continues,  costal  respiration  ceases  on  account  of  tlie  impulses  that 
pass  normally  from  the  respiratory  center  to  the  intercostal  muscles 
being  then  cut  off.  If  the  cord  be  divided  however  above  the  origin 
of  the  phrenic  nerves  both  diaphragmatic  and  costal  breathing  soon 
cease  though  respiratory  movements  of  the  larynx,  face,  mouth,  and 
neck  may  persist.  The  opening  of  the  glottis,  which  we  have  al- 
ready described  as  accompanying  synchronously  inspiration,  is  due 
to  impulses  transmitted  from  the  respiratory  center  by  the  fibers  of 
the  laryngeal  branches  of  the  pncumogastric  nerves,  particularly  by 
those  of  the  inferior  laryngeal.  If  the  pncumogastric  be  divided 
above  the  origin  of  its  laryngeal  branches  tlirough  the  paralysis  of 
the  muscles  of  the  larynx  the  vocal  membranes  become  flaccid,  the 
glottis   is  narrowed,  little  or   no  air  enters,  and   respiration  soon 


EFFERENT  RESPIRA  TOR  Y  NER  VES.  637 

ceases.  In  forced  breathing  the  spinal  nerves  innervating  the 
extraordinary  muscles  of  respiration,  the  facial  hypo-glossal  and 
spinal  accessory  nerves,  are  involved,  as  well  as  the  nerves  just 
mentioned.  The  respiratory  center  is  not  only  connected  with 
the  periphery  by  afferent  and  efferent  nerves  but  also  with  the 
cerebral  cortex,  as  shown  by  the  fact  already  mentioned  that  we 
can  modify  voluntarily  our  breathing,  at  least  to  some  extent.  By 
many  physiologists  respiratory  centers  are  said  to  exist  in  the  optic 
thalami,  corpora  quadrigemina,  pons  Varolii,  and  other  situations, 
as  well  as  in  the  medulla.  If  such  centers  do  exist,  which  is  ex- 
tremely doubtful,  they  can  exert  only  a  secondary  influence  upon 
respiration. 

The  cesophageal  brandies  of  the  })iu'umogastric  given  off  both 
above  and  below  the  pulmonary  ones  unite  to  form  the  cesophageal 
plexus,  which  supplies  the  muscular  tissue  and  the  mucous  mem- 
brane of  the  lower  third  of  the  oesophagus.  These  branches  con- 
tain both  sensory  and  motor  fibers,  the  latter  being  probably  more 
numerous,  since  the  mucous  membrane  cannot  be  said  to  be  acutely 
sensitive  to  heat,  cold,  or  strong  irritants. 

That  the  motor  fibers  supplying  the  oesophagus  are  derived  from 
the  pneumogastric  nerve  can  be  shown  by  experiments  like  those  of 
Bouchardat  and  Sandras,  ^  Chauveau,  ^  Longet,  ^  Bernard,  *  in  which, 
after  division  of  the  pneumogastric  nerve,  the  oesophagus  was  par- 
alyzed and  distended  by  the  food  Avhich  the  animal  vainly  endeav- 
ored to  swallow.  It  is  still  a  question,  however,  from  what  nerve 
the  motor  fibers  of  the  lower  third  of  the  oesophagus  are  derived, 
since,  according  to  Chauveau,  stimulation  of  the  bulbar  roots  of 
the  spinal  accessory,  the  most  prol)able  source,  do  not  excite  con- 
tractions of  the  oesophagus.  The  abdominal  l)ranches  of  the  pneu- 
mogastric nerve  differ  somewhat  in  their  course,  according  as  they 
are  distributed  to  the  two  sides.  That  of  the  left  side,  situated  an- 
teriorly to  the  cardiac  opening  of  the  stomach,  immediately  after 
passing  with  the  tesophagus  into  the  abdominal  cavity,  gives  off 
numerous  branches,  some  of  which  are  distributed  to  the  muscular 
walls  and  mucous  membrane  of  the  stomach,  while  others  pass,  in 
company  with  the  sympathetic,  along  the  course  of  the  portal  vein 
to  the  liver.  That  of  the  right  side,  situated  posteriorly,  passes 
through  the  oesophageal  opening  of  the  diaphragm,  and,  after  send- 
ing a  few  filaments  to  the  muscular  coat  and  the  mucous  membrane 
of  the  stomach,  is  distributed  to  the  liver,  s])leen,  kidneys,  supra- 
renal in  com|)any  with  the  sympathetic  capsules,  the  small  and  large 
intestine.  The  gastric  branches  of  the  pneumogastric  nerves  con- 
sist of  motor,  secretory,  and  probably  of  afferent  libers  as  well. 

There  can  be  no  doubt,  also,  that  stimulation  of  the  pneumogastric 
nerves  causes  the  stomach  to  contract,  and  that  the  movements  of 

'  Comptes  rendus,  Tome  xxiv.,  p.  59.     Paris,  1847. 
^Journal  de  la  jdiysiologie,  Tome  v.,  p.  3-42.     Paris,  1862. 
''Traite  de  Physioloifie,  Tome  iii.,  p.  547.     Paris,  1869. 
*Systeme  Nerveux,  Tome  ii.,  p.  422.     Paris,  1858. 


638  THE  NERVOUS  SYSTEM. 

the  stomach  may  to  a  certain  extent  at  least,  be  reestablished  by 
stimulation  of  the  peripheral  extremities  of  the  divided  nerves.  In- 
asmuch, however,  as  several  seconds  elapse  between  the  application 
of  the  stimulus  and  the  contraction,  it  is  probable  that  the  mus- 
cular contractions  of  the  stomach  induced  by  the  stimulation  of 
the  pneumo<jastrics,  are  due  to  its  sympathetic  fibers,  rather  than  to 
the  stimulation  of  the  nerve  fibers  of  the  pneumogastric  proper,  the 
tardiness  in  action  just  mentioned  being  characteristic,  as  we  shall 
see,  of  the  sympathetic.  If  such  be  the  case,  it  would  appear  that 
the  impressions  due  to  the  presence  of  food  in  the  stomach  are 
transmitted  by  the  abdominal  l)ranches  of  the  pneumogastric  to  the 
medulla,  the  efferent  impulses  being  reflected  thence  to  its  muscu- 
lar walls  by  sympathetic  fibers. 

According  to  some  physiologists  the  gastric  branches  of  the 
vagus  contain  inhibitory  as  well  as  motor  fibers ;  the  former  appear 
however  to  be  derived  from  the  splanchnic  nerves  which  we  shall 
see  hereafter  pass  from  the  sixth  to  the  tenth  thoracic  ganglia  to 
the  solar  plexus  and  thence  to  the  stomach.  As  it  is  well  known, 
however,  that  the  stomach,  even  when  entirely  removed  from  the 
body,  still  executes  movements  of  a  normal  character,  it  appears 
that  the  vagi  regulate  the  movements  of  the  stomach  rather  than 
originate  them,  the  latter  l>eing  due  probably  to  stimuli  emanating 
from  Auerbach's  plexus,  situated  betAveen  the  muscular  coats  of 
the  intestine  and  Meissner's  plexus  in  the  submucous  coat.  That 
the  vagi  contain  secretory  fibers  is  shown  by  the  fact  that  direct 
stimulation  of  the  nerves,  proper  precautions  l)eing  taken,  gives 
rise  to  a  marked  secretion  of  gastric  juice.  That  the  secretion 
can  be  also  excited  indirectly  reflexly  by  afferent  impulses  trans- 
mitted from  the  periphery  to  the  medulla  and  thence  by  the  secre- 
tory fibers  of  the  vagi  to  the  stomach  is  shown  by  the  following 
considerations.  In  cases  of  gastric  fistuke  in  man  and  animals,  it  has 
often  been  noticed  that  the  placing  of  food  in  the  mouth  or  even  the 
sight  of  food,  excited  a  copious  secretion  of  gastric  juice.  This  was 
also  observed  in  experiments  made  upon  dogs  in  which  the  food,  after 
being  taken  into  the  mouth,  instead  of  l:)cing  swallowed  and  entering 
the  stomach,  passed  by  a  fistulary  opening  in  the  oesophagus  out  of 
the  body,  the  food  constituting  therefore  only  a  "  fictitious  meal.'" 
That  gastric  digestion  is  profoundly  influenced  by  the  pneumogas- 
tric nerves  is  further  shown  by  the  fact  that  if  they  be  divided 
during  full  digestion  in  a  liying  animal  in  which  a  gastric  fistula 
has  been  established,  so  that  the  interior  of  the  stomach  can  be 
examined,  the  muscular  contractions  will  be  observed^  to  cease 
instantly,  the  nnicous  membrane  to  become  pale  and  flaccid,  the 
secretion  of  the  gastric  juice  to  l)e  arrested,  and  the  organ  to  have 
become  insensible. 

It  must  be  mentioned,  however,  that  even  when  l)oth  pneumo- 

'  Puwlow  u.  Schuniowii  Simiiiiowskaja,  Du  Bois  Keymond  Arcliiv,  18'jr),  s.  53. 
2  Bernard,  op.  cit. ,  Tome  ii. ,  p.  422. 


ABDOMINAL  FIBERS  OF  VAGUS.  639 

gastric  nerves  are  divided,  if  the  animal  survive  the  operation,  in  a 
day  or  two  digestion  may  be  partly  reestablished  ^  if  the  food  be 
finely  divided  and  carefully  introduced  into  the  stomach.  It  is 
quite  possible  that  the  impression  due  to  the  presence  of  food  in  the 
stomach  and  intestines,  after  reaching  the  plexus  of  Meissner,  situ- 
ated in  the  submucous  tissue,  and  the  plexus  of  Auerbach,  lying 
between  the  muscular  coats  is  at  once  reflected  back  to  the  stomach 
without  being  transmitted  to  the  medulla.  Whether  the  reflex 
nervous  mechanism  involved  in  gastric  digestion  be  such  as  just 
mentioned  or  not,  there  can  be  no  doubt  that  digestion  in  man  is 
very  much  influenced  by  the  nervous  system.  Every  one  is  famil- 
iar with  the  fact  that  digestion  may  be  at  once  stopped  by  nervous 
excitement,  such  as  a  piece  of  bad  news,  etc.;  that  there  exists  an 
intimate  sympathy  between  the  brain  and  the  stomach  at  all  times, 
and  it  is  diliicult  to  understand  by  what  avenues,  other  than  the 
abdominal  branches  of  the  pneumogastric  nerve,  impressions  are 
carried  to  and  from  these  organs.  That  the  abdominal  branches  of 
the  pneumogastric  influence  also  absorption  from  the  stomach  and  in- 
testinal digestion  may  be  inferred  from  the  foct  that,  after  division  of 
the  pneumogastric  nerves,  the  absorption  of  poisons  is  retarded,  if  not 
prevented,  and  that  the  most  powerful  cathartics  fail  to  produce  their 
characteristic  purgative  effects,^  just  as,  under  similar  circumstances, 
digitalis  fails  to  diminish  the  action  of  the  heart.^ 

The  branches  of  the  pneumogastric  nerves  supplying  the  small  and 
large  intestine  appear  to  contain  motor  fibers,  at  least  stimulation  of 
the  pneumograstic  nerves  causes  contraction  of  the  intestine,  the 
stimulus  acting,  however,  as  in  the  case  of  the  stomach,  indirectly 
through  the  plexuses  of  Auerbach  and  Meissner.  According  to 
some  observers  the  intestinal  nerves  contain  also  inhibitory  fibers. 
It  has  not  yet  been  established,  however,  whether  the  inhibitory 
fibers  pass  to  the  intestine  by  the  pneumogastric  or  the  sympathetic, 
or  by  both  nerves.  In  all  prol)ability  the  pneumogastric  contains 
also  fibers  which  excite  the  intestinal  secretion,  since  it  has  been  es- 
tablished that  stimulation  of  the  pneumogastric  after  a  long  latent 
period  causes  a  flow  of  the  secretion  of  the  pancreas.  It  is  said  that 
division  of  the  pneumogastric  nerve  through  its  abdominal  branches 
produces,  also,  congestion  of  the  liver,  renders  the  bile  Avatery,  and 
arrests  its  glycogenic  function.  The  production  of  sugar  is,  how- 
ever, exaggerated  by  stimulation  of  the  central  ends  of  the  divided 
nerves.  The  action  is  a  reflex  one,  stimulation  of  the  peripheral 
ends  having  no  effect  in  this  respect.  The  efferent  impulses  appear 
to  be  transmitted  from  tlie  center,  in  the  medulla,  by  the  sympathetic, 
rather  than  by  tlie  pneumogastric  nerve,  since  division  of  the  latter 
between  the  lungs  and  liver  does  not  affect  the  production  of  sugar. 

^  ScliiflfJ  Lecons  sur  la  physiologie  de  la  digestion,  Tome  ii.,  o89.  Florence, 
1867.     Longet,  op.  cit..  Tome  iii.,  p.  549. 

2Brodie,~Phil.  Trans.,  Vol.  xiv.,  p.  104.  London,  1814.  Eeid,  Phys.  Anat. 
and  Path.  Eesearches.  London,  1848.  "Wood,  American  Journal  of  the  Med. 
Sciences,  Vol.  Ix.,  p.  75.     Phila.,  1870. 

^Traube,  Gesammelte  Beitriige  zur  Path.  u.  Physiologie,  Bd.  i.,  s.  190.     Berlin. 


040  THE  NERVOUS  SYSTEM. 


The  Eleventh  Nerve. 


The  spinal  accessory  or  the  eleventh  nerve  (Fig.  355),  consisting 
of  from  2000  to  2500  fibers  arises  by  two  distinct  sets  of  roots — 
upper  and  lower.  The  upper  root  or  the  bulbar  portion,  originat- 
ing in  a  nucleus  lying  close  to  the  central  canal,  and  continuous 
with  the  nucleus  of  the  pneumogastric  nerve  (Fig.  337,  XI), 
emerges  from  the  side  of  the  medulla  below  the  latter  nerve.  The 
lower  roots  or  the  spinal  portion,  originating  in  the  anterior  cornu 
of  the  cord,  curve  backward,  and,  passing  through  the  gray  sub- 
stance and  lateral  columns  of  the  cord,  emerge  from  the  latter  as  six 
or  eight  filaments  between  the  anterior  and  posterior  roots  of  the 
first  and  seventh  cervical  nerves  inclusive.  The  spinal  accessory 
nerve  so  formed  enters  the  cranial  cavity  by  the  foramen  magnum, 
and  leaves  the  latter  by  the  jugular  foramen  in  company  with  the 
pneumogastric  and  glosso-pharyngeal,  and  the  jugular  vein.  Dur- 
ing its  course  the  spinal  accessory  receives  from  or  gives  off  some 
filaments  to  adjacent  nerves.  Frequently,  as  it  enters  the  cranial 
cavity,  it  receives  filaments  from  the  posterior  roots  of  the  first  two 
cervical  nerves,  to  which  its  recurrent  sensibility  is  due ;  occasion- 
ally also  it  gives  off  a  filament  to  the  superior  ganglion  or  ganglion 
of  the  root  of  the  pneumogastric.  It  also  receives  filaments  from 
the  anterior  branches  of  the  second,  third,  and  fourth  cervical 
nerves.  After  emerging  from  the  jugular  foramen  the  spinal  acces- 
sory gives  off  also  two  branches — internal  and  external — meriting 
special  notice.  The  internal  branch,  consisting  principally,  if  not 
entirely,  of  the  fibers  derived  from  the  medulla,  passes  to  the  pneu- 
mogastric, subdividing  as  it  joins  the  latter  into  two  small  branches, 
the  first  of  which  constitutes  a  part  of  the  pharyngeal  branch  of 
the  pneumogastric  as  already  observed ;  the  second,  however,  be- 
comes so  intimately  united  with  the  pneumogastric  nerve  that  its 
final  distribution  cannot  be  made  out  by  dissection  alone,  experi- 
ment only  indicating  its  functional  significance,  as  we  shall  see  pres- 
ently. The  external  branch  of  the  spinal  accessory,  larger  than 
the  internal,  and  derived  principally  from  the  fibers  of  the  spinal 
cord,  pass  through  the  posterior  portion  of  the  upper  third  of  the 
sterno-cleido-mastoid  muscle,  receiving  filaments  in  its  course 
througli  the  muscle  from  the  second  and  third  cervical  nerves,  to 
be  finally  distributed  to  the  trapezius  muscle. 

That  the  spinal  accessory  nerve  is  essentially  motor  in  function, 
supplying  the  muscles  just  mentioned,  can  l)e  demonstrated  experi- 
mentally by  cutting  through  the  occipito-atloid  ligaments  and  stim- 
ulating the  roots  of  the  nerve  within  the  spinal  canal  by  electricity. 
If,  liowever,  the  filaments  arising  from  the  medulla  only  be  stimu- 
lated contractions  of  the  muscles  of  the  larynx  and  i)harynx  alone 
ensue,  no  movements  of  the  sterno-cleido-mastoid  or  trapezius  be- 
ing observed.  On  the  other  hand,  if  the  filaments  arising  from  the 
spinal  cord  only  be  stimulated  then  the  sterno-cleido-mastoid  and 


THE  ELEVENTH  yERVE.  <341 

trapezius  muscles  aloue  contract,  the  laryugeal  and  pharyngeal  mus- 
cles remaining  cpiiescent.  Xot  only  does  this  striking  experiment 
contirm  what  the  distribution  of  the  spinal  accessory  would  lead  us 
to  suppose  as  to  its  general  motor  functions,  but  it  also  clearly  shows 
that  the  muscles  of  the  larynx  must  be  supplied  by  the  spinal  acces- 
c;orv — that  is,  that  the  fibers  of  the  recurrent  laryngeal  nerves  sup- 
plying the  muscles  of  the  larynx,  except  the  crico-thyroid,  are  de- 
rived not  from  the  pneumogastric  but  from  the  spinal  accessory 
nerve/  The  spinal  accessory  nerve  appears  to  be  endowed  also 
with  a  certain  amount  of  dii-ect,  apart  from  the  recurrent,  sensi- 
bility already  referred  to.  Whatever  sensibility  it  does  possess  is, 
however,  due  undoubtedly  to  those  filaments  derived  from  the 
pneumogastric  and  cervical  nerves.  In  speaking  of  the  functions 
of  the  inferior  laryngeal  branches  of  the  pneumogastric  nerve  it 
was  mentioned  that  those  nerves  consisted  of  two  kinds  of  fibers, 
one  set  influencing  the  respiratory  action  of  the  glottis,  another 
regulating  phonation,  and  that  the  latter  were  in  reality  derived 
from  the  internal  branch  of  the  spinal  accessory.  It  only  remains, 
therefore,  to  descril^e  the  manner  in  which  this  can  be  demonstrated, 
since  the  fibers  of  the  inferior  laryngeal  nerves  influencing  phona- 
tion cannot  be  traced  by  dissection  back  to  the  spinal  accessory. 
Bischoff  was  the  first  to  demonstrate  the  influence  exerted  by  the 
internal  branch  of  the  spinal  accessory  nerve  upon  the  production 
of  the  voice  by  opening  in  a  goat  the  spinal  canal  through  the 
occipito-atloid  space,  and  dividing  all  its  roots  on  both  sides,  the 
result  being  entire  extinction  of  the  voice,  whatever  sound  was 
emitted  after  the  experiment  being  one  which  in  no  wise  could  be 
called  voice.^  As  this  method  of  procedure  was  however  unsuc- 
cessful in  the  six  preceding  experiments,  five  of  which  were  per- 
formed upon  dogs  and  one  upon  the  goat,  even  in  the  hands  of  such 
a  skilful  anatomist  and  physiologist  as  Prof.  Bischolf,  that  intro- 
duced later  and  habitually  practiced  by  Bernard  is  a  far  more  sat- 
isfactory one.  This  consists  in  following  by  dissection  the  external 
or  muscular  branch  of  the  spinal  accessory  up  to  the  point  where  it 
emerges  from  the  jugular  foramen,  and  where  it  separates  from  the 
internal  branch,  and  then,  after  seizing  the  combined  trunk  between 
the  blades  of  a  forceps,  by  steady  and  continuous  traction  to  extract 
the  whole  nerve  with  both  its  medullary  and  spinal  roots  entire  ;  or 
to  remove  the  medullary  portion  with  the  internal  branch  aloue, 
leaving  the  spinal  portion  with  the  external  branch  intact,  in  which 
case  the  voice  is  entirely  lost ;  or  to  remove  the  spinal  portion  with 
the  external  branch,  leaving  the  medullary  portion  with  the  internal 
branch  intact,  in  which  case  the  voice  is  unaffected  or  in  some  cases 
even  rendered  clearer.^  It  is  an  interesting  fact  that  in  a  chimpan- 
zee dissected  by  Vrolik  the  internal  branch  of  the  spinal  accessory 

'Bernard,  Systeme  Xerveux,  Tome  ii.,  p.  296. 

2  "Qui  neutiquam  vox  appellari  potiiit."     Bisclioff',   Xervi  Aeees-sorii  Williiiii 
Anatomia  et  Physiologie,  p.  94.     Darrastadii,  1832. 
^Bernard,  op.  cit.,  Tome  ii.,  p.  29(5. 
41 


642  THE  NEE rOUS  SYSTEM. 

was  found  passing  directly  to  the  larynx  instead  of  to  the  pueumo- 
gastric.  The  usual  disposition  in  this  anthropoid  appears,  however, 
to  be  the  same  as  obtains  in  man,  at  least  such  was  found  to  be  the 
case  in  three  individuals  dissected  by  the  author.  After  what  has 
been  said  of  the  influence  exerted  by  the  pharyngeal  branches  of 
the  glosso-pharyngeal  and  of  the  pharyngeal  and  inferior  laryngeal 
branches  of  the  pneumogastric  in  deglutition,  and  of  the  inhibitory 
effects  upon  the  heart  by  the  cardiac  fibers  of  the  latter  nerve,  it  is 
only  necessary  here  to  mention  again  that  the  motor  fibers  involved 
in  the  perfoi'mance  of  the  above  functions  are  derived  from  the  in- 
ternal branch  of  the  spinal  accessory;  at  least  partly  so  in  the  case 
of  deglutition,  and  entirely  so  in  that  of  the  inhibition  of  the  heart. 
As  to  the  function  of  the  external  or  muscular  branch  of  the  spinal 
accessory,  it  would  appear  that  its  action  is  to  excite  contraction  of 
the  sterno-cleido-mastoid  and  trapezius  muscles,  synchronously  with 
the  action  exerted  by  the  internal  branch  upon  the  laryngeal  and 
pharyngeal  muscles,  the  harmonious  action  of  the  muscles  so  brought 
about  being  of  advantage  under  certain  circumstances.  Thus,  in 
prolonged  vocal  efforts,  as  in  singing,  for  example,  in  which, 
as  we  shall  see,  the  vocal  membranes  are  put  on  the  stretch,  the 
upper  portion  of  the  chest  is,  at  the  same  time,  fixed  through 
the  action  upon  the  shoulders,  to  a  certain  extent  at  least,  of  the 
sterno-cleido-mastoid  and  trapezius  muscles,  and  in  this  way  the 
expulsion  of  air  through  the  glottis,  and  upon  which  the  singing 
depends,  can  be  well  regulated.  In  the  same  manner,  when  one 
makes  a  muscular  effort,  the  glottis  is  closed  at  the  same  moment 
that  the  chest  is  fixed,  respiration  being  temporarily  arrested.  The 
same  synchronism  in  the  action  of  the  external  and  internal  branches 
of  the  spinal  accessory  obtain,  therefore,  in  this  instance,  as  in  the 
former.  That  the  external  branches  of  the  spinal  accessory  exert 
some  influence  upon  the  respiratory  movement  is  well  seen  in  ani- 
mals in  which  the  branches  on  both  sides  have  been  divided,  such 
suffering  from  shortness  of  breath  after  any  very  great  muscular 
effort,  and  presenting,  also,  irregularity  in  the  movements  of  the 
anterior  extremities,  the  shortness  of  breath  being  apparently  due 
to  the  want  of  synchronous  action  of  the  sterno-cleido-mastoid  and 
trapezius  muscles. 

The  Twelfth  Nerve. 

The  twelfth  nerve,  the  hypo-glossal  or  sublingual,  consisting  of 
from  4500  to  5000  fibers,  arises  from  a  long  column  of  nerve  cells, 
the  lower  part  of  which  lies  in  front  of  the  central  canal  on  each 
side,  the  upper  part  forming  a  prominence  upon  the  floor  of  the 
fourth  ventricle  (Fig.  337,  XII ).  Passing  thence  through  the 
inner  part  of  the  olivary  body,  the  fibers  emerge  as  eleven  or  twelve 
filaments  from  the  furrow  between  the  anterior  pyramid  and  the 
olivary  body  (Fig.  338),  which,  passing  as  two  distinct  bundles 
through  two  distinct  opanings  in  the  dura  mater  into  the  anterior 


THE  TWELFTH  XERVE. 


643 


cond}'loid  foramen,  unite  into  a  single  trunk  as  they  emerge  from 
the  cranial  cavity.  Occasionally,  the  hypo-glossal  nerve,  as  it  passes 
through  the  foramen,  receives  a  filament  having  a  ganglion  upon  it, 
arising  from  the  postero-lateral  portion  of  the  medulla.  This 
gangliouated  filament,  or  posterior  root,  so  to  speak,  of  the  hypo- 
glossal nerve,  while  exceptionally  present  in  man,  is,  however, 
found  normally  in  the  dog,  cat,  rabbit,  hog,  horse,  and  calf,  and  is 
sensory  in  function  in  these  animals,  the  anterior  portion  of  the 
common  trunk  corresponding   to  the  hypo-glossal  in  man,  being 

Fig.  3(59. 


Distribution  of  tht  suljlingiial  ne^^e  1  Root  of  the  tifth  nerve.  2.  Ganglion  of  Gasser.  3,4, 
5,  6,  7,  9,  10,  12.  15ranchc>  and  anabtomo^es  of  the  fifth  nerve.  11.  Submaxillary  ganglion.  13. 
Anterior  belly  of  the  digastric  mu--cle  1-t  '^ettion  of  the  mylo-hyoid  muscle.  15.  Glosso-pharyn- 
geal  nerve.  16.  L+anguon  oi  Anaerscn.  i7.  in.  Brancties  of  the  glosso-pharyngeal  nerve.  19,19. 
Pneumogastric.  20,  21.  Ganglia  of  the  pneumogastric.  22,  22.  Superior  laryngeal  branch  of  the 
pneumogastric.  23.  Spinal  accessory  nerve.  24.  Sublingual  nerve.  2.5.  Descendens  noni.  26. 
Thyro-hyoid  branch.  27.  Terminal  branches.  28.  Two  branches,  one  to  the  genio-hyo-glossus, 
and  the  other  to  the  genio-hyoid  muscle.     (Sappey.) 

motor.  After  the  hypo-glossal  passes  out  of  the  cranial  cavity  it 
gives  oif  filaments  to  the  sympathetic,  to  the  pneumogastric,  to  the 
upper  two  cervical  nerves,  and  to  the  lingual  branch  of  the  fifth. 
Descending  behind  the  pneumogastric  nerve  (Fig.  369)  it  curves 
downward  and  forward  to  the  outer  side  of  the  latter,  between  the 
internal  carotid  artery  and  the  jugular  vein,  and  penetrates  the 
genio-hyo-glossal  muscle,  which  it  supplies,  as  also  the  hyo-glossus, 
linffualis,  sxenio-hvoid,  and  stvlo-irlossus  muscles. 


644  THE  NERVOUS  SYSTEM. 

The  hypo-glossal  gives  off,  also,  an  important  branch,  the  descen- 
dens  noni,  but  which,  according  to  the  classification  of  the  nerves 
usually  adopted,  would  be  more  correctly  called  the  descending^ 
branch  of  the  twelfth,  supplying  the  sterno-thyroid,  sterno-hyoid^ 
and  omo-hyoid  muscles,  the  thyro-hyoid  muscle  being  supplied  by 
the  branch  of  the  same  name.  From  the  distribution  of  the  hypo- 
glossal nerve  it  might  naturally  be  inferred  that  it  is  essentially 
motor  in  function,  any  sensibility  that  it  possesses  being  due  to  the 
filaments  communicating  with  the  cervical  and  pneumogastric  nerves, 
and  the  lingual  branch  of  the  fifth.  That  such  is  the  case  is  shown 
by  the  effect  of  division  of  the  hypo-glossal  in  a  living  animal,  and 
of  its  paralysis  in  man.  Under  such  circumstances,  through  paralysis 
of  the  tongue,  though  the  tactile  and  gustatory  senses  are  not 
affected,  mastication  is  rendered  very  difficult,  if  not  impossible, 
while,  through  paralysis  of  the  muscles  depressing  the  larynx  and 
hyoid  bone,  deglutition  is  made  difficult ;  in  man  the  power  of 
articulation  is  lost  as  well.  This  is  well  seen  in  cases  of  g-losso- 
labio-laryngeal  paralysis,  in  which  the  nuclei  of  origin  in  the 
medulla  of  the  hypo-glossal,  as  well  as  the  facial,  spinal  accessory, 
and  glosso-pharyngeal  nerves  are  affected  by  disease,  which  involves 
a  gradual  and  progressive  paralysis  of  the  tongue,  palate,  lips,  and 
laryngeal  muscles,  rendering  articulation,  and  ultimately  deglu- 
tition, impossible. 

In  cases  of  hemiplegia  the  hypo-glossal  nerve  is  usually  more  or 
less  involved.  In  such  eases  the  patient  protrudes  the  tongue,  the 
point  being  deviated  to  the  side  atfected  with  the  paralysis,  owing^ 
to  the  unopposed  action  of  the  genio-hyo-glossus  muscle  of  the  sound 
side.  That  the  hypo-glossal  nerve  is  a  motor  nerve — the  motor 
nerve  of  the  tongue,  etc. — is  further  shown  by  the  effect  of  stimu- 
lating the  peripheral  end  of  the  divided  nerve,  the  tongue,  and  the 
muscles  to  Avhich  the  nerve  is  distributed  at  once  contracting.  The 
hypo-glossal  nerve,  together  with  the  small  or  motor  root  of  the  fifth 
and  the  facial  nerves,  constitutes  the  efferent  fibers,  by  Avhich  the 
reflex  action  involved  in  mastication  is  accomplished,  the  lingual 
branch  of  the  fifth  and  the  glosso-pharyngeal  nerves,  containing  the 
afferent  fibers,  the  center  being  situated  in  the  medulla. 

Having  described  the  distribution  and  function  of  the  ten  ])airs 
of  cranio-mednllary  nerves,  and  having  seen  that  they  arise  from 
gray  nuclei  in  the  medulla  oblongata,  it  is  evident  that  the  medulla 
consists,  not  only  as  we  have  seen,  of  fibers  passing  from  the  cord 
to  the  ganglion  of  the  base  of  the  brain,  but  may  be  regarded,  also^ 
as  being  composed  of  so  many  distinct  reflex  centers,  of  which  the 
cranio-medunary  and  spinal  nerves  constitute  tlie  afl'erent  and  effe- 
rent fibers;  the  existence  in  the  mcdulhi  of  about  fourteen  such  cen- 
ters, probably  more,  has  been  estaV>lishe(l.  First.  That  for  closing^ 
the  eyelids,  the  efferent  fibers  being  contained  in  the  optic  nerve, 
and  the  l)ranches  of  the  fiftli  distributed  to  the  conjunctiva  and  to 
the  skin  of  the  lids,  the  efl'erent  fil)crs  in  the  facial.      Second.     The 


REFLEX  CEXTEBS  OF  MEDULLA.  645 

center  for  sneezino-,  tlie  afferent  fibers,  being  in  the  olfactory  and 
the  fifth  nerve,  the  efferent  in  the  spinal  nerves  inflneneing  expira- 
tion. Third.  The  center  for  conghing,  the  afferent  fillers  rising  in 
the  ])nenniogastric,  the  efterent  being  the  same  as  those  last  men- 
tioned. Fourth.  The  respiratory  center,  or  nrjeud-vital  of  Flourens. 
Fifth.  The  masticatory  center.  Sixth.  The  center  of  insaliva- 
tion.  Seventh,  The  center  of  deglutition.  Eighth.  The  cardio- 
inhibitory  centers,  the  afferent  and  efferent  fibers  of  which  have 
already  been  referred  to.  Ninth.  The  center  for  sucking,  the  af- 
ferent fibers  of  which  are  in  the  fifth  and  glosso-pharyngeal  nerves, 
the  efferent  the  facial  supplying  the  lips*.  Tenth.  The  center 
influencing  the  act  of  vomiting,  the  afferent  fibers  being  in  the  pneu- 
mogastric,  the  efferent  in  the  nerves  of  expiration.  Eleventh.  The 
center  of  speech — that  is,  with  r(>ference  to  the  movements  of  the 
lips,  tongue,  and  larynx.  Twelfth.  The  vasomotor  center.  Thir- 
teenth. The  center  inhibiting  the  reflex  centers  of  the  spinal  cord. 
The  medulla  oblongata  being  the  seat  of  the  centers  receiving  the 
afferent  fibers  and  giving  off  the  efferent  ones  involved  in  the  per- 
formance of  mastication,  insalivation,  deglutition,  respiration,  circu- 
lation, etc.,  is,  therefore,  the  great  coordinating  center  of  the  reflex 
actions  essential  to  the  maintenance  of  life.  Even  if  all  the  parts 
of  the  brain  above  the  medulla  be  removed  in  a  living  animal,  or  be 
undeveloped,  as  in  anencephalous  infants,  life  may  yet  be  main- 
tained by  artificial  means,  since,  if  food  be  introduced  into  the 
mouth  it  ^vill  be  swallowed,  the  respiratory  and  circulatory  move- 
ments will  go  on  in  the  usual  rhythmical  manner,  the  animal  or 
infant  will  react  to  impressions  made  upon  the  general  sensory  sur- 
face, withdrawing  its  limbs,  etc.,  if  pulled  or  pinched,  may  even 
utter  a  cry,  as  if  in  pain,  and  yet  such  an  animal  or  human  being 
cannot  be  said  to  be  really  a  sentient,  still  less  an  intelligent,  being, 
but  merely  a  nutritive  reflex  mechanism. 


CHAPTER   XXXIII. 

THE   NEEVOUS   SYSTE'M.— {Continued.) 


THE  PONS  VAROLII.     CRURI  CEREBRI.    CORPORA    STRIATA. 

THALAMI  OPTICI.     CORPORA  aUADRIGEMINA. 

CEREBELLUM. 

Whether  reflex  action  of  the  spinal  cord  or  medulla  be  accom- 
panied or  not  in  the  lower  animals  with  sensation,  volition,  con- 
sciousness, there  can  be  no  doubt  that  the  physical  seat  of  what  we 
call  feeling,  thinking,  etc.,  in  man  is  situated  in  some  part  of  the 
brain  above  the  level  of  the  medulla  oblongata,  since  in  the  absence 
of  such  parts  one  neither  feels,  thinks,  nor  wills.  Pons  Varolii. 
Just  as  we  have  seen  that  the  spinal  cord  and  medulla  consist  of 
nervous  centers  as  well  as  of  fibers  passing  through  them  to  the  ganglia 
at  the  base  of  the  brain,  so  the  pons  Varolii  or  mesencephalon  (Fig. 
370,  1)  may  be  regarded  as  consisting,  not  only  of  ascending  sensory 

Fig.  370. 


^0  •■■X\  t  It  f  /,.<  "^  ^ S^s 


Diagram  of  liiimau  hrain  in  transverse  vertical  section.    1.  Tuber  annulare.    2,2.  Crura  cere- 
bral.   3,  3.  Internal  capsule.    4,  4.  Corona  radiata.    5,  C.  Cerebral  ganglia.    7.  Corpus  callosum. 

(D  ALTON.) 

and  descending  motor  fibers  connecting  the  cortex  Avith  the  cord^ 
and  of  bridging  fibers  connecting  the  lateral  lobes  of  the  cerebellum 
— hence  its  name — but  of  gray  matter  performing  the  functions  of 
a  distinct  nerv'ous  center  or  centers.  That  the  gray  matter  or 
tuber  annulare  (Fig.   370,   1)  is   the  essential    part  of  the  pons 


CEUBA  CE REBEL  647 

Varolii  is  shown  by  the  fact  of  the  bridtiino;  fibers  of  the  pons  being 
absent  in  animals  in  Avhich  the  lateral  lobes  of  the  cerebellnm  are 
undeveloped  as  in  birds.  That  tlie  tuber  annulare,  or  vesicular 
matter  of  the  pons  Varolii,  is  that  part  of  the  encephalon  in  the 
lower  mammals  in  Avhich  consciousness  first  awakens  in  response  to 
impressions  transmitted  by  the  spinal  and  cranial  nerves  from  the 
external  world  appears  probable  from  experiments,  such  as  tliose  of 
Longet,^  Yulpian,-  etc.,  in  which,  after  removal  of  the  whole  en- 
cephalon except  the  pons,  medulla,  and  cerebellum,  sensibility  to 
pain  still  persisted,  the  cries  emitted  by  an  animal  so  mutilated  not 
being  simply  reflex  in  character,  such  as  are  heard  in  an  animal 
possessing  only  the  medulla  already  referred  to,  but  as  indicating 
the  perception  of  painful  impressions.  AVhile  it  is  true  that  the 
appreciation  of  painful  and  other  impressions  is  not  acute,  but  ob- 
scure, nevertheless  that  such  an  animal  is  conscious  to  a  certain 
extent  at  least,  there  appears  to  be  little  doubt,  their  condition  being 
apparently  similar  to  patients  undergoing  a  severe  surgical  oper- 
ation, but  imperfectly  under  the. influence  of  an  antesthetic,  and 
who,  while  undoubtedly  suffering  ])ain  at  the  time,  have  no  recol- 
lection of  it,  the  impressions  due  to  the  operation  not  being  con- 
veyed to  the  cerebral  hemispheres,  and  therefore  not  memorized. 

Even  admitting  however  that  the  physical  seat  of  incipient  con- 
sciousness lies,  in  the  lower  mammals,  in  the  pons,  there  is  little 
reason  to  suppose  that  the  same  part  of  the  encephalon  in  man  pos- 
sesses such  a  function.  Lesions  of  the  pons,  at  least  in  man,  ap- 
pear to  show  that  its  function  is  rather  of  a  commissural  than  of  a 
psychical  character. 

Crura  Cerebri. 

It  has  alreadv  been  mentioned  that  the  motor  tract  beQ-innino-  in 
the  cortex  of  one  hemisphere  is  continued  downward  through  the 
anterior  or  inferior  portion  of  the  cms  cerebri  (crusta)  to  the  decus- 
sating fibers  of  the  medulla,  and  thence  to  the  antero-lateral  columns 
of  the  opposite  side  of  the  cord  ;  that  the  sensory  tract  beginning  on 
the  opposite  side  of  the  body  crosses  the  middle  line,  is  continued  up- 
ward through  the  medulla  and  posterior  or  superior  portion  of  the  crus 
cerebri  (tegmentum)  to  terminate  in  the  cortex  of  the  same  side.  Such 
being  the  case,  as  might  be  anticipated  if  botli  crura  (Fig.  371,  2,  2) 
are  completely  divided,  sensation  and  voluntary  movement  are  en- 
tirely annihilated  throughout  the  body,  division  of  one  of  the  crura 
involving  paralysis  of  sensation  and  motion  on  the  opposite  side  of 
the  body  only.  The  constant  tendency  to  turn  toward  the  side  op- 
posite that  of  the  lesion,  the  "  evolution  du  manege  "  of  Louget, 
observed  when  one  cms  is  imperfectly  divided  appears  to  be  due  to 
the  balance  of  the  muscular  action  being  destroyed  through  the 
weakening  of  the  sensori  motor  apparatus  of  the  opposite  side. 
Division  of  the  crus  cerebri  involves  also   paralysis  of  the  oculo- 

'  Physiologic,  Tome  iii.,  p.  306.  ^  gyateme  Xerveux,  p.  542.     Paris,  1866. 


(348  THE  NERVOUS  SYSTEM. 

motorius  of  the  same  side,  and  partial  paralysis  of  the  facial  nerve 
of  the  opposite  side,  and  is  also  followed  by  contraction  of  the 
arteries,  a  rise  in  blood  pressure,  and  the  loss  of  power  to  influence 
voluntarily  the  action  of  the  sphincter  ani,  and  the  constrictor 
urethrse.  In  addition  to  the  motor  and  sensory  fibers  just  referred 
to,  the  crura  cerebri  contain  also  fibers  passing  from  the  gray  mat- 
ter of  the  medulla  and  ])ons  to  the  hemispheres,  and  of  fibers  pass- 
ing forward  and  backward  from  the  locus  niger,  or  the  gray  matter 
separating  the  crusta  from  the  tegmentum,  to  the  cerebellum,  and 
of  fibers  passing  from  the  corpora  quadrigemina  to  the  cerebellum. 
The  functions  of  these  fibers,  so  far  as  known,  appear  to  be  com- 
missural in  character. 

Corpora  Striata  and  Thalami  Optici. 

If  the  hemispheres  of  the  brain  be  removed  to  the  level  of  the 
corpus  callosum,  or  the  bridge  of  white  substance  uniting  the  cere- 
bral hemispheres,  and  the  fi)rmer  be  divided  and  turned  aside, 
the  lateral  ventricles  will  be  exposed — that  is,  the  two  cavities 
having  for  their  roof  the  corpus  callosum,  their  floor  the  fornix, 
their  inner  walls  the  septum  lucidum  with  its  enclosed  fifth  ven- 
tricle, their  outer  walls  the  corpora  striata. 

Each  corpus  striatum,  so  called  from  presenting  a  striated  ap- 
pearance on  section,  projects  as  a  half  pyriform  prominence  into  the 
lateral  ventricle,  constituting,  as  just  said,  its  outer  wall,  the  largest 
anterior  ])ortion  being  known  as  the  head  ;  the  narrowest  posterior 
portion  the  tail,  the  latter  curving  backward  to  the  outer  side  of 
the  thalamus  0])ticus. 

Each  corpus  striatum  (Fig.  371)  consists  of  two  parts,  the  in- 
traventricular, or  nucleus  caudatus  (G),  and  the  extraventricular, 
or  nucleus  lenticulares  (7).  The  latter  consists  of  three  parts 
separated  by  white  matter,  the  striae  medullares  ;  the  two  inner 
central  parts  being  called  the  globus  pallidus,  on  account  of  their 
pale  color,  the  outer  external  part  the  putamen.  The  caudate  and 
lenticular  nuclei  are  separated  by  the  internal  capsule  (9)  or 
the  diverging  fibers  of  the  cms  cerebri,  to  which  the  corpus 
striatum  owes  its  name,  the  external  capsule  (10)  with  the  clas- 
trum  (11)  lying  to  the  outer  side  of  the  nucleus  lenticularis  and 
close  to  the  insula  or  island  of  Reil  (5).  If  now  the  fornix  or 
floor  of  the  lateral  ventricle  be  removed,  a  narrow  triangular  cavity 
will  be  exposed,  the  third  ventricle,  communicating,  on  the  one 
hand,  with  the  lateral  ventricles  by  the  foramina  of  jNIonro,  and  on 
the  other  with  the  fourth  ventricle  by  the  iter,  the  latter  passing 
under  the  corpora  quadrigemina,  to  be  mentioned  presently.  The 
floor  of  the  third  ventricle  is  formed  from  l)eforc  backward  by  the 
optic  conmiissure,  iufundibulum,  mammillary  eminences,  posterior 
l)erforated  space,  and  cerebral  crura  ;  its  walls  by  the  thalami  optici, 
situated  on  the  inner  side  of  the  crura  cerebri,  and  separated  from 
the  corpora  striata  by  the  internal  capsule  and  taniia  semicircularis. 


CORPORA  SlllIATA  ASD  THALAMI  OFTICI. 


049 


Each  tlialamus  opticus  consists  internally  of  white  matter,  ex- 
ternally of  both  white  and  gray  matter.  The  most  prominent 
parts  of  the  thalamus  opticus  anteriorly,  are  known  as  its  tuber- 
cles, posteriorly  as  the  pulvinar.  Beneath  the  latter  are  situated 
the  corpora  geniculata  from  which  arise  partially  the  optic  tracts. 


Fig.  371. 


Horizontal  section  of  the  hemispheres  at  the  level  of  the  cerebral  ganglia.  1.  Great  longitudinal 
fissure,  between  frontallobes.  2.  Great  longitudinal  fissure,  between  occipital  lobes.  3.  ABterior 
part  of  corpus  callosum.  4.  Fissure  of  Sylvius.  .5.  Convolutions  of  the  insula.  6.  Caudate  nucleus 
of  corpus  striatum.  7.  Lenticular  nucleus  of  corpus  striatum.  S.  Optic  thalamus.  9.  Internal 
ca])sule.    10.  External  capsule.     11.  Claustrum.     (Daltox.) 


One  of  the  best  established  facts  in  human  or  animal  cerebral 
pathology  is  that  a  destructive  lesion  of  the  corpus  striatum, 
whether  produced  by  disease  or  experimentally,  is  followed  by  a 
paralysis  of  motion  of  the  opposite  side  of  the  body,  sensation  re- 
mained unimpaired.  It  is  true  that  in  some  exceptional  cases  the 
paralysis  is  on  the  same  side  of  the  body,  but  there  is  no  question 
in  such  cases  as  to  the  paralysis  due  to  the  lesion  of  the  corpus 
striatum  being  that  of  motion. 

It  has  also  been  shown  that  electrical  stimulation  of  the  corpus 


650  THE  NERVOUS  SYSTEM. 

striatum  in  a  living  animal,  monkeys,  clogs,  cats,  etc.,  causes  a  gen- 
eral unilateral  contraction  of  the  muscles  of  the  opposite  side  of 
the  body,  the  latter  being  thrown  into  a  condition  of  pleurostho- 
toniis,  in  Avhich  it  is  bent  to  the  opposite  side,  the  flexor  muscles 
being  contracted  apparently  more  than  the  extensor  ones.  It  is 
well  known  also,  that  in  the  cetacea — the  whale,  dolphin — the  ele- 
phant, etc.,  very  muscular  animals,  the  corpora  striata  are  not  only 
absolutely  but  relatively  large  and  well  developed.  The  facts  of 
pathology,  experiment,  and  comparative  anatomy,  confirm,  there- 
fore, the  view  based  upon  their  anatomy  that  the  function  of  the 
corpora  striata  is  essentially  motor. 

It  has  been  etjually  well  established,  however,  that  in  man,  unless 
the  disorganization  of  the  corpus  striatum  giving  rise  to  hemi- 
plegia is  situated  in  the  internal  capsule  the  loss  of  voluntary  mo- 
tion is  not  persistent.  It  is  obvious,  therefore,  that  the  axis-cylin- 
ders originating  in  the  motor  areas  of  the  cortex,  traverse,  as 
already  mentioned,  the  internal  capsule  and  that  disease  of  the 
corpus  striatum  causes  permanent  paralysis  of  motion  only  so  far 
as  it  involves  the  internal  capsule.  AVhatever,  therefore,  may  be 
the  functions  of  the  corpora  striata  in  the  lower  animals,  these 
s-anglia  can  onlv  be  said  to  have  a  motor  function  in  the  sense  that 
they  are  traversed  by  the  motor  tracts  from  the  cortex. 

While  lesions  of  the  thalami  optici  are  not  of  infrequent  oc- 
currence in  man,  from  the  fact  that  the  corpora  striata  and  adja- 
cent parts  of  the  hemispheres  are  usually  involved,  conclusions  as  to 
the  functions  of  these  ganglia,  based  upon  the  loss  of  sensibility, 
etc.,  following  their  destruction,  cannot  be  accepted  with  the  same 
confidence  as  in  the  case  of  the  corpora  striata.  Nevertheless,  if  the 
lesion  be  limited,  as  is  sometimes  the  case,  to  the  corpus  striatum 
and  the  thalamus  opticus,  and  the  destruction  of  these  two  ganglia 
is  followed  by  loss  of  motion  and  of  sensibility  on  the  opposite  side 
of  the  body,  and  if  it  be  admitted  that  the  function  of  the  corpus 
striatum  is  motor,  the  conclusion  that  the  thalamus  opticus  is  sen- 
sory in  function  becomes  then  unavoidable.  Indeed,  it  could  not 
be  otherwise,  since  after  destruction  of  the  thalamus  opticus  no 
other  avenue  is  left  by  which  sensory  impressions  can  be  transmit- 
ted from  the  general  periphery  of  the  body  to  the  cerebral  hemi- 
spheres, except  by  the  posterior  third  of  the  posterior  segment  of  the 
internal  capsule  or  the  "  sensory  crossway."  That  the  thalamus 
opticus  has  some  sensory  function  appears  to  be  shown  by  the  fact 
of  its  destruction  in  man  being  follow^ed  by  loss  of  general  and 
special  sensibility  on  the  opposite  side  of  the  body,  tactile  sensation 
being  impaired,  and  hearing  and  vision  in  some  cases  affected.^ 

It  miglit  ])e  urged,  however,  that  in  the  case  of  man  whatever 
sensory  functions  the  thalami  optici  may  be  endowed  with  are  only 
due  to  some  of  the  axis-cylinders  of  the  sensory  tract  simply  travers- 

^  Luys,  Reclierc'lies  sur  le  Systerae  Xerveux,  1865,  p.  o38.  Cricliton  Browne^ 
West  Riding  Asylum  Reports,  Vol.  v.,  p.  227,  1876.     Ferrier,  op.  cit.,  p.  239. 


CORPORA  STRIATA  ASD  THALAMI  OPTICI.  651 

ing  it  to  terminate  in  the  sensory  area  of  tlie  cortex.  That  the 
paralysis  of  motion  and  sensation  folloMing  lesions  of  the  corpora 
striata  and  thalami  optici  is  not  due  simply  to  the  motor  and 
sensory  impulses  being  normally  transmitted  through  these  ganglia 
from  or  to  the  convolutions  of  the  hemispheres,  and  that  after  the 
destruction  of  these  ganglia  no  avenues  are  left,  therefore,  for  the 
transmission  of  such  impulses,  is  shown  by  the  fact  that  after  re- 
moval of  the  cerebral  convolutions  in  a  mammal  the  power  of 
voluntary  movement  and  sensation  remains.  Thus,  for  example, 
in  a  rabbit  the  cerebral  hemispheres  having  been  removed,  while 
there  is  nothing  observed  to  indicate  that  its  sensations  ever  give 
rise  to  ideas — that  is,  that  it  perceives — nevertheless,  it  feels  even 
it  does  not  think  ;  it  sees,  hears  ;  if  pinched,  it  cries  ;  when  stirred 
up,  it  runs  or  leaps  forward,  avoiding  with  more  or  less  success  ob- 
stacles placed  in  its  path.  The  animal  has  undoubtedly  possession 
of  its  senses,  can  execute  all  its  bodily  movements,  but  its  intelli- 
gence appears  to  be  gone,  at  least  objects  which  would  have  ordi- 
narily pleased  or  terrified  it  make  no  impression  whatever  upon  it. 
It  must  be  borne  in  mind,  however,  that  in  any  application  to  be 
made  of  such  results  with  the  view  of  elucidating  the  functions  of  the 
basal  sranoflia  in  man,  that  it  does  not  necessarilv  follow  that  a  hu- 
man  being,  or  even  a  dog  deprived  of  its  cerebral  hemispheres, 
should  be  in  exactly  the  same  mental  condition  as  a  rabbit  under 
similar  circumstances.  On  the  contrary,  there  is  a  good  reason  for 
supposing  that,  as  we  pass  from  the  lower  to  the  higher  mammals, 
the  seat  of  voluntary  motion  and  sensation  is  removed  to  higher 
and  higher  levels  in  the  encephalon  ;  the  cerebral  convolutions  beings 
more  important  in  this  respect  in  man  than  in  a  dog,  and  the  basal 
ganglia  more  important  in  the  dog  than  in  the  rabV)it,  and  so  on. 
The  most  marked  contrast  in  this  respect  is  presented  by  fishes,^  in 
which  the  corpora  striata  are  relatively  well  developed,  the  cerebral 
hemispheres  but  little  so — in  fact,  the  latter  are  only  represented, 
more  particularly  in  the  cartilaginous  fishes,  by  the  thin  film  of 
nervous  matter  covering  in  the  cavity  or  ventricle,  of  which  the 
corpora  striata  constitute  the  floor ;  the  so-called  optic  lobes  in 
fishes  representing,  probably  not  only  the  optic  lobes  of  the  higher 
vertebrates,  but  the  thalami  optici  as  well.  Undoubtedly  a  rabbit 
can  do  more  without  its  basal  ganglia  and  cerebral  convolutions  than 
a  dog,  and  a  dog  with  its  basal  ganglia  but  without  its  hemispheres 
than  a  man  without  the  latter.  It  becomes,  therefore,  a  very  difficult 
matter  to  say  just  where  sensation  begins  in  man,  and  still  more, 
where  sensation  is  accompanied  or  gives  rise  t(i  ideation  and  volition. 

It  has  been  suggested  that  if  an  impression  made  upon  the  pe- 
riphery must  be  transmitted  to  the  cerebral  convolutions  to  be  thor- 
oughly appreciated,  and  that  a  voluntary  impulse  developed  in  re- 
sponse to  such  a  sensation  must  emanate  in  the  same,  the  connections 
of  the  basal  ganglia  through  the-  corona  radiata,  with  the  convolu- 

^  L.  Edinger,  Yorlesungen  iiber  Den  Ban  Der  Xervosen  Centralorgane,  1S9G,  s.  72. 


<)52  THE  NERVOUS  SYSTEM. 

tions  of  the  hemispheres,  and  with  each  other,  offer  an  avennc  for 
the  performance  of  reflex  actions  already  referred  to,  Avliich  origi- 
nally being  accompanied  with  both  sensation  and  volition,  in  time 
come  to  be  performed  withont  either.  For  with  the  constant  rej)- 
etition  of  a  particular  action  involving  sensation  and  volition,  it 
is  natural  to  suppose  that  the  circuit  traversed  might  become 
shorter  and  shorter,  and  that  impressions  which  originally  reached 
the  cerebral  hemisphere  before  being  reflected  back,  simply  passing 
through  the  basal  ganglia  to  and  fro,  gradually  take  a  shorter 
course,  and  reaching  the  thalanuis  opticus  are  at  once  reflected  back 
through  the  corpus  striatum,  short-circuted,  so  to  speak. 

Optic  Lobes. 

It  has  already  been  mentioned  that  the  iter  or  way  by  which 
the  third  and  fourth  ventricles  communicate  with  each  other,  passes 
underneath  the  corpora  quadrigemina.  The  latter  consist  of  a 
white  ({uadrate  mass  more  or  less  divided  upon  its  upper  surface 
by  a  crucial  depression  into  four  eminences,  the  so-called  nates  and 
testes,  optic  lobes,  or  quadrigeminal  bodies,  whence  their  name. 
The  corpora  quadrigemina,  or  the  optic  lobes,  as  we  shall  hereafter 
for  brevity  designate  them,  are  attached  laterally  to  the  thalami 
optici  between  which  they  are  situated,  and  also  to  the  geniculate 
bodies,  and  therefore  indirectly  with  the  optic  tracts.  Inferiorly 
they  are  connected  with  the  cerebellum  by  the  superior  peduncles 
between  which  is  attached  the  valve  of  A^ieussens  and  with  the 
motor  columns  of  the  cord  by  the  fibers  descending  through  the 
pons  and  embracing  the  olivary  body.  The  optic  lobes  are  not, 
however,  in  man,  as  their  name  would  imply,  the  seat  of  the  centers 
of  vision,  since  the  visual  path,  as  we  shall  see  presently,  is  con- 
tinued as  that  part  of  the  optic  tract  that  passes  beyond  the  optic 
lobes  through  the  posterior  limb  of  tlie  internal  capsule  as  the  optic 
expansion  or  radiation  to  the  cuneus  in  the  occipital  lobe.  On  the 
other  hand,  as  in  many  mammals,  the  occipital  lobe  is  undeveloped, 
the  cerebellum  being  entirely  uncovered,  it  is  obvious  that  the  cen- 
ter of  vision  must  be  situated  in  such  mammals  at  least  in  some 
other  part  of  the  brain  than  the  cuneus,  the  latter  being  absent. 
As  a  further  proof  that  the  center  of  vision  is  not  situated  in  all 
animals  in  the  same  part  of  the  brain,  it  may  be  mentioned,  as  we 
shall  see  presently,  that  the  sense  of  sight  persists  in  the  lower 
vertebrata  even  after  tlie  entire  removal  of  the  cerebral  hemi- 
sphere. The  optic  lobe,  as  might  be  expected,  constitutes  also  an 
important  part  of  the  reflex  mechanism  by  which  the  coordination 
of  the  eyeballs  and  the  contraction  of  the  pupil  are  effected,  the 
()))tic  nerve  being  the  afferent  nerve  and  the  oculo-motorius  the 
efferent  nerve,  tlie  reflex  centers  being  situated  either  in  the  optic 
lobe  or  immediately  beneath  it.  Apart  from  the  anatomical  fact 
that  the  optic  lobes  are  connected  with  the  motor  tracts  of  the 
spinal  cord,  which  would,  as  already  remarked,  indicate  that  these 


OPTIC  LOBES.  653 

ganglia  influence  muscular  action  in  some  way,  it  is  well  known 
that  the  optic  lobes  arc  not  invariably  developed  in  proportion  to 
the  eyes,  but,  on  the  contrary,  may  be  quite  large,  though  the  eyes 
and  optic  tracts  be  but  small,  little  developed,  or  even  wanting 
altogether,  as,  for  example,  in  the  myxine  or  hag  fish,  and  the 
Apterichthys  ctccus  among  fishes,  in  the  proteus  and  cecilia  among 
batrachians,  and  in  moles  and  shrews  among  mammals,  Avhich 
show  that  the  optic  lobes  have  other  functions  beside  those  influ- 
encing vision.  Now,  while  it  has  been  established  that  destruction 
of  the  optic  lobes  in  animals  involves  disorders  of  equilibrium  and 
want  of  muscular  coordination,  nevertheless,  it  must  l)e  mentioned 
that  a  very  great  difi:erence  prevails  in  this  respect  according  to 
whether  the  animal  upon  which  the  experiment  is  performed  be  a 
batrachian,  bird,  or  mammal,  the  optic  lobes  relatively  to  the  cere- 
bral hemispheres  being  so  much  better  developed  in  the  lower  than 
in  the  higher  vertebrates.  Thus,  for  example,  a  frog  with  its  optic 
lobes  intact,  but  without  its  cerebral  hemispheres,  can  coordinate 
its  muscles  for  the  performance  of  ordinary  actions  better  than  a 
pigeon  or  a  rabbit  similarly  conditioned,  and  the  latter  better  than 
a  monkey  or  man.  It  may  be  mentioned,  also,  in  this  connection, 
that  the  want  of  coordinating  power,  etc.,  following  destruction  of 
the  optic  lobes  is  not  due,  as  might  be  supposed,  to  the  blindness 
entailed,  since  in  the  frog,  for  example,  if  the  e}^s  be  destroyed, 
but  the  optic  lobes  be  left  intact,  such  disorders  as  those  ensuing 
upon  the  destruction  of  these  ganglia  are  not  observed.  It  is  well 
known  that  if  all  the  encephalic  centers  above  the  optic  lobes  be 
removed  in  the  frog,  gentle  stroking  of  the  l)ack  excites  the  animal 
to  croak.  The  croaking  entirely  ceasing,  however,  if  the  optic 
lobes  be  removed,  the  natural  inference  is  that  these  ganglia  con- 
tain the  reflex  centers  through  which  the  croaking  is  produced. 
As  certain  plaintive  cries  emitted  by  the  rabbits  cease  after  removal 
of  the  optic  lobes,  it  is  possible  that  a  similar  reflex  center  exists 
in  the  optic  lolies  of  mammals  as  well  as  in  those  of  frogs. 

Taking  this  latter  fact  into  consideration,  together  with  that  of 
the  circulation  and  respiration  being  modified  by  electrical  stimula- 
tion of  the  optic  lobes,  the  blood  pressure  being  increased,  the 
heart  slowed,  the  respiration  deepened  exactly  in  the  same  manner 
as  when  the  sensory  nerves  are  powerfully  excited,  and  that  con- 
tractions of  the  stomach,  intestines,  and  bladder  also  follow,  it 
would  appear  that  the  optic  lobes  influence  nutrition  as  well  as 
muscular  coordination  and  vision. 

The  Cerebellum. 

The  cerebellum,  constituting  about  one-eighth  of  the  bulk  of  the 
brain,  and  situated  in  the  posterior  fossae  of  the  cranial  cavity, 
consists  of  two  lateral  portions,  the  hemispheres,  the  anterior 
rounded  eminences  of  which  are  known  as  the  amygdalaj,  or  the 
tonsils.     The  hemispheres,  though  separated  behind  and  below  by 


'654  THE  NERVOUS  SYSTEM. 

a  wide  deep  groove,  the  vallecula  or  valley,  are  connected  by  an  in- 
termediate worm-like  ridge,  the  vermiform  process,  the  portion  of 
the  latter  situated  between  the  tonsils  being  called  the  uvula, 
while  just  above  the  tonsils,  and  separated  from  them  by  a  fissure, 
may  be  seen  the  flocculi,  or  pneumogastric  lobules,  so  called  from 
their  vicinity  to  the  nerve  of  the  same  name.  Each  lateral  hemi- 
sphere and  vermiform  process  essentially  consists  internally  of  a 
prismoid  trunk  of  white  substance,  from  which  emanate  about  a 
dozen  broad,  thin  laminae ;  the  latter  subdividing  again  into  secondary 
thinner  laminae,  and  the  gray  substance  enfolding  them,  gives  rise  to 
the  convolutions  and  fissures  observal^le  on  the  surface  of  the  organ. 

It  has  already  been  mentioned  incidentally  that  the  optic  lobes 
-are  connected  posteriorly  with  the  cerebellum  through  the  superior 
peduncles  of  the  latter.  The  fibers  of  the  superior  peduncles  pass- 
ing forward  and  upward  to  the  testes  ascend  through  the  crura 
<;erebri  to  the  thalamus  ojTticus  and  corona  radiata,  and  thence  to 
the  frontal  temporal  and  occipital  lobes,  some  of  the  fibers  decus- 
sating beneath  the  optic  lobes.  Inferiorly  the  superior  peduncles 
are  connected  with  the  vermiform  process  of  the  cerebellum  and 
with  the  corpus  dentatum,  or  punch-like  layer  of  gray  matter  within 
the  white  matter  of  the  lateral  hemispheres.  The  middle  pedun- 
cles of  the  cerebellum  constituting,  as  already  mentioned,  the  trans- 
verse commissural  fibers  of  the  pons  Varolii  connect  the  two  lateral 
hemispheres,  while  the  inferior  peduncles  pass  downward  into  the  res- 
tiform  bodies  of  the  medulla,  and  are  collected  with  the  spinal  cord. 

According  to  most  histologists  each  lateral  lobe  of  the  cerebellum 
is  connected  with  the  olivary  body  of  the  opposite  side,  the  tract 
constituting  the  so-called  "  cerebro-olivary  "  system. 

If  the  cerebellum  be  removed  in  a  bird,  a  pigeon,  for  example 
(Fig.  372),  though  the  animal  still  feels,  thinks,  wills,  it  is  unable 

Fig.  372. 


Pigeon,  after  removal  of  the  cerebellum.     (Dalton.) 


THE  CEBEBELLIM.  655 

to  stand  or  flv.  If  placed  upon  the  back,  it  is  unable  to  rise.  If 
food  be  placed  within  its  reach,  though  it  sees  it,  it  cannot  pick  up 
the  food.  Instead  of  remaining  (juiet,  it  is  in  a  continual  state  of 
restlessness  and  agitation.  In  a  \\ord,  though  able  to  make  volun- 
tary movement,  the  animal  has  lost  the  power  of  coordinating  its 
movements  for  the  performance  of  a  definite  object,  or  of  maintain- 
ing its  equilibrium.  Its  movements  highly  resemble  those  of  a 
drunken  man.  Essentially  the  same  results  are  obtained  if  the 
cerebellum  be  removed  in  a  mammal.  Undoubtedly  then,  very 
remarkable  disorders,  both  as  regards  the  maintenance  of  equi- 
librium and  power  of  locomotion  ensue  upon  destruction  of  the 
cerebellum  in  mammals  and  birds,  although,  as  already  mentioned, 
no  perceptible  change  is  observable  in  these  respects  in  the  case  of 
frogs,  in  which  the  cerebellum  has  been  removed. 

Differences  of  opinion  still  prevail  among  pathologists  as  to 
whether  lesions  of  the  cerebellum  in  man  give  rise  to  the  same  dis- 
orders as  observed  in  mammals  and  birds,  in  which  the  cerebellum 
has  been  removed,  and  even  though  it  has  been  held  by  some  phy- 
siologists that  entire  absence  of  the  cerebellum,  as  shown  by  post- 
mortem examinations,  was  not  accompanied  during  life  ^vith  loss  of 
the  power  of  locomotion,  or  of  the  maintenance  of  equilibrium, 
nevertheless,  it  may  be  questioned  whether  there  is  a  well-authenti- 
cated case  in  which  locomotion  and  ec|uilibrium  remained  unaf- 
fected, extensive  lesions  of  the  cerebellum  existing.  Such  cases  as 
where  there  was  a  congenital  absence  of  the  cerebellum,  unaccom- 
panied Mith  any  disorders  of  locomotion,  etc.,  being  explainable  on 
the  supposition  that,  as  in  the  case  of  the  frog,  the  function  of  the 
cerebellum  was  performed  by  other  ganglia,  probably  the  optic  lobes. 
On  the  supposition  that  the  cerebellum  is  the  center  for  the  main- 
tenance of  equilibrium  and  of  muscular  coordination,  it  ought  to  be 
best  developed  in  those  animals  which  exhibit  such  powers  in  a 
marked  degree,  and  such  we  find  to  be  the  case.  Thus  in  the 
shark,  for  example,  in  which,  of  all  fish,  the  muscular  system  is 
best  developed,  and  the  power  of  coordination  so  perfect,  as  shown, 
for  example,  in  the  manner  in  which  it  seizes  its  prey,  the  cere- 
bellmn  is  larger  and  more  complex  in  its  structure  than  in  any  other 
fish.  Among  birds,  also,  the  cerebellum  is  particularly  well  devel- 
oped in  the  carnivorous  raptores,  in  which  muscular  actions,  such 
as  are  involved  in  the  swooping  down  by  them  upon  prey  from 
immense  heights,  require  very  nice  adjustment  of  coordination. 
Among  mammals  the  cerebellum  is  large ;  in  the  kangaroo,  whose 
peculiar  mode  of  progression  necessitates  considerable  muscular  co- 
ordination, while,  in  the  elephant,  in  which  great  nuiscular  coordi- 
nation is  demanded,  owing  to  the  enormous  muscular  development, 
and  in  the  case  of  the  posterior  extremities  to  the  absence  of  the 
round  ligament  of  the  hip-joint,  the  cerebellum  is  very  large,  being 
equal  to  one  of  the  hemispheres. .  In  the  anthropoid  apes,  also, 
which  not  nnfrequently  assume  the  semi-erect  attitude,  the  cerebel- 


656  THE  NERVOUS  SYSTEM. 

lum  is  larger  than  iu  the  remaiuing  monkeys.  Indeed,  in  the  young 
chimpanzees  and  orangs  dissected  by  the  anther^  the  cerebellum  was 
found  so  Avell  developed  as  to  extend  slightly  beyond  the  posterior 
lobes  of  the  cerebrum,  Avhich  is  not  the  case  in  monkeys  generally, 
in  adult  chimpanzees  or  orangs  and  in  baboons,  macacques,  spider- 
monkeys,  etc.,  the  cerebellunj  being  perfectly  covered  by  the  pos- 
terior lobes  of  the  cerebrum  as  in  man.  That  the  cerebellimi,  at  least 
in  mammals,  birds,  and  fishes,  is  concerned  in  some  way  in  the 
maintenance  of  equilibrium  and  muscular  coordination  is  not  only 
shown  by  experiment,  pathology,  and  comparative  anatomy,  but 
from  the  fact  of  the  tactile,  visual,  labyrinthine,  and  perhaps 
visceral  impressions  upon  which  the  maintenance  of  equilibrium 
and  muscular  coordination  depend,  being  transmitted  from  the 
periphery  through  nerves  which  directly  or  indirectly  terminate 
in  the  cerebellum,  as  we  shall  now  endeavor  to  show.  It  has 
already  been  mentioned  that  a  frog  from  which  the  cerebral  hemi- 
spheres have  been  removed,  but  which  still  preserves  its  optic 
lo])cs  and  cerebellum,  retains  the  power  of  maintaining  its  equili- 
brium and  of  muscular  coordination.  If,  however,  the  skin  be 
removed  from  the  hinder  legs  of  such  a  frog,  the  animal  at  once 
loses  this  power  and  falls  like  a  log  if  the  position  of  its  support 
be  changed,  the  removal  of  the  skin  making  impossible  the  trans- 
mission of  those  afferent  tactile  impressions  which  through  some 
reflex  center  give  rise  to  those  efferent  muscular  actions  requisite  for 
the  maintenance  of  equilibrium.  That  this  reflex  center  is  situated 
in  man  in  the  cerebellum,  and  that  these  afferent  tactile  impressions 
are  transmitted  by  the  posterior  columns  of  the  spinal  cord,  is  ren- 
dered very  probable  from  the  fact  that  sclerosis  of  these  columns 
causes  locomotor  ataxia,  a  disease  especially  characterized  not  by  a 
loss  of  sensibility  but  of  power  of  coordination,  and  that  the  pos- 
terior columns  of  the  cord  through  the  restiform  bodies  of  the  me- 
dulla terminate  in  the  cerebellum.  While  visual  are  not  as  impor- 
tant as  either  tactile  or  labyrinthine  impressions  in  the  maintenance 
of  equilibrium,  since  the  latter  almost  suffice  in  the  absence  of  the 
former,  nevertheless  they  exercise  a  certain  amount  of  influence. 
Thus,  in  cases  of  locomotor  ataxia,  for  example,  equilibrium  and 
coordination  are  not  altogether  impossible,  even  though  the  tactile 
impressions  be  wanting,  so  long  as  the  labyrinthine  and  visual  im- 
pressions persist,  and  in  such  cases  when  the  transmission  of  tactile 
and  labyrintliiuc  impressions  are  perfect,  the  absence  of  visual  ones 
always  entails  some  slight  want  in  the  coordinating  power.  That 
such  visual  impressions  are  transmitted  to  the  cerebellum,  is  ren- 
dered very  probable  when  it  is  remembered  that  the  optic  lobes  are 
connected  with  the  cerebellum  both  through  the  superior  peduncles 
and  valye  of  Yieussens.  As  is  well  known,  remarkal^le  disturb- 
ances of  equilibrium  ensue  if  the  membranous  semicircular  canals 
of  the  internal  car  be  divided  in  a  bird  or  mammal,  or  if  they  are 
'H.  C.  Cliapman,  Proc.  Acad,  of  Xat.  Sciences,  1879,  p.  68  ;  1880,  p.  172. 


THE  CEREBELLUM.  657 

diseased  as  lu  ^Meniere's  disease  iu  man,  wliieh  vary  accordiug  to 
the  seat  of  the  lesion.  Thus,  if  the  horizontal  canals  be  divided 
in  a  pigeon,  for  example,  rapid  movements  of  the  head  in  a  hori- 
zontal plane,  from  side  to  side,  follow,  with  oscillation  of  the  eye- 
balls, and  a  tendency  to  spin  around  on  a  vertical  axis  is  manifested. 
If,  however,  the  posterior  or  inferior  vertical  canals  be  divided, 
the  head  is  moved  rapidly  backward  and  forward,  and  the  animal 
tends  to  turn  somersaults  backward  head  over  lieels,  whereas  if 
the  superior  vertical  canals  be  divided,  the  head  is  moved  rapidly 
forward  and  backward,  and  the  animal  tends  to  make  forward 
somersaults  heels  over  head.  It  would  appear  from  the  researches 
of  Goltz,^  Mach,'  Brewer,-^  and  Crum  Brown^  among  others,  that 
the  character  of  the  impressions  made  upon  the  vestibular  nerves 
depends  upon  the  degree  and  relative  variations  in  the  pressure 
exerted  by  the  endolymph  upon  the  ampulhe  of  the  membranous 
canals,  to  which,  as  we  shall  see  hereafter,  these  nerves  are  dis- 
tributed. Such  being  the  case,  it  is  obvious  that  if  the  semi- 
circular canals  be  divided  disturbances  of  equilibrium  must  ensue, 
the  natural  tension  of  the  endolymph  l)eing  thereby  altered,  which 
will  vary  according  to  the  particular  semicircular  canal  aifected. 
It  may  be  mentioned  in  this  connection,  that  pigeons  in  which  the 
semicircular  canals  have  been  divided  on  one  side  in  time  regain 
the  power  of  maintaining  their  equilibrium,  but  if  the  canals  bo 
divided  on  both  sides,  they  never  again  are  able  to  assume  their 
natural  position,  the  most  strange  and  bizarre  attitudes  being  taken. 
Whatever  may  be  the  natiu-e  and  mechanism  of  the  labyrinthine 
impressions,  there  can  be  no  doubt  as  to  the  influence  exerted  by 
them  in  the  maintenance  of  equilibrium,  since  in  their  absence  the 
same  becomes  impossible  even  though  the  tactile  and  visual  im- 
pressions persist.  That  the  membranous  semicircular  canals  and 
the  auditory  nerve  together  constitute  an  afferent  system  by  which 
impressions  are  transmitted  to  the  cerebellum,  acting  as  a  reflex 
coordinating  center,  appears  highly  probable  when  it  is  remembered 
that  division  of  the  auditory  nerve  entails  disturbances  of  equi- 
librium, that  the  auditory  nerve  through  the  restiform  bodies  is 
directly  connected  with  the  cerebellum,  and  that  a  great  similarity 
exists  between  the  effects  of  destruction  of  the  cerebellum  and  division 
of  the  semicircular  canals.  Thus,  destruction  of  the  anterior  por- 
tion of  the  middle  lobe  of  the  cerebellum,  like  that  of  the  superior 
vertical  canal,  involves  displacement  of  equilibrium  fonvard  around 
a  horizontal  axis,  destruction  of  the  posterior  part  of  the  median 
lobe  like  that  of  the  posterior  vertical  canal,  displacement  backward 
around  a  horizontal  axis,  destruction  of  the  lateral  lobes  of  the 
cerebellum,  like  that  of  the  horizontal  canals,  lateral  displacement 
around  a  vertical  axis.  The  cerebellum  appears,  therefore,  to  be 
the  reflex  center  by  which  the  afferent  impressions  transmitted  by 

iPfluger's  Archiv,  1870.  ^^itz.  u.  der  K.  Acad,  der  Wiss.,  Wien,  1873. 

3 Med.  .Jahrbucher,  Hefti.,  1874.    *, Journal  of  Anat.  and  Phys.,  May,  1874. 

42 


6 5  S  THE  NER  VO  US  SYSTEM. 

the  cutaneous,  optic,  and  acoustic  nerves  are  coordinated  with  the 
efferent  ones  for  the  maintenance  of  equilibrium  and  locomotion. 
That  such  reflex  actions  are  accompanied  now,  or  originally  at 
least,  with  consciousness,  and  that  the  cerebellum  is  that  part  of 
the  encephalon  in  which  the  ideas  of  space  are  developed,  is  ren- 
dered very  probable  when  it  is  remembered  that  many  actions  in- 
volving muscular  coordination,  which  are  performed  now  uncon- 
sciously, w^ere  originally  accompanied  by  both  sensation  and  volition, 
and  that  the  disorders  of  equilibrium  and  locomotion  following 
destruction  of  the  cerebellum  or  of  the  afferent  system  leading  to  it, 
imply  a  perversion  in  the  ideas  of  space  relations. 

From  the  fact  that  the  loss  of  coordinating  power,  etc.,  following 
division  of  the  cerebellum  in  the  middle  line  is  only  transitory  it  is 
usually  held  that  each  half  of  the  cerebellum  is  associated  with  the 
medulla  and  cord  of  the  corresponding  side  of  the  body.  The  rela- 
tion of  the  cerebellum  to  the  cerebrum  however  is  a  crossed  one, 
each  cerebellar  hemisphere  being  connected  with  the  cerebral  hemi- 
sphere of  the  opposite  side  of  the  body.  It  appears  also  that  the 
tracts  connecting  the  cerebellum  with  the  medulla,  etc.,  on  the  one 
hand,  and  with  the  cerebrum  on  the  other,  constitute  double  path- 
ways, the  cerebellum  sending  as  Avell  as  receiving  impulses  to  and 
from  the  different  regions  with  which  it  is  associated. 


CHAPTER    XXXIV. 

THE  NERVOUS  QYSTE^L— {Continued.) 


Fig.  37: 


THE  CEREBRAL  HEMISPHERES. 

The  cerebral  hemispheres,  so  called  on  account  of  their  hemi- 
spherical form,  are  two  ovoidal  masses  flattened  at  their  mesial  sur- 
face, where  they  are  separated  by  the  great  longitudinal  fissure. 
They  consist  of  gray  or  vascular  and  of  white  or  filn'ous  nervous 
tissue.  The  gray  substance,  like  that  of  the  cerebellum,  situated 
externally  and  varying  between  two  and  three  millimeters  in  thick- 
ness, sinks  at  intervals  into  the  white  substance  to  a  depth  of  from 
ten  to  twenty-five  millimeters,  invaginating  itself — that  is,  folds  in- 
ward to  return  upon  itself  again,  and  so  gives  rise  to  the  convo- 
luted and  fissured  surface  so  characteristic 
of  the  brain  of  man  and  of  many  mammals. 
It  is  evident  that  through  this  convoluted 
arrangement  the  hemispheres  contain  far 
more  gray  matter  than  if  they  were  smooth, 
■on  the  same  principle  that  a  pocket  hand- 
kerchief occupies  much  less  room  when 
folded  up  than  when  laid  out  smooth,  and 
that  the  deeper  and  more  numerous  the  fis- 
sures the  greater  the  amount  of  gray  matter 
present.  The  gray  matter  of  the  convo- 
lution or  cortical  layer  of  the  hemispheres, 
consists  of  a  granular  matrix  in  which  are 
imbedded  nerve-cells  with  their  axons,  dis- 
posed in  four  or  more  layers  (Fig.  373),  the 
latter  being  distinguished  by  the  character 
of  their  nerve  cells. 

Among  the  most  striking  of  these  cells 
may  be  mentioned  the  so-called  pyramidal 
cells,  varying  in  diameter  from  the  ^^^  to 
:^^  of  a  millimeter  (2-5V0  ^^  eh'S  ^^  ^'^  inch), 
and  characterized  by  their  quadrangular 
base  and  tail-like  extremity,  the  latter  point- 
ing outwardly.  The  pyramidal  cells  are 
more  numerous  and  larger  in  the  anterior 
portion  of  the  hemispheres  in  the  convo- 
lutions of  the  frontal  lobe,  for  example, 
the  cells  of  the  so-called  nuclear  layer  in 
the  occi])ital  and  temporal  lobes.  Certain 
so-called  giant  pyramidal  cells,  attaining  a  diameter  of  from  the  ^^jj- 
to  the  yL  of  a  millimeter  ( -^i^  to  -^^-^  of  an  inch),  i)robably  motor 
in  function,  like  those  of  the  anterior  cornu  of  the  spinal  cord,  are 


Section  of  a  cerebral  convo- 
lution stained  by  Golgi's 
method.  1.  Xeuroglia  layer. 
2.  Layer  of  small  cells. "  3. 
Layer  of  large  pyramidal 
cells.  4.  leaver  of  'irregulai 
cells.    (Landois.) 


660 


THE  NERVOUS  SYSTEM. 


also  found  more  particularly  in  the  posterior  portion  of  the  frontal 
lobe  in  the  anterior  central  convolution,  the  processes  of  which  ap- 
pear to  be  prolonged  downward  as  the  axons  traversing  the  antero- 
lateral columns  of  the  spinal  cord  and  which  we  have  seen  are  in  re- 
lation with  the  anterior  roots  of  the  spinal  nerves,  wdiile  other  cells^ 
having  no  processes  or  axons,  are  found  more  especially  in  the  pos- 
terior part  of  the  hemispheres  in  the  occipital  lobe.  Although  the 
convolutions  or  gyri  and  the  fissures  or  sulci  do  not  run  in  exactly 
the  same  manner  in  diHerent  brains,  and  are  not  symmetrically  dis- 
posed even  in  the  two  hemispheres  of  the  same  brain,  nevertheless 
the  general  disposition  is  so  constantly  the  same  that  the  most  im- 
portant of  them  can  be  readily  recognized  and  identified,  and  on 
account  of  their  supposed  functional  importance  demand  at  least  a 
brief  description.  The  most  striking  fissure  observable,  if  the  hemi- 
sphere be  viewed  laterally,  both  on  account  of  its  depth  and  con- 
stancy, it  existing  not  only  in  man  but  in  all  animals  whose  brain  is 
fissured  at  all,  is  the  fissure  of  Sylvius.     Beginning  as  a  transverse 

Fig.  374. 


Outer  surface  of  the  left  hemisphere.    The  regions  bouiidi^^il  bj'  the  line  ( )  represent  the 

territories  over  which  the  branches  of  the  anterior  ccixliral  urtcry  are  distributed.     The  regions 

bounded  by  the  line  ( )  represent  the  tcrritdries  over  which  the  branches  of  the 

jiosterior  cerebral  artery  are  distributed.  /■'.  I'rontallobe.  1'.  Parietal  lobe.  O.  Occipital  lobe. 
T.  Temporo-sjjhenoidal  lobe.  S.  Fissure  of  Sylvius.  ,S'',  Horizontal;  S",  Ascending  ramus  of 
tlie  same.  c.  Sulcus  centralis  or  fissure  of  ItoUuido.  A.  Anterior  central  or  ascending  frontal 
convolution.  B.  Posterior  central  or  ascending  jiarietal  convolution.  i'V  Superior  ;  /'"„,  Middle, 
and  F^  Inferior  frontal  convolution.  J\,  Suporinr,  and/^  Inferior  frontal  sulcus  ;  f^  Sulcus  prse- 
centralls.  P,.  Sujierior  parietal  of  postero-jiarietal  lobule,  viz.:  P^,  Gyrus  supramarginalis  ;  P'„, 
(iyrus  angularis.  ip.  Sulcus  intraparictalis.  cm.  Termination  of  the  calloso-margiual  fissure. 
Oj  First,  Oj  Second,  O3  third  occipital  ccuivolutions.  pa.  Parieto-occipital  fissure.  0.  Sulcus 
occipitalis  transversus ;  o.^,  Sulcus  occipitalis  longitudinalis  inferior.  7*,,  first;  7'„,  second  ;  T3, 
third  temporo-sphenoidal  convolutions.  ^,,  first  ;  t^,  second  temporo-sphenoidal  fissures.  (After 
EcKER  and  DuunT.) 


THE  CEREBRAL  HEMISPHERES.  661 

furrow  on  the  under  side  of  the  brain,  it  runs  thence  outward,  back- 
Avard,  and  upward,  separating  the  temporal  [T,  Fig.  374)  from  the 
frontal  lobe  {F),  and  divides  on  the  outer  side  of  the  hemisphere 
into  an  anterior  (.S')  and  posterior  (<S'')  branch,  the  convolutions  in- 
cluded between  these  two  branches,  and  known  as  the  operculum, 
covering  the  insula  or  island  of  Reil.  An  important  fissure, 
readily  identified  on  account  of  its  constant  course,  is  the  fissure 
(c)  of  Kolando,  or  central  fissure,  passing  from  about  the  middle 
line  of  the  hemisphere  downward,  outward,  and  forward,  reaching 
very  nearly  the  fissure  of  Sylvius,  and  serving  to  divide  the  fron- 
tal from  the  parietal  lobe.  The  fissure  of  Rolando  is  bordered  by 
two  important  convolutions  running  parallel  with  itself  and  known 
as  the  anterior  and  posterior  central  convolutions,  or  the  ascending 
frontal  and  ascending  parietal  convolutions.  Through  the  very 
•constant  presence  of  the  long  superior  frontal  (/j)  and  inferior  fron- 
tal fissure  (/,)  the  latter  running  into  the  precentral  fissure  ( /g), 
the  anterior  portion  of  the  frontal  lobe  naturally  divides  itself  into 
the  superior  (-Fj),  middle  (jF!,),  and  inferior  {I\^  frontal  convolu- 
tions. Through  the  presence  of  the  first  and  second  temporo- 
sphenoidal  fissures  in  the  same  manner,  the  temporal  lobe  (^)  is 
divided  into  the  first  (T^),  second  (7,),  and  third  (J!^)  temporo- 
sphenoidal  convolutions.  The  most  important  fissure  of  the  pari- 
etal lobe  (P)  is  the  iutraparietal  fissure  {ip).  Starting  from  the 
posterior  central  convolution,  it  extends  backward  and  downward, 
and  dividing  the  parietal  lobe  into  the  superior  (Pj)  and  inferior 
(P.,)  parietal  lobules,  terminates  toward  the  posterior  extremity  of 
the  hemisphere.  Beneath  the  intraparietal  fissure,  and  as  con- 
stituent parts  of  the  inferior  parietal  lobule,  are  situated  two  im- 
portant convolutions,  the  supra-marginal  (P.,)  convolution  arching 
around  the  fissure  of  Sylvius  and  the  angular  (P'o)  convolution 
around  the  first  temporo-sphenoidal  fissure.  The  parietal  is 
separated  from  the  occipital  (0)  lobe  by  the  parieto-occipital 
{Po)  fissure,  the  latter  being,  however,  just  visible  from  a  lat- 
eral view,  should  be  viewed  from  the  mesial  surface  of  the  hemi- 
sphere, as  in  Fig.  375,  where  it  {Po)  will  be  observed  to  descend 
downward  and  inward,  separating  the  cuueus  {Oz)  from  the  prse- 
cuneus  (P'g)  ^^^  terminating  in  an  acute  angle  in  the  calcarine 
fissure  {oc),  the  latter  fissure  being  so  called  on  account  of  its  mark- 
ing the  inner  concave  border  of  the  calcar  avis  or  hippocampus  minor 
in  the  posterior  cornu  of  the  lateral  ventricle.  The  occipital  lobe 
(Fig.  374,  0)  is  made  up  of  the  first  (Oj),  second  (O,,),  and  third  (O3) 
occipital  convolutions,  the  first  occipital  being  separated  from  the  sec- 
ond occipital  convolution  by  the  transverse  occipital  fissure  (0),  and 
the  second  occipital  convolution  from  the  third  by  the  inferior  longi- 
tudinal occipital  fissure  (o„).  As  the  calcarine  fissure  (oc.  Fig.  375) 
does  not  run  into  the  hippocampal  ( /;)  fissure,  it  will  be  observed  that 
the  convolution  lying  above  the  corpus  callosum,  and  known  as  the 
gyrus  fornieatus  {Gf),  passes  continuously  into  tlie  convolution  of 
the    hippocampus  {H).     The  latter  convolution   terminates  ante- 


662 


THE  NERVOUS  SYSTEM. 


riorly  in  a  crook-like  extremity  or  crotchet,  tlie  so-called  iin- 
nicate  gyrus  or  subiculiim  cornu  ammonis  (  U).  Below  the  calcarine 
fissure  are  situated  two  convolutions,  the  lobulus  fusiformis  {T^, 
and  lobulus  lingualis  (^.),  separated  by  the  occipito-temporal  fissure, 
while  above  the  gyrus  fornicatus  (Gf)  is  separated  from  the  mesial 
surface  of  the  first  {F^  frontal  convoluticm  by  a  well-marked  fissure, 
the  calloso-marginal  {cm),  which,  like  the  parieto-occipital  fissure,  is 
also  just  visible  from  a  lateral  view  of  the  hemisphere.     It  must 

Fig.  375. 


Inner  surface  of  right  hemisphere.  CC.  Corpus  callosum,  longitudinally  divided.  Gf. 
Gyrus  fornicatus.  //.  Gyrus  hippocampi,  h.  Sulcus  hippocampi.  U.  Uncinate  gyrus,  cm. 
Sulcus  calloso-marginalis.  /\.  Median  aspect  of  the  lirst  frontal  convolution,  c.  Terminal  ]ior- 
tion  of  the  sulcus  centralis,  or  fissure  of  Rolando.  .1.  Anterior.  B.  Posterior  central  ciuivdlu- 
tion.  Pj".  Prfecuneus.  On.  Cuneus.  Pa.  Parieto-occipital  fissure,  o.  Sulcus  occipitalis  iraus- 
versus.  oc,  Calcarini' tissure  ;  oc",  Inferior  ramus  of  the  same.  I).  Gyrus  descendens.  T^.  Gyrus 
occipito-temporal  is  later  alis  (lobulus  fusiformis).  T^,.  Gyrus  occipito-temporalis  medialis  (lobulus 
lingualis).     (After  i;(  k  i;k  and  I)uret.  ) 

not  be  supposed  from  the  fact  of  names  l)eing  given  to  certain  well- 
defined  convolutions  that  the  latter  are  entirely  distinct,  or  do  not 
run  into  each  other ;  on  the  contrary,  as  may  be  seen  from  Figs, 
\MA  and  875,  it  is  evident  that  directly  or  indirectly  they  are  all 
continuous  with  each  other.  Thus  the  third  frontal  {F.^  runs  into 
the  anterior  (^4)  central,  the  latter  into  the  ])osterior  [B)  central, 
the  three  occipital  convolutions  into  the  superior  parietal  lobule 
(P),  the  angular  gyrus  and  third  tem])oro-sphcnoidal  ( J!,)  convoki- 
tions  respectively,  and  so  on.  In  addition  to  these  ])rincipal  iis- 
sures  just  mentioned,  there  are  numerous  other  less  important  ones 
which  increase  considerably  the  number  of  convolutions  and  obscure 
somewhat  those  already  described.  That  these  fissures  are  of  a  sec- 
ondary character,  however,  becomes  at  once  evident  when  the  arach- 
noid and  ])ia  mater  are  removed,  they  being  then  seen  to  be  mere  su- 
])erficial  indentations  and  not  deep  tissures  penetrating  into  the  brain. 
Tiic  internal  or  white  substance  of  the  cerebral  hemispheres  is 


THE  CEREBBAL  HEMISPHERES. 


663 


composed  largely  of  libers  Avliich  in  general  radiate  from  the  basal 
ganglia  internally  to  the  gray  or  cortical  substance  outwardly. 
The  amount  of  white  substance  yaries  very  much  in  different  por- 
tions of  the  hemisphere,  thus,  in  the  region  of  the  island  of  Reil, 
where  the  gray  substance  penetrates  to  a  considerable  depth,  but 
little  of  it  is  present,  whereas,  in  the  posterior  portions  of  the 
hemisphere,  where  the  gray  matter  is  relatively  less  well  developed, 
the  Avhite  substance  is  present  in  great  quantity.  The  fibers  of  which 
the  white  substance  consists  may  be  said  to  be  essentially  of  three 
kinds  :  First,  commissural  libers,  such  as  those  composing  the  corpus 
callosum  or  the  broad  commissure  connecting  the  two  hemispheres 
at  the  bottom  of  the  great  longitudinal  lissure  or  the  anterior  commis- 
sure situated  a  little  in  front  of  the  thalami  optici  and  spreading  out 
from  the  latter  into  the  lower  and  anterior  parts  of  the  temporal 
lobes.  Second,  association  libers,  or  fibers  which,  lying  just  beneath 
the  gray  matter,  connect  the  different  convolutions  of  the  same  hemi- 
sphere. Third,  medullary  fibers  including  both  the  fibers  that  connect 
the  cortex  cerebri  with  the  basal  ganglia,  as  well  as  those  that  pass  to 
and  from  the  cortex  through  the  internal  capsule  to  the  crura  cerebri 
and  medulla.  One  of  the  most  striking  facts  with  reference  to  the 
cerebral  hemispheres,  the  bulk  of  the  latter  being  taken  into  con- 
sideration, is  the  large  amount  of  blood  which  they  receive,  one-fifth 
of  the  whole  mass  of  the  blood  probably  going  to  the  encephalon 

Fig.  370. 


Circle  of  "Willis.     (QfAiN  and  Shakpey. 

The  manner  in  which  the  blood  is  distributed  to  the  brain  is  also 
very  remarkable,  the  branches  of  the  basilar  (5)  and  internal  (1)  caro- 
tid arteries  anastomosing  so  freely,  as  the  circle  of  Willis  (Fig.  376), 


664  THE  NERVOUS  SYSTEM. 

that  the  supply  of  blood  to  any  one  part  of  the  brain  is  not  in- 
terrupted, even  though  the  principal  branch  supplying-  such  a  })art 
be  obstructed.  The  importance  of  this  peculiarity  in  the  distri- 
bution of  the  cerebral  blood  vessels  becomes  at  once  apparent 
when  it  is  rememl^ered  that  with  the  cessation  of  the  blood  su])- 
ply  the  functional  activity  of  the  brain  at  once  ceases,  and  it 
may  be  aj^propriately  mentioned  in  this  connection  that  while  in 
all  probability  the  energy  of  the  brain  depends  largely  on  the 
size  of  its  arteries  and  the  freedom  with  which  the  blood  circu- 
lates through  them,  the  special  manifestation  of  brain  power  de- 
pends upon  the  particular  areas  of  distribution.  It  has  already 
been  mentioned  that  the  gray  matter  of  the  nervous  system  is 
more  vascular  than  the  white,  and  that  in  all  probability  it  is  in 
the  gray  or  vascular  substance  that  the  nervous  force  is  generated, 
the  white  or  fibrous  substance  transmitting  it.  The  significance, 
therefore,  of  the  development  of  the  convolutions  just  described 
produced  through  the  invaginating  of  the  gray  substance  into  the 
white,  together  with  their  pia  mater  or  vascular  tunic,  thereby  in- 
suring a  far  greater  supply  of  l>lood  than  would  be  possible  if  the 
brain  were  smooth,  becomes  evident.  Further,  ^vhcn  it  is  borne 
in  mind  that  the  brain  is  enclosed  in  a  bony,  unyielding  case, 
and  that  the  amount  of  blood  sent  to  the  brain  from  the  heart 
must  vary  with  the  force  of  the  latter,  and  that  cerebral  disturb- 
ances ensue  with  any  increase  or  diminution  in  pressure  it  might 
be  anticipated  that  some  provision  must  exist  by  which  a  uniform 
pressure  within  the  cerebral  substance  is  maintained.  The  latter 
function  appears  to  be  fulfilled  by  the  cerebro-spinal  fluid  found 
in  the  sul)arachnoid  cavity  of  the  brain  and  cord,  since  if  this 
fluid  be  withdrawn  from  a  living  animal,  cerebral  disturbances 
attril)utable  to  changes  in  pressure  ensue.  The  cerebro-spinal 
fluid  amounts  to  at  least  two  ounces,  and  probably  more,  and  ap- 
pears to  be  as  ra])idly  absorbed  as  produced,  and  as  it  readily 
passes  from  the  subarachnoid  space  through  the  foramen  of 
Magendie  or  the  triangular  orifice  in  the  pia  mater  situated  at  the 
inferior  angle  of  the  fourth  ventricle  into  the  ventricles  of  the 
brain  or  the  central  canal  of  the  cord,  it  evidently  serves  to 
equalize  the  pressure  in  the  cranial  cavity,  merely  allowing  blood 
vessels  to  expand  and  contract  within  such  limits  as  do  not  induce 
any  marked  change  in  the  pressure  to  which  the  brain  substance  is 
usually  subjected.^ 

Tlie  entire  cncephalon  in  the  adult  male  brain  weighs  on  an 
average  about  fifty  ounces,  that  of  the  female  a  little  less,  about 
forty-four  ounces.  On  this  supposition,  the  relative  weights  of  the 
cerebrum,  cerebellum,  etc.,  are  as  follows  :  ^ 

'  Mast'iidie,  .Journal  de  Plivsiologio,  Tonii' v.,  p.  27.  Paris,  1825.  Tome  vii., 
pp.  \-m,  1827. 

2Quain's  Anatomy,  8tli  cd.,  \'ol.  ii.,  \).  ijSl. 


THE  CEREBRAL  HEMISPHERES. 


665 


Average  weight. 

Male. 

Female. 

Cerebrum    .... 

43.98  oz. 

1244.63 

grammes. 

38.75  oz. 

1096.62  grammes. 

Cerebellum. 

5.25   " 

148.57 

" 

4.76  " 

134.70 

Pons  and  medulla     . 

0.98  " 
50.21   " 

27.73 

11 

1.01   " 

28.58 

Entire  enceplialon    . 

1420.93 

44.52  " 

1259.90        " 

Eatio  of  cerebrum  to 

cerebellum. 

I'toSi 

1  to  SI 

The  human  brain  is  absolutely  heavier  than  that  of  any  other 
animal  except  the  elephant  and  the  cetacea,  the  brain  of  the  ele- 
phant usually  weighing  from  3022.4  to  4528  grammes^  (8  to  10 
pounds)  or  even  more,  that  of  the  young  male  elephant  which 
died  at  the  Philadelphia  Zoological  Gardens  having  been  found  by 
the  author  to  weis-h  immediatclv  after  removal  from  the  skull 
4754.4  grammes  (10.5  poiuids).  The  brain  of  the  whale  weighs 
about  2264  grammes  (5  pounds);-  that  of  a  grampus  (Delphinus 
Risso)  as  found  by  the  author,  3169.6  grammes  (7  pounds). 
Relatively,  however,  to  the  size  of  the  body  the  brain  is  larger  in 
certain  birds  and  mammals  than  in  man,  as,  for  example,  in  the 
canary  bird,  field  mouse,  and  ouisitite  monkey.  With  reference, 
however,  to  the  size  of  the  nerves  given  off  from  its  base,  the  brain 
of  man  is  larger  than  that  of  any  other  animal  without  exception. 

In  considering  the  functions  of  the  medulla,  pons,  cerebellum, 
and  basal  ganglia,  we  have  necessarily  anticipated  somewhat,  by  a 
process  of  exclusion,  the  functions  of  the  cerebral  hemispheres.  It 
only  now  remains  for  us  to  offer  the  positive  evidence  bearing  upon 
the  questions  and  confirming  the  general  conclusions  already  reached 
by  the  manner  just  mentioned. 

Fig.  377. 


Pigeou,  after  removal  of  the  liemispheres.     (Dalton.) 

If  the  cerebral  hemispheres  be  removed  in  a  pigeon,  for  example, 
the  animal  at  once  falls  into  a  condition  of  stupor,  its  whole  ap- 
pearance being  very  peculiar  and   most  characteristic  (Fig.  377). 

1  Cyclopaedia  of  Anat.  Phys.,  Vol.  lii.,  p.  664.     Loud.,  18.39-47. 
2Rudolphi,  Grundriss  der  Pbysiologie,  B.  ii.,  s.  12.     Berlin,  1823. 


QQQ  THE  NERVOUS  SYSTEM. 

With  its  head  ahiiost  buried  within  the  feathers  of  the  neck,  with 
closed  eyes,  the  pigeon  stands  sufficiently  firmly,  but  without  mov- 
ing, apparently  utterly  indifferent  to  its  surroundings.  From  time 
to  time  it  open  its  eyes,  stretches  its  neck,  or  smooths  its  feathers, 
but  soon  again  relapses  to  its  former  condition  of  apathy.  That 
the  pigeon,  however,  still  feels  there  can  be  no  doubt.  Pinch  its 
neck  or  one  of  its  toes  and  a  persistent  eifort  is  made  to  withdraw 
the  part  from  the  grasp.  Fire  oflP  a  pistol,  the  pigeon  will  open  its 
eyes  and  turn  its  head  round  as  if  it  had  heard  the  report  and  was 
looking  whence  it  came.  The  report  of  the  pistol,  however,  causes 
no  alarm,  for  the  pigeon  makes  no  effort  to  escape.  While  the 
animal  undoubtedly  hears  and  sees,  the  sensations  do  not  give  rise 
to  the  usual  ideas  associated  with  or  developed  out  of  them,  the 
pigeon  feels  but  does  not  perceive  the  sensation  of  sound  ;  the  re- 
port of  the  pistol  does  not  give  rise  to  any  idea  of  danger  usually 
associated  with  the  production  of  sound.  In  the  same  way  the 
presence  of  food,  though  seen  and  smelt  by  the  pigeon,  does  not 
excite  the  idea  of  hunger,  the  animal  making  no  effort  to  feed^ 
starving  to  death  amidst' plenty.  That  this  entire  loss  of  memory, 
volition  and  conscious  intelligence,  following  loss  of  the  cerebral 
hemispheres  in  a  pigeon  is  not  due  simply  to  the  effects  of  shock, 
hemorrhage,  etc.,  is  shown  not  only  by  the  entirely  different  effect 
following  destruction  of  the  cerebellum,  but  that  a  pigeon  from 
which  the  cerebral  hemispheres  have  been  removed  can  be  kept 
alive  for  months  by  artificial  feeding,  and,  although  the  effects  of 
shock  have  long  since  passed  away,  nevertheless,  the  animal  never 
regains  its  intelligence,  remaining  ever  afterward  in  this  character- 
istic condition  of  stupor  and  apathy.  The  absence  of  intelligence 
that  follows  the  removal  of  the  cerebrum  is  even  more  marked  in 
the  case  of  a  mammal  than  in  that  of  the  bird.  Thus,  according 
to  Goltz,^  a  dog  in  which  the  cerebrum  has  been  removed  is  reduced 
to  the  condition  of  a  mindless  machine,  conscious  sensations,  feel- 
ings, emotions,  etc.,  being  all  wanting.  Although  the  effects  of 
destruction  or  compression  of  the  cerebral  hemispheres  in  man, 
whether  due  to  disease  or  injury,  are  not  as  well  established  as  in 
the  case  of  birds  and  mammals  through  the  imperfect  localization 
of  the  disease,  the  basal  ganglia,  etc.,  being  usually  involved  as 
well  as  the  cerebral  hemispheres ;  nevertheless,  a  sufficient  number 
of  cases  have  been  observed  by  pathologists  which  show  that  loss 
or  compression  of  the  cerebral  hemispheres  in  man  involves,  as  in 
the  case  of  l)irds  and  mammals,  the  loss  of  memory,  volition,  con- 
scious intelligence,  the  nutritive  functions,  however,  remaining  un- 
impaired. Among  such  cases  may  be  mentioned  that  of  the  sailor 
related  by  Sir  Astley  Cooper,^  who,  having  fallen,  probably  from 
the  yard-arm,  was  picked  uyt  on  the  deck  insensible,  practically  de- 
prived of  all  powers  of  mind,  volition,  or  sensation,  in  which  con- 

^Pfiii.£;er's  Arc'liiv,  IjuikI  xli. 

2  Lectures  on  the  PrineipleH  and  I'raetieeof  Siir<,a'rv,  p.  18S.     PliihKU'lpliia,  1S89. 


THE  CEREBRAL  HEMISPHERES.  667 

dition  he  remained  for  thirteen  months,  being  kept  alive  all  this 
time  bv  artificial  feeding,  the  grinding  of  the  teeth  and  the  sucking^ 
of  the  lips  indicating  to  his  attendants  the  necessity  of  giving  food 
and  drink.  During  this  period  the  man  lived  almost  entirely  a 
vegetable  existence,  the  only  movements  he  made,  with  the  excep- 
tions of  the  lips,  etc.,  being  with  the  lingers,  which  he  moved  to- 
and-fro  to  the  time  of  the  pulse.  In  this  condition  the  sailor  was 
seen  by  Cline,  the  famous  surgeon  of  the  day,  who,  satisfying  him- 
self that  a  depression  in  the  skull  existed,  trephined,  and  with  the 
happy  result  that  within  a  short  time  after  the  operation  the  patient 
^vas  able  to  get  out  of  bed,  talk,  and  tell  where  he  came  from,  his 
mind  having  been  restored  through  the  removal  of  the  pressure 
exerted  by  the  depressed  bone  upon  the  cerebral  hemispheres. 

In  general,  it  may  be  said  that  injury  or  disease  of  the  cerebral 
hemispheres  in  man  entails  disturbance  or  loss  of  the  intellectual 
powers,  according  to  the  seat  and  extent  of  the  lesion.  Impairment 
and  then  loss  of  memory,  weakening  and  failure  of  the  reasoning 
powers  and  of  the  judgment,  invariably  follow  disease  or  injury  of 
the  cerebral  hemispheres,  while  the  facts  that  under  such  circum- 
stances there  is  no  loss  of  sensation  or  motor  power,  and  that  the 
vegetative  functions  also  remain  unimpaired,  as  in  the  case  of  idiots 
and  the  insane,  clearly  show  that  the  cerebral  hemispheres  are  in- 
dispensable to  the  manifestation  of  the  intelligence.  On  the  other 
hand,  the  fact  already  mentioned  of  animals  deprived  of  their  cere- 
bral hemispheres  living  for  a  longer  or  shorter  time  when  supplied 
with  food,  and  of  human  beings  being  born  anencephalous,  and  yet 
were  kept  alive  some  time,  and  who  sucked  and  cried  like  ordinary 
infants,  proves  that  the  cerebral  hemispheres  are  not  concerned  in 
the  performance  of  those  functions  not  involving  intellection,  which 
have  been  assigned  to  other  parts  of  the  encephalon.  That  the  in- 
tellectual powers  depend  upon  the  development  of  the  encephalon 
is  also  shown  by  the  facts  of  comparative  anatomy,  the  encephalon 
of  the  more  intellioent  animals  beino-  much  heavier  both  absolutelv 
and  relatively,  with  reference  to  the  weight  of  the  body,  than  that 
of  the  less  intelligent  ones.  Thus,  in  fishes  the  ratio  of  the  en- 
cephalon to  the  body  is  as  1  to  5,668,  in  the  reptiles  as  1  to  1,321, 
in  birds  as  1  to  212,  in  mammals  1  to  189  ^  and  in  man  as  1  to  50, 
supposing  the  body  of  the  man  to  weigh  68.1  kil.  (150  pounds)  and 
the  brain  about  1.37  kil.  (3  pounds). 

Further,  the  brain  of  the  lowest  races  of  mankind,  at  least  as  es- 
timated from  their  cranial  capacity,  is  not  as  heavy  as  that  of  the 
higher  and  more  intellectual  ones,  the  brain  of  the  Australian,  for  ex- 
ample, weighing  only  1190  grammes  (42  oz."),-  and  correspondingly 
less  bulky.     It  is  also  well  known  that  individuals  distinguished  by 

^  Leiiret,  Anatomie  Comparee  du  Svsteme  Xerveux,  pp.  153,  234,  284,  422. 
Paris,  1839. 

^ Davis,  Journal  of  the  Acad,  of  Xat.  Stionces,  Phila.,  1869.  Morton,  Cranica 
Americana,  p.  253,  Pliila.,  1839. 


668 


THE  NERVOUS  SYSTEM. 


great  intellectual  power  possessed  large,  heavy  brains.  Thus  the 
brain  of  Abercrombie  ^  weighed  1783  grammes  (63  oz.),  that  of 
Cuvier-  1820  grammes  (64.33  oz.).  On  the  other  hand,  the  brain 
of  idiots  has  been  found  in  some  instances  to  weigh  not  more  than 
r)66  grammes  (20  oz.).  It  should  be  mentioned  in  this  connection, 
however,  that  the  weight  of  the  brain  in  man  depends  not  only 
upon  race,  but  on  the  age,  weight,  and  stature  of  the  individual, 
and  even  upon  the  manner  in  which  the  brain  is  weighed,^  whether 
as  a  whole  or  in  parts,  with  or  without  the  j)ia  mater  and  also  in 
reference  to  the  amount  of  blood  it  may  contain. 

It  will  be  observed  also  from  a  comparison  of  the  brain  of  the 
lower  with  that  of  the  higher  vertebrates,  that  it  is  the  greater  de- 
velopment of  the  cerebral  hemispheres  in  the  latter  to  which  are 
due  the  greater  bulk  and  weight  of  the  encephalon.  Thus,  as  we 
pass  from  the  brain  of  the  fish  (Fig.  378)  to  that  of  the  reptile 
(Fig.  379),  from  the  brain  of  the  reptile  to  that  of  the  bird  (Fig. 
380),  from  the  latter  to  the  brains  of  mammals  (Fig.  381),  includ- 
ing that  of  man,  one  cannot  but  be  impressed  with  the  fact  that  the 
cerebral  hemispheres  become  successively  more  and  more  developed 


Fig.  378. 


Brain  of  carj).  A.  Cor- 
pora striata.  B.  Optic  lobes. 
C   Cerebellum. 


Fig.  380. 


Brain  of  lizard. 

(I.  Cerebral  hemispheres. 

/.  Optic  lobe.s. 

0.  Cerebellum. 

''.  Medulla. 

d.  Spinal  cord. 


Brain  of  the  pigeon.  A.  Cere- 
bral hemispheres.  B.  Optic  lobes. 
C.  Cerebellum. 


until  in  monkeys  (Fig.  382)  and  man  they  completely  cover  the 
cerebellum.  Further,  it  may  also  be  seen  from  such  a  comparison 
that  while  the  brain  in  fish,  reptiles,  birds,  and  the  lower  orders  of 
mammals,  such  as  the  marsupiala,  rodentia  (Fig.  381),  sirenia,  etc., 
is  smooth  or  nearly  so,  in  the  higher  orders,  including  the  probos- 
cidea,  cetacea,  the  ungulata,  the  carnivora  and  primates  (Figs.  382, 
383),  it  is  more  or  less  convoluted.  Indeed,  so  much  is  this  the 
case  that  in  tlie  proboscidea  it  is  particularly  convoluted,  even  more 
so  than  in  man.     In  general,  it  maybe  said  that  the  development  of 

^Edinbursli  Med.  and  .Surg.  Journal,  LS-i"),  Vol.  Ixiii.,  p.  448. 

2  "  Trois  livres  onze  onces  (juatres  gros  ot  demi,"  is  the  number  given  in  the  ac- 
count of  the  autopsv  of  Cuvier  in  the  Arcliives  generales  de  Medeeine,  Tome  xxix., 
p.  144.     Paris,  18.32. 

3R.  Boyd,  riiil.  Trans.  Lond.,  Vol.  I-jI,  18G2,  p.  241. 


THE  CEREBRAL  HEMISPHERES. 


669 


the  intellectual  powers  depends  not  only  upon  that  of  the  encepli- 
alon,  but  more  particularly  upon  that  of  its  cerebral  hemispheres, 
and   especially,   as    affirmed  long  ago  by  Erasistratus,^  upon  the 


Fig.  381. 


Fig.  382. 


Brain  of  the  rabbit.  A.  Cere- 
bral hemispheres.  O.  Olfactory 
bulb.    C.  Cerebellum. 


Brain  of  the  orang. 


number  and  depth  of  the  convolutions  of  the  gray  matter  of  the 
same.  Further,  in  the  savage  races  of  mankind,  characterized  by 
a  low  order  of  intelligence,  the  convolutions  are  not  so  deep,  are 


Fig.  383. 


Fig.  384. 


Cerebrum 


Fossa  svlvia 


— -  Cerebrum. 


Corp. 
quadrig. 

Cerebellum. 


' Med.  oblong. 

Brain  of  human  embryo,  three  months. 


Cerebellum 


Med.  oblong. 


Brain  of  human  embrvo,  five  months 


less  numerous,  and  are  more  simply  disposed  than  in  the  civilized 
races  distinguished  by  the  development  of  their  mental  faculties. 
^Galenus,  De  Usu  Partium,  Lib.  8,  Cap.  13. 


<)70  THE  NERVOUS  SYSTEM. 

It  is  well  known  that  in  individuals  especially  remarkable  lor  intel- 
lectual power,  as  in  the  case  of  Gauss/  for  example,  a  distinguished 
mathematician,  the  convolutions  of  the  cerebral  hemispheres  are 
found  to  be  very  numerous  and  deep,  and  far  from  simply  arranged. 
On  the  other  hand,  in  idiots  the  convolutions  are  few,  comparatively 
superficial,  and  simply  disposed. 

The  development  of  the  l)rain  also  confirms  the  conclusions  based 
upon  the  facts  of  comparative  anatomy  and  ethnology,  the  transitory 
stages  through  which  the  ftetal  brain  passes  being  permanently  re- 
tained in  the  brains  of  the  lower  animals.  Thus,  at  about  three 
weeks  of  intrauterine  life  the  l)rain  of  the  human  foetus  resembles 
that  of  the  adult  fish,  there  being  but  little  difference  at  this  early 
period  in  the  relative  development  of  the  cerebral  hemispheres, 
optic  lobes,  cerebellum,  etc.  As  development  advances  the  hemi- 
spheres enlarge  and  grow  backward ;  at  three  months  (Fig.  383), 
though  still  smooth,  they  slightly  overlap  the  optic  lobes,  the  latter 
not  having  yet  divided  into  the  corpora  quadrigemina.  At  about 
the  fifth  month  (Fig.  384)  the  cerebral  hemispheres  in  the  human 
foetus  overlap  the  cerebellum,  and  here  and  there  exhibit  a  rudi- 
mentary fissure,  though  their  surface  is  still  almost  entirely  smooth, 
as  in  those  of  the  rodentia.  Finally,  at  about  the  seventh  month, 
the  optic  lobes  are  subdivided  into  the  corpora  quadrigemina,  while 
at  full  term  or  at  birth  the  convolutions  are  all  formed. 

The  brain  of  the  human  foetus,  however,  at  this  period,  both  as 
regards  the  number,  depth,  and  simplicity  of  arrangement  of  the 
cerebral  convolutions,  resembles  rather  the  brain  of  the  chimpanzee 
than  that  of  the  adult  man,  while  the  brain  of  the  uneducated  child 
resembles,  in  similar  respects,  that  of  the  savage  races  of  mankind 
rather  than  that  of  the  civilized  ones  (Fig.  385) ;  a  physical 
correspondence  in  harmony  with  their  intellectual  acquirements. 
While  the  facts  of  experiment,  pathology,  comparative  anatomy, 
etc.,  with  but  few  exceptions,  and  those  usually  more  apparent 
than  real,  undoubtedly  agree  in  establishing  the  view  that  asso- 
ciates intellectual  power  with  the  development  of  the  cerebral 
hemispheres,  and  more  })articularly  with  that  of  the  convolutions, 
or  the  gray  matter  of  the  same,  it  must  be  borne  in  mind  that  the 
quality  of  the  chemical  composition  of  the  latter  is  (piite  as  im- 
portant a  condition  as  its  mere  quantity. 

It  need  hardly  be  added  that  the  exercise  of  the  mental  faculties 
necessitates  the  connections  between  the  gray  or  vescular  substance 
of  the  convolutions  and  the  fibers  of  the  white  substance  being 
maintained  in  their  normal  condition,  just  as  the  action  of  a  mus- 
cle depends  on  the  position  and  manner  of  insertion  ;  and,  above 
all,  upon  the  free  supply  of  blood  and  active  circulation,  both  that 
the  materials  for  the  nourishment  of  the  hemispheres  and  the  pro- 
duction by  them  of  thought,  may  be  supplied  in  sufficient  quantity, 
and  that  the  effete  and  worn-out  materials  incidental  to  mental  ac- 
^Quuin,  Anatomy,  1878,  Vol.  ii.,  pp.  521),  581. 


THE  CEREBRAL  HEMISRHERES. 


671 


tivity  may  be  carried  away  to  the  proper  emunctories  as  rapidly  as 
produced.  As  we  have  already  seen  that  the  different  structures 
of  which  the  encephalon  consists,  medulla,  pons,  cerebellum,  basal 
ganglia,  cerebral  convolutions,  etc.,  have  undoubtedly  different 
functions,  it  is  reasonable,  therefore,  to  suppose  that  the  different 


Fio 


Cerebrum  of  man.  Lateral  view  of  the  right  cerebral  hemisphere.  1.  Fissure  of  Eolaudo.  2. 
Ascending  frontal  convolution,  o,  Superior  ;  .3',  Middle,  and  7,  Inferior  frontal  convolutions.  4. 
A  bridging  convolution  between  the  superior  and  middle  frontal  convolutions.  5.  Ascending 
parietal  fonvolution.  (5,8.  Supramarginal  convolution  (S  in  front  points  to  part  of  the  inferior 
frontal  convolution).  9,  9.  Superior  temporo-sphenoidal  convolution.  10,  11,  12.  Convolutions 
of  the  island  of  Reil.  or  central  lobe.  13.  Orbital  convolutions.  14.  Lower  extremity  of  middle 
temporo-sphenoidal  convolutions.    15.  Occipital  lobe.     (From  Sappey  after  Foville")    J^. 


convolutions,  or  the  gray  matter  of  the  cerebral  hemispheres,  have 
also  special  faculties  or  functions.  Phrenology  has,  therefore,  a 
basis  worthy  of  consideration.  Phrenology,  however,  as  under- 
stood by  the  vulgar,  is  based  upon  the  untenable  assumption  that 
the  f  >rm  of  the  surface  of  the  brain  can  be  inferred  from  the  ex- 
ternal configuration  of  the  skull,  that  any  protuberance,  or 
"  bump,"  of  the  latter  is  to  be  taken  as  an  indication  of  a  similar 
excessive  development  of  the  former  and  the  possession  of  some 
l)articularly  well-developed  mental  faculty.  Apart,  however,  from 
the  tacts  that  the  skull  consists  of  two  tables,  and  that  the  outer 
surjface  of  the  brain  is  separated  from  the  inner  surface  of  the  skull 
by  the  dura  mater,  arachnoid,  pia  mater,  and  cerebro-spinal  fluid, 
the  latter  variable  in  quantity,  the  figure  of  the  brain,  except  in  a 
general  way,  does  not  correspond  to  the  figure  of  the  skull.  So 
much  so  is  this  the  case  that  in  certain  animals,  as  in  the  elephant, 
for  example,  through  the  enormous  development  of  the  frontal 
sinuses  the  anterior  portion  of  the  skull  is  no  indication  of  the 
form  of  the  brain  whatever.  Further,  the  surface  of  the  brain  is 
not  elevated  into  l)unips,  the  convolutions,  as  we  have  seen,  being 
formed  through  the  invagination,  or  dipping  down  of  the  gray  mat- 
ter into  the  white.     Even  though,  then,  osseous  "bumps"  be  ever 


672 


THE  NERVOUS  SYSTEM. 


so  well  developed,  there  are  never  any  cerebral  "  bumps "  with 
special  functions  or  faculties  corresponding  to  the  osseous  ones. 
Phrenology,  as  such,  nuist  be  relegated,  then,  to  the  charlatan  and 
itinerant  showman,  Avho  amuse  their  audience  by  feeling  their 
heads  and  illustrating  their  views  by  showing  plaster  casts  of  the 
heads  of  Napoleon,  Schiller,  noted  murderers,  idiots  and  the  like. 

Within  recent  years,  however,  another  kind  of  phrenologv  has 
been  developed  and  established,  more  or  less  satisfactorily  based 
upon  entirely  different  methods  of  investigation,^  such  as  exposing 
the  brain  in  a  living  animal,  and  stimulating  with  a  Aveak  electrical 
current  a  particular  convolution,  and  so  determining  whether  the 
latter  is  excitable,  and  whether  its  stimulation  causes  sensory  or 
motor  effects ;  or,  destroying  a  particular  convolution  by  cutting, 
corrosion,  etc.,  and  observing  Avhether  the  animal  is  deprived  of  any 
of  its  faculties,  and  so  learning  whether  the  convolution  has  motor 
or  sensory  functions. 

By  such  experimental  methods  it  has  been  established  that  the 
convolutions  of  the  brain  in  animals  possesses  definite  functions,  and 
the  same  has  been  shown  to  be  true  of  the  homologous  convolutions 
of  the  brain  in  man  by  experiment,  clinical  and  post-mortem  in- 
vestigation.^ 

FiCx.  386. 


The  loft  hemisphere  of  the  monkey.     (Ferrier.  ) 


Thus,  electrical  irritation  of  the  convolution  bordering  the  fissure 
of  Kolando  in  the  brain  of  the  monkey  (Fig.  386,  1,  2,  3,  4,  5,  6, 
7,  8,  a,  b,  c,  (!)  and  in  man^  (Fig.  387),  gives  rise  to  certain  well- 

'Fritscli  and  Hitzig,  Archiv  f.  Anat.,  Physiologie,  etc.,  s.  300,  1870.  Ferrier, 
Functions  of  the  Brain,  1876.  Carville  and  Duret,  Archives  de  Physiologie  2ieme 
serie,  Tome  ii.,  p.  352.  Paris,  1875.  Dalton,  New  York  Medical"  Journal,  1875, 
p.  225. 

^  Hughlings  Jackson  Ferrier,  Localization  of  Cerebral  Disease,  p.  42.     London, 

1879.  Gra.sset,   Des  Localisations  dans  les  Maladies  Cerebrales,   p.   143.     Paris, 

1880.  Cliarcot,  Logons  sur  les  Localisations  dans  Ics  ^laladies  du  Cerveau,  p.  166. 
Paris,  1878.  Kendii,  Kevue  des  Sciences  Medicales,.  Tome  xiii.,  p.  314.  Paris, 
1879.     Gowers,  op.  cit.,  Vol.  2d,  p.  15.     Mills,  op.  cit.,  p.  332. 

^Bartholow,  American  Journal  of  the  Medical  Sciences,  April,  1874. 


THE  CEBEBBAL  HEMISPHERES. 


673 


defined  constant  movements  of  the   hands,  feet,  arms,  legs,  facial 
muscles,  mouth,  and  tongue,  on  the  opposite  side  of  the  body. 


Fig.  387. 


Lateral  view  of  the  human  brain.     Tlie  circles  and  letters  have  the  same  significance  as  those  in 
the  brain  of  the  monkey,  Fig.  386.     (Fereier.) 

That  the  muscular  contractions  induced  through  electrical  stimu- 
lation of  these  or  other  convolutions  are  not  due  to  an  escape  or 
diffusion  downward  of  the  electrical  current,  and  so  affecting  the 
corpus  striatum,  etc.,  is  shown,  apart  from  the  fact  that  stimulation 
by  chemical  agents  produces  the  same  effect,  by  several  consider- 
ations, among  which  may  be  mentioned  the  feebleness  of  the  current 
used,  the  close  approximation  of  the  electrodes,  the  imperfect  con- 
ductivity of  the  brain  substance,  the  muscular  contractions  occurring 
on  the  opposite  side  of  the  body,  and  not  occurring  at  all  when 
other  convolutions  were  stimulated.  That  these  convolutions  are 
in  reality  motor  centers,  constituting  the  indispensable  physical 
substratum  for  the  volitional,  psychical  initiation  of  movements 
corresponding  to  those  induced  by  electrical  stimulation,  the  latter 
acting  in  the  same  manner  as  the  stimulus  of  the  will,  is  further 
shown  by  the  fact  that  destruction  of  these  convolutions  in  the 
monkey^  by  experiment  and  in  man^  by  disease  causes  complete 
hemiplegia  of  the  opposite  side  of  the  body  without  affecting  sensa- 
tion.    On  the  other  hand,  destruction  in  the  monkey  by  experi- 

iFerrier,  Functions  of  the  Brain,  187G,  p.  -201. 

^  Lepine,  De  la  Localisation  dans  les  Maladies  C'erebrales,  p.  33.     Paris,  1875. 
Glikv,  Deutsches  Archiv  fiir  klin.  INIed.,  Dec,  1875. 
43 


674 


THE  NERVOUS  SYSTEM. 


ment^  and  in  man'  by  disease  of  certain  convolutions,  such  as  the 
cuneus,  visual  area,  or  temporo-sphenoidal  convolutions,  auditory 
area  (Figs.  388,  389),  while  not  affecting  the  motor  functions  entails 

Fig.  388. 

\h      0      T      0 


Cortical  eeuters.    Lateral  aspect  of  the  liemisiihere. 
Fig.  389. 
0         J         0         r. 


^ 


Cortical  centers,     ^lesal  asjiect  of  the  hemisphere. 

^Horslev&Schafer,  Phil.  Trans.,  Vol.  179,  1889,  p.  1.     Beevor  et  Hoi-sley,  Ebend, 
Vol.  181,  1891,  p.  129.  2  Gowers,  op.  cit.,  Vol.  2d,  pp.  21,  24. 


THE  CEREBRAL  HEMISPHERES. 


6 


(0 


Fr  A  Si/.  Motor  speech  region  in  tlie  left  hemisphere. 


impairment  or  entire  loss  of  vision  or  hearing,  according  as  one  or 
l)otli  liemispheres  are  involved.  Such  observations  prove  that  there 
are  special  sensory  as  well  as  motor  convolutions  in  the  brain  of 
man.  The  condition  of  aphasia,  whether  presented  in  the  usual,  or 
iigraphic,  or  amnesic  form,  depending,  as,  without  doubt,  it  does, 
upon  disease  in  the  region  of  the  posterior  extremity  of  the  third 
left  frontal  convolution,  where  the  latter  abuts  on  the  fissure  of 
Sylvius,  and  overlaps  the  island  of  Reil,  is  a  most  convincing  argu- 
ment in  favor  of  the  view  of 

the  cerebral   functions  being  Fig.  390. 

localized  in  the  convolutions 
of  the  hemispheres.  Merely 
referring  incidentally  to  the 
researches  of  Petit,^  Bouil- 
laud,"  Dax,^  Broca,*  Hugh- 
lings  Jackson,^  etc.,  upon  the 
subject  of  aphasia,  the  detailed 
consideration  of  which  be- 
longs rather  to  the  study  of 
clinical  medicine  and  patho- 
logical anatomy,  it  may  be 
briefly  said  that  a  person  presenting  the  condition  of  aphasia  as  ex- 
hibited in  its  most  usual  form  is  deprived  of  the  faculty  of  articu- 
late speech,  though  such  a  person  comprehends  perfectly  the  mean- 
ing of  words  spoken  by  others ;  having  a  clear  idea  of  language 
and  of  the  meaning  of  words,  and  being  able  to  write  perfectly 
well.  In  other  cases,  however,  the  patient  cannot  express  ideas  in 
writing  (agraphia),  or  cannot  remember  the  words  wanted  (amnesia); 
the  idea  even  of  language  being  lost.  That  the  inability  to  speak 
exhibited  by  the  person  suffering  from  aphasia,  whether  simple  or 
combined  with  the  amnesic  or  agraphic  form,  is  not  due  to  paralysis 
of  the  muscles  of  articulation  is  shown  by  the  fact  that  the  aphasic 
individual  makes  use  of  these  muscles  in  mastication  and  deglutition. 
Though  the  center  for  the  co(')rdination  of  the  muscles  effecting 
articulation  be  diseased,  since  the  action  of  the  center  of  the  artic- 
ulating muscles  is  bilateral — that  is,  the  center  in  one  hemisphere 
innervating  the  muscles  of  articulation  of  both  sides — there  is  no 
difficulty  in  understanding  that  such  should  be  the  case. 

"While  disease  of  the  center  of  articulation  of  the  left  hemisphere, 
for  the  reason  just  given,  does  not  entail  paralysis  of  the  muscles 
of  articulation,  it  does  entail  paralysis  of  articulation  or  speech,  the 
center  for  the  coordination  of  the  muscles  involved  in  the  produc- 
tion of  speech  being  then  affected.  When  it  is  remembered,  how- 
ever, that  speech  is  gradually  acquired  through  the  constant  and 

'Recneil  d' observations  d'anatomie  et  de  cliirurgie,  p.  74.     Paris,  1766. 

2  Archives  de  M^decine,  1825. 

''(Tazette  hebdomadaire,  A2)ril,  1865. 

^Bulletin  de  la  societe  anatomique,  Tome  iv.,  1861. 

5  London  Hospital  Kej)orts,  Vol.  i. 


676 


THE  NERVOUS  SYSTEM. 


Fig.  391. 


continual  association  in  the  mind  of  sounds  or  written  signs  with 
the  corresponding  spoken  words,  that  the  acquisition  of  speech,  phys- 
iologically speaking,  is  the  develoi)ment  in  the  brain  of  an  organic 
nexus  between  the  sound  or  symbol,  and  the  articulation,  it  becomes 
intelligible  why  if  this  nexus  be  broken,  that,  though  the  sound  be 
heard  and  the  symbols  seen,  and  the  corresponding  ideas  developed, 
the  words  expressing  the  ideas  cannot  be  uttered,  the  individual  is 
speechless,  because,  as  Ferrier  expresses  it,^  the  motor  part  of  the  sen- 
sori-motor  cohesion,  sound-articulation  situated  in  the  inferior  frontal 
convolution,  is  broken.     Further,  owing  to  the  close  proximity  of 

the  motor  center  of  the  hand 
and  facial  muscles  (Fig.  391), 
it  is  easy  to  see,  therefore,  why 
dextral  and  facial  paralysis  are 
so  often  present,  though  not 
necessarily  so  in  the  case  of 
aphasia.  At  first  sight  it  may 
appear  strange  that  the  center 
for  coordinating  the  muscles 
eifectinff  articulation  should  be 
located  exclusively  in  one 
hemisphere ;  in  reality,  how- 
ever, there  is  nothing  more 
strange  in  this  than  that  most 
persons  are  right-handed. 
Dextral  movement,  like  articu- 
late speech,  is  gradually  ac- 
quired, and  there  is  no  more 
reason  to  doubt  that  in  the 
absence  of  the  coordinating 
centers  of  articulation  of  the 
left  hemisphere  that  of  the 
right  could  be  educated,  than 
that  in  the  absence  of  the  right 
hand  one  could  learn  to  use  the 
left.  Indeed,  it  has  been  found 
that  in  left-handed  persons 
suffering  with  aphasia  the  in- 
ferior frontal  convolution  af- 
fected is  situated  in  the  right 
instead  of  the  left  hemisphere,  as  is  usually  the  case.  The  ef- 
ferent fibers  involved  in  the  production  of  speech  pass  from  the 
island  of  Rcil  to  the  knee  of  the  internal  ca})sule,  thence  through 
the  crusta  of  the  left  cerebral  peduncle,  left  half  of  the  pons, 
to  the  opposite  side  of  the  medulla,  from  whence  emerge  the 
nerves  supplying  the  articulating  muscles.  It  may  be  mentioned 
in  this  connection  that  in  cases  of  ^' word  blindness,"  that  is  where 
a  person,  although  seeing  Well  in  most  respects,  cannot  name  a  let- 

iQp.  cit.,  p.  274. 


Schema  to  illustrate  aphasia.  V.  Visual  center. 
A.  Auditory  center.  11'.  Writing  center.  Z'.  Vo- 
cal center,  v  and  a  afferent  filter.s  from  larynx 
and  ear.  SS'  S".  Afferent  fibers  from  arliculatdry, 
hand  and  orbital  muscles.  */(.  /*('.  Elicrent  tiliers 
from  vocal  and  writing  centers.  Dotted  lines, 
fibers  connecting  centers.     (L.\?juois.) 


PITUITABY  BODY.  677 

ter  or  word,  the  cerebral  center  involved  is  situated  in  the  angular 
gyrus  (P'2,  Fig.  374),  and  in  cases  of  "word  deafness,"  where  al- 
though ordinary  sounds  are  heard  words  are  not,  the  center  is  situated 
in  the  first  temporal  convolution  (Tj,  Fig.  374).^ 

Bv  the  same  methods  made  use  of  in  determining  the  functions 
of  the  convolutions  about  the  fissure  of  Rolando,  the  angular  gyrus, 
the  inferior  frontal  convolution,  etc.,  the  functions  of  the  remaining 
convolutions  have  been  more  or  less  satisfactorily  made  out,  and 
may  be  resumed  as  follows  :     (Figs.  387,  388,  389.) 

1.  Postero-parietal  lobule  :  movement  of  the  hind  foot,  as  in 
walking. 

2,  3,  4.  Convolutions  bounding  the  fissure  of  Rolando  :  move- 
ments of  the  arm  and  leg,  as  in  climbing,  swimming,  etc. 

5.  Posterior  extremity  of  the  superior  frontal  convolution  :  exten- 
sion forward  of  the  arm  and  hand. 

G.  Anterior  central  convolution  :  supination  and  flexion  of  the 
forearm  through  action  of  biceps. 

7,  8.  Anterior  central  convolution  :  elevation  and  depression  of 
the  angle  of  the  mouth,  respectively. 

9,  10.  Inferior  or  third  frontal  convolution  :  movements  of  the 
lips  and  tongue,  as  in  articulation,  disease  of  which  causes  aphasia. 

11.  Posterior  central  convolution  :  retraction  of  the  angle  of  the 
mouth. 

a,  b,  c,  d.  Posterior  central  convolution  :  movements  of  the  hand 
and  wrist,  as  in  clinching  the  fist. 

12.  Superior  and  middle  frontal  convolutions  :  lateral  movements 
of  the  head  and  eyes,  elevation  of  the  eyelids,  and  dilatation  of  the 
pupil. 

13.  Center  of  sensation. 

13'.  Occipital  lobe,  cuneus,  supramargiual  lobule,  angular  gyrus: 
center  of  vision. 

14.  Superior  temporo-sphenoidal  convolution:  center  of  audition. 
V.  Subiculum  cornu  ammonis :  centers  of  olfaction,  gustation,  etc. 
H.  Hippocampal  region  :  center  of  touch. 

O.  Occipital  lobes  :  centers  of  organic  sensations,  hunger. 
F.  Frontal  lobes  :  intellectual  and  reflective  powers. 

Pituitary  Body. 

The  pituitary  body  or  hypophysis  cerebri  is  not  a  single  organ 
as  the  name  would  imply,  but  consists  of  two  distinct  lobes  which 
differ  histologically,  in  their  mode  of  origin,  and  functionally.  The 
anterior  or  glandular  lobe  is  developed  as  an  invagination  of  the 
buccal  epithelium.  It  resembles  somewhat  in  its  minute  structure 
the  thyroid  gland,  but  differs  from  the  latter  in  being  provided  with 
more  or  less  perfect  ducts  opening  between  the  dura  and  pia  mater. - 
It  would  appear,  therefore,  that   the   "  internal  secretion "  which 

'  Gowers,  oj).  cit.,  \n\.  "J,  ]i.  ll"J. 

2Haller,  Morpliolo.uischcs  .Jalirliucli,  18'J6,  xxv.,  s.  31. 


678 


THE  NERVOUS  SYSTEM. 
Fig.  392. 


The  projection  tracts  joining  the  cortex  with  lower  nerve  centers.  Sagittal  section,  showing  the 
arranKenients  of  tracts  in  the  internal  capsule.  A.  Tract  from  the  frontal  lobe  to  the  pons,  thence 
to  the  circlielhir  licniisjihere  of  the  opposite  side.  B.  ]Motor  tract  from  the  central  convolutions 
to  the  facial  nucleus  in  the  pons  and  to  the  spinal  cord;  its  decussation  is  indicated  at  K.  C. 
Sensory  tract  from  posterior  culumns  of  the  cord,  through  the  posterior  part  of  the  medulla,  pons, 
crus,  and  capsule  to  the  jiurielal  lobe.  I).  Visual  tract  from  the  optic  thalamus  (OT)  to  the 
occipital  lobe.  E.  Auditory  tract  from  the  intergeniculate  body,  to  which  a  tract  jjasses  from  the 
"VIII.  N.  Nucleus  (J)  to  the  temporal  lobe.  F.  Sujierior  cereii<'llar  peduncle.  G.  Middle  cere- 
bellar peduncle.  H.  Inferior  cereliellar  peduncle.  CN.  Caudate  nucleus.  CQ.  Corpora  quadri- 
gemiua.     VT.  Fourth  ventricle.     The  numerals  refer  to  the  cranial  nerves. 


Fig.  IWc 


Eyes  opened. 
Eyes  turned. 
Mouth  opened. 

Head  turned. 
Tongue. 

Mouth  retracted. 
Shoulder. 
Ellmw. 
Wrist. 
Fingers. 
Thumb, 
inlc. 
Hi}}. 
Ankle. 
Knee 
Hallux. 
Toes. 


Schema  of  the  arrangement  of  the  motor  fibers  i 
internal  capsula.     (Bkkvor  and  Hoksley.) 


is  elaborated  fulfills  some 
function  in  the  economy  of 
the  brain.  The  posterior 
or  infundibular  lobe  is  de- 
veloped as  an  outgrowth  of 
the  brain.  Histologically 
it  consists  of  nerve  cells, 
neuroglia,  closed  vesicles 
lined  with  epithelial  cells 
containing  a  colloidal  ma- 
terial. I^ess  is  known  even 
of  the  functions  of  the  pos- 
terior lobe  than  of  the  an- 
terior one. 

The  general  course  of  the 
tracts  connecting  the  cere- 
bral convolutions  whose 
functions  have  just  been 
mentioned  with  tlie  cord  are 
shown  in  Fig.  392  and  the 
relation  of  the  fibers  to  each 
other  as  they  pass  through 
the  internal  capsule  in  Fig. 
o03.     The  descriptions    of 


SLEEP.  679 

the  tracts  of  the  special  senses  will  be  deferred,  however,  until  the 
subjects  of  olfaction,  vision,  audition,  etc.,  are  considered. 

Sleep. 

The  brain,  like  every  other  organ  in  the  body,  from  time  to 
time  must  rest,  not  only  that  the  waste  incidental  to  its  functional 
activity  may  be  repaired,  but  that  its  cells  or  whatever  other  struc- 
tural elements  concerned  in  the  elaboration  of  consciousness  may 
not  be  overtaxed,  worn  out  by  constant  activity.  This  need  of 
rest  is  especially  manifest  in  the  case  of  the  brain,  for  no  work  is 
so  exhaustinf*;  as  brain  work,  and  when  once  the  brain  is  fagged, 
worn  out,  nothing  is  so  difficult  as  to  restore  it  to  its  natural,  healthy 
activity.  This  necessity  of  periods  of  rest  rhythmically  alternat- 
ing with  those  of  activity,  is  undoubtedly  the  underlying  cause  of 
sleep — however  the  latter  may  be  brought  about  and  concerning 
which  there  still  prevails  considerable  difference  of  opinion  among 
physiologists.  Thus  it  is  held  by  Sommer  ^  that  as  oxygen  appears 
to  be  gradually  stored  up  during  sleep,  as  shown  by  the  experi- 
ments of  Pettenkofer,  after  a  time  it  will  have  accumulated  in  such 
an  amount  as  to  accelerate  materially  the  nutritive  changes  going 
on  in  the  brain,  etc.,  the  effect  of  which  is  that  awakening  occurs. 
On  the  other  hand,  during  the  waking  state  this  store  of  oxygen  is 
gradually  used  up,  as  shown  by  increase  in  the  amount  of  carbon 
dioxide  eliminated,  the  consequence  of  which  is  that  exhaustion  and 
general  relaxation  are  experienced,  followed  by  a  desire  to  sleep. 
According  to  Pfliiger,^  the  combination  of  this  intra-molecular  oxy- 
gen with  the  carbon  of  the  lirain  tissue  is  so  violent  as  to  amount 
to  an  explosion,  which,  taking  place  at  successive  intervals,  main- 
tains the  brain  in  a  waking  condition ;  as  the  stored-up  oxygen, 
however,  is  gradually  used  up  the  explosions  diminish  in  frequency 
and  violence  until  they  cease  altogether,  and  as  a  consequence  sleep 
follows.  A  very  plausil)le  theory  of  the  causation  of  sleep  is  that 
advanced  by  Dr.  Cappie,^  who  holds  that  the  molecular  activity  of 
the  cerebral  cells  is  diminished  through  less  blood  being  supplied 
to  them  by  the  capillaries,  and  that  consequently  the  brain  occupies 
less  space.  But  inasmuch  as  the  brain-case  must  be  full,  the  veins 
of  the  pia  mater  become  proportionally  distended,  the  effect  of 
which  is  that  although  the  absolute  quantity  of  blood,  and  conse- 
(][uently  the  pressure  remains  the  same,  the  direction  of  the  pres- 
sure is  modified,  being  less  from  within  and  more  on  the  surface  of 
the  brain,  the  latter  or  the  altered  direction  of  the  pressure  giving 
rise  to  sleep.  This  view  is  confirmed  V)y  the  researches  of  Dur- 
ham,* by  whom  it  was  shown  that  the  brain  during  sleep  is  in  an 
essentially  bloodless  condition,  that  not  only  the  quantity  of  the 
blood,  but  the  velocity  of  its  flow  is  diminished,  and  also  by  the 

iZeits.  f.  Eat.  Med.,  Band  xxxii.,  s.  214,  1868.  s^Arcliiv,  1875,  s.  468. 

3  The  Causation  of  Sleej),  Kdinlmr<;li,  1882. 
*  Guy's  Hospital  Reports,  3d  ser.,  Vol.  vi. 


680  THE  NERVOUS  SYSTEM. 

observations  of  Dr.  Hughlings  Jackson/  who  showed  by  ophthal- 
moscopic examination  that  the  optic  disc  during  sleep  was  whiter, 
the  arteries  smaller,  the  veins  larger  and  the  adjacent  parts  of  the 
retina  more  ana?mic  than  during  the  waking  state. 

Among  the  conditions  favoring  sleep  may  be  mentioned  the  ces- 
sation of  stimuli,  diminished  excitability  of  the  tissues  in  response  to 
stimuli,  and  the  quality  of  the  blood.  The  influence  exerted  by  the 
latter  condition  is  well  shown  by  the  well-known  experiment  of 
iNlosso,^  in  which  the  blood  of  a  dog-  tired  out  with  running;  was 
transfused  into  that  of  one  who  had  been  resting,  the  effect  being 
that  the  dog  at  once  showed  signs  of  fatigue  and  soon  went  to  sleep. 

The  amount  of  sleep  required  is  affected  by  so  many  conditions, 
such  as  age,  temperament,  habit,  mental  and  physical  exhaustion, 
that  it  is  absurd  to  lay  down  any  rule  upon  the  subject.  In  this 
respect,  as  in  all  others  physiological,  nature  is  our  best  guide.  The 
mere  fact  that  some  individuals  get  along  with  only  four  or  five 
hours'  sleep  without  their  health  being  aflPected  is  no  argument  what- 
ever that  such  a  small  amount  of  sleep  is  only  required  and  should 
suffice  for  every  one.  Xo  greater  mistake  is  made,  and  that  so 
often,  by  students  of  medicine,  physicians,  and  literary  men  gener- 
ally, than  to  rob  themselves  of  their  natural  sleep,  at  the  cost  of 
broken-down  health  and  lost  spirits,  too  often  never  to  be  regained. 
It  will  be  observed  that  up  to  the  present  moment,  in  our  expo- 
sition of  the  functions  of  the  encephalon,  we  have  endeavored  to 
offer  only  wliat  appears  to  us  to  be  well-established  anatomical  and 
physiological  facts,  merely  mentioning,  or  not  referring  at  all,  to  the 
remaining  portions  of  the  encephalon,  whose  functions  have  not  as 
yet  been  made  out.  It  is  needless  to  say,  however,  that  whether  or 
no  the  different  parts  of  the  encephalon  and  the  different  convolu- 
tions of  the  hemispheres  really  possess  the  functions  assigned  to 
them,  that  the  phenomenon  of  consciousness  is  thereby  in  no  wise 
explained.  Admitting,  for  example,  that  the  cuneus  is  the  center 
of  vision,  and  that  the  exact  nature  of  the  molecular  changes  occur- 
ring in  its  cells  when  the  perception  of  sight  is  experienced  were 
understood,  we  would  be  still  unable  to  understand  how  the  vibra- 
tions of  light  falling  upon  the  retina  give  rise  ultimately  to  visual 
perceptions — that  is,  the  manner  in  which  a  physical  impression  be- 
comes a  conscious  perception.  In  the  present  state,  at  least,  of  the 
development  of  our  consciousness  it  appears  impossible  even  to  con- 
ceive of  how  the  gap  between  matter  and  mind,  the  objective  and  sub- 
jective, can  ever  be  bridged  over.  We  can  say  that  the  brain  is  the 
organ  of  the  mind,  even  that  it  converts  heat  into  thought,  but,  as 
viewed  subjectively,  the  functions  of  the  brain  are  synonymous  with 
mental  operations.  The  phenomenon  of  consciousness  must  be 
studied,  not  only  objectively  by  the  physiologist,  but  subjectively  by 
the  psychologist ;  nevertheless,  too  much  stress  must  not  be  laid  upon 

n^oval  I^ondiin  Ojilith.  IIosp.  Keports. 
2  1>u"Boi.s  Keymond,  Arcliiv,  18'J0,  s.  89. 


MATTER  AM)  MIXD.  681 

the  distinction  of  matter  and  mind,  of  object  and  subject,  as  made 
by  the  metaphysician,  since  the  existence  of  matter  or  mind,  as 
shown  by  ultimate  analysis,  is  only  an  inference.  We  are  conscious 
of  the  perceptions  of  hardness,  roundness,  Aveight,  extension,  etc., 
and  we  infer  the  existence  of  something  underlying  these  qualities, 
which  we  call  matter,  and  which  produces  in  us  these  sensations. 
We  are  directly  conscious  of  these  perceptions,  not  of  the  matter 
supposed  to  cause  them.  The  existence  of  matter  being,  therefore, 
an  inference  from  our  consciousness,  it  is  impossible  to  say,  not 
knowiup;  auvthinor  whatever  about  its  nature,  Avhether  it  is  akin  to 
mind  or  not.  On  the  otlier  liand,  supjiose  that  matter  does  exist,  it 
is  certain  that  the  various  modes  of  motion  ordinarily  known  as 
heat,  light,  sound,  etc.,  are  transformable  in  us  into  equivalent 
modes  of  consciousness,  and  we  infer  from  these  modes  of  motion 
the  existence  of  something,  the  mind  underlying  these  modes  of 
consciousness,  but  of  whose  nature  we  know  just  as  little  as  that  of 
the  matter,  from  the  effects  of  which  its  existence  is  inferred.  The 
idealist  may  argue  that  there  is  no  such  thing  as  matter  apart  from 
mind,  since  material  forces  are  only  cognizable  as  modes  of  con- 
sciousness, and  the  materialist  may  argue  that  there  is  no  mind  apart 
from  matter,  that  the  modes  of  consciousness  are  material,  since 
what  exists  in  us  as  consciousness  is  transformable  into  modes  of 
motion,  but  it  is  evident  that  the  forces  of  the  inner  are  correlated 
with  those  of  the  outer  world,  the  forces  of  the  outer  with  those  of 
the  inner  world,  that  if  we  begin  with  mind  we  end  with  matter,  if 
with  matter  we  end  in  mind ;  matter  and  mind  being  merely  sym- 
bols of  the  unknown  reality  underlying  both.^ 

'  Herbert  Spencer,  First  Principles,  p.  558. 


chaptp:r  XXXV. 

THE    NERVOUS    SYSTEM.— {Continued.) 

SYMPATHETIC  NERVOUS   SYSTEM. 

The  sympathetic  system  of  nerves,  or  the  system  of  organic 
vegetative  life,  also  known  as  the  trisplanchnic  nerve,  great  inter- 
costal nerve,  etc.,  consists  of  a  double  chain  of  symmetrically  dis- 
posed ganglia  extending  the  entire  length  of  the  vertebral  column, 
which,  gradually  converging,  terminates  finally  as  a  single  ganglion, 
the  ganglion  impar,  resting  upon  the  coccyx.  While  there  is  no 
doubt  as  to  the  manner  in  which  the  double  ganglionated  cord  of 
which  the  sympathetic  consists  ends,  it  has  not  as  yet  been  made 
out  exactly  how  it  begins  ;  the  observation  of  Ribes^  that  it  begins 
as  it  ends,  in  a  ganglion  impar  situated  upon  the  anterior  commu- 
nicating artery,  not  having  been  confirmed  by  other  anatomists. 
Intercommunicating  with  the  nerves  of  the  cerebro-spinal  system, 
and  giving  off  during  its  course  numerous  branches  forming  intricate 
plexuses,  such  as  the  cardiac,  solar,  and  hypogastric,  the  sympathetic 
nerves,  as  a  general  rule,  follow  the  course  of  the  great  blood  ves- 
sels, entwining  the  latter  as  the  ivy  the  oak,  to  supply  the  viscera 
of  the  great  cavities  of  the  body,  etc. 

The  nerves  of  the  sympathetic  system  are  usually  much  smaller, 
softer,  and  less  distinctly  seen  than  those  of  the  cerebro-spinal  sys- 
tem, present  a  grayish  aspect,  and  adhere  closely,  by  connective 
tissue,  to  contiguous  structures.  While  consisting  of  medullated 
nerve  fibers,  they  are  largely  composed  of  the  pale  gray,  gelatinous 
fibers  of  Eemak,  the  latter  resembling  eml)ryonic  nerve  fibers  and 
the  nerve  fibers  developed  in  the  reunion  of  nerves.  The  ganglia 
of  the  sympathetic,  whether  of  the  ganglionated  cord  or  its  branches, 
do  not  differ  essentially  in  structure  from  the  ganglia  of  the  pos- 
terior roots  of  the  spinal  nerves,  large  root  of  the  fifth,  trigeminal, 
glosso-pharyngeal,  pneumogastric,  etc.  They  consist  of  a  mass  of 
nerve  cells  smaller  than  those  of  the  spinal  ganglia,  imbedded  in  a 
stroma  of  connective  tissue,  which  is  traversed  by  nerve  fillers,  the 
whole  being  enclosed  by  a  tightly  adherent  membrane  continuous 
M'ith  the  sheath  of  the  nerves  upon  which  the  ganglia  occur,  the 
latter  looking  like  so  many  grayish-white  or  reddish-gray  swellings 
or  knots.  The  main  ganglia  and  branches  of  the  sympathetic  being 
situated  in  the  cervical,  thoracic,  abdominal,  and  pelvic  regions,  we 
may  begin  in  our  necessarily  brief  account  of  the  physiological  re- 
lation of  the  parts  involved  with  the  ganglia  of  the  cervical  region, 
and  first  with  the  superior  cervical  ganglion  (Fig.  394). 
'Mem.  de  la  Soc.  Med.  d' Emulation,  Tome  viii.,  yi.  G06. 


SYMPA  THETIC  XEE  VO US  SYSTEM.  Q^'^ 

Fig.  394. 


pi 


ofthe  .synipkthetic.  6.  SuperioVVervica/yairfflim,'''"--"V''''  ■\"""ng"a'-  •^,  5,  5.  Chain  of  Kanglia 
8.  Nerve  of.Iacobson.  9.  Two  fiJaments  tiumlCfJi  /^'■»"<-t*^\f'-"m  t'^s  ganglion  to  the  caroUd 
mem  f?' n  f?"^"°"-  ^'^-  ^^"'"^  oculfexter^^s'  "n"'  r,  iuhfln?,v'''  spheno-pafatine  and  toe  other 
r>  sr i  1?  '^1  r'*"""  '•"•"  t^ommunis  and  a  sensor v  h  n.  m  ^f„f.?^''''°'  "Teiving  a  motor  tila- 
1-'.  i^plieuo-palatme  ganglion.  1.3.  Otic  eanVlionVaT,  ^"^  *'*^  "'"'"=''  l>ranch  ofthe  fifth 
maxillary  ganglion.  16,  17.  SunerW  far  ."^- i  -  ^'"«''?' I".'""^'*  "'"">e  fifth  nerve  1.5  Si  hi 
Recurrent  laryngeal  nerm  21  •«  f  fn". "f  L'',  "^^'V'-  H'  K-^'ernal  laryngeal  nerve  io  20 
ing  ti  aments  to  the  superior  cervicaT  sv4^  Xh  '''^"'''r  "^  *'',^  "PP^"-  fo"  cervicafnerves  .end! 
and  sixth  cervical  nerves,  sending  .^^}^^!:\,^^^,  ^^i^'S^^"^^^ 


684  THE '  NEE  VO  US  SYSTEM. 

branches  of  the  seventh  and  eighth  cervical  and  tlie  first  dorsal  nerves,  sending  filaments  to  the 
inferior  cervical  ganglion.  27.  Middle  cervical  ganglion.  28.  Cord  connecting  the  two  ganglia. 
29.  Inferior  cervical  ganglion.  30,  31.  Filaments  connecting  this  with  the  middle  ganglion.  32. 
.Snperior  cardiac  nerve.  33.  Middle  cardiac  nerve.  34.  Inferior  cardiac  nerve.  35,  35.  Cardiac 
plexus.  36.  (janglion  of  the  cardiac  plexus.  37.  Xerve  following  the  right  coronary  artery.  38, 
38.  Intercostal  nerves,  with  their  two  filaments  of  communication  with  the  thoracic  ganglia.  39, 
40,41.  Great  splanchnic  nerve.  42.  Lesser  splanchnic  nerve.  43,43.  Solar  plexus.  44.  Left  pneu- 
mogastric.  45.  Eight  pneumogastric.  4G.  Lower  end  of  the  jihrenic  nerve.  47.  Section  of  the  right 
hronchus.  48.  Arch  of  the  aorta.  49.  Right  auricle.  50.  Right  ventricle.  51,  .52.  Pulmonarv 
artery.     53.  Right  half  of  the  stomach.    54.  .Section  of  the  diaphragm.     (Sappey.) 

The  superior  or  first  cervical  ganglion,  lying  upon  the  rectus 
major  muscle  opposite  the  second  and  third  cervical  vertebrae  and 
behind  the  internal  carotid  arterv,  is  connected  bv  intervening;  fila- 
ments  ^vith  the  upper  four  spinal  nerves — the  ganglia  of  the  glosso- 
pharyngeal, pneumogastric,  and  the  hypo-glossal  nerves.  In  addi- 
tion to  its  cord  of  communication  with  the  second  cervical  ganglion, 
the  superior  cervical  gives  off  an  ascending  branch,  vascular  and 
pharyngeal  branches,  and  the  superior  cardiac  nerve.  The  ascend- 
ing branch  accompanying  the  internal  carotid  artery  through  the 
carotid  canal  divides  into  two  branches,  which,  subdividing  and 
communicating  with  each  other  around  the  artery^  so  form  the  caro- 
tid plexus.  From  the  latter  are  given  off  filaments  to  the  abducens 
nerve,  and  the  deep  petrosal  which  passes  to  the  spheno-palatine,  or 
Meckel's  ganglion,  the  latter  connected  with  the  spinal  system  by 
the  superior  maxillary  and  great  petrosal  nerve.  Continuing  up- 
ward around  the  artery,  on  reaching  the  cavernous  siiius,  the  sym- 
pathetic plexus  l^ccomes  then  the  cavernous  plexus,  an  impor- 
tant one,  since  it  communicates  with  the  semilunar  oano-lion  and 
ophthalmic  branch  of  the  trigeminal  with  the  ophthalmic  ganglion, 
the  latter  connected  Avith  tlie  spinal  system  by  the  ophthalmic  and 
oculo-motor  nerves,  and  with  the  oculo-motor  and  pathetic  nerves. 
From  the  carotid  and  cavernous  plexuses  fine  filaments  are  also 
given  off  which  entwine  themselves  around  all  the  branches  of  the 
internal  carotid  artery.  The  vascular  branches  of  the  superior 
cervical  ganglion  form  plexuses  upon  the  internal  carotid  artery 
and  its  branches.  By  the  plexuses  on  the  internal,  maxillary,  and 
facial  arteries  the  syin])athetic  communicates  with  the  otic  and  sub- 
maxillary ganglia  respectively,  the  otic  ganglion  being  connected 
with  the  spinal  system  by  the  small  petrosal,  the  submaxillary 
ganglia  by  the  chorda  tympani.  The  pharyngeal  branches,  two  or 
three  in  number,  descending  to  the  side  of  the  pharynx,  together 
with  branches  from  the  glosso-pharyngeal  and  pneumogastric  nerves, 
form  the  pharyngeal  plexus,  which,  as  we  have  already  mentioned, 
supplies  the  mucous  membrane  and  constrictor  muscles  of  the  pliar- 
ynx.  The  superior  cardiac  nerve,  derived  from  the  first  cervical 
ganglion  and  from  the  cord  below  it,  descends  behind  the  great 
blood  vessels  of  the  neck,  and  entering  the  thorax  passes  on  the 
right  side  either  in  front  of  or  behind  the  subclavian  artery,  thence 
along  the  innominate  to  tlie  l)ack  of  tlie  arch  of  the  aorta,  to  end 
in  the  cardiac  plexus.  ( )n  the  left  side  the  nerve  follows  the  carotid 
artery  in  its  course  to  the  cardiac  plexus. 


CARDIAC  XERVES.  685 

The  superior  cardiac  nerve  commimicates  with  the  pneiimoprastric, 
aud  gives  off  iilanients  to  the  inferior  thyroid  artery.  The  middle, 
or  second  cervical  ganglion,  resting  upon  the  inferior  thyroid  artery, 
aud  situated  opposite  the  fifth  cervical  vertebra,  is  connected  with 
the  third  cervical  ganglion  by  several  branches,  and  gives  off  fila- 
ments to  the  fifth  and  sixth  spinal  nerves,  branches  which  follow 
the  inferior  thyroid  arteiy  to  the  thyroid  body,  and  the  middle  car- 
diac nerve.  The  latter,  as  it  descends  the  neck,  receives  filaments 
from  the  superior  and  inferior  cardiac  and  pneumogastric  nerve, 
and  ends  in  the  cardiac  plexus.  Occasionally  the  middle  cervical 
ganglion  is  indistinct,  or  even  absent  ;  in  such  cases  it  appears  to  be 
fused  "vvith  the  inferior  or  third  cervical  ganglion.  The  latter,  sit- 
uated behind  the  vertebral  artery  and  between  the  transverse  pro- 
cess of  the  last  cervical  vertebra  and  the  first  rib,  gives  off,  in  ad- 
dition to  the  branches  going  to  the  first  thoracic  ganglion,  branches 
to  the  seventh  and  eighth  spinal  nerves,  to  the  vertebral  artery, 
and  the  inferior  cardiac  nerve,  M'liich,  after  receiving  filaments 
from  the  middle  cardiac  and  inferior  laryngeal  nerves,  and  some- 
times from  the  first  thoracic  ganglion,  terminates  in  the  cardiac 
plexus.  Occasionally  the  inferior  cardiac  nerve  of  the  left  side 
becomes  blended  with  the  middle  cardiac  nerve.  The  three 
cardiac  and  pneumogastric  nerves,  together  wdth  branches  from 
the  first  thoracic  ganglion,  form  the  cardiac  plexus.  The  latter 
situated  behind  and  beneath  the  arch  of  the  aorta,  gives  off 
branches  which,  accompanying  the  coronary  arteries,  constitute 
the  coronary  plexuses. 

While  the  cervical  portion  of  the  sympathetic  consists,  as  we 
have  seen,  of  three  ganglia,  etc.,  the  thoracic  portion  consists  of  usu- 
ally twelve  ganglia,  resting  upon  the  heads  of  the  ribs  and  covered 
by  the  pleura.  The  first  thoracic  ganglion,  as  already  mentioned, 
is  connected  with  the  last  cervical,  and  the  last  thoracic  with  the 
first  lumbar,  the  connecting  cord  of  the  latter  passing  through 
the  diaphragm.  Each  thoracic  ganglion  usually  gives  off  two 
narrow  cords,  the  rami  communicantes,  which  pass  to  the  nearest 
intercostal  nerve.  The  upper  six  thoracic  ganglia  give  off,  also, 
branches  to  the  aorta,  intercostal  blood  vessels,  and  the  arsopha- 
geal  and  pulmonary  plexuses  of  the  pneumogastric  nerve.  The 
lower  six  thoracic  ganglia  give  off,  in  addition  to  the  branches 
going  to  the  aorta,  branches  which  go  to  form  the  three  splanch- 
nic nerves.  The  great  splanchnic  nerve,  deriving  its  roots  from 
the  sixth  to  the  tenth  thoracic  ganglia,  inclusive,  perforates  the 
cms  of  the  diaphragm,  and  terminates  in  the  semilunar  ganglion. 
The  small  splanchnic  nerve,  deriving  its  roots  from  the  tenth 
and  eleventh  thoracic  ganglia,  passes  through  the  diaphragm 
with  the  preceding  nerve,  and  terminates  in  the  solar  plexus. 
The  third  splanchnic,  sometimes  absent,  coming  from  the  twelfth 
thoracic  ganglion,  pierces  the  diaphragm,  and  terminates  in  the 
renal  plexus, 


686 


THE  SEEVOUS  SYSTEM. 


The  solar  plexus  (Fig.  395),  so  called  on  account  of  the  numer- 
ous filameuts  radiating  from  it,  is  situated  behind  the  stomach  and 
in  front  of  the  aorta  and  crura  of  the  diaphragm,  and  surrounding 
the  cceliac  and  commencement  of  the  superior  mesenteric  artery, 
extends  to  between  the  suprarenal  bodies.  It  consists  of  an  intri- 
cate mixture  of  nerves  and  ganglia  ;  among  the  former  may  be  men- 


FiG.  ?.9o. 


IS  21  2 


Solar  plexus.     (Hirschfeld.) 

tioned  the  great  and  small  splanchnics,  as  well  as  filaments  from 
the  pneumogastric  nerve  ;  among  the  latter  the  semilunar  ganglion 
(Fig.  396),  so  called  on  account  of  its  being  situated  on  each  side 
of  the  plexus,  at  the  side  of  the  coeliac  and  superior  mesenteric 
arteries.  From  the  solar  plexus  emanate  numerous  plexuses, 
named  after  the  vessels  around  which  the  branches  entAvine  them- 
selves, as  follows  :  the  phrenic,  coronary,  hepatic,  splenic,  supra- 
renal, renal,  and  spermatic,  superior  mesenteric,  and  aortic  plexus. 
The  aortic  plexus,  descending  upon  the  aorta  from  the  solar  plexus,  of 
which  it  is  the  continuation,  after  giving  off  the  inferior  mesenteric 
plexus  terminates  below  in  the  hypogastric  plexus.  The  latter  very 
intricate  plexus,  situated  between  the  common  iliac  blood  vessels, 
extends  downward  as  the  inferior  hypogastric  plexus  on  each  side 
of  the  rectum,  and  after  receiving  branches  from  the  lower  lumbar 
and  sacral  ganglia,  the  lower  two  or  three  sacral  nerves,  and  the  in- 
ferior mesenteric  plexus,  gives  off  the  vesico-prostatic,  or  the  vesico- 
vaginal and  uterine  plexuses,  according  to  the  sex  respectively. 

The  lumbar  portion  of  the  sympathetic  (Fig.  396)  consists  of  four 
or  five  ganglia  situated  at  the  sides  of  the  vertebne  which  communi- 
cate with  each  other,  and  with  the  adjacent  lumbar  nerves,  as  in  the 
case  of  the  thoracic  ganglia,  and  give  off  branches  to  the  aortic  and 


HYPOGASTRIC  PLEXUS. 


687 


1  i;.i  n^iviUv  four  in  number,  are 

hvpogastric  plexus.    .Tl«,-^".l  ^"^^  t-e '  ^rf  .ive  off  branches  to 
Jnected  likewise  ...h  "- .^'^^       .uToncUho  siugle  eoce>-gea 
the  hypogastno  plex«^;     A  ^^^-     ^^^„,  similar  to  those  otte 
ganglion  ov  ganglion  ""1«  -;;   '^   "o  svmpa<hetie  nerves.     ^^  h.le 
«icnll  ganglia,  is  common  to  tlu   tuo  ..     i 

Fio.  39C. 


K^ 


Lower  end  ot  the  ngUt  l'n!-"°^"|'       splanchnic  nerve.    U.  \*-J-^^^  IZ^^M-a     IS.  superior  mesen- 
J^rve     i:^.  Lower  cud  of  the  lesser  spiJ.  ^.^.^^^^  ^j^g  luniljar  gaugii^^^^^^  i  ^^^^^^^1 

The  four  lumbar  gangha.^  ^^.JtVlimbafp'exus.    20.  luterior  niesentenc^plexu>     -^  ^^^^.^^ 


688  THE  NERVOUS  SYSTEM. 

coDsiderable  difference  of  opinion  prevailed  at  one  time  as  to  whether 
the  gantrha  of  the  sympathetic  were  sensitive,  there  is  no  doubt  on 
this  point  at  present ;  mechanical  or  chemical  irritation  of  the  tho- 
racic or  semilunar  ganglia  in  dogs,  calves,  and  rabbits,  having  been 
shown  l)y  Flourens/  Brachet,-  Muller,^  Longet,^  etc.,  to  give  rise 
to  pain.  The  sensibility  of  the  sympathetic,  however,  is  far  from 
acute,  being  indeed,  dull,  as  compared  with  that  of  the  cerebro- 
spinal system.  As  regards  the  excitability  of  the  s}nipathetic,  it 
has  also  been  shown  by  JNIuller,''  Longet,''  and  others,  thatj  stimula- 
tion of  the  ganglia,  splanchnic  nerves,  etc.,  by  electricity  or  chem- 
ical irritants  causes  contractions  of  the  muscular  coat  of  the  intes- 
tines. Inasmuch,  however,  as  the  muscular  coat  of  the  intestines 
consists  of  unstriated  muscular  tissue,  the  contraction  does  not 
immediately  follow  the  stimulation,  as  in  the  case  of  the  cerebro- 
spinal system  and  striated  muscle,  and  further,  the  contraction  lasts 
longer,  another  characteristic  of  the  effect  of  stimulating  unstriated 
muscular  tissue.  Since,  however,  the  most  important  effects  follow- 
ing stimulation  of  the  sympathetic  can  be  obtained,  as  we  shall  see 
presently,  by  the  stimulating  of  the  cerebro-spinal  system,  and  as 
the  ganglia  and  fibers  of  the  sympathetic  lose  their  properties 
through  atrophy,  degeneration,  etc.,  when  separated  from  the 
cerebro-spinal  system,  with  which  Ave  have  just  seen  they  are  in- 
variably connected,  as  shown  by  the  ex})eriments  of  Bernard," 
Courvoisier,^  etc.,  it  would  appear  that  whatever  properties  are  pos- 
sessed by  the  sympathetic  are  due  to  its  connections  with  the  cere- 
bro-spinal system.  That  the  sym])athetic  system,  in  fact,  is  only 
an  appendage  of  the  cerebro-spinal  system,  is  not  only  shown  by 
the  facts  just  referred  to,  but  also  by  the  very  important  one  in  this 
connection  that  in  the  lowest  fishes,  amphioxus,  myxine,  the  sym- 
pathetic system  is  undeveloped  or  absent,  which  would  not  be  the 
case  were  its  presence  an  indispensable  element  in  the  nervous  or- 
ganization of  a  vertebrate.  Up  to  the  beginning  of  the  eighteenth 
century  it  may  be  said  that  absolutely  nothing  had  been  definitely 
established  with  regard  to  the  functions  of  the  sympathetic  system. 
In  1712,  however,  Pourfour  du  Petit  ^  divided  the  cervical  sym- 
pathetic in  a  dog,  repeating  the  experiment  in  1725,  in  the  presence 
of  Winslow  and  Senac,  and  called  attention  among  its  consequences 
to  the  redness  and  injected  condition  of  the  conjunctiva,  the  con- 
tracted  condition   of  the   pupil,"'  etc.     The  conclusion   drawn  by 

^  Reclic'irhes  experimentale  sur  les  proprietes  et  les  functions  du  systeme  nerveux, 
p.  230.     Paris,  1842. 

2  Keclieirlies  experimentale  sur  les  functions  du  svsteme  ganglionaire,  p.  305. 
Bruxelles,  1834.  ^Mnller,  Piiysiology,  Vol.  i.,  p. '712.     London,  1840. 

*  Physiologic,  Tome  iii.,  p.  593.     Paris,  1809.  ^0\).  cit.,  j).  713. 
^Op.  cit.,  p.  595,  Systeme  Nerveux,  Tome  ii.,  p.  568.     Paris,  1842. 
'Journal  de  la  pliysiologie,  Tome  v.,  p.  407.     Paris,  1862. 

*  Archiv  of  Micros.  Anat,  Band  ii.,  s.  30.  •  Bonn,  1886. 
^Memoires  de  r  Acad,  des  Sciences,  p.  1.     Paris,  1827. 

^''Due  to  the  unopposed  action  of  tlie  tliird  pair  (jf  nerves  supplying  the  circular 
muscular  fibere  of  tlie  iris. 


VASOMOTOR  NERVES.  689 

Petit  from  his  experiments  and  observations  was  that  tlio  intercos- 
tal nerve,  as  the  sympathetic  Avas  then  called,  "  furnished  spirits  to 
the  conjunctiva,  to  the  glands,  and  to  the  vessels  "which  are  found 
in  these  parts,  the  relaxation  of  the  parts  being  so  evident  that 
there  almost  always  ensues  a  slight  inflammation  of  the  conjunctiva 
due  to  the  swelling  of  the  vessels ; "  that  the  influence  exerted  by 
the  sympathetic  was  propagated  from  below  upward  toward  the 
brain,  and  not  from  the  brain  downward,  as  was  often  supposed. 
Notwithstanding  the  importance  of  the  conclusions  correctly  drawn 
from  his  experiments  by  Petit  with  reference  to  the  influence  of  the 
sympathetic  upon  the  circulation,  nutrition  of  the  eye,  etc.,  nearly 
a  century  passed  without  anything  further  being  added  to  our 
knowledge  of  the  functions  of  the  sympathetic.  In  1812,  however, 
Dupuy,  of  Alfort,  having  removed  the  superior  cervical  ganglion  in 
horses,  called  attention  among  the  effects  of  the  experiment,  partic- 
ularly to  the  injected  condition  of  the  ocular  conjunctiva,  and  to 
the  elevation  of  temperature  in  the  ears,  head,  and  neck,  which 
were  bathed  in  sweat ;  the  general  conclusion  arrived  at  by  Dupuy  ' 
l)eing  that  the  sympathetic  exercises  a  great  influence  on  the  nutri- 
tive functions.  A\  hile  Petit  described  the  effects  of  cutting  the 
cervical  sympathetic,  and  Dupuy  of  removing  the  superior  cervical 
ganglion,  neither  of  these  experimenters  offered  any  definite  explana- 
tion of  the  hyperemia  noted  in  both  cases,  nor  Dupuy  of  the  rise 
in  temperature 'in  the  latter  one.  Indeed,  the  true  explanation  of 
the  phenomena  at  that  period  would  have  been  impossible,  the 
structure  of  the  arteries  not  yet  being  understood. 

Even  though  Valentin-  had  shown,  in  18')9,  that  the  arteries 
contracted  in  response  to  stimulation  of  the  nerves  distributed  to 
them,  it  was  not  admitted  that  the  middle  coat  of  the  arteries  con- 
tained muscular  fibers  until  1840,  when  such  was  actually  demon- 
strated to  be  the  case  beyond  doubt  by  Henle.^  During  the  same 
year,  Stilling,^  like  Henle,  was  led  to  the  conclusion  that  there  ex- 
isted nerves  comparable  to  those  distributed  to  the  muscles  gener- 
ally, which  act  upon  the  blood  vessels,  either  directly  or  reflexlv, 
and  which  he  called  "  vasomotor  nerves."  In  1852  Brown- 
Sequard  '"  divided  the  cervical  sympathetic  on  one  side  in  rabbits, 
and  called  attention,  as  Bernard ''  had  done  in  the  previous  year,  to 
the  hyperpemia  and  elevation  of  temperature,  often  amounting  to  as 
much  as  11°  F.  (6.1°  Cent.)  on  the  corresponding  side  of  the  head 
and  ear,  and  for  the  first  time  gave  the  true  explanation  of  the  phe- 
nomena in  attributing  the  rise  in  temperature  of  the  parts  aflected 

1. Journal  de  C'orvisart  et  Leroux,  ISIH,  Tome  xxxvii.,  p.  340.  Meckel's 
Archiv,  1818,  Band  iv.,  s.  105. 

^Dq  Functionibus  Nervorum  Cerebralium  ct  Nervi  Svnipatlietici,  p.  153. 
Bernas  1839. 

''Wochenschrift  fiir  die  gesammte  Ilcilknnde,  lS-10,  Xo.  29,  s.  329. 

* Eecherches  path,  et  med.  pratkpies  sur  1' Irritation.     Leipziji-,  1S40. 

^The  Medical  Examiner,  New  Series,  Vol.  viii.,  p.  489.  Phila(lel|)liia,  August, 
1852. 

^Comptes  rendus  de  la  society  de  biologic,  Tome  iii.,  p.  163.     Paris,  1851. 
44 


690  THE  NEB  VO  US  SYSTEM. 

to  the  supply  of  blood  being  increased  through  the  dilatation  of  the 
blood  vessels,  and  by  showing  that  while  section  of  the  sympathetic 
in  paralyzing  the  muscular  coats  of  the  arteries  permits  of  their 
dilatation,  electrical  stimulation  of  the  central  cut  end  of  the  sym- 
pathetic causes  their  contraction  again,  and  with  the  latter  the 
restoration  of  the  parts  to  their  normal  condition.  To  Brown- 
S6quard  must  be  accorded,  therefore,  the  discovery,  not  exactly  of 
vasomotor  nerves,  since  the  existence  of  such  had  been  previously 
indicated  by  Henle  and  Stilling,  but,  more  especially,  of  the  vaso- 
constrictor nerves  of  the  cervical  sympathetic,  and  of  their  mode 
of  action  in  influencing  the  calibre  of  the  blood  vessels,  temperature, 
etc.,  of  the  parts  to  which  the  latter  are  distributed.  It  should  be 
mentioned,  however,  injustice  to  Bernard,  that  three  months  after 
Brown-Sequard's  discovery,  and  without  being  aware  of  it,  Bernard' 
offered  the  same  explanation  of  the  experiments  performed  by  him 
during  the  previous  year  (1851),  but  at  that  time  by  him  incorrectly, 
interpreted. 

The  calibre  of  the  veins  as  well  as  that  of  the  arteries  is  regu- 
lated by  vaso-constrictor  nerves.  Thus,  for  example,  stimulation 
of  the  peripheral  cut  end  of  the  splanchnic  nerve  causes  contraction 
of  the  portal  vein  "  and  of  the  sciatic  nerve,  the  femoral  artery  being 
ligated,  contraction  of  the  superficial  veins  of  the  limb.^  The  modi- 
fication in  calibre  of  blood  vessels  due  to  the  action  of  vaso-con- 
strictor nerves  can  be  shown  not  only  by  the  methods  just  men- 
tioned, but  also  by  measuring  the  amount  of  blood  that  flows  from 
a  vein  before  and  after  stimulation  of  the  vaso-constrictor  nerve 
supplying  it,  the  outflow  being  much  less  in  the  latter  than  in  the 
former  case.  Another  method  also  made  use  of  is  based  upon  the 
fact  that  stimulation  of  a  vaso-constrictor  nerve  in  contracting  the 
blood  vessels  of  a  limb  will  cause  a  rise  of  l)lood  pressure  in  that 
limb,  the  general  blood  pressure  remaining  however  unaltered,  as 
shown  by  means  of  a  manometer  connected  with  the  opposite  limb. 

Contractions  of  the  blood  vessels  in  a  limb  as  due  to  vasomotor 
influence  can  also  be  studied  by  means  of  the  plethysmograph  of 
Mosso,  already  described,  the  contractions  of  the  vessels  being- 
shown  by  the  diminution  in  the  volume  of  the  limb  used,  the  latter 
being  indicated  by  the  fall  of  the  recording  lever. 

The  vaso-constrictor  nerves  are  found  not  only  in  the  cervical, 
but  also  in  the  thoracic  and  abdominal  portions  of  the  sympathetic, 
and  in  the  trachial  and  sciatic  plexuses,  supplying  the  upper  and 
lower  extremities.  While  the  vaso-constrictor  nerves  are  given  off 
as  fibers  from  the  cells  of  the  sympathetic  ganglia,  the  latter  are  in 
relation  functionally  with  the  axons  that  pass  from  the  cells  situated 
in  the  cord  at  different  levels,  they  being  in  turn  in  relation  with 
the  axons  that  descend  from  cells  in  the  medulla.     Hence,  division 

ilbid.,  1852,  Tome  i v.,  p.  169. 

2  Mall,  Du  P>()is  Keyinond  Archiv,  1890,  s.  57  ;  1892,  s.  409. 

3Thomp.son,  Dii  Bois  Keyraond  Archiv,  1893,  .s.  104. 


VASOMOTOR  CENTER.  691 

or  stimulation  of  the  peripheral  eut  ends  of  the  medulla  cord,  or  of 
certain  spinal  nerves  in  certain  definite  regions,  is  followed  by  dilata- 
tions or  contractions  of  the  blood  vessels,  just  as  if  the  vaso-con- 
strictor  nerves  had  themselves  been  divided  or  stimulated.^  Thus, 
for  example,  while  the  vaso-constrictor  nerves  of  the  head  are  de- 
rived from  the  superior  cervical  ganglion,  they  can  be  traced  indi- 
rectly by  their  division  and  electrical  stimulation  through  the  cervical 
cord  of  the  sympathetic  to  the  anterior  roots  of  the  first  three  dorsal 
spinal  nerves,  and  thence  into  the  anterior  columns  of  the  cord. 
Further,  according  to  Bernard,^  whilst  the  fibers  distributed  to  the 
dilating  muscular  fibers  of  the  iris,  thereby  causing  dilation  of  the 
pupil,  are  derived  from  the  first  two  dorsal  nerves  (cilio-spinal 
center),  those  distributed  and  influencing  the  caKber  of  the  blood 
vessels  are  derived  from  the  third  dorsal  nerve.  In  the  same 
manner,  the  vaso-constrictor  nerves  supplying  the  blood  vessels  of 
the  upper  extremity,  while  emanating  from  the  first  thoracic  ganglion, 
are,  functionally,  derived  from  the  spinal  cord,  passing  off  from  the 
latter  with  the  anterior  roots  of  the  third  to  the  seventh  dorsal 
nerves  inclusive,  and  thence  traversing  the  thoracic  portion  of  the 
sympathetic  and  the  inferior  thoracic  ganglion,  reach  the  brachial 
plexus  by  the  rami  communicantes,  to  be  finally  distributed  with 
the  branches  of  the  plexus,  while  such  of  the  vaso-constrictor  nerves 
as  are  derived  from  the  plexus  itself  are  given  oiF  with  the  anterior 
roots  of  the  cervical  nerves.  The  vaso-constrictor  nerves  supplying 
the  blood  vessels  of  the  abdominal  viscera,  more  especially  the 
splanchnic  nerves,  are  largely  derived  from  the  dorsal  and  lumbar 
portion  of  the  cord  ;  the  latter,  together  with  the  sacral  portion  of 
the  cord,  giving  oiF  fibers  which  pass  through  the  lumbar  and  sacral 
plexuses  to  the  sympathetic,  and  thence  into  the  lower  extremities, 
supphdng  the  blood  vessels  of  the  latter. 

Inasmuch,  then,  as  the  vaso-constrictor  nerves  are  derived  from 
the  spinal  cord,  traversing  more  particularly  its  anterior  columns, 
it  might  naturally  be  supposed  that  all  these  nerve  fibers  at  some 
point  of  the  cord,  the  upper  portion  most  probably,  would  be 
brought  to  a  focus,  so  to  speak,  and  that  stimulation  of  such  a  por- 
tion of  the  cord  would  cause  all  of  the  blood  vessels  to  contract 
and  a  corresponding  rise  in  blood  pressure  and  division  of  the 
same,  a  dilatation  of  the  vessels  and  fall  in  blood  pressure. 

Such  a  focus  or  vasomotor  center  has  indeed  been  found  in 
animals,  not  exactly  by  anatomical  demonstration,  but  by  means  of 
successive  sections  of  the  cord  below  upward,  and  from  above 
downward,  and  localized  in  the  rabbit,  for  example,  by  Owsjani- 
kow  ^  and  Dittmar  ^  in  the  floor  of  the  fourth  ventricle  on  either  side 
of  the  middle  line  just  one  millimeter  behind  the  optic  lobes  and 

'Budge  and  "Waller,  Comptes  rendus,  Tome  xxxiii.,  p.  372.  Paris,  1S51. 
Ludwig  and  Thiry,  Wiener  Sitzungsberichte,  1864,  Band  xlix.  II.  Abtlieilung,  s. 
4'21.     Vulpian,  Leyons  snr  I'Appareil  vaso  njoteur,  p.  189.     Paris,  1875. 

^Comptes  rendus,  Tome  iv.,  p.  383. 

^Ludwig's  Arbeiten,  1871,  s.  210.  "Ebenda,  1873,  s.  110. 


692  THE  NERVOUS  SYSTEM. 

extending  ab^nt  four  millimeters  toward^  the  net  of  the  calamus 
scriptorius. 

From  this  "tonic"  center  emanate  impulses,  which  transmitted 
through  the  anterior  columns  of  the  cord  and  anterior  roots  of  the 
spinal  nerves  pass  thence  to  the  sympathetic  ganglia  and  vaso-con- 
strictor  nerves,  and  through  the  latter  maintain  the  normal  calibre 
of  the  vessels  or  the  vascular  tonus. 

It  has  also  been  established  ^  that  vaso-constrictor  centers  exist 
in  the  spinal  cord,  since  after  section  of  the  cord  the  tonicity  of  the 
vessels  beloAV  the  seat  of  section  is  to  a  certain  extent  still  main- 
tained. That  the  sympathetic  ganglia  contain  also  vaso-constrictor 
centers  is  shown  by  the  fact  of  the  tonicity  of  the  vessels  in  the 
limb  of  a  dog  being  maintained  even  after  removal  of  a  consider- 
able portion  of  the  spinal  cord.-  Tlie  action  of  the  centers  in  the 
cord  and  sympathetic  ganglia  i<  usually  regarded,  however,  as  be- 
ing of  a  secondary  character  to  that  excited  by  the  principal  center 
in  the  medulla. 

Inasmuch  as  the  muscular  fibers  of  the  middle  coat  of  the  blood 
vessels  are  disposed  in  a  circular  manner  at  right  angles  to  the  long 
axis  of  the  vessels,  it  is  not  difficult  to  understand  why  stimulation 
of  the  vaso-constrictor  nerves  is  followed  by  contraction  of  the  ves- 
sels— indeed,  the  disposition  of  the  nervous  and  muscular  fibers 
being  such,  it  can  hardly  be  conceived  how  it  should  be  otherwise, 
and  vet,  strange  as  it  may  appear,  as  first  shown  by  Bernard,'^  there 
are  also  nerves  the  stimulation  of  which  causes  dilatation  of  the 
blood  vessels  instead  of  contraction,  and  which  may,  therefore,  be 
called  vaso-dilator  nerves ;  among  such  may  be  mentioned  the 
chorda-tympani,  the  auriculo-temporal,  the  nervi-erigentes  of  the 
penis ;  stimulation  of  these  nerves  causing  dilatation  of  the  vessels 
of  the  tongue,^  of  the  ear,  and  of  the  corpora  cavernosa  of  the  penis,^ 
respectively.  Though  numerous  explanations  have  been  oifered  of 
the  manner  in  which  the  vaso-dilator  nerves  act,  it  must  be  admit- 
ted that  none  of  them  are  satisfactory,  and  that  it  is  not  yet  under- 
stood how  their  stimulation  causes  dilatation  of  the  blood  vessels. 
Thus,  it  has  been  said  that  the  stimulation  of  a  vaso-dilator  nerve 
causes  the  vein  of  the  part  to  contract,  and  that  in  consequence  an 
obstacle  is  oifered  to  the  passage  of  the  blood  from  the  artery  to  the 
capillary,  which  is  the  cause  of  the  dilatation  of  the  artery.  As  a 
matter  of  fact,  however,  the  vein  does  not  contract,  but  dilates  as 
much  as  the  artery.  It  has  also  been  suggested  that  the  stimula- 
tion of  a  vaso-dilator  nerve  excites  the  activity  of  the  anatomical 
elements  of  the  part  to  which  the  nerve  is  distributed,  the  eifect  of 
which  in  the  case  of  a  salivary  gland,  for  example,  would  be  that 

^Goltz  u.  FroiisberfT,  Pfliiger's  Arcluv,  1874,  s.  46:5. 

2  Golf/,  u.  Ewald,  Pfliifier's  Archiv,  1896,  s.  .'389. 

^Systemc  Xcrvoux,  Tome  ii.,  p.  144.  Pivris,  18.38.  Liquides  de  rOrjj:imisiiie, 
Tome  i.,  ]>.  'M2.  *^'ulpian,  op.  cit.,  p.  1.38. 

•'Eckliard,  UiitersiK-hun<i'cn  nber  die  Erection  des  IViiis  heim  Llunde,  Beitrage 
zur  Anat.  u.  Pliys.,  Abliand.  vii.     Giessen,  18()2. 


VASO-DILATOE  NERVES.  G93 

its  secretory  activity  being  increased  more  blood  would  flow  to  the 
part,  and  the  vessels  would  dilate.  Unfortunately,  however,  for 
this  hypothesis,  in  the  absence  of  all  secretion,  as  in  the  case  of  an 
animal  poisoned  with  atropine,  the  vessels  of  the  tongue  will  still 
dilate  if  the  chorda-tympani  be  stimulated.  Another  explanation, 
a  too  common  one  when  physiological  phenomena  remain  unex- 
plained, is  that  of  inhibition,  it  being  held  that  vaso-dilator  nerves 
inhibit  or  paralyze  the  vaso-constrictor  nerves.  Apart,  however, 
from  the  fact  that  the  dilatation  of  an  arterv  followino;  stimulation 
of  a  vaso-dilator  nerve  is  greater  than  that  following  paralysis  of 
the  vaso-constrictor  nerve,  to  say  that  the  one  nerve  inhilnts  the 
other  is  rather  another  way  of  stating  the  fact  to  be  explained  than 
an  explanation  of  it.  Whatever  value  may  be  attached  to  the  ex- 
planations offered,  whether  they  be  accepted  or  not,  nevertheless, 
there  can  be  no  question  as  to  the  fact  of  there  being  vaso-dilator  as 
well  as  vaso-constrictor  nerves,  and  that  in  all  probability  they 
emanate  from  a  focus  or  center  close  to  the  vasomotor  or  constric- 
tor one,  already  described,  if  not  actually  in  the  latter. 

The  conditions  favoring  vaso-dilator  phenomena  differ  in  many 
respects  from  those  favoring  vaso-constrictor  ones.  Thus  the  vaso- 
dilator nerves  respond  more  cjuickly  to  stimuli  than  the  vaso-con- 
strictor ones,  cold  and  single  induction  shocks  excite  the  vaso-dilator 
nerves,  heat  and  rajiidly  repeated  induction  shocks  excite  the  vaso- 
constrictor nerves,  the  latent  period  of  the  vaso-dilator  nerves  is 
lono^er  than  that  of  the  vaso-constrictor  ones.  These  differences 
are  of  practical  importance,  since  by  bearing  them  in  mind  the  ex- 
perimenter is  enabled  to  determine  whether  a  nerve  contains  vaso- 
constrictor or  vaso-dilator  fibers  or  both  as  obtains,  for  example, 
in  the  case  of  the  sciatic  nerve.  The  vaso-constrictor  or  vaso- 
dilator nerves  can  he  excited  reflexly  as  well  as  directly.  Thus,  as 
first  shown  by  Brown-Sequard  ^  and  Tholozan,  if  a  thermometer  be 
held  in  one  hand  and  the  other  hand  surrounded  by  ice  or  very 
cold  water,  in  a  very  short  time  the  temperature  of  the  hand  hold- 
ing the  thermometer  will  fall,  the  general  temperature  of  the  body, 
however,  remaining  unaffected,  an  effect  which  can  only  be  ex- 
plained on  the  supposition  that  the  impression  due  to  the  cold  is 
transmitted  by  the  sensory  nerves  to  the  spinal  cord  and  thence  re- 
flected by  the  vaso-constrictor  nerves  to  the  vessels  of  the  hand  hold- 
ing the  thermometer.  For  the  same  reason,  according  to  Brown- 
Sequard,'-  if  one  foot  be  immersed  in  water  at  about  5°  C.  (41°  F.) 
the  temperature  of  the  other  foot  will  fall  in  a  few  minutes  perhaps 
3.8°  C.  (7°  F.).  It  has  also  been  shown  by  Vulpian  ^  that  if  the 
sciatic  nerve  be  divided,  as  in  a  dog,  for  example,  and  the  central  end 
stimulated,  not  only  the  vessels  of  the  limb  contract,  but  also  al- 
most all  the  vessels  of  the  body,  the  under  surface  of  the  tongue 
•even  becoming  pale  through  constriction  of  its  vessels.     The  same 

'Journal  de  Brown-Sw^uard,  l<So8,  Tome  i.,  p.  407. 
Mbid.,  p.  502.  3 Op.  cit.,  p.  237. 


694  THE  NERVOUS  SYSTEM. 

reflex  efiect  cau  also  be  induced  by  stimulation  of  almost  any  of  the 
sensory  nerves,  of  the  posterior  roots  of  the  spinal  nerves,  by  irri- 
tation of  the  skin  and  even  by  impulses  set  up  in  the  blood  vessels 
themselves.  As  illustrations  of  reflex  vaso-dilator  action  may  be 
mentioned  the  dilatation  of  the  internal  saphenous  artery  following 
stimulation  of  the  central  cut  end  of  the  dorsal  nerve  of  the  foot, 
and  the  dilatation  of  the  vessel  of  the  ear,  brought  about  through 
excitation  of  the  central  end  of  the  auriculo-temporal  nerve,  or 
through  stimulation  of  the  central  end  of  the  sciatic  nerve. 

From  the  well-known  fact  that  stimulation  of  an  afferent  nerve 
causes  reflexly  sometimes  constriction  and  at  other  times  dilatation 
of  the  blood  vessels,  it  is  inferred  by  many  physiologists  that  spe- 
cial reflex  constrictor  or  "  jiressor  nerves  "  exciting  the  vasomotor 
center  and  causing  a  rise  in  blood  pressure  and  special  dilatus  or 
"  depressor "  fibers  inhibiting  it  ancl  causing  a  fall  in  blood  pres- 
sure may  run  in  the  same  nerve.  Among  such  depressor  fibers 
may  be  mentioned  the  depressor  nerve  of  the  rabbit  whose  influ- 
ence upon  the  circulation  has  already  been  mentioned. 

We  have  already  seen  that  through  the  contractions  and  dilata- 
tions of  the  cutaneous  blood  vessels  the  blood  either  remains  in  the 
deeper  portions  of  the  skin,  or  comes  to  the  surface  of  the  body,  the 
heat  produced  in  the  body,  in  the  one  case  being  retained  within  it, 
and  in  the  other  lost  by  either  radiation,  conduction,  etc.,  and  that 
the  application  of  cold  to  the  general  surface  so  constringes  the 
cutaneous  blood  vessels  that  the  blood  does  not  rise  to  the  surface, 
the  heat  thereby  being  retained,  which  would  otherwise  be  lost. 
That  this  effect  is  due  to  the  impression  made  by  the  cold  being 
transmitted  by  the  sensory  nerves  to  the  spinal  cord,  and  thence  re- 
flected by  the  vaso-constrictor  nerves  to  the  cutaneous  blood  vessels, 
is  shown  by  the  fact  of  a  curarized  hot-blooded  animal  losing  this 
compensating  power,  through  which  the  heat  of  the  body  is  nor- 
mally retained,  even  though  the  latter  be  exposed  to  cold,  the  tem- 
perature of  the  curarized  animal  not  being  a  constant  one,  but,  like 
that  of  the  cold-blooded  one,  varying  within  narrow  limits  with  the 
temperature  of  its  surroundings. 

While  the  functions  that  we  have  attributed  to  the  sympathetic 
nerve  are  those  possessed  by  that  of  animals,  there  is  no  doubt  that 
the  functions  of  the  sympathetic  in  man  are  essentially  the  same. 
The  blush  and  pallor  due  to  emotion  are  familiar  examples  of  reflex 
vasomotor  actions  in  man.  A  number  of  cases  have  been  now  re- 
corded by  J.  W.  Ogle,'  Panas,^  Verneuil,^  Trelat,^  Poitcau,'"'  "W. 
Ogle,''  Bartholow,"  Seeligmullcr,^   Nicati,^  Eulenberg,'"    in   which 

iMed.-Chir.  Trans.,  Vol.  xli.,  p.  397. 
2 Mem.  de  la  Soc.  de  C'hirurfi-ie,  1S()4,  T.  vi.,  p.  383. 
^Bnl.  de  la  Soc.  de  ('iiiniriiie,  1<S()4,  'Jd  .serie,  T.  v.,  p.  1()7. 

^Gaz.  des  hopitaiix,  Paris,  '1  Jiiin,  1SG8.  ^xii^se  de  Paris,  IHOt),  No.  2. 

6Med.-Chir.  Trans.,  Vol.  lii.,  p.  150.     London,  1869. 

'  Quarterly  Journal  of  Psyeli.  Medicine,  Vol.  iii.,  p.  134.     New  York,  1869. 
s  Berlin,  klin.  Wochenschrift,  1872,  No.  2. 
*  La  paralvsie  da  nerfsvrnpatlieti(|ue.      Lausanne,  1873. 
1" Berlin,  klin.  Wochenschrift,  1S()9,  s.  287. 


SYMPATHETIC  AXD  XUTEITIOX.  095 

rise  of  temperature,  unilateral  s^A•eatino:  of  the  neek  and  liead,  hy- 
peremia of  the  conjunctiva,  contraction  of  tlic  pupil,  were  all  ol)- 
served  more  or  less  in  consequence  of  paralysis  of  the  sympathetic 
due  to  pressure  exerted  by  aneurisms,  tumors,  etc.,  while,  according 
to  Vulpian/  lesions  of  the  spinal  cord  may  be  localized  from  the 
vascular  dilatation  developed  in  the  upper  extremities  as  a  conse- 
quence of  the  injury  to  the  vasomotor  nerves  arising  from  it.  It 
may  also  be  mentioned  in  this  connection  that  before  most  of  these 
observ^ations  had  been  made,  Wagner  -  had  noticed  that,  in  the  case 
of  a  decapitated  woman,  powerful  galvanization  of  the  sympathetic 
caused  dilation  of  the  pupil. 

AVhile  the  scope  of  this  work  does  not  permit  of  a  detailed  ac- 
count of  the  influence  exerted  by  the  sympathetic  nervous  system 
upon  nutrition,  it  will  have  been  seen,  no  doubt,  from  what  has 
been  already  said,  that  its  influence  must  be  very  great,  since  the 
amount  of  blood  distributed  to  the  stomach,  intestine,  liver,  kidney, 
etc.,  is  regulated  by  the  vasomotor  nerves.  The  reflex  flow  of  the 
alimentary  secretions  in  response  to  the  excitement  developed 
through  the  presence  of  food,  their  natural  stimulus,  the  great  vas- 
cularity of  the  liver,  spleen,  pancreas,  during  digestion,  is  brought 
about  through  the  influence  of  the  sympathetic  nerves  distributed 
to  these  organs.  The  rapidity  and  extent  with  Avliich  the  absorp- 
tion of  the  digested  food  takes  place  depends  largely  upon  the  con- 
dition of  the  portal  circulation,  as  influenced  by  the  vasomotor 
nerves,  and  more  particularly  by  the  splanchnic.  The  circulation 
of  the  blood,  as  we  have  already  seen,  is  modified  by  the  combined 
eifects  of  the  depressor  and  vasomotor  nerves.  It  is  also  through 
the  intermediate  action  of  the  latter  that  the  cerebro-spinal  centers, 
more  especially  those  of  the  medulla,  influence  the  biliary  and  gly- 
cogenic functions  of  the  liver  and  the  secretion  of  urine  by  the 
kidneys.  That  the  amount  of  blood  circulating  through  the  latter, 
and  therefore  the  amount  of  urine  secreted,  is  influenced  by  the 
vasomotor  nerves  has  already  been  shown  by  means  of  the  oncom- 
eter by  which  it  will  be  remembered  that  the  volume  of  the  kid- 
ney on  the  living  animal  can  be  shown  to  vary  Avith  the  blood  cir- 
culating throngh  it,  the  amount  of  the  latter  being  regulated  l)y 
the  vasomotor  nerve. 

It  may  be  mentioned  in  conclusion  that,  Avhile  vasomotor  nerves 
have  not  as  yet  been  demonstrated  in  the  brain,  it  is  highly  prob- 
able that  such  exist.  Vasomotor  phenomena,  however,  are  pro- 
duced by  impulses  emanating  from  the  brain  as  from  other  parts  of 
the  body  peripheral  to  the  vasomotor  center. 

^Op.  c'it.,  p.  19->.  ^.Journal  de  pliy.siologie,  Tome  iii.,  p.  ITo.     Paris,  18G0. 


CHAPTER   XXXVI. 

THE   SKIN  AND   ITS  APPENDAGES.     SEBACEOUS   MAMMARY 

AND  SUDORIFEROUS  GLANDS.     PERSPIRATION, 

TACTILE  AND  OTHER  F0R3IS  OF 

CUTANEOUS  SENSATION. 


Fig.  397. 


The  Skin. 

The  skill  or  integunient  (Fig.  397)  constitutes  a  general  protec- 
tive and  sensory  covering  for  the  surface  of  the  body.  In  addition 
to  these  important  functions  in  eliminating  the  sweat,  carbon  diox- 
ide, urea,  etc.,  the  skin  acts  also  as  an  excretory  organ,  supplementing, 

in  this  respect,  the  action  of  the  lungs 
and  kidneys.  As  we  have  already 
seen,  the  skin,  too,  in  a  great  measure 
regulates  the  production  and  distribu- 
tion of  heat.  To  a  certain  extent,  also, 
the  skin  acts  as  an  absorbing  surface. 
Further,  through  special  modifications 
of  its  sensory  structure,  the  skin  min- 
isters to  the  sense  of  touch  and  other 
forms  of  cutaneous  sensation.  The 
skin,  in  addition,  then,  to  being  sensory 
and  protective,  possesses,  as  well,  ex- 
cretory, calorilic,  alisorbing,  and  tactile 
functions.  The  general  appearance  of 
the  skin,  its  extensibility,  flexibility, 
elasticity,  and  color  are  sufficiently  fa- 
miliar to  all.  It  may  be  mentioned  in 
this  connection,  however,  that  the  color 
of  the  skin  in  the  diiferent  races  of 
mankind  and  the  varieties  of  complex- 
ion observed  in  different  individuals  of 
tlie  same  race,  are  due  to  the  amount  of 
pigmentary  matter  present  in  the  deeper 
layers  of  the  epidermis  and  that  the 
color  of  the  true  skin,  or  dermis,  is 
whitisli  and  semi-transparent,  its  ap- 
parent pinkish  color  being  due  rather 
to  that  of  underlying  parts  and  the 
blood  circulating  tlirough  the  latter. 
The  furrows  and  folds  of  the  skin  are 
caused  partly  by  the  muscles  and  joints  and  partly  by  loss  of  elas- 
ticity in  the  skin  itself  and  by  the  deposition  in  it  of  fat.  Faint, 
irregular  lines  are  also  observed  on  most  parts  of  the  surface  of 


^  s 


Xcili'-al 


forefinger  across  two  of  the  ridges 
the    surface,    highly     magnified. 


'.1  the 
of 
1. 
Dermis  composed  of  an  intertextiire 
of  bundles  of  librous  tissue.  2.  ICpi- 
dermis.  3.  It.s  cuticle.  4.  Its  soft 
layer.  5.  Subcutaneous  connective 
and  adipose  tissue.  (>.  Tactile  pa- 
jjillse.  7.  Sweat  glands.  8.  Duet.  ii. 
Spiral  jiassagc  from  the  latter  tlirough 
the  (-iiidcrmis.  10.  Termination  of 
llic  iiassage  on  the  summit  of  ridge. 
(M:iDY.) 


THE  DERMIS,   OB  TRUE  SKIX.  <>^'7 

the  skin,  upon  the  pahns  of  the  hand  and  soles  of  the  feet  and 
particularly  upon  the  palmar  surface  of  the  last  phalanges ;  these 
lines  are  well  marked  in  the  latter  situation,  being  disposed  as  con- 
centric curves  depending  upon  the  regular  arrangement  of  the 
underlying  papillae  of  the  true  skin  or  dermis.  According  to  Sap- 
pev,^  the  cutaneous  surface,  on  the  average  in  man,  is  equal  to  about 
1.5  square  meters  (1(5  S(|uare  feet),  though  in  men  above  the  ordi- 
narv  size  it  may  amount  to  as  much  as  2  S(|uare  meters  (21.4 
square  feet).  The  significance  of  such  variations  physiologically 
will  become  apparent  presently  when  we  consider  the  excretory 
functions  of  the  skin. 

In  harmony  with  the  protective  functions  of  the  skin,  its  thick- 
ness varies  very  much  in  different  parts.  Thus,  where  naturally 
exposed  to  constant  pressure  and  friction,  as  on  the  soles  of  the  feet 
or  the  palms  of  the  hands,  the  skin,  as  we  shall  see,  is  much  thicker 
than  that  of  the  face,  eyelids,  etc. 

The  skin  consists  of  two  layers,  the  dermis  and  epidermis,  special 
modifications  of  the  latter  constituting  the  hair  and  nails,  the 
sebaceous,  mammary,  and  sweat  glands.  The  dermis,  or  true  skin, 
also  known  as  the  cutis,  vera,  corium,  etc.  (Fig.  397),  constituting 
the  deeper  layer  of  the  skin,  is  more  or  less  closely  connected  to 
the  underlying  parts  by  the  connective  tissue  of  the  adipose  layer 
of  the  superficial  fascia,  or  when  the  adipose  layer  is  absent,  by 
the  loose  connective  tissue  to  the  deeper  layer  of  the  fascia  or  sub- 
jacent structure,  thereby  allowing  the  skin  a  certain  amount  of 
movement  backward  and  forward.  The  thickness  of  the  adipose 
layer  varies  very  ranch  in  different  individuals  and  in  different 
parts  of  the  same  individual.  Thus  while  there  is  no  fat  beneath 
the  skin  of  the  eyelids,  the  upper  and  outer  part  of  the  ear,  the 
penis,  and  the  scrotum,  a  layer  about  2  millimeters  (J^  of  '^i^  inch) 
in  thickness  is  usually  present  beneath  the  skin  of  the  cranium, 
the  nose,  the  neck,  the  knee  and  elbow^,  and  the  dorsum  of  the 
hand  and  foot ;  the  adipose  layer,  on  an  average,  in  other  situa- 
tions, measuring  from  4  to  12  millimeters  (^  to  |  of  an  inch). 
In  fat  persons,  however,  it  may  attain  a  thickness  of  25  milli- 
meters (1  inch)  or  even  more.  There  is  no  well-defined  line  of 
demarcation  between  the  dermis  and  the  underlying  adipose  tis- 
sue, and  after  separating  the  two  the  dermis  looks  like  a  coarsely 
corded  network,  the  meshes  being  occupied  by  small  round  masses 
of  adipose  tissue.  The  dermis  consists  principally  of  a  dense  inter- 
texture  of  bundles  of  fibrous  tissue  crossing  one  another  at  acute 
angles  in  different  directions,  mingled  with  amorphous  matter  and 
some  elastic  tissue,  the  latter  l)eing  most  abundant  on  the  front  of 
the  body  and  around  the  joints.  It^  contains  also  unstriated  mus- 
cular fibers,  the  erector  pili  muscle,  which,  passing  downward  from 
the  more  superficial  part  of  the  dermis,  are  inserted  into  the  hair 
follicles,  and  which,  when  excited  to  contract  through  the  stimulus 
'Anatomie,  Tomeiii.,  p.  5(>-l.     Paris,  1877. 


698  THE  SKIN  AND  ITS  APPENDAGES. 

of  cold,  emotions  of  fear,  or  electricity,  elevate  the  hairs  and  so  give 
rise  to  the  condition  known  as  "  goose  flesh."  In  consequence  of 
the  gradual  transition  of  the  dermis  into  the  subjacent  tissues,  its 
exact  thickness  is  difticult  to  estimate.  It  may  be  said,  however, 
to  be  about  ^  of  a  millimeter  {-^^  of  an  inch)  thick  on  the  eye- 
lids, about  1  millimeter  (J^  of  an  inch)  on  the  front  of  the 
body,  and  3  millimeters  (^  of  an  inch)  on  the  back  of  the  body  and 
the  heels,  being  thickest  where  the  entire  skin  presents  that  con- 
dition. 

The  dermis  is  thinner  in  the  female  than  in  the  male,  about  half 
as  thick  in  children  as  in  adults  and  becomes  thinner  in  old  age. 
At  its  outer  surface  the  dermis  is  quite  dense,  being  defined  by  a 
more  lioraogeneous  layer  or  basement  membrane,  and  projects  here 
and  there  as  small  eminences,  the  papillje,  into  the  deeper  layers  of 
the  epidermis.  The  papillae,  on  which  the  perfection  of  the  skin  as 
an  organ  of  touch  largely  depends,  they  being  highly  developed 
where  the  sense  of  touch  is  exquisite,  and  vice  versa,  are  of  two 
kinds,  simple  and  compound,  tlie  latter  consisting  of  two,  three,  or 
more  simple  papilhe  springing  from  a  common  base.  The  papilhe, 
composed  of  a  continuation  of  the  fibrous  and  amorphous  structure 
of  the  dermis  and  defined  by  the  basement  membrane  of  the  latter, 
vary  in  number  and  size  in  diiferent  parts  of  the  body.  They  are 
most  numerous  and  longest  in  the  pahns  of  the  liands  and  soles  of 
the  feet,  attaining  in  these  situations  a  length  of  from  J^  to  ^  of 
a  millimeter  (the  g-i-g-  to  the  j^-^  of  an  inch),  and,  being  here  dis- 
posed in  double  rows  on  the  ridges  of  the  dermis,  of  which  they 
are  the  continuation,  give  rise,  as  already  mentioned,  to  the  curved 
lines  so  noticeable  on  the  palmar  surfaces  of  the  skin  of  the  last 
phalanges  of  the  fingers  and  toes.  The  papilhe  are  also  quite  nu- 
merous on  the  prepuce,  glans  penis,  nynq)h[e,  clitoris,  and  nipple. 
In  other  portions  of  the  body  they  are  less  numerous  and  small, 
measuring  only  the  -^^  of  a  millimeter  (the  -^^^  of  an  inch).  In  the 
face,  for  example,  the  papillae  are  so  little  developed  as  to  be  hardly 
recognizable.  Most  of  the  papilla^  of  the  palms,  fingers,  soles,  toes, 
and  nipples,  especially  the  compound  kind,  contain  tactile  corpus- 
cles in  Avhich,  as  already  mentioned,  the  cutaneous  nerves  termi- 
nate. It  will  be  rememl)ered  also  that  the  dio-ital  nerves  of  the 
fingers  and  toes  appear  to  terminate  in  similar  shaped,  though 
larger  bodies,  the  Pacinian  corj^uscles,  situated  in  the  subcutaneous 
tissue  and  the  nerves  suj)])lying  tlie  skin  of  tlie  glans  penis  and 
clitoris  in  the  Krause  corpuscles,  reseml)ling  the  tactile  and  Paci- 
nian corpuscles,  though  smaller  than  either.  The  dermis  with  its 
])apillie  is  richly  supplied  Avith  blood  vessels  and  l^anphatics,  as 
well  as  nerves.  Tlie  arteries  penetrating  tlie  dermis  from  beneath 
end  in  a  capillary  network,  the  latter  extending  as  single  loops  into 
the  papilhe,  Mliile  the  veins,  more  numerous  and  larger  than  the 
arteries,  terminate  in  the  superficial  venous  trunks.  The  lym- 
phatics   already  referred    to  are  most  numerous  on  the  fore  and 


THE  EPIDERMIS. 


699 


inner  part  of  the  body  and  limbs,  being  particularly  well  devel- 
oped in  the  palms  and  soles.  The  dermis,  consisting  largely  of 
white  fibrous  tissue,  is  by  boiling  resolved,  in  a  great  measure,  into 
gelatine,  the  ordinary  source  of  glue,  hence  also  its  conversion  into 
leather  by  tanning.  The  fibrous  structure  of  the  dermis,  the 
papilla?,  the  mouths  of  hair  follicles,  etc.,  may  usually  be  seen  in 
the  cut  edge  and  rough  surface  of  a  piece  of  leather.  Deprived  of 
its  fatty  matters,  etc.,  the  dermis,  when  properly  thinned,  forms 
also  parchment. 

The  epidermis,  also  kn<jwn  as  the  cuticle  or  scarf  skin,  con- 
stituting the  superficial  layer  of  the  skin,  bears  the  same  relation  to 
the  dermis  that  the  epithelium  does  to  the  deeper  layer  of  the 
mucous  membranes.  Indeed,  the  transition  of  skin  into  mucous 
membrane  at  the  mouth  and  anus  is  so  gradual,  that  it  is  impossible 
to  say  where  one  ends  and  the  other  begins  ;  in  fact,  as  well  known, 
if  the  skin  be  inverted  in  these  places,  it  becomes  raucous  mem- 
brane, and  if  the  mucous  membrane  be  everted,  it  becomes  skin. 
The  internal  surface  of  the  epidermis  is  applied  directly  to  the 
papillae  (Fig.  398)  of  the  dermis,  and  follows  closely  all  their  in- 
equalities ;    its  external  surface 

is     marked     by    very     shallow  Fig.  398. 

grooves  corresponding  to  the 
furrows  between  the  latter.  The 
epidermis  is  entirely  destitute  of 
blood  vessels  and  lymphatics, 
deriving  its  nutritive  fluid  (like 
all  other  vascular  parts),  l)y  os- 
mosis, from  the  blood  of  the 
dermis.  It  was  for  a  long  time 
supposed  that  the  epidermis  was 
also  without  nerves.  Modern 
investigations,  however,  make  it 
probable  that  some  of  the  cu- 
taneous nerves  pass  through  tin 
dermis,  terminating  as  non- 
medullated  nerve  fibers  among 
the  deeper  layers  of  the  epi- 
dermis  in  slightly  bulbous-like 

extremities,  or  in  a  plexus  of  fine  fibrils.  However  this  may  be, 
impressions  made  upon  the  epidermis  will  be  appreciated,  whether 
the  latter  be  provided  M^ith  nerves  or  not,  being  transmitted  through 
pressure  to  the  exquisitely  sensitive  dermis  beneath.  The  epi- 
dermis serves  as  a  protective  covering  to  the  soft  and  delicate 
dermis,  which  would  be  otherwise  constantly  exposed  to  laceration 
and  drying. 

Indeed,  if  the  epidermis  be  removed,  contact  of  the  atmosphere 
alone  will  inflame  the  dermis,  which,  after  death,  rapidly  dries. 
The  epidermis  is  therefore  thicker  in  those  parts  which  are  most 


Epidermis  elevated  so  as  to  show  papilla?. 

(HiR.SCIIFELD.) 


TOO  THE  SKIN  AND  ITS  APPENDAGES. 

exposed,  as  in  the  palms  and  soles,  Avherc  it  may  measure  as  much 
as  2  millimeters  (the  Jg  of  an  inch  or  more),  being  very  thin,  on 
the  other  hand,  upon  the  face,  the  eyelids,  and  in  the  external 
auditory  meatus,  attaining  in  these  situations  only  a  size  of  the 
2i  ^^  sV  *^'^  '^  millimeter  (gl^  to  the  -^^-^  of  an  inch).  The 
whole  skin  then,  including  the  dermis,  in  its  thickest  part  would 
measure  about  5  millimeters  (the  \  of  an  inch).  The  thickness 
of  the  epidermis  is,  however,  dependent  to  a  great  extent  u])on  the 
amount  of  pressure  to  which  the  skin  is  subjected,  being  very  thick 
in  the  palm  of  the  laborer  and  the  sole  of  the  plowman.  •  Corns  are 
thickened  portions  of  the  epidermis,  and  are  due  to  the  parts  af- 
fected being  exposed  to  excessive  pressure  or  friction,  hence  they 
are  developed  not  only  in  the  feet  l)y  tight  shoes,  but  on  the  knee 
of  the  shoemaker  by  constant  hammering,  and  in  front  of  the  clavicle 
of  the  soldier  by  the  pressure  of  the  musket.  The  pain  caused  by 
corns  is  due  to  inflammation  of  the  dermis,  which  they  excite  by 
pressing  upon  its  delicate  structure,  just  as  any  foreign  body,  a 
small  stone,  will  do  under  similar  circumstances.  The  epidermis 
consists  of  two  layers,  the  rete  mucosum  and  the  cuticle.  The  rete 
mucosum  or  Malpighii,  with  a  thickness  varying  from  -J^  to  ^ 
of  a  millimeter  (the  ^^V^  **'  ^^^^  y\  ^^  ^^^  inch),  constituting 
the  deeper  internal  soft  layer  of  the  epidermis,  is  moulded  upon 
the  adjoining  surflice  of  the  dermis,  and  when  separated  by  macer- 
ation or  putrefaction  presents  impressions  corresponding  exactly 
with  the  pa])illee,  furrows,  depressions,  etc.,  of  the  latter,  the  more 
prominent  irregularities  of  the  dermis  being,  as  already  mentioned, 
visible  upon  the  outer  surface  of  the  cuticle,  but  less  distinctly. 
The  rete  mucosum  consists  of  several  irregular  layers  of  cells  of 
different  forms,  more  or  less  agglutinated  together.  Those  Iving 
next  to  the  dermis  are  somewhat  elongated  in  figure,  varying 
in  length  from  the  ^,1^-  to  -^-^^  of  a  millimeter  (^-^^-^^  to  the 
2F00'  ^^  '^'^  inch),  and  disposed  perpendicularly,  while  the  suc- 
ceeding ones  are  of  a  rounded  form  and  often  marked  with  ridges 
and  furrows,  in  sections  appearing  as  spines.  As  the  cells  are 
gradually  pushed  from  below  upward  through  the  continual  de- 
velopment of  new  cells  at  the  surface  of  the  dermis,  they  become 
more  and  more  flattened,  lose  their  soft,  granular  contents  and 
nucleus,  and,  becoming  keratose,  give  rise  to  the  different  layers 
of  the  rete  mucosum,  and  are  finally  transformed  into  the  dry, 
horny  scales  of  the  cuticle.  AMiile  in  the  white  race  the  cells  of 
the  rete  mucosum  are  colorless  and  like  those  of  the  cuticle  trans- 
lucent, allowing  the  color  of  the  underlying  dermis  to  be  seen,  in 
those  of  the  black  races,  the  negro  especially,  the  deeper  ones  (Fig. 
399)  are  filled  with  brown  or  black  pigmentary  matter,  which  gives 
rise  to  their  characteristic  dark  color,  and,  when  present  in  smaller 
(|uantities,  to  the  various  shades  of  complexion  of  other  races,  of 
different  individuals,  and  of  different  parts  of  the  skin  of  the  same 
individual,  while  the  accumulation  of  this  pigmentary  matter  in 


THE  CUTICLE. 


roi 


Fig.  399. 


spots  causes  freckles.  As  the  cells  of  the  deeper  layers  of  the  rete 
niucosLiiu  are  gradually  transformed  into  those  of  the  cuticle,  the 
pigmentary  matter  gradually  diminishes  and  finally  disappears.  It 
is  interesting  in  this  connection  to 
note  that  the  color  of  the  dermis  in 
the  negro  is  the  same  as  that  of  the 
white,  and  that  the  whole  skin  of  the 
negro  foetus  is  as  pale  as  that  of  the 
white  one.  The  fact  of  the  pigment 
being  developed  in  the  deep  cells  of 
the  rete  mucosum  only  at  or  after 
birth  would  indicate  that  the  black 
race  had  descended  from  the  white 
one  rather  than  the  reverse.  Further, 
since  in  the  dark  races  and  the  semi- 
burnt  ones  of  the  white  races,  the 
pigment  is  developed,  not  in  the 
superficial,  but  in  the  deep  layers  of 
the  rete  mucosum,  it  is  to  be  inferred 
that  the  pigment  is  eliminated  by  the 
cells  of  the  rete  mucosum  from  the 
blood  of  the  dermis,  and  that  the 
effect  of  the  heat  of  the  sun  in  tem- 
perate or  tropical  climates  is  not  to 
modify  directly  the  color  of  the  skin, 
but  in  rendering  the  liver  torpid,  to  throw  upon  the  skin  the  elimi- 
nation of  the  coloring  and  other  matters  of  the  bile,  and,  hence,  only 
indirectly  affecting  it.  That  such  is  the  case  is  rendered  probable 
also  from  the  fact  of  the  cutaneous  pigment  being  essentially  car- 
bonaceous in  nature,  as  is  that  of  bile.  While  there  is  no  doubt 
that  the  cells  of  the  rete  mucosum  are  gradually  transformed  into 
those  of  the  cuticle,  they  themselves  are  derived  from  those  of  the 
dermis,  since,  as  we  shall  see  hereafter,  the  epidermis  is  derived 
from  the  epil)last  or  external  blastodermic  membrane  of  the  embryo, 
and  the  dermis  from  the  mesoblast  or  middle  blastodermic  mem- 
brane. Such  being  the  case,  it  is  more  probable  that  the  deep  epi- 
dermal cells  of  the  adult  are  derived  by  unl)roken  descent  from  the 
original  epiblastic  ones  of  the  embryo  than  from  those  of  its  dermal 
mesoblastic  ones. 

The  cuticle,  or  cuticula,  constituting  the  most  external  superficial 
portion  of  the  epidermis,  consists  of  numerous  layers  of  hard,  flat- 
tened, nearly  dry,  yellowish  translucent  cells,  irregularly  jiolygonal 
in  form,  generally  granular,  but  without  nuclei,  measuring  from  the 
To  *®  3ir  ^^  ^  millimeter  (^-^^  to  yi^  of  an  inch)  in  diameter,  and 
composed  chemically  of  keratin,  or  horny  matter  ;  the  deejier  cells 
being  rather  thicker  and  rounder  than  those  of  the  superficial  layers. 
As  the  deeper  surface  of  the  cuticle  is  being  continually  renewed  by 
fresh  cells  from  the  rete  mucosum,  its  free  surface  is  as  constantly 


Skin   of  ih  _  jitical   section, 

magnified  2">ii  iiKiiuiiir>.  «,  a.  ('uta- 
ueous  papillte.  h.  Lndermost  and  dark- 
colored  layer  of  oblong  vertical  epider- 
mis-cells, f.  Mucous  or  Malpighian 
layer.    </.   Horny  layer.     (Kollikek.) 


ro2 


THE  SKIX  AND  ITS  APPENDAGES. 


worn  away,  or  .shed  off  in  flakes,  constituting  tlie  so-called  scurf 
(Fig.  400)  and  dandruff  (Fig.  401).  In  many  of  the  lower  ani- 
mals, as  in  snakes,  for  example,  tlie  cuticle  exfoliates  from  time  to 
time  entire.     By  treating  the  cuticle  witli  a  solution  of  potash  its 


Fig.  400. 


Fig.  401. 


Scurf  from  the  leg.  1.  A  fragment  of 
scurf,  consisting  of  dried,  llatteued  non- 
nucleated  cells  or  scales.  2.  A  few  cells 
with  a  nucleus.  .3.  A  cell  more  highly 
magnified,  to  exhibit  its  polyhedral 
form. 


Fragment  of  dandruft'  from  the  head.  1.  Portion  of 
daudrutf,  consisting  of  non-nucleated  cells.  2.  Several 
fragments,  consisting  of  nucleated  cells.  .3.  Isolated 
cells,  some  with  and  without  nuclei.  4.  A  cell  more 
highly  magnified,  exhibiting  granular  contents  and  a 
nucleus. 


scales  separate  from  one  another,  swelling  up  into  vesicles  ;  it  is  for 
this  reason  that  alkaline  solutions  remove  the  epidermis.  In  tan- 
ning, for  example,  the  epidermis  is  removed  by  macerating  the  skin  in 
lime,  etc.  A  blister  or  l)urn,  in  producing  inflammation  of  the  dermis 
and  effusion  of  liquid,  breaks  up  the  soft  cells  of  the  rete  mucosum, 
and  so  elevates  the  cuticle.  If  the  skin  be  macerated  after  death,  the 
cuticle,  through  disorganization  of  the  rete  mucosum,  detaches  itself, 
and  wlien,  under  sucli  circumstances,  it  is  thick  and  strong,  as  in  the 
case  of  the  hand  and  foot,  it  may  be  stripped  off' like  a  glove. 

The  Nails. 

The  nails,  or  ungues,  appendages  of  the  skin  corresponding  to  the 
€laws  and  hoofs  of  other  animals,  and  situated  upon  the  dorsal  sur- 
faces of  the  distal  phalanges  of  the  fingers  and  toes,  not  only  serve 
to  protect  these  parts,  but  are  also  important  as  prehensile  organs, 
in  civilized  races  more  especially,  in  the  case  of  the  fingers,  but  in 
certain  barbarous  ones,  in  that  of  the  toes  as  well.  The  nails  are 
thin,  flexible,  translucent,  quadrilateral  plates,  continuous  with  the 
epidermis  (Fig.  402),  with  which  they  are  detached  if  the  latter  be 
separated  by  maceration  from  the  dermis.  The  nail  resting  upon 
the  depressed  surface  of  the  dermis,  known  as  the  matrix,  or  bed, 
as  described  by  anatomists,  consists  of  the  root,  body,  and  free 
border.  The  root  is  lodged  in  a  deep  groove  of  the  matrix,  the 
vallecula  unguis,  while  the  lateral  borders  of  the  body  of  the  nail 
fit  into  rather  shallow  grooves,  the  free  border  of  the  nail  being 
that  part  detached  from  the  skin.  Tlie  color  of  the  nail  is  due  to 
its  translucency,  which  allows  the  color  of  the  highly  vascular,  or 
underlying  dermis,  or  matrix  to  be  seen  ;  the  lunula,  or  whitish 
spot  at  the  root,  defined  by  the  semicircular  line,  is  due  to  the 
matrix  being  there  less  vascular.  The  grooves  exhibited  more  par- 
ticularly on  the  under  surface  of  the  nail  are  the  impressions  made 


THE  XAILS. 


703 


by  the  fine  longitudinal  ridges  and  papilke  of  the  dermis  of  matrix 
upon  which  the  nail  is  moulded.  The  nail,  like  the  epidermis, 
consists  of  two  lavers — a  hornv  laver  and  a  soft  layer.     The  soft 


Fig.  403. 


^e 


Vertical  section  of  the  end  of  a  finger.  1. 
Epidermis  on  the  back  of  the  finger.  2. 
Point  at  which  it  is  reflected  to  become  con- 
tinuous Tvith  the  nail.  3.  The  nail.  4.  Epi- 
dermis at  the  end  of  the  finger.  5,  6,  7,  8. 
Surface  of  the  dermis  corresponding  with 
the  position  of  the  soft  epidermic  layer.  9. 
10,  11,  12.  Dermis.  i:i.  Last  phalanx.  14. 
Flexor  tendon. 


/ 


Vertical  transverse  sect iirii  ilii..Ligh  a  small  por- 
tion of  the  nail  and  matrix,  highly  magnified.  A. 
Corium  of  the  nail  bed,  raised  "into  ridges,  or 
laminte ;  a.  Fitting  in  between  corresponding 
laminae  ;  h.  Of  the  nail.  B,  Malpighian,  and  (.', 
horny  layer,  d.  Deepest  and  vertical  cells,  e. 
Upper  flattened  cells  of  Malpighian  laver.    (Kol- 

LIKEK. ) 


layer  corresponding  to  the  rete 
mucosum  of  the  epidermis, 
consists,  like  the  latter,  of 
delicate,  polyhedral  nucleated 
cells,  which  are  being  contin- 
ually transformed  into  the 
scales  of  the  horny  layer.  The  latter,  corresponding  to  the  cuticle  of 
the  epidermis,  consists  of  a  number  of  layers  of  flattened  nucleated 
cells,  or  scales,  Ijut  so  intimately  associated  that  they  can  only  be  rec- 
ognized under  the  microscope,  after  separation  from  one  another  bv 
treatment  with  alkalies,  etc.  The  thickness  of  the  true  nail — that  is, 
of  its  horny  layer  at  the  root^ — is  from  |^  to  |^  of  a  millimeter  (2^-0  to 
■j-^Q-  of  an  inch),  and  at  the  middle  of  the  body  of  the  nail,  from  |-  to  |- 
of  a  millimeter  {^-^  to  J^j  of  an  inch).  Through  the  constant  addition 
of  cells,  the  root  of  the  nails  grows  in  length,  and  through  addition 
of  the  cells  beneath,  in  tliickness — the  free  cut  edge  of  the  nail 
consisting  of  the  horny  layer  only  (Fig.  404). 


The  average  rate 


Fig.  404. 


Longitudinal  section  through  the  middle  of  the  nail  and  bed  of  the  nail.  a.  Bed  of  the  nail  and 
cutis  of  the  back  and  points  of  the  fingers,  b.  Mucous  layer  of  the  points  of  the  fingers,  c.  Of 
the  nail.  (A  Of  the  bottom  of  the  fold  of  the  nail.  e.  Of  the  back  of  the  finger.  /.  lioruy  layer 
of  the  points  of  the  fingers,  g.  Beginning  of  tliem  under  the  edge  of  the  nail.  h.  Horny  layer 
of  the  Dack  of  the  fingers,  i.  Ends  of  it  upon  the  upper  surface  of  the  root  of  the  nail.  /;."  Boiy. 
I.  Root.    m.  Free  edge  of  the  proper  substance  of  the  nail.    Magnified  8  diameters.    (Kolliker.) 


704 


THE  SKIN  AND  ITS  APPENDAGES. 


of  growth  of  the  nails  is  said  to  be  -^L  of  a  millimeter  [-^-^  of  an 
inch)  per  week,  and  to  be  more  rapid  in  summer  than  in  winter/ 


Fig.  40o. 


The  Hairs. 

The  hairs,  or  pili,  like  the  nails,  appendages  of  the  skin,  and  more 
particularly  of  the  rete  mucosum  of  the  epidermis,  are  first  noticed 

at  about  the  third  or  fourth  month  of 
intrauterine  life,  as  little  black  specks 
beneath  the  cuticle,  consisting  of  a  mass 
of  cells,  defined  l)y  a  basement  mem- 
brane (Fig.  405),  developed  through 
invagination,  or  the  growing  downward 
of  the  cells  of  the  rete  mucosum  into 
the  dermis.  As  development  advances, 
the  cells  of  which  this  flask-like  body 
consists  are  differentiated  into  a  central 
and  a  lateral  portion  (Fig.  40G,  A), 
the  former  the  rudiment  of  the  future 
hair,  the  latter  the  root-sheath,  or  the 
lining  of  the  hair  follicle,  while  the 
projecting  of  the  dermis  into  the  bot- 
tom of  the  flask-like  hair  forms  its  pajHlhe.  With  the  gradual  up- 
ward growth  of  the  hair  and  the  development  of  the  different  parts, 
of  which,  as  we  shall  see,  it  consists  (Fig.  406,  B,  C),  the  root-sheath 


Rudiment  of  the  hair  from  the  brow 
of  a  human  embryu,  sixteen  weeks 
old,  magnified  350  diameters,  a. 
Horuy  layer  of  the  epidermis,  h.  Its 
mucous  layer.  ».  Structureless  mem- 
brane surrounding  the  rudiment  of 
the  hair,  and  continued  between  the 
mucous  layer  aud  the  coriuqi.  m. 
lioundish,  ]iartly  elongated  cells 
which  especially  compose  the  rudi- 
ments of  the  hair.     (Kolliker.  ) 


Fk;.  406. 


A.  Hair  rudiment  from  an  embryo  of  six  weeks,  a.  Horny,  and  h,  mucous  or  Malpighian  layer 
of  cuticle.  /.  Hasenient  membrane,  m.  Cells,  some  of  wliich  are  assuming  an  obhjng  figure, 
which  chiefly  form  the  future  liair.  B.  Hair  rudiment,  with  the  young  hair  lormed,  but  not  yet 
risen  through  the  cuticle,  n.  Horny  layer,  h.  Maljiighian  layer  of  epidermis,  o.  Outer, '/,  inner 
root  sheath,  e.  Hair-knob.  /.  Stem,  and  ,*/,  point  of  the  hair.  /(.  ilair-ijapilla.  «,  m.  Commencing 
sebaceous  follicles.     ('.   Hair-follicles  with  the  hair  just  protruded.     (Koli.iker.) 

JQuain's  Anatomy,  1878,  Vol.  ii.,  p.  219. 


THE  HAIRS. 


705 


Fig.  407. 


-6 
-5 


divides  into  the  inner  and  outer  root-sheaths,  tlie  former,  except  at 
the  bottom,  subdividing  into  Huxley's  and  Henle's  layers,  the  latter 
surrounded  and  defined  by  a  fibrous  membrane  derived  from  the 
dermis,  constituting  the  wall  of  the  hair  follicle. 

Finally,  the  hair,  being  fully  formed,  penetrates  the  cuticle,  the 
papilla  to  which  it  is  attached  having  been  provided  with  nervous 
filaments  and  capillary  blood  vessels.  The  hair  is  usually  described 
as  consisting  of  a  root  beginning  in  the  skin  as  a  club-like  expansion, 
the  bulb  and  a  shaft  or  stem  projecting  from  the  skin,  and  terminating 
in  the  end  or  point.  It  is  composed  (Fig.  407)  usually  of  a  medulla, 
or  central  axis,  around  which  are  con- 
centrically disposed  the  cortical  sub- 
stance  and  cuticle.  The  medulla  con- 
sists of  cuboidal  cells,  having  a 
diameter  of  from  the  -^^  to  -^-^  of  a 
millimeter  (2-oVTr  ^'^  TI 00"  ^^  ^^^  inch), 
with  granular  contents,  and  an  in- 
distinct nucleus,  usually  intermingled 
A\ith  small  bubbles  of  air,  which  have 
penetrated  from  the  ends  of  the  hair, 
and,  when  present,  giving  rise  to  the 
white  silvery  luster  of  the  latter.  In 
downy  hairs  the  medulla  is  absent. 
The  cortical  substance,  or  the  cortex, 
constitutes  the  chief  bulk  of  the  hair, 
and  is  that  part  upon  which  the  color 
of  the  hair  principally  depends  in 
different  individuals  and  races.  It  is 
composed  of  several  layers  of  flexible 
fibers,  the  latter  consisting  of  elon- 
gated fusiform  cells.  With  the  loss 
of  the  coloring  matter,  which  is  gen- 
erally diffused  through  the  cortical 
substance,  the  latter  becomes  white. 
The  cuticle  consists  of  a  single  layer 
of  thin,  colorless,  quadrilateral  cells, 
overlapping  each  other  like  the  shin- 
gles of  a  roof.  The  edges  of  these 
scales  being  directed  upward  and  outward  along  the  shaft  offer 
an  obstacle  to  any  movement  of  the  hair  otherwise  than  with 
its  root  forward  when  rubbed  between  two  surfaces.  It  is  upon 
this  fact  that  the  felting  of  hair  and  wool  of  various  animals  de- 
pends. The  hair,  like  the  eiDidermis,  being  destitute  of  blood  ves- 
sels, derives  its  nutritive  liquid  by  osmosis  from  the  blood  of  the 
vessels  of  the  papilla.  While  analogy  would  lead  one  to  suppose 
the  nerve  filaments  of  the  papilla  penetrate  the  hair,  as  a  matter  of 
fact,  no  nervous  filaments  having  as  yet  been  demonstrated  in  it, 
any  sensibility  that  the  hair  may  possess  must  depend,  therefore, 
45 


Diagi-am  of  structure  of  the  root  of  a 
hair  within  its  follicle.  1.  Hair  papilla. 
2.  Capillary  vessel."  3.  Nerve  fibers.  4. 
Fibrous  wall  of  the  hair  follicles.  5. 
Basement  membrane.  6.  Soft  epidermis, 
lining  of  the  follicle.  7.  Its  elastic  cutic- 
ular  layer.  8.  Cuticle  of  the  hair.  9. 
Cortical  substance.  10.  >redullary  sub- 
stance. 11.  Bulb  of  the  hair  composed 
of  soft  polyhedral  cells.  12.  Transition 
of  the  latter  into  the  cortical  substance, 
medullary  substance,  and  cuticle  of  the 
hair.     (Leidy.) 


706  THE  SKIN  AND  ITS  APPENDAGES. 

upon  that  of  the  papilla  which  the  hair  bulb  tightly  encloses  or  caps. 
The  hairs  are  continually  renewed  by  constant  growth.  In  some 
instances,  especially  after  disease,  they  are  cast  off  or  shed,  new  ones 
being  produced.  Permanent  baldness  is  due  to  atrophy  of  the 
papillte,  while  the  sudden  blanching  of  the  hair,  occurring  some- 
times in  a  single  night,  is  due  to  the  greater  part  of  the  medulla  and 
cortex  becoming  filled  Avith  air.^ 

Chemically,  hairs  are  composed  of  fats,  a  gelatine-like  substance, 
albuminous  matters,  containing  a  large  proportion  of  sulphur,  per- 
oxide of  iron,  traces  of  manganese,  silica,  sodium,  and  potassium 
chlorides,  calcium  sulphate  and  phosphate,  and  magnesium  sul- 
phate.^ With  the  exception  of  the  palms  of  the  hands  and  soles 
of  the  feet,  the  jialmar  surface  of  the  fingers  and  toes,  the  lips, 
lining  of  the  prepuce  and  glans  penis,  hairs  cover  nearly  every  part 
of  the  surface  of  the  body.  The  hairs  generally  project  obliquely 
from  the  skin,  and  are  regularly  disposed,  usually  in  curving  lines 
from  particular  points.  They  differ  very  much  as  regards  their 
size,  fineness,  color,  form,  and  number,  in  diflPerent  races,  sexes,  in- 
dividuals, and  parts  of  the  body.  Of  the  long  hairs,  attaining 
sometimes  in  women  a  length  of  90  cm.  (three  feet)  or  more,  and 
a  diameter  of  from  the  g^^  to  ■^^r  of  a  millimeter  (y-g^o'o'  ^°  ^^o"  ^^ 
an  inch),  the  finest  are  found  upon  the  head.  The  short,  stiff  hairs 
of  the  nostrils  and  edges  of  the  eyelids,  are  from  the  Jg-  to  i  of 
a-  millimeter  {^^-^^  to  the  y^^  of  an  inch)  in  diameter,  the  fine 
downy  ones  from  the  J^  to  gig-  of  a  millimeter  (g-oVo  ^^  *^^  i2Vo" 
of  an  inch).  While  the  fine  silken  hair  of  the  head  in  the  white 
race  is  cylindrical,  the  crisp  hair  of  the  head  and  beard  of  the  negro 
is  more  or  less  flattened  cylindrical.  It  has  been  estimated^  that 
upon  a  square  inch  of  scalp  there  are  about  1,000  hairs,  the  num- 
ber upon  the  entire  head  amounting  to  120,000.  The  hairs  are 
elastic,  readily  electrified  by  friction,  especially  in  cold,  dry  weather, 
and  very  hygrometric.  The  latter  property  is  taken  advantage  of 
in  the  making  of  delicate  hygrometers,  the  hair  elongating  through 
the  absorption  of  moisture.  The  hairs  not  only  serve  to  protect 
the  general  surface,  as  in  shielding  the  head  from  excessive  cold  or 
heat,  but  also  guard  certain  orifices,  as  those  of  the  ears  and  nose. 
The  eyebrows  prevent  the  perspiration  from  the  forehead  running 
on  to  the  lids,  the  eyelashes  the  surface  of  the  conjunctiva  from 
dust,  etc.  Hair,  being  a  bad  conductor  of  heat,  serves  also  to  re- 
tain that  produced  within  the  body.  It  has  already  been  mentioned 
that  the  hairs  are  quite  regularly  disposed,  and  it  will  be  further 
observed  that  if  a  man  assume  a  crouching  attitude,  with  elbows 
upon  the  knees,  and  the  chin  resting  upon  the  hands,  that  their 
general  direction  u]ion  the  extremities  is  oblicpiely  downward,  a  dis- 
position such,  that  if  the  })erson  be  exposed  to  wet  weather,  the  rain 

'Landois,  Yirchow's  Arch.,   1866,   Band  xxxv.,   s.   375.     Wilson,   Proe.  Eoy. 
Soc.  Lond.,  1S67,  Vol.  xv.,  p.  406.  ^Quain's  Anatoniv,  ^'ol.  ii.,  p.  226. 

3  Wilson,  Healthy  Skin,  I).  84.     Philadelphia,  1854. 


SEBA  CEO  US  GL  A  XDS. 


707 


■will  l)e  drained  off,  an  effect  obvionsly  (»f  advanta<ro  to  the  primi- 
tive man,  as  well  as  to  those  who  go  naked  at  the  present  day. 
Finally,  the  hairs  may  l)e  regarded,  to  a  eertain  extent  at  least,  as 
.so  many  excretory  organs,  since  their  growth  necessarily  involves 
the  excreting  from  the  blood  the  different  principles  of  which  we 
have  seen  that  they  chemically  consist,  and  which,  if  retained 
within  the  system,  in  all  pr(tl)al)ility  would  give  rise  to  disease. 

Sebaceous  Glands. 

The  sebaceous  glands,  like  the  nails  and  hair,  are  appendages  of 
the  epidermis,  being  developed  during  the  fourth  and  fifth  months 
of  intrauterine  life  as  outgrowths  of  the  hair  follicles,  into  which, 
with  but  few  exceptions,  they  eventually  open.  Each  sebaceous 
gland  begins  (Fig.  408,  A)  as  a  solid  bud  sprouting  out  into  the 


r^ 


The  development  of  the  sebaceous  glands  in  a  six  months'  IVetus.  a.  Hair.  b.  Inner  root- 
sheath,  here  more  closely  resembling  the  horny  layer  of  the  epidermis,  c.  Outer  root-sheath,  d. 
Rudiments  of  the  sebaceous  glands.  A.  Flask-shaped  rudiments  of  the  gland,  with  fat  devel- 
oped in  the  central  cells.    B.  Larger  rudiments.     (Kollikee.) 

dermis  from  the  external  root-sheath  of  the  hair  follicle,  and  con- 
sists entirely  of  nucleated  cells.  As  development  advances,  how- 
ever, the  cells  in  the  central  portion  of  the  flask-like  (Fig.  408,  B) 
bud  develop  fat,  which  gradually  extending  themselves,  penetrate 
the  root-sheaths  of  the  hair  follicle,  and  so  pass  into  the  cavity  of  the 
latter  as  the  primitive  sebaceous  secretion,  while  through  the  further 
division  and  subdivision  of  the  primitive  bud  the  latter  assumes 
the  form  of  a  simple  or  compound  alveolar  gland.  The  sebaceous 
gland  when  fully  developed  consists  of  a  delicate  wall  of  fibrous 
tissue  defined  by  a  basement  membrane  lined  with  an  epithelium 
consisting  of  polyhedral  nucleated  cells,  ^^'ith  granular  contents,  the 
<3avity  of  the  gland  being  filled  with  sebaceous  matter.  The  lat- 
ter or  the  sebum,  consists  of  water,  epitheliiun,  oleiu  and  palma- 
tin,  soaps,  cholesterin  and  inorganic  salts,  principally  insoluble 
■earthy  phosphates  and  alkaline  chlorides.     The  sebum,  somewhat 


708 


THE  SKIN  AND  ITS  APPENDAGES. 


modified,  constitutes  the  smegma  pneputii,  the  veruix  caseosa  of 
the  newborn  child,  the  meibomian  secretion  of  the  eyes,  and,  when 
mixed  with  that  of  the  sweat  glands  of  the  ear,  the  cerumen,  or 
ear  wax. 

The  sebaceous  glands  are  very  numerous,  existing  almost  every- 
where, except  in  the  palms  and  soles.  Usually  associated  with  the 
hair  follicles  (Fig.  409),  they  are  disposed   around  the  latter  in 

Fig.  409. 


A  large  gland  from  the  nose,  with  a  little  hair-sac  opening  into  it ;  magnified  fifty  diameters, 

(KOLLIKER.) 


groups  varying  from  two  to  eight  to  each  follicle,  and  imbedded  in 
the  more  superficial  part  of  the  dermis,  appearing  as  round  whitish 
bodies,  and  measuring  on  an  average  from  ^^g-  to  ^  of  a  millimeter 
(t2"o  *^  To  ^^  ^^  inch)  in  diameter.  The  largest  sebaceous  glands 
are  those  of  the  nose,  concha  of  the  ear,  skin  of  the  penis,  the 
scrotum,  labia,  and  areola  surrounding  the  female  nipple. 

The  use  of  the  sebaceous  matter  is  to  smear  the  hairs  with  oil  as 
they  grow  out  of  the  skin  and  thoroughly  to  imbue  the  cuticle  with 
the  same,  through  which  it  is  rendered  repellant  of  water.  The 
greasiness  of  the  skin  thus  produced  is  the  cause  of  smut  and  dirt 
adhering  to  the  person  so  readily  and  necessitating  the  use  of  soap 
for  the  removal  of  the  same.  The  too  free  use  of  alkaline  washes, 
however,  in  depriving  the  cuticle  of  its  natural  oil,  renders  the  skin 
dry  and  harsh.  The  sebaceous  matter  often  becoming  inspissated, 
distends  the  glands  producing  it,  especially  in  those  of  the  nose, 
and  becoming  incorporated  at  the  mouth  of  the  duct  with  dirt  if 
squeezed  out  is  often  regarded  on  account  of  the  shape  as  a  worm, 
the  dirt  being  supposed  to  be  the  head.  It  should  be  mentioned, 
however,  that  the  sebaceous  matter  frequently  contains  the  so-called 
pimple  mite,  the  Acarus  or  Demodex  folliculorum. 


MAMMA  BY  GLANDS  AND  MILK. 


709 


Fig.  410. 
/ 


Mammary  Glands  and  Milk. 

The  mammary,  like  the  sebaceous  glands  just  described,  are  also 
appendages  of"  the  epidermis,  being  developed  in  the  fourth  or  fifth 
month  of  intrauterine  life  (Fig.  410, 1,  2) 
as  solid  invaginations  or  projections  of  the 
rete  mucosum  into  the  dermis,  the  latter 
furnishing  the  dense  layer  investing  them. 
As  development  advances  each  primitive 
gland  gives  oif  a  number  of  buds,  the 
future  lobes,  numbering  at  birth  from 
twelve  to  fifteen,  which,  through  con- 
tinued division  and  subdivision  into 
lobules,  and  the  latter  into  acini  or  se- 
creting vesicles,  ultimately  assume  the 
constitution  of  a  gland  (Fig.  411),  such 
as  the  parotid  or  submaxillary,  the  whole, 
however,  being  so  closely  associated  by 
connective  tissue  as  to  give  the  appear- 
ance of  being  homogeneous  rather  than 
lobulated.  Just  before  the  ducts  from 
the  lobes  reach  the  nipple  they  expand 
beneath  the  areola  into  the  so-called 
lactiferous  sinuses,  especially  observable 
in  the  human  female  during  lactation, 
and  constituting  the  large  milk  reser- 
voirs in  the  cow.  As  the  lacteal  or 
galactophorous  ducts  from  each  lobe 
terminate  at  the  summit  of  the  nipple  in  a  small  orifice,  the  num- 
ber of  the  latter,  usually  twelve  to  fifteen,  correspond  with  the 


Development  o  f  the  lacteal 
gland.  1.  Kudimeut  of  the  gland 
in  a  male  embryo,  at  five  months. 
a.  Horny  layer,  b.  Mucous  layer 
of  the  epidermis,  c.  Process  of  the 
latter  or  rudiment  of  the  gland. 
(/.  Fibrous  membrane  around  the 
same.  2.  Lacteal  gland  of  a  female 
fcetus,  at  seven  months,  seen  from 
aljove.  a.  Central  substance  o  f 
the  gland,  with  larger  (6)  and 
smaller  (c)  solid  outgrowths,  the 
rudiments  of  the  large  gland  lobes. 


Fig.  411. 


Mammary  Gland,  Acini,  and  Ducts. 


number  of   lobes.     The  mamma,   as  a  whole,  is  of  a   firm  con- 
sistence ;   of  a  pinkish-white  color,  of  circular  form  with  its  ex- 


710 


THE  SKIN  AND  ITS  APPENDAGES. 


ternal  surface  convex  and  prolonged  to  the  nipple.  The  latter^ 
provided  with  sensitive  papillte,  is  highly  vascular  and  capable 
of  erection.  The  nipple,  reddisli  or  brownish,  is  surrounded  by 
an  areola  of  skin  usually  of  the  same  color,  and  containing  seba- 
ceous glands  appearing  as  whitish  eminences,  which,  during  suck- 
ing, secrete  a  fatty  substance  which  protects  the  part  from  excoria- 
tion. The  mammae  exist  in  the  male,  but  usually  only  in  a 
rudimentary  condition.  Their  presence  in  animals  gives  rise  to  the 
name  mammalia,  the  highest  order  of  vertebrates,  and  while,  as  a 
general  rule,  they  are  attached  in  such  to  the  abdominal  walls,  in 
man,  monkeys  and  the  elephant,  they  are  situated  on  the  anterior 
part  of  the  tliorax. 

It  has  been  shown  by  modern  investigations  ^  that  while  the  se- 
creting cell  of  the  mammary  gland  during  the  inactive  period 
(Fig.  412,  I)  are  polyhedral,  flat,  and  uninucleated,  they  become  dur- 
ing the  active  period  (Fig.  412,  II)  cylindrical,  tall,  and  multinucle- 

FiG.  412. 


I.  Inactive  acinus  of  the  mamma.    //.  During  the  secretion  of  milk — </,  h,  milk-globules  ;  c,  d, 
f,  colostrum  corpuscles;/,  pale  cells  (bitch).     (Landois.) 


ated  and  finally  disintegrate  their  contents,  forming  the  milk.  The  se- 
cretion of  the  mammary  glands  or  milk,  having  a  specific  gravity  of 
from  ]  .026  to  1.035  and  constituting  a  perfect  emulsion,  consists  of  a 
colorless  li(|uid,  the  milk  plasma,  and  innumerable  fat-like  bodies, 
the  milk  corpuscles,  or  globules.  The  latter,  to  which  the  opaque, 
whitish  color  of  milk  is  due,  are  very  variable  in  size,  -^^^  to  -^^  of 
a  millimeter  (Y27iro  ^^  ^^^  T2Vo'  ^^  ^^  inch),  and  consist  of  minute 
drops  of  fat  surrounded  apparently  by  a  thin  film  of  casein,  the  so- 
called  "  paptogen  "  membrane. 

Milk  is  composed  in  one  hundred  parts  in  round  numbers  of: 
Water,  88.58  ;  proteids,  3.09  ;  fat,  3.52  ;  lactose,  4.29  ;  salts, 
0.16.^  The  proteids  of  milk  are  casein,  lactalbumin,  and  lacto- 
globulin,  the  two  latter  occurring,  however,  in  much  smaller  quan- 
tities than  the  casein.  The  fat  consists  chicfiy  of  stearin,  palmitin, 
and  olein,  with  small  amounts  of  butyric  and  caproie  acids  and  of 
small  quantities  of  cholesterin,  lecithin,  and  a  yellow  pigment. 
The  salts  consist  of  sodium    and    potassium  chloride,  potassium^ 

^Hcldenhain,  in  Hermann,  Handlmcli,  Bd.  v.,  1883,  s.  381. 
2  Halliburton,  op.  cit.,  p.  o77. 


SUDORIFEROUS  GLANDS.  711 

calcium,  magnesium,  and  ferric  phosphate,  sodium  and  })otassium 
sulphate,  and  traces  of  silica.  With  the  exception  of  the  water  and 
salts  the  constituents  of  the  milk  are  elaborated  by  the  cells  of  the 
mammary  gland  out  of  materials  supplied  by  the  blood,  they  not 
existing  as  such  in  the  latter.  That  the  fat  of  the  milk  is  not  de- 
rived exclusively  from  the  fat  of  the  food  is  shown  by  the  fact  that 
the  milk  of  a  l)itch  fed  upon  a  purely  flesh  diet  contains  larger 
amounts  of  fat — the  albumin  splitting,  as  already  mentioned,  into 
a  nitrogenous  (urea)  and  non-nitrogenous  molecule  (fat).  That  the 
salts  of  the  milk  even  are  not  derived  from  the  blood  by  a  mere 
process  of  filtration,  but  are  elaborated  by  the  cells  of  the  gland,  is 
shown  by  the  fact  of  the  amount  in  which  they  are  ]>resent  in  the 
two  fluids  being  so  difivrent.  The  (piantitv  of  milk  secreted  in 
twenty-four  hours  varies  very  much,  depending  upon  the  c(»ndition 
of  the  female,  kind  of  food,  etc.  Perhaps  it  may  be  said  that  the 
daily  production  of  milk  by  the  human  female  amounts  to  about 
one  liter  or  nearly  a  (piart.  The  gases  of  human  milk  have  not 
been  investigated  ;  that  of  the  cow  contains  in  100  volumes  :  Nitro- 
gen, 1.41  ;  oxygen,  0.16;  carbon  dioxide,  0.72. 

The  milk  formed  at  the  beginning  of  lactation — the  colostrum 
— differs  from  the  later  in  having  a  higher  specific  gravity,  in  be- 
ing thinner,  yellowish  in  color,  and  containing  many  of  the  milk 
cells  in  an  entire  condition. 

During  the  intervals  of  lactation  the  mammary  glands  secrete 
only  a  small  quantity  of  viscid  mucus. 

The  secretion  of  milk  appears  to  be  influenced  if  not  controlled 
by  the  central  nervous  system  through  vasomotor  or  secretory 
nerves.^  It  is  well  known  to  obstetricians  that  the  milk  of  a  woman 
affected  by  some  strong  emotion  or  attacked  by  disease  will  not 
only  be  altered  in  quality  but  even  suppressed  altogether.  The  re- 
sults of  experiments  made  upon  animals,  though  conflicting  in  some 
respects,  confirm  upon  the  whole  the  above  view,  division  of  the 
spermatic  nerve  being  usually  followed  by  an  increased  flow  of 
milk,  stimulation  by  a  diminished  one.  The  effect  is  probably  due 
to  vasomotor  action,  though  according  to  one  observer  secretory 
fibers  have  been  traced  directly  to  the  cells  of  the  mammary  gland. - 
From  the  fact,  however,  that  after  the  severance  of  all  nervous 
connections  milk  is  still  secreted,  it  may  be  inferred  that  the  mam- 
mary gland  acts  automatically,  even  though  influenced  by  the  cen- 
tral nervous  system. 

Sudoriferous  Glands. 
The  sudoriferous  or  sweat  glands,  like  the  sebaceous  and  mammary 
glands,  are  appendages  of  the  epidermis,  beginning  about  the  fifth 
month  of  intrauterine  life  as  flask-like  involutions  of  the  cells  of  the 

illeidenhain  in  Hermann's  Handlnich,  Band  v.,  Thl.  1,  s.  302.  Eolirig,  Yir- 
chow's  Archiv,  Band  67,  1876,  s.  llt».  Eckhard,  Beitnige,  IS.'jo,  s.  12,  1S77,  s.  117. 
Mironow,  Art-hives  des  Sciences  biolooiques,  St.  Petersburg,  Tome  iii.,  1894,  p.  353. 

^Arnst^in,  Anat.  Anzeiger,  Band  x.,  1895,  s.  410. 


712  THE  SKIN  AXD  ITS  APPENDAGES. 

rete  mucosum  of  the  epidermis  into  the  dermis  (Fig.  413).  As  de- 
velopment advances  this  solid  liask-like  rudiment  becomes  trans- 
formed into  a  hollow  tube,  Avhich,  extending  itself  through  the 
dermis  to  the  subcutaneous  adipose  tissue,  terminates  at  the  one  end 
in  a  coil,  and  at  the  other  end  as  the  sweat 
pore  on  the  surface  of  the  skin,  a  passage-way 
in  the  meantime  being  formed  in  the  epidermis 
leading;  from  the  latter  into  the  hollow  tube. 
Each  sweat  gland,  when  fully  formed,  consists 
of  a  tube  convoluted  at  its  commencement,  the 
secreting  portion  of  a  yellowish-red  color, 
spheroidal  in  form,  with  an  average  diameter 
of  1.2  millimeters  (the  ^^  of  an  inch),  and  pass- 
ing thence  upward,  as  the  sweat  duct,  in  a 
slightly  tortuous  manner  to  the  external  surface 
of  the  dermis.  The  tube  consists  of  an  external 
pa^'m?i'^L"nVoVrh"Jimau  Abrous  layer,  succecdcd  by  a  basement  mem- 
embrvo  at  five  months;    branc,  the  lattcr  Supporting  an  epithelium  of 

niaguineu  350  diameters.  '  t^i  ^  .    . 

a.  Horny  layer  of  the    polyhedral  nucleated  cells  containing  granular 

epidermis,     b.  Mucous  t  n         •   i  •  *        • 

layer,  c.  Corium.  d.  and  ycUoWlSh  pigment  matter.  As  just  men- 
vet  without^  any  "ca^'ity*  tioned,  at  the  point  where  the  sweat  duct 
,l°mdTeTK""^  ''  '""'"  opens  on  the  surface  of  the  dermis  a  passage- 
way is  continued  through  the  epidermis  to 
the  exterior.  Where  the  epidermis  is  thin  the  passage-way  is 
straight,  but  where  thick,  as  in  the  palms  and  soles,  it  takes  a 
spiral  course,  terminating  at  the  surface  in  a  funnel-shaped  orifice. 
The  openings  of  the  sweat  ducts  may  be  distinctly  seen  disposed  in 
a  single  row  on  the  summits  of  the  ridges  of  the  skin  of  the  palms 
and  soles,  if  the  latter  be  viewed  with  a  common  pocket  lens.  In 
other  situations,  however,  they  are  far  less  apparent.  With  the  ex- 
ception of  the  concave  surface  of  the  concha  of  the  ear,  the  glans 
penis,  the  inner  layer  of  the  prepuce,  and  perhaps  a  few  other 
places,  the  sweat  glans  are  found  in  every  part  of  the  skin.  The 
number  varies,  however,  very  much  according  to  the  part  of  the 
skin  examined.  Thus,  while  according  to  Krause,^  in  the  palmar 
surface  of  the  hand  there  may  be  as  many  as  2,736  sweat  glands  in 
6.7  sq.  cm.  (1  square  inch)  of  skin,  in  that  of  the  nates  there  may 
be  as  few  as  417  per  sq.  cm.  It  is  this  variation  in  the  number  of 
sweat  glands  existing  in  different  ])arts  of  the  skin  that  renders  any 
determination  as  to  their  total  number,  as  estimated,  for  example,  by 
Krause  at  2,381,248,  so  very  uncertain.  Assuming  that  the  se- 
creting portion  of  the  coil  of  each  sweat  duct,  when  unravelled, 
measures  1.5  millimeters  (J^r  of  an  inch)  in  length  on  the  above 
estimate,  if  the  tubes  were  placed  end  to  end  they  would  extend  a 
distance  of  3.8  kilometers  (2^  miles).  It  should  be  mentioned, 
however,  with  reference  to  this  last  estimate,  that  the  length  of  the 
excretory  portion  of  the  <luct  is  not  taken  into  consideration,  which 
MVagner,  PJiysiologic,  Band  ii.,  s.  131.     Braunscliweig,  1844. 


PEES  PIE  A  TIOX.  713 

will  depend  on  the  thickness  of  the  skin.  Supposing  the  latter  to 
be  5  millimeters  (4-  of  an  inch),  the  mean  of  its  thickest  and  thin- 
nest parts,  the  total  length  of  the  excretory  portion  of  the  sweat 
ducts  would  amount  to  12.5  kilometers  (7|  miles),  a  somewhat  ex- 
aggerated estimate,  and  very  approximate,  it  must  be  admitted. 
The  sweat  glands,  somewhat  modified,  constitute  the  ceruminous 
glands  of  the  ear,  which  will  be  referred  to  again  in  our  account  of 
that  organ,  and  also  the  odoriferous  glands  of  the  axilla. 

In  the  latter  situation  they  form  a  patch  in  the  subcutaneous  con- 
nective and  adipose  tissue  often  an  inch  and  a  half  or  more  in  diam- 
eter, being  largest  in  the  center  of  the  patch  and  gradually  diminish- 
ing toward  the  circumference,  where  they  become  undistinguishable 
from  the  ordinary  sMeat  glands.  The  odoriferous  glands  of  the 
axilla  not  only  secrete  sweat  but  a  strongly  odorous  substance, 
lience  their  name,  which  varies  somewhat  in  character  in  the  diifer- 
ent  races  of  mankind.  Indeed,  it  is  to  this  secretion  that  the  pecu- 
liar odor  of  negroes  is  to  a  great  extent  to  be  attributed,  the  glands 
as  a  general  rule  being  better  developed  in  the  negro  than  in  the 
white  man,  attaining  in  the  former  the  size  of  a  pea. 

Perspiration. 

The  secretion  of  the  sudoriferous  or  sweat  glands,  the  perspira- 
tion or  sweat,  although  being  continually  elaborated  by  the  latter 
from  the  blood,  does  not  always  appear  as  such  upon  the  surface  of 
the  skin,  passing  from  the  body  in  the  form  of  an  insensible  vapor 
as  rapidly  as  produced.  If,  however,  through  the  amount  of  the 
sweat  secreted  being  increased,  or  from  the  condition  of  the  atmos- 
phere, as  regards  temperature  and  moisture,  the  evaporation  of  the 
sweat  is  prevented,  the  sweat  remains  in  the  form  of  minute  drops, 
and  constitutes  what  is  commonly  understood  as  sweat  or  perspira- 
tion. There  is  no  difference,  therefore,  between  the  insensible  and 
sensible  perspiration,  the  form  in  which  it  may  be  exhaled,  whether 
as  liquid  or  vapor,  depending  simply  upon  the  conditions  just  men- 
tioned. 

Sweat  is  a  clear  watery  liquid,  of  a  specific  gravity  of  1.003  to 
1.004,  having  a  saline  taste  and  a  peculiar  odor  according  to  the 
part  of  the  skin  from  which  it  is  obtained.  The  reaction  of  the 
sweat  appears  to  be  acid,  though,  according  to  many  ol)servers,  it  is 
alkaline,  the  acidity  being  due  to  the  latter,  to  the  admixture  of 
fatty  acids  derived  from  the  sebum. ^  Sweat  consists  of  more  than 
nine-tenths  water,  the  remaining  constituents  being  salts,  fats,  urea, 
and  other  organic  matters  in  traces,  and  epithelium.-  The  inorganic 
salts  consist  principally  of  sodium  chloride,  0.2  to  0.3  per  cent., 
though  alkaline  sulphates  and  phosphates  are  present  in  small  quan- 
tities. The  fatty  matters,  amounting  to  0.4  per  cent,  are  produced 
by  the  sebaceous  glands.  Urea  is  usually  present  only  in  small 
quantities,  0.08  per  cent.     It  may  be  mentioned,  in  this  connection, 

'  Plammarsten,  op.  cit.,  p.  3'27.        ^Charles,  Phvsiologioal  C'liemistry,  p.  349. 


714  THE  SKIN  AND  ITS  APPENDAGES. 

that  of  the  carbon  dioxide  eliminated  by  the  system  about  -jL  to 
g-g-Q  is  exhaled  by  the  skin  together  with  the  sweat. 

So  far  as  known  to  the  author,  the  celebrated  Sanctorius  was  tlie 
first  to  endeavor  to  determine  experimentally,  during  the  seven- 
teenth century,  the  amount  of  the  perspiration.  The  method  made 
use  of  was  to  weigh  daily  the  body,  and  all  the  solid  and  liquid 
ingesta  and  egesta,  and  from  the  loss  of  weight  experienced  by  the 
body,  to  deduce  the  amount  of  vapors  transpired.  Thus,  if  from 
every  8  pounds  of  ingesta  taken  in  24  hours  there  were  3  pounds  of 
sensible  egesta  (44  ounces  urine,  and  4  ounces  feces),  it  was  inferred 
that  the  remaining  5  pounds  of  ingesta  passed  from  the  body  in- 
sensibly in  the  form  of  vapor.  Unfortunately,  however,  as  the  lat- 
ter included  the  vapor  exhaled  from  the  lungs  as  well  as  that  from 
the  skin,  and  the  observations  being  simply  embodied  as  aphorisms,^ 
no  numerical  tables  given,  the  results  obtained  have  now  but  little 
value,  although  Sanetorius  experimented  daily  in  the  manner  de- 
scribed for  a  period  of  thirty  years.  ^Vlthough  numerous  and  inter- 
esting observations  and  experiments  were  made  during  the  eight- 
eenth century  by  Dodart,  Keill,  Rye,  Gorter,  Joining,  Hales,  Stark, 
with  a  view  of  determining  the  amount  of  the  perspiration  and  the 
conditions  aifecting  it,  it  will  not  be  necessary  to  dwell  upon  them, 
since  the  pulmonary  and  cutaneous  perspiration  were  estimated  to- 
gether by  these  observers.  The  first  attempt  to  estimate  separately 
the  vapor  exhaled  by  the  skin  from  that  by  the  lungs  was  made  by 
Lavoisier^  and  Seguin  in  1700,  the  experiments  consisting  in  enclos- 
ing Seguin  in  a  bag  of  gummed  taifeta  which  was  tied  above  the 
head,  an  aperture  in  the  coat  when  fixed  around  the  mouth  by  a 
mixture  of  turpentine  and  pitch  enabling  Seguin  to  inspire  fresh 
air  and  exhale  the  breathed  air,  Ijut  only  permitting  the  pulmonary 
vapor  of  the  latter  to  escape  from  the  body.  By  then  deducting 
the  amount  of  the  pulmonary  vapor  as  determined  by  the  loss  of 
Aveight  when  enclosed  in  the  gum  coat  from  the  total  quantity  of 
vapor  exhaled  as  determined  by  the  loss  of  weight  when  not  so  en- 
closed, the  amount  of  the  cutaneous  vapor  was  at  last  experimentally 
determined,  and  was  found  to  be  nearly  2  kilos.  (2  pounds)  which 
does  not  differ  very  considerably  from  the  later  results  obtained  by 
Krause  ^  and  Valentin.^ 

The  amounts  of  perspiration  exhaled  by  the  skin,  as  shown  by 
Lavoisier  and  Seguin  and  subsequent  ol)servers,  vary  very  consid- 
erably, however,  depending  upon  the  quantity  and  temperature  of 
the  liquid  food,  the  relative  dryness  or  moisture  and  temperature 
of  the  atmosphere,  the  amount  of  exercise  taken,  and  the  activity 
of  the  lungs  and  kidneys,  with  which  the  skin  acts  vicariously. 
The  skin,  however,  not  only  suj^plements  the  action  of  the  lungs  as 

'  Sanctorii  Sanctorii,  De  Statica  Medecina  aphorisruorum.  LuL^duni  Batavorimi, 
MDCCIII. 

^Mem.  del' Acad,  des  Sciences,  p.  609.     Pans,  1797. 

^  AVagner,  Plivsiolooy,  Band  ii.,  s.  819. 

*  Physiology,  Band  i.,  s.  174.     Braunschweig,  1844. 


PERSPIEA  TIOX.  7 1  •> 

regards  the  exhalation  of  watery  vapor  and  carbon  dioxide,  but  that 
of  the  kidneys  also,  and  not  only  with  reference  to  the  water  but  to 
the  urea  eliminated  as  well.  Thus,  according  to  Carpenter,^  in  one 
experiment  the  entire  quantity  of  perspiration  for  the  whole  body 
being  in  one  hour  3,320  grains,  (\\  grains  of  urea,  containing  3.0."> 
X,  were  obtained.  It  is  not  likely,  however,  that  the  excretion  of 
urea  would  have  continued  during  the  whole  twenty-four  hours  at 
such  a  rate.  It  should  be  mentioned  in  this  connection  also,  ac- 
cording to  Funke,-  that  through  the  desquamation  of  the  epidermic 
scales  about  0.7  gramme  (1 1  grains)  of  nitrogen  are  also  daily  elim- 
inated by  the  skin.  According  to  recent  researches  the  amount  of 
urea  excreted  in  the  s^veat  is  also  much  increased  by  muscular  work.'* 
That  the  sweat,  however,  contains  other  substances  than  those 
already  mentioned  is  rendered  very  probal^le  from  the  fact  that 
death  soon  ensues  when  the  perspiration  is  suppressed,  as,  for  ex- 
ample, when  the  skin  is  varnished  in  animals*  and  also  in  human 
beings,  as  in  the  celebrated  case  of  the  child,  who,  being  covered 
^^'ith  gold-leaf  to  personate  an  angel  at  the  coronation  of  Leo  X., 
died  a  few  hours  afterward.'  While  death  in  such  cases  is  no  doubt 
partly  due  to  the  imperfect  arterialization  of  the  blood  and  the  rapid 
fall  of  temperature,  the  varnish  favoring  the  loss  of  heat  in  pro- 
ducing a  cutaneous  hyperemia  similar  to  that  induced  through 
paralysis  of  the  vasomotor  nerves,  symptoms  like  that  of  uniemic 
poisoning,  tremors,  tetanic  cramps,  movements  of  rotation,  increased 
reflex  excitability,  present  as  well,  lead  one  to  suppose  that  urea 
and  other  poisonous  substances  not  yet  isolated  are  retained  in  the 
system  Avhich  are  usually  carried  away  in  the  sweat.  That  such  is 
the  case  is  shown  h\  the  fact  that  if  human  sweat  be  injected  into 
the  blood  of  the  rabbi  t*"  the  pulse  of  the  latter  may  be  increased  from 
192  beats  per  minute  to  326,  the  respiration  from  82  to  105,  and 
the  temperature  raised  from  37.2°  to  40°  C.  (99°  to  104°  F.). 
Even  if  it  be  admitted  that  the  exact  cause  of  death  is  not  yet  posi- 
tively determined  there  can  be  no  doubt  that  imperfect  action  of" 
the  sweat  glands  must  be  a  source  of  disease,  various  matters  then 
accumulating  in  the  system  which  would  otherwise  be  eliminated. 
Indeed,  too  much  stress  cannot  be  laid  upon  the  importance  of 
keeping  the  skin  clean — of  the  free  use  of  Avater.  Especially  is 
such  the  case  in  tropical  climates  where  the  true  secret  of  main- 
taining one's  health  lies  in  attending  to  the  condition  of  the  skin, 
and  where  febrile  diseases  are  more  successfully  treated  by  active 
diaphoresis  than  in  any  other  way.  The  great  importance  of  daily 
baths  in  the  maintenance  of  health  cannot  be  exaggerated,  and  ap- 

'Phy^iol<),£r}-,  p.  491.  2 ;^Iolescliott  Untei-s.,  1858,  Band  iv.,  s.  56. 

'' Argutinsky,  Pflnger's  Archiv,  Band  xxxxvi.,  1890,  s.  552. 

*Fouicauet,  Comptes  rendus.  Tome  vi.,  p.  369.  Paris,  1S:]S.  Ibid.,  1843, 
Tome  xvi.,  p.  139.  Valentin.  Arcliiv  f.  Physiologie  Ileilknnde,  1858,  Band  ii.,  s. 
433.     Bernard,  Liqnides  de  I'Organisme,  Tome  ii.,  p.  177.     Paris,  1859. 

^Laschkewitsch,  D\\  Bois  Reymond's  Arch.,  1868,  s.  61. 

^Rohrig,  Jahrb.  t'iir  Balneologie,  1873,  Band  i.,  s.  1. 


716  THE  SKIN  AND  ITS  APPENDAGES. 

parently  was  more  appreciated  by  the  ancients  than  the  moderns, 
as  the  ruins  of  the  magnificent  baths  of  Caracal  la  and  Diocletian,  at 
Rome,  still  to  this  day  testify.  Noble  institutions  they  were  ;  the 
baths  or  thermae  fed  by  stupendous  aqueducts  stretching  for  miles 
across  the  Campagna,  their  perpetual  streams  of  hot  and  cold  water 
flowing  through  mouths  of  solid  silver  into  capacious  basins,  accom- 
modating at  one  time  thousands  of  bathers,  and  where  for  the  eighth 
of  an  English  penny  the  meanest  Roman  of  them  all  could  enjoy  the 
luxury  that  might  have  well  excited  the  envy  of  the  kings  of  Asia/ 

The  secretion  of  sweat,  like  other  secretions,  is  influenced  by  the 
nervous  system,  the  sweat  center  or  centers,  being  situated,  accord- 
ing to  Luchsinger,^  in  the  anterior  horns  of  the  gray  matter  of  the 
spinal  cord  and  medulla.  From  these  centers  nerve  fibers  arise, 
which,  passing  down  the  cord,  emerge  principally  with  the  anterior 
roots  of  the  third,  fourth,  and  fifth  cervical  nerves  to  pass  with  the 
brachial  plexus  to  the  skin  of  the  upper  extremity,  and  with  the 
anterior  roots  of  the  lumbar  nerves  to  supply  the  lower  extremity. 
The  sweat  centers  may  be  stimulated  directly  and  reflexly.  It  is 
in  the  latter  manner  that  the  sweat  centers  are  excited  by  muscular 
exercise,  dyspnoea,  fear,  heat,  various  substances  such  as  pilocarpin, 
nicotin,  muscarin,  and  inhibited  by  cold  and  atropin. 

While  the  sweat  nerves  emerge  from  the  spinal  cord  and  run  in 
company  with  the  vasomotor  nerves,  the  secretion  of  sweat  is  in- 
dependent of  vasomotor  influence  except  in  so  far  as  the  blood 
supplies  in  the  long  run  the  materials  for  the  elaboration  of  the 
secretion.  This  is  shown  by  the  fact  that  stimulation  of  the  sci- 
atic nerve  in  the  cat  causes  secretion  of  sweat  in  the  soles  of  the 
feet  after  ligation  of  the  aorta  or  even  after  amputation  of  the 
limb.^  It  is  also  a  matter  of  daily  observation  that,  although  a 
person  may  be  pale  from  terror  or  nausea,  sweating  may  be  pro- 
fuse, and  on  the  other  hand,  though  the  skin  may  be  flushed  with 
fever,  sweating  is  absent.  That  the  sweat  nerves  are  true  secretory 
nerves  is  still  furtlier  shown  by  receut  histological  researches/  their 
terminal  fillers  having  been  followed  directly  to  the  secretory  cells 
of  the  sweat  glands. 

The  manner  in  which  the  skin  regulates  the  temperature  of  the 
body  through  the  radiation,  conduction,  etc.,  of  the  heat  produced 
within  it  having  already  been  sufficiently  considered,  it  will  not  be 
necessary  to  treat  further  of  the  function  of  the  skin  in  this  re- 
spect. While  there  can  be  no  doubt  that  absorption  in  the  lower 
animals  and  in  many  of  the  higher  is  to  a  considerable  extent 
carried  on  by  the  skin,  frogs,  lizards,  etc.,  rapidly  gaining  in  weight 
when  immersed  in  water,  some  difference  of  opinion  still  prevails 
among  piiysiologists  as  to  what  extent  the  skin   in  man  normally 

^  Gibbon,  Decline  and  Fall  of  the  Eoman  Empire,  Vol.  v. ,  p.  237.     London,  1807. 

^Pfliiger's  Archiv,  Band  xiii.,  s.  212;  Band  xiv.,  s.  545;  Band  xv.,  s.  482; 
Band  xvL,  s.  538. 

''  Goltz,  Pfliiger's  Archiv,  Band  xi.,  1875,  s.  71.  Langley,  Journal  of  Physiology, 
^'ol.  xii.,  1891,  p.  347.  ^Arnstein,  Anatomische  Anzeiger,  Band  x.,  1895. 


A  B SORPTION  B  Y  SKIX.  7 1  7 

acts  as  an  absorbing  snrface.  It  may  not  appear  snpcrflnous,  there- 
fore, if  attention  bo  called  to  those  instances  or  conditions  in  which 
absorption  does  take  place  in  man  by  the  skin.  It  is  well  known, 
as  already  mentioned,  in  speaking  of  the  cause  of  thirst,  that  in 
the  case  of  the  shipwrecked  sailor  the  thirst  was  very  much,  if  not 
entirely,  temporarily  relieved  by  the  immersion  of  the  bodv  in  the 
sea,  or  by  wearing  clothes  wet  with  the  same.^  In  certain  cases 
also,  where  the  introduction  of  solid  or  liquid  food  by  the  mouth 
had  become  impracticable,  immersion  of  the  patient  in  a  bath  of 
tepid  milk  morning  and  evening  not  only  relieved  the  thirst,  but 
for  some  time  maintained  life,  the  weight  gained  being  unaccounted 
for  by  the  enemata  also  given.-  It  has  also  been  shown  that  not 
only  does  the  body  gain  in  weight  after  immersion  in  a  bath  through 
the  absorption  of  the  liquid,  but  that  the  skin  will  also  absorb  cer- 
tain salts  M'hen  dissolved  in  the  same.  That  the  skin  is  permeable 
by  gas  is  also  well  known,  it  having  l)een  shown  by  Bichat  that  if 
a  limb  be  immersed  in  a  putrid  gas  the  latter  will  be  absorbed  by 
the  skin,  and  by  Aubert  that  the  skin  absorbs  about  the  -^^  of  the 
oxygen  absorbed  by  the  lungs.  Admitting,  then,  that  under  cer- 
tain circumstances  the  skin  undoubtedly  can  absorb,  it  still  remains 
undetermined  to  what  extent,  under  normal  conditions,  it  does  ab- 
sorb. Covered,  as  the  skin  usually  is  in  man,  almost  entirely  with 
more  or  less  clothing,  it  is  difficult  to  comprehend  how  or  what  the 
skin  under  such  circumstances  can  absorb,  the  gain  in  weight  of 
the  body  through  absorption  of  the  watery  vapor  of  the  atmosphere 
sometimes  instanced '  being  due  to  the  absorption  of  the  vapor  by 
the  lungs  rather  than  by  the  skin.  "We  have  further  seen  that 
through  the  presence  of  the  sebaceous  matter  the  skin  is  rendered 
repellant  of  water,  which  thereby  renders  it  very  insusceptible  to 
the  taking  up  of  foreign  substances.  Indeed,  it  is  very  question- 
able whether  such  are  ever  introduced  into  the  system  unless  the 
epidermis  be  disintegrated,  the  view-  sometimes  advanced  *  that  sub- 
tances  are  absorbed  by  the  sweat  ducts  being  very  improbable, 
since  the  latter  are  already  filled  with  sweat,  and  the  movement  of 
the  sweat,  being  from  below  upward,  would  tend  to  wash  away 
foreign  substances  rather  than  favor  their  absorption.  It  would 
appear,  therefore,  as  we  pass  from  the  lower  to  the  higher  animals, 
that  the  skin  loses  its  significance  as  an  absorbing  surface,  becoming 
essentially  protective  and  excretory  in  function.  Nevertheless, 
though  the  absorbing  power  of  the  skin  in  the  economy  of  the 
higher  animals  may  have  been  superseded  by  that  of  the  lungs  and 
alimentary  canal,  under  certain  conditions  it  may  even  in  them  act 

^  Madden,  Experimental  Enquirv  into  the  Phvsiologv  of  Cutaneous  Absoi-ption, 
p.  64.     Edinb.,  1838. 

^Currie,  Medical  Reports,  Vol.  i.,  pp.  308-326.  AVatson,  Chemical  Essays,  Vol. 
iii.,  p.  100. 

3 Lining,  Phil.  Trans.,  1743,  p.  49G.  Klapp,  Inaugural  Essay  on  Cuticular  Ab- 
sorption, p.  30.     Philadelphia,  1805. 

*Auspitz,  Wiener  med.  Jalirb.,  1871.  Neumann,  Wiener  med.  Wochenschrift, 
1871. 


718  THE  SKIN  AND  JTS  APPENDAGES. 

vicariously  with  the  same,  as  no  doubt  it  does,  as  regards  the  ex- 
cretion of  water  by  the  kidneys  as  well  as  the  lungs. 

Sense  of  Touch  or  Locality. 
The  skin  acts  not  only  as  a  general  sensory  surface  through  the 
impressions  made  upon  the  epidermis  being  transmitted  thence  to 
the  more  deeply  situated  cutaneous  nerves,  but  through  its  Tactile, 
Pacinian,  and  Krause  corpuscles,  it  is  endowed  with  a  special  modi- 
fication of  sensibility — the  tactile  sensibility,  or  the  sense  of  touch, 
by  means  of  which  we  not  only  feel  but  appreciate  to  a  certain  ex- 
tent the  form,  size,  character  or  surface,  weight,  and  temperature  of 
objects.  While  the  skin  as  a  whole,  therefore,  is  endowed  with  a 
general  sensibility  more  or  less  acute  in  different  parts  of  the  body, 
its  tactile  sensibility,  however,  is  restricted  to  certain  portions  of  it, 
and  most  delicate  in  those  situations  where  the  corpuscles  are  most 
abundant.  Thus,  if  the  blunt  but  fine  ends  of  a  pair  of  dividers 
provided  with  a  graduated  bar,  or  sesthesiometer,  be  applied  to  the 
tip  of  the  tongue — the  individual  being  blindfolded — the  two  ends 
of  the  dividers,  though  only  separated  l)y  so  much  as  the  -^-^  of  an 
inch,  will  be  appreciated  as  two  distinct  objects.  If,  however,  the 
dividers  be  approximated  until  they  are  separated  by  less  than  that 
distance,  the  two  impressions,  a  moment  previous  distinctly  appre- 
ciated as  such,  now  fade  into  one,  as  if  l)ut  a  single  object  was 
touching  the  tongue.  Experimenting  in  this  manner,  it  was  first 
shown  by  \Yeber,^  and  afterward  by  Valetin,"  that  the  sense  of 
touch  varies  very  much  in  different  parts  of  the  body,  being  most 
acute  at  the  tip  of  the  tongue  and  ends  of  the  fingers ;  least  so  in 
the  back,  as  shown  as  follows  : 

Tactile  Sensibility.' 

Both  points  of  dividers 
Parts  of  surfaces.  felt  when  separated 

by  these  distances. 

Tip  of  tongue  .         .         .         .         .         .  0.50  of  a  line. 

Palmar  surface  of  third  phalanx  of  fingers  1.00  "  " 

"             u        u  second     "         "       '^  2.00  "  " 

Dorsal          "        "   third        "         "        "  3.00  "  '' 

Middle  of  dorsum  of  tongue     .         .         .  4.00  "  " 

End  of  the  great  toe         .         .         .         .  5.00  "  " 

Center  of  hard  palate        .         .         .         .  6.00  "  " 

Dorsal  surface  of  first  phalanx  of  fingers  7.00  "  " 

"       quarter  of  heads  of  metacarpal  bones  8.00  "  " 

Back  of  the  heel 10.00  "  " 

Dorsum  of  the  hand          ....  14.00  ''  " 

''           "        foot 18.00  "  " 

Sternum 20.00  "  " 

Five  upper  dorsal  vertebrae       .         .         .  24.00  "  " 

Middle  of         "             "              ...  30.00  "  " 

When  points  of  dividers  are  brought  closer  than  these  dis- 
tances they  are  felt  as  one. 

1  Warner,  Physiologic,  Band  iii.,  Zweite  Abtli.,  s.  524. 

2  Physiologic,  Band  ii.,  s.  558. 

3Cari)onter,  article  Touch,  Cyclopaedia  of  Anat.  and  Phys.,  Vol.  iv..  Part  2d,  p.  11G9. 


SENSE  OF  TOUCH  OB  LOCALITY.  "19 

The  sense  of  touch,  like  the  other  senses,  can  l)e  very  much  im- 
proved by  attention  and  practice.  Thus,  it  is  said  ^  that  the  female 
silk  throwsters  of  Bengal  can  distinguish  twenty  diiferent  degrees 
of  fineness  in  the  unwound  cocoons  by  the  touch  alone,  and  that 
the  Indian  muslin  weaver  makes  the  finest  cambric  vnth  a  loom  of 
such  simple  construction  that,  if  worked  by  the  haiids  of  a  Euro- 
pean, would  turn  out  but  little  better  than  canvas.  It  is  also  a 
well-known  fact  that  those  persons  who  are  employed  in  mints,  etc., 
in  the  daily  haljit  of  handling  coins,  detect  at  once,  and  with  cer- 
tainty, a  light  piece.  As  might  be  expected,  the  sense  of  touch  is 
very  much  developed  in  those  who  have  lost  the  sense  of  sight,  or 
who  have  been  blind.  One  of  the  most  remarkable  of  such  cases 
is  that  of  Giovanni  Gonelli,  who,  at  twenty  years  of  age  lost  his 
sight,  but  who,  nevertheless,  after  a  lapse  of  ten  years,  developed  a 
great  talent  as  a  sculptor,  modelling  such  an  excellent  statue  out  of 
clay  of  Cosmo  de  Medici  from  feeling  one  of  marble  that  the  Grand 
Duke  of  Tuscany  sent  him  to  Rome  to  make  a  statue  of  Pope  I"r- 
ban  VIII.,  which  was  a  very  successful  one,  the  likeness  being  said 
to  be  excellent.  Stranger  still,  even  a  good  knowledge  of  botany 
and  couchology  has  been  acquired  through  the  sense  of  touch  by 
persons  who  have  been  born  blind,  or  who  had  lost  their  sight  early 
in  life.  It  is  well  known,  also,  as  in  the  case  of  Baczko,"  that  the 
blind  can  learn  to  distinguish  the  colors  of  fabrics  by  the  sense  of 
touch.  It  is  related  that  Sanderson,  the  blind  professor  of  mathe- 
matics at  Cambridge,  could  not  only  distinguish  diiferent  medals, 
but  could  detect  imitations  of  them  often  better  than  professed  con- 
noisseurs, while  his  appreciation  of  variations  of  temperature,  it 
may  be  mentioned  also,^  was  so  acute  that  he  could  tell,  through 
slight  modifications  in  the  temperature  of  the  air,  when  very  slight 
clouds  were  passing  over  the  sun's  disk.  It  is  a  familiar  fact,  also, 
that  the  blind  learn  to  read  with  great  facility  by  passing  their 
fingers  over  raised  letters  of  about  the  size  of  those  of  a  folio  Bible. 
Terrible  a  calamity  as  the  loss  of  sight  is,  it  should  not  be  forgotten, 
as  the  above  examples  teach  us,  what  a  delicate  sense  in  that  of  touch 
we  possess  if  cultivated,  and  that  sources  of  pleasure  and  recreation 
through  its  development  may  be  offered  to  those  who  are  born  blind, 
or  who  have  lost  their  sight  later  in  life. 

The  sense  of  touch  next  to  that  of  sight  is  the  most  important 
means  bv  which  we  oaiu  our  knowledo;e  of  the  external  world. 
Indeed  our  appreciation  of  the  form  and  qualities  of  external  ob- 
jects is  based  almost  entirely  upon  the  association  of  tactile  and 
visual  sensations  together  with  those  due  to  the  so-called  muscular 
sense.  It  may  be  recalled  in  this  connection  that  the  center  for 
touch  is  usually  regarded  as  being  located  in  the  hippocampal  re- 
gion of  the  cortex. 

'Carpenter,  op.  cit.,  p.  1177. 

'^  Eiidolphi,  Phvsiologie,  Band  ii.,  s.  85. 

^Uunglison,  Physiology,  Vol.  i.,  p.  697.     Pliila.,  185(5. 


720  THE  SKIN  AND  ITS  APPENDAGES. 

Sense  of  Pressure  or  Weight. 
The  sense  of  pressure  or  of  weight  is  the  sense  by  means  of  which 
we  appreciate  the  amount  of  pressure  that  is  exerted  upon  the  skin. 
The  part  of  the  skin  endowed  with   this  sense  appears  to  be   es- 
pecially modified,  being  character- 
p,f,   4^4  ized    by  the   presence  of  the    so- 

^^^.  called  "pressure  spots"  or  "  pres- 

.•..,:;.*•"        :'••'.*''.•••;*'        .'}.'''.'.'.       ^^^Q   points"   (Fig.   414)   for  the 
**..  .V '••!.'•;        '.'y\<.] .'•       y/'-'f::        reception  of  stimuli. 
•'-*••)•*•..       :'.''.•::•         '"'.'  The  minimal  distance  at  which 

^  b-  c  two   pressure   spots,  when    stimu- 

Pressu re-spots,    a.  Middle  of  the  sole  of      latcd,    givC    risC    tO    distiuct    SCUSa- 
the  foot.    h.  Skin  of  zygoma,    c.  Skin  of  the        ,.  ^.  .         t/v>  ,  ,  /> 

back.    (Landois.)  tious,  varics  HI  Gitierent  parts  ot 

the  skin,  being  in  the  palm  of  the 
hand,  for  example,  from  0.1  to  0.5  mm.,  on  the  back  from  4  to  6  ram. 
The  smallest  perceptible  pressure  varies,  also,  according  to  the  lo- 
cality. Thus  a  pressure  exerted  by  0.002  grms.  will  be  appreci- 
ated if  the  weight  be  applied  to  the  forehead,  temple,  back  of  the 
hand,  and  forearm,  0.005  to  0.015  grms.  are  felt  by  the  fingers,  0.04 
to  0.5  grms.  by  the  chin,  abdomen,  and  nose,  1  gr.  by  the  finger 
nail.^  Variations  are  also  manifested  by  the  skin  in  the  power  of 
discriminating  differences  of  pressure.  Thus,  according  to  Eulen- 
berg,  the  forehead,  lips,  and  temples  appreciate  the  difference  be- 
tween 200  and  205  grms,  or  -^-^  and  300  and  310  grms,  or  -^-^, 
the  head,  fingers,  and  forearm,  the  difference  between  200  and  220 
grms.  or  Jg-  and  200  and  210  grs.  or  J^. 

The  smallest  additional  weight  appreciated  as  a  difference  when 
added  to  1  grm.  resting  upon  the  skin  is  according  to  Dohrn  in  the 
case  of  the  first  phalanx  of  the  finger  0.02  grm,,  third  phalanx 
0.49  grm.,  back  of  the  foot  0,5  grm.,  palm  1.01  grm,,  back  3.8 
grms,^  It  is  a  well-known  fact  that  pressure  due  to  a  uniform 
compression  such  as  is  exerted  upon  a  finger  dipped  into  mercury, 
for  example,  is  not  felt  as  such  but  only  at  the  surface  of  the  level 
of  the  fluid.  If  the  weights  made  use  of  in  experimenting  upon 
the  sense  of  pressure  are  comparatively  heavy  ones  and  the  pres- 
sure has  been  exerted  for  some  time  the  sensation  produced  persists 
even  after  removal  of  the  weight  as  the  so-called  "  after-pressure." 
Even  in  the  case  of  light  weights  being  used  an  interval  of  time 
amounting  to  at  least  from  ^i^  to  ■^\-^  of  a  second  must  elapse 
in  order  to  appreciate  the  difference,  the  sensations  becoming  fused 
Avhen  the  intervals  of  application  are  shorter.  Thus  it  has  been 
shown  that  when  the  fingers  are  pressed  against  a  toothed  wheel, 
the  sensation  experienced  -was  a  smooth  one  wdien  the  teeth  touched 
the  skin  at  the  intervals  just  mentioned,  whereas  each  tooth  caused 
a  distinct  sensation  when  the  wheel  was  rotated  more  slowly.  It 
is  also  well  known  that  vibrations  of  strings  cease  to  be  distin- 

^Anbertu.  Kammler,  Moleschott  Uiitersiiclningcn,  Eaml  v.,  1859,  s.  145. 
^Landois,  op.  cit.,  p.  105:5. 


SENSE  OF  PRESSURE  OR   WEIGHT. 


721 


guished  as  such  Avhen  the  rate  of  vibration  exceeds  that  of  1,600 
per  second. 

It  has  been  established  l:)y  the  researches  of  Weber  ^  and  Fech- 
ner  -  that  in  the  case  of  the  sense  of  pressure,  and  as  we  shall  see 
presently,  in  that  of  all  kinds  of  sensation  there  is  a  strength  of 
stimulus  varying  for  each  sense,  the  so-called  "  liminal  intensity," 
which  is  just  powerful  enough  to  awaken  sensation.  On  the  other 
hand,  there  is  also  a  strength  of  stimulus,  the  so-called  "  maximum 
of  excitation,"  beyond  which  no  increase  of  sensation  will  l)e  felt  by 
any  further  increase  of  stimulus.  There  is,  therefore,  for  each 
sense  a  "  range  of  sensibility,"  the  range  extending  between  these 
two  limits.  It  has  also  been  shown  that  as  the  strength  of  the 
stimulus  increases,  so  also  does  the  sensation,  but  that  the  latter  in- 
crease equally  when  the  amount  of  stimulus  necessary  to  cause  a 
perceptible  increase  of  sensation  bears  the  same  ratio  to  the  amount 
of  stimulus  already  applied.  Thus,  for  example,  the  eyes  being 
bandaged  and  the  hand  extended  and  supported,  if  Aveights  such  as 
10,  100,  1000  grammes  be  successively  placed  in  the  hand,  it  will 
be  found  that  one-third  of  the  original  weight,  3.3  or  33.3  grs., 
etc.,  must  be  always  added,  according  to  whichever  weight  be 
used  in  order  to  appreciate  any  increase  in  weight.  The  fractional 
increment  of  the  original  weight  necessary  for  the  discrimination, 
one-third  in  the  case  of  weight,  is  called  "  the  constant  pro- 
portion." The  "  liminal  intensity  "  and  the  "  constant  proportion  " 
being  known,  the  data  are  given  by  which  the  general  relation  of 
the  sensation  to  the  stimulus  can  be  shown  graphically. 

Suppose,  for  example,  that  the  sensation  under  consideration  be 
one  of  pressure,  let  the  horizontal  line  o  .r,  or  the  abscissa  (Fig. 
415),  be  divided  into  equal  parts,  1,  2,  3,  4,  to  represent  equal  in- 


FiG.  415. 


O  /  2  J  ^ 

Graphic  illustratioa  of  reaction  of  sensation  to  stimuli. 

crements  of  sensation,  the  zero  corresponding  to  the  minimum  of 
sensation,  the  vertical  lines,  or  the  ordinate  0«,  lb,  '2c,  3d,  -ie,  the 


46 


'  Vorlesungen,  Band  i.,  Leipzig,  s.  133. 

^Elemente  Der  Psjchophysik,  Band  ii.,  Leipzig,  s,  377. 


722  THE  SKIN  AND  ITS  APPENDAGES. 

stimuli,  Oa  corresponding  to  the  minimum  stimulus,  say  one-fiftieth 
of  a  gramnie,  each  ordinate  being  equal  to  the  preceding  one  plus  a 
third  of  the  same,  according  to  the  determination  of  the  constant 
proportional  in  the  case  of  weight ;  it  is  evident  that  the  difference 
of  length  between  the  line  Oa  and  the  lines  16,  2c,  3c?,  4e,  indicates 
the  weights  that  must  be  used  in  order  that  the  successive  sensa- 
tions should  be  equal. 

As  the  logarithms  of  the  stimuli  increase,  however  equally,  as 
well  as  the  sensations,  when  the  stimulus  is  increased  in  such  con- 
stant proportion  it  follows  that  the  sensation  is  not  proportional  to 
the  stimulus  but  to  the  logarithm  of  the  stimulus.^  In  other  words, 
if  the  sensations  are  as  1,  2,  3,  the  stimuli  are  as  10,  100,  1000; 
1,  2,  3,  being  the  logarithms  respectively  of  1,  10,  1000."  This 
so-called  Fechner's  psycho-physical  law  of  sensation  only  holds 
good,  however,  when  the  stimuli  used  are  of  medium  strength,  since 
as  we  have  seen  when  very  light  or  very  heavy  weights  are  used, 
the  increment  of  pressure  necessary  for  sensation  is  not  a  constant 
proportion  of  the  original  stimulus. 

Muscular  Sense. 
By  means  of  the  muscular  sense  we  learn  the  position  of  the  dif- 
ferent parts  of  our  bodies,  become  aware  of  the  density,  elasticity, 
immobility  due  to  the  resistance  offered  by  external  objects,  realize 
the  effort  we  make  when  exerting  a  pressure  upon  the  same,  and 
ap^jreciate  the  condition  of  our  muscles  and  the  extent  of  their  con- 
traction. By  the  muscular  sense  we  learn  far  more  accurately  the 
weight  of  an  object  when  supported  by  the  hand  by  muscular  effort 
than  when  the  object  simply  presses  upon  the  hand,  the  latter  being 
supported  and  extended,  we  not  only  feel  in  the  first  case  the  pres- 
sure of  the  object,  but  are  also  conscious  of  the  exertion  required  to 
lift  and  support  the  weight.  It  is  well  known  that  an  individual 
affected  Avith  locomotor  ataxia,  while  retaining  the  sensations  of 
touch,  temperature,  pain,  is  unable  to  coordinate  his  muscles,  and  on 
the  other  hand,  that  in  certain  kinds  of  nervous  diseases,  while  sen- 
sation may  be  impaired  or  abolished,  the  power  of  muscular  coordi- 
nation may  be  retained.  A  frog  can  also  coordinate  his  muscles  after 
entire  removal  of  the  skin,  and,  therefore,  in  the  absence  of  all 
cutaneous  sensation.  It  has  also  been  shown  by  Weber,^  as  a  gen- 
eral rule,  that  while  differences  in  weight  are  appreciated  most 
acutely  by  those  parts  of  the  skin  which  are  most  sensitive  to  the 
impressions  of  touch,  as  that  of  the  fingers,  for  example,  that, 
while  by  the  sense  of  pressure  alone  a  difference  in  weight  of  not 
less  than  one-eighth  can  only  be  determined,  by  making  a  muscular 

^  W.Wundt,  Grundziige  Der  Physiologischen  Psychologie,  Band  i.,  1880,  s.  358. 

2  A  logaritlini  of  a  nniiibcr  is  the  exponent  of  tlie  jjower  to  which  it  is  necessary 
to  raise  a  fixed  number  to  pnxhice  tlie  given  nnml)er.  Suppose  tlie  fixed  number  to 
be  10,  tlie  given  nvmil)er  100  or  1000,  then  2  and  o  will  be  the  logarithms  of  100  and 
1000  respectively,  since  10^  =  100,  lO''  =  1000. 

^AVagner,  Physiology,  Band  iii.,  Zweite  Abtli.,  s.  543. 


SENSE  OF  TEMPERATURE.  723 

effort,  as  in  lifting,  a  difference  of  one-sixteenth  can  be  accurately 
appreciated. 

Such  considerations  as  those  just  mentioned  have  led  many  phys- 
iologists to  regard  the  muscular  sense  as  due  to  impvdses  derived 
from  the  muscles,  tendons,  and  joints  as  well  as  from  the  skin.  On 
the  other  hand,  the  ataxic  symptoms  present  in  certain  nervous  dis- 
eases, where  sensation  is  impaired  and  often  referred  to  as  a  proof 
of  the  existence  of  a  special  muscular  sense  normally,  are  perfectly 
well  accounted  for  by  other  physiologists  by  the  loss  of  general 
sensibility.  Since  the  impression  made  by  the  foreign  bodv, 
whether  it  be  the  ground  we  tread  upon  or  the  child  A\e  hold  in 
our  arms,  not  being  transmitted  to  the  encephalon,  in  such  cases  it 
will  not  be  reflected  consciously  or  otherwise  to  the  appropriate 
jnuscles  whose  action  enables  us  to  stand  securely  or  grasp  firndv, 
hence  our  inability  to  Avalk  upon  the  ground  or  hold  a  child  in  our 
arms  unless  we  look  at  the  one  or  the  other,  the  essential  reflex 
action  being  then  effected  by  the  eye  and  optic  nerve  instead  of 
the  skin  and  cutaneous  nerves. 

The  "  constant  proportion"   for    the  muscular  sense  is  usually 
regarded  as  being  yf-g-. 

Sense  of  Temperature. 
By  means  of  the  sense  of  temperature  we  appreciate  the  changes 
in  the  heat  of  the  skin,  the  latter  being  specially  modified,  pre- 
senting the  so-called  "  temperature  spots"  for  the  reception  of  im- 
pulses from  hot  and  cold  bodies.  The  cold  (o)  and  hot  (6)  spots 
(Figs.  416,  417)  can  be  mapped  out  by  touching  the  skin  with  a 


Fig.  416.  Fig.  417, 

a  6 


m 


I  •.::::  y.v:  •  •  • 

.  ^  ■_*— ^^  

:::::::•:::     i-  ■...     ■ 

Cold- aucl  hot-spots  from  the  same  part  of  the-anterior  surface  of  the  forearm,  a.  (.'old-spots. 
6.  hot-spots.  The  dark  ])arts  are  the  more  sensitive,  the  hatched  the  medium,  the  dotted  the 
feeble,  and  the  vacant  spaces  the  non-sensitive. 


724  THE  SKIN  AXD  ITS  AFFEXDAGES. 

blunt-i)ointed  metal  rod  previously  Avarmed  or  cooled.  The  cold 
points  appear  to  be  more  numerous  than  the  hot  ones.  The  minimal 
distance  at  Avhich  the  cold  spots  can  be  appreciated  is,  in  the  case  of 
the  forehead,  0.8  mm.,  and  in  that  of  the  hot  spots  4  to  5  mm. 
The  skin  is  more  sensitive  to  cold  than  to  heat,  that  of  the  left  hand 
greater  in  this  respect  than  that  of  the  right.  The  skin  varies  very 
much  also  in  regard  to  its  susceptibility  to  changes  in  temperature, 
that  of  the  palm,  for  example,  appreciating  a  diifereuce  of  0.2°  C, 
of  the  breast  0.4°  C,  leg  0.6°  C,  back  0.9°  C.  In  the  case  of  the 
sense  of  temperature,  as  in  that  of  pressure,  the  "  constant  propor- 
tion" is  one-third  of  the  original  stimulus. 

It  is  worthy  of  mention  in  this  connection  that  the  mucous  mem- 
brane of  the  alimentary  canal,  from  the  oesophagus  to  the  rectum 
inclusive,  is  not  endowed  with  the  power  of  discriminating  between- 
differences  of  temperature.  An  enema  of  water  cooled  down  is  only 
appreciated  as  being  cold  when  the  water  passes  over  the  skin  of 
the  arms. 

Sense  of  Pain. 

It  has  already  been  mentioned  that  difference  of  opinion  still 
prevails  as  to  whether  the  sense  of  pain  is  due  to  impulses  trans- 
mitted by  special  nerves,  or  to  the  impulses  usually  giving  rise  to 
pressure,  heat  and  cold  being  simply  exaggerated.  Those  who  hold 
the  former  view,  argue  that  the  skin  is  endowed,  like  other  tissues, 
with  general  sensibility  and  when  the  afferent  nerves  ministering 
to  the  latter  are  so  excited  as  to  affect  consciousness,  pain  results. 


CHAPTER   XXXVII. 

THE  XOSE  AND  OLFACTION.     THE  TONGUE  AND 
GUSTATION. 


Fig.  418. 


Just  as  Ave  have  seen  that  the  skin,  in  addition  to  its  other 
functions,  acts  as  a  general  sensory  organ,  so  we  shall  soon  learn 
throngli  the  study  of  Development,  that  parts  of  it  being  especially 
modified  become  very  susceptible  to  certain  external  impressions, 
and  that  such  modifications,  together  with  corresponding  ones  de- 
veloped in  the  terminal  nerves  supplying  the  parts,  constitute 
special  sensory  organs,  such  as  the  nose,  tongue,  eye,  and  ear,  and 
inasmuch  as,  of  such  organs,  the  nose  is  the  most  simple  in  struc- 
ture, we  will  begin  the  consideration  of  the  special  senses  with  the 
study  of  Olfaction. 

Olfaction. 

The  nose,  the  special  organ  of  the  sense  of  smell,  is  regarded 
anatomically  as  being  limited  to  the  pyramidal  eminence  of  the 
face,  extending  from  the  forehead  to  the  upper  lip  ;  physiologically, 
however,  the  nose — that  is,  the  organ  of  olfaction — includes  not  only 
the  parts  just  mentioned,  con- 
sisting of  the  septum,  carti- 
lages, etc.,  but  of  the  nasal 
cavities  as  well  ;  the  mucous 
membranes  lining  the  latter  be- 
ing endowed  not  only  with 
general  sensibility,  as  we  have 
seen,  but  with  the  special  sense 
of  olfaction,  its  upper  half  be- 
ing supplied  (Fig.  418)  by  the 
olfactory  nerve,  the  special 
nerve  of  the  sense  of  smell. 
The  skin  of  the  nose,  thin 
above  but  thick  below,  as  else- 
where, is  furnished  with  sudor- 
iferous and  sebaceous  glands 
and  hairs  ;  the  hairs  are  usually 
small  except  within  the  margin 
of  the  nostrils,  in  the  latter  po- 
sition, however,  they  are  well 
developed  from  all  sides,  and  to  a  certain  extent  act  like  a  fine  sieve 
in  keeping  out  dust,  etc.  The  nasal  cavities  communicating  with 
the  exterior,  in  front,  by  the  anterior  nares,  and  with  the  jiharynx, 
behind,  by  the  posterior  nares,  are  lined  with  a  mucous  membrane 


Iiistributiiin  of  nerves  in  the  nasa!  pas.sages.  1. 
()lt"aet')ry  ganglia,  with  its  nerves.  2.  Nasal 
branch  of  tilth  jiair.     3.  .'^pheuo-palatine  ganglion. 

(l).\LTON.) 


72(3      XOSE  AXD  OLFACTION:   TONGUE  AND  GUSTATION. 

closely  applied  to  the  adjacent  periosteum  and  perichondrium, 
which  becomes,  at  the  nostrils,  continuous  with  the  skin,  at  the 
posterior  nares,  with  the  mucous  membrane  of  the  pharynx, 
and  at  the  lachrymo-nasal  duct  and  lachrymal  canals  with  the  con- 
juuctiya.  The  nasal  mucous  membrane  differs  very  much  in  its 
character  according  to  its  situation.  Thus  on  the  part  lining  the 
so-called  "  olfactory  region,"  or  that  coyering  the  upper  part  of 
the  septum,  the  superior  and  part  of  the  middle  turbinated  bones  is 
thick,  highly  yascular,  and  coyered  with  a  columnar  epithelium 
amidst  the  cells  of  which  occur  peculiar  rod-like  cells.  The  latter 
we  shall  see  presently  are  the  olfactory  cells  in  which  the  fibers  of 
the  olfactory  nerye  terminate  or  rather  arise  just  as  we  haye  seen 
the  axis-cylinders  iu  the  anterior  roots  arise  from  cells  in  the  cord. 
On  the  other  hand,  the  remaining  portion  of  the  nasal  mucous 
membrane,  the  so-called  Schneidcrian  or  pituitary  membrane,  or 
the  part  lining  the  "  respiratory  region,"  that  is  coyering  the  lower 
part  of  the  septum,  part  of  the  middle  and  inferior  turbinated 
bones,  is  covered  with  a  columnar  ciliated  epithelium  (except  within 
the  nostrils  where  it  is  squamous),  the  current  due  to  the  cilia  be- 
ing directed  towards  the  pharynx.  The  nasal  mucous  membrane  is 
also  provided  with  glands  whose  secretion  keeps  the  surface  moist, 
a  condition  essential  to  the  accurate  perception  of  odoriferous  im- 
pressions. The  glands  of  the  true  olfactory  membrane,  the  so- 
called  Bowman  glands,  are  tubular  or  mixed  glands. 

The  special  nerves  of  the  sense  of  smell  or  the  true  olfactory 
nerves  are  given  off  as  fifteen  to  eighteen  filaments  from  the  olfac- 
tory bulb  to  the  olfactory  region.  The  olfactory  tract,  of  which  the 
ganglionic  bulb  is  the  expansion,  is  usually  described  as  the  olfac- 
tory nerve,  but  improperly,  since,  as  development  sho^vs,  the  olfac- 
tory tracts  are  outgrowths  of  the  cerebral  hemispheres,  their 
morphological  significance  masked  in  man  by  the  excessive  de- 
velopment of  the  former.  The  olfactory  tracts  are  two  cords  or 
bands,  soft  and  friable,  consisting  of  both  white  and  gray  nervous 
matter,  which,  passing  forward  and  inward  on  the  under  surface  of 
the  anterior  lobe  of  the  cerebrum  to  the  ethmoid  bone,  expand  at 
the  side  of  the  crusta  galli  into  the  olfactory  bulbs,  from  which  are 
given  off,  as  just  mentioned,  the  true  olfactory  nerves,  which,  pass- 
ing through  the  cribriform  foramina  of  the  ethmoid  bone,  are  dis- 
tributed to  the  inner  and  outer  walls  of  the  upper  parts  of  the 
nasal  cavities.  Each  olfactory  tract  arises  apparently  by  three 
roots,  from  the  inferior  and  internal  surface  of  the  anterior  lobe  of 
the  cerebrum  in  front  of  the  anterior  perforated  space,  the  external 
and  internal  roots  being  composed  of  white  matter,  the  middle  of 
gray,  the  large  proportion  of  the  gray  substance,  one-third,  entering 
into  the  composition  of  the  olfactory  tract,  confirming  what  has 
just  been  said  as  to  the  true  nature  of  the  latter.  AVhile  the  ante- 
rior root  can  be  traced  into  the  middle  lobe  and  the  middle  and 
internal  roots  into  the   anterior  lobe,  considerable    obscurity  still 


OLF ACTIO  y. 


rii 


prevails  as  to  the  deep  origin  of  all  three  roots.  It  would  appear, 
however,  that  the  long  or  external  root  originates  in  the  island  of 
Reil,  the  thalamus  opticus  and  the  nucleus  in  the  temporo-sphe- 
noidal  lobe  in  front  of  the  hippocampus,  the  middle  or  gray  root  in 
the  gray  substance  of  the  anterior  perforated  space,  the  inner  root 
in  the  gyrus  fornicatus.  The  true  olfactory  nerves,  or  the  filaments 
given  off  from  the  olfactory  bulb,  as  they  descend  from  the  cribri- 
form plate  ramify,  and,  uniting  in  a  plexiform  manner,  spread  out 
laterally  in  brush-like  and  flattened  tufts  (Fig.  418).  In  their 
minute  structure,  the  olfactory  differ  from  the  ordinary  cerebral 
and  spinal  nerves  in  being  pale  and  finely  granular,  in  not  pos- 
sessing a  substance  of  Schwann,  in  adhering  to  one  another,  and  in 
presenting  oval  corpuscles. 

Their  manner  of  termination  is  also  peculiar,  each  olfactory  fiber 
appearing  to  pass  into  the  spindle-shaped  bodies  (6)  interspersed  be- 
tween and  among  the  epithelial  cells  (a)  of  the  olfactory  mem- 
brane (Fig.  419).     These  olfactory  cells,  so-called  on  account  of  their 


Fig.  419. 


Fig.  420. 


Cells  and  terminal  nerve-fibers  of  the 
olfactory  region,  highly  magnified.  1. 
From  tlie  frog.  2.  From  man.  a.  Epi- 
thelial cell,  extending  deeply  into  a 
ramified  process,  h.  Olfactory  cells,  c. 
Their  peripheral  rods.  e.  Their  ex- 
tremities, seen  in  1  to  be  prolonged  into 
fine  hairs.  <1.  Their  central  filaments. 
3.  Olfactory  nerve-fibers  from  the  dog. 
a.  The  division  into  tine  fibrillae.  (Frey 
after  Schultze.  ) 


campal  convolution,'  in  whi 
localized  (Fig.  420),  is  prov 

^  Obersteiner,  op.  cit. ,  s.  360. 


Inner  aspect  of  the  right  hemisphere,  po, 
position  of  tlie  visual  center  in  the  occipital  lobe 
t"  of  the  olfactory  center  in  the  uncinate  gyrus. 

(GOWEKS. ) 

supposed  function,  present  a  very 
characteristic  appearance,  the  cen- 
tral nucleated  portion  passing  on 
the  one  hand  internally  into  a 
beaded  varicose-like  thread  ((/)  ap- 
parently continuous  with  the  termi- 
nal olfactory  fibril,  and,  on  the 
other,  externally  into  a  rod-like 
structure  (e),  which  in  the  frog  is 
prolonged  into  fine  hairs.  That 
the  olfactory  cells,  nerves,  bulbs, 
and  tracts,  constitute  the  essential 
structures,  by  which  external  im- 
pressions are  transmitted  to  the 
subiculum  cornu  of  the  hi])po- 
ch  the  sen.se  of  smell  is  supposed  t<>  be 
ed  by  the  harmonious  results  of  experi- 
Edinger,  op.  cit.,  s.  "201.     Rauber,  op.  cit.,  s.  (374. 


728      NOSE  A ND  OLFA  CTIOX:  TOXG  UE  AND  G  USTA  TION. 

ments  performed  upon  animals,  of  pathological  cases  observed  in 
man,  and  of  the  facts  of  comparative  anatomy.  Thus,  among  the 
numerous  experiments  in  which  the  olfactory  tracts  were  divided, 
and  the  loss  of  the  sense  of  smell  noticed,  may  be  mentioned  those 
performed  upon  hunting  dogs  by  Vulpian  ^  and  Philipaux,  in  which 
cases  the  animals,  although  deprived  of  food  for  thirty-six  hours  after 
complete  recovery  from  the  effects  of  the  operation  failed  to  find  the 
cooked  meat  concealed  in  the  corner  of  the  laboratory.  That  destruc- 
tion of  the  olfactory  nerves,  bulbs,  or  tracts  in  man  due  to  disease  or 
injury  involves  the  impairment  or  loss  of  the  sense  of  smell  is  well 
known  to  pathologists,  a  number  of  such  cases  having  been  observed 
by  Schneider,  Rolpinck,  Eschricht,  Fahner,  Valentin,  Rosenmuller, 
Ceneti,  Pressat,^  Hare,^  Notta,*  Ogle,'^  Flint.*'  That  the  olfactory 
bulbs  and  nerves  are  the  essential  organs  of  the  special  sense  of  smell 
is  still  further  shown  by  the  fact  that  they  are  usually  best  developed 
in  animals  in  which  the  sense  of  smell  is  most  acute,  being  better  de- 
veloped, for  example,  in  the  mammalia  than  in  the  remaining  ver- 
tebrates, while  of  the  former  class  it  is  among  those  orders,  as  in 
the  carnivora,  in  which  the  sense  of  smell  is  very  acute,  that  the 
olfactory  region  is  most  developed,  in  the  dog,  for  example,  in 
which  the  sense  of  smell,  as  well  known,  is  very  remarkable.  The 
olfactory  nerves,  though  readily  impressed  by  odorous  emanations, 
are  but  little  affected  by  ordinary,  while  the  olfactory  tracts  ap- 
pear entirely  insensible  to  the  latter."  That  the  appreciation  of 
odors  or  olfaction  is  due  to  the  material  emanations  given  off  by 
odoriferous  substances  being  carried  by  the  inspired  air  to  the 
terminal  filaments  of  the  olfactory  nerves,  the  olfactory  cells,  is 
shown  by  the  manner  in  which  one  sniffs  the  air  in  order  to  per- 
ceive an  odor,  and  from  the  fact  that  if  the  air  does  not  pass 
through  the  nostrils,  as  in  occlusion  of  the  posterior  nares  or  in  di- 
vision of  the  trachea,  the  sense  of  smell  is  abolished.  In  every 
case  where  odorous  emanations  are  i)erceived,  the  latter  must  im- 
pinge upon  the  olfactory  membrane,  come  in  contact,  excite  the 
peripheral  ends  of  the  olfactory  nerves. 

According  to  Passy  *  as  small  a  quantity  of  musk  as  the  0.000005 
gramme  in  one  liter  of  air  can  be  appreciated,  the  amount  of 
oil  of  peppermint  that  can  be  recognized  being  still  smaller, 
0.000000005  gramme,  while  according  to  Fisher  and  Penzoldt^ 
■^eiroTo^Too"  ®^  ^  milligrame  of  mercaptan  in  1  c.cm.  of  air  can  be 

'  Leyons  sur  la  physiologie  generale  et  comparee  du  systeme  nervenx,  p.  882, 
note.     Paris,  1866. 

^  Cited  bv  Longet,  Anat.  et  Phvs.  du  svsteme  nerveux,  Tome  ii.,  p.  88.  Paris, 
1842. 

'A  View  of  the  Structure,  etc.,  of  tlie  Stomach  and  Alimentary  Organs,  p.  145. 
London,  1S21. 

*  Archives  generales  de  medicine,  p.  385.     Paris,  Avril,  1870. 

^  Medico-Chirur.  Trans.,  Lond.,  2d  ser.,  Vol.  xxxvii.,  p.  263. 

''Flint,  Pliysiology,  1874,  \o\.  v.,  p.  39. 

"  Magendie,  .Journal  de  piivsiologie,  Tome  iv.,  p.  169.     Paris,  1824. 

8  Comptes  Kendus  Soc.  de  Biologic,  1892,  p.  84. 

"Landois,  op.  cit.,  p.  1039. 


THE  TONGUE  AND  GC STATION.  729 

detected.  Like  the  sense  of  touch,  and  the  other  special  senses, 
that  of  smell  may  be  very  much  developed  by  practice  ;  as  ex- 
emplified in  the  discrimination  of  the  quality  of  \vine,  drugs,  etc. 
It  is  Avell  known  that  the  boy,  James  Mitchell,  who  was  deaf, 
dumb,  and  blind,  made  use  of  his  sense  of  smell  like  a  dog  to  dis- 
tinguish persons  and  objects. 

The  sense  of  smell  is,  however,  far  more  acute  in  the  lower  races 
of  mankind  than  in  the  higher  ones,  to  Avhatever  extent  in  the 
latter  it  may  have  been  developed  by  cultivation.  Thus  it  is  said 
that  the  Mincopies  of  the  Andaman  Islands  scent  the  ripeness  of 
the  fruits  ;  that  the  Peruvian  Indians  distinguish  the  different  races 
of  mankind  l)y  scent  alone  ;  that  Arabs  can  smell  a  fire  thirty  miles 
off;  that  the  North  American  Indians  pursue  by  smell  their  enemies 
or  their  game.  However  the  sense  of  smell  may  be  developed  in 
man,  it  is  far  surpassed  in  acuteness  by  that  of  animals.  Every 
sportsman  is  aware  that  odors  are  recognized  by  hunting  dogs,  to 
which  he  is  entirely  insensible. 

The  sense  of  smell  is  intimately  related  to  that  of  taste,  so  much 
so,  indeed,  that  if  the  nose  be  held,  or  plugged  up,  the  characteristic 
taste  of  certain  substances  when  swallowed,  is  not  appreciated  at  all, 
as  illustrated  in  drinking  different  kinds  of  wine,  it  being  difficult, 
usually  impossible,  to  distinguish  the  same  under  such  circum- 
stances. Further,  it  has  been  observed  in  those  cases  in  which  the 
sense  of  smell  is  lost,  that  of  taste  is  usually  lost  also. 

As  a  general  rule,  persons  having  offensive  emanations  from  the 
respiratory  organs  are  not  aware  of  such,  not  appearing  to  be  af- 
fected by  odors  passing  from  within  outward  through  the  nostrils. 
This  is  due,  not  so  much  to  the  odor  being  carried  by  the  air  ex- 
pired through  the  nostrils  instead  of  by  that  inspired,  as  to  the  fact 
that  one  becomes  in  time  accustomed  to  such  odors,  and  ceases  to 
notice  them,  however  fetid  they  may  be. 

The  influence  exercised  by  the  nose  upon  respiration  has  already 
been  mentioned.  We  shall  see,  hereafter,  that  the  nose,  also,  modi- 
fies very  much  the  quality  of  the  voice. 

The  Tongue  and  Gustation. 

The  sense  of  taste,  or  gustation,  enabling  us  to  appreciate  the 
savor  of  sapid  substances  when  introduced  into  the  mouth,  is  due 
to  the  susceptibility  of  the  terminal  filaments  of  the  chorda  tym- 
pani  and  glosso-pharyngeal  nerves,  of  being  imj)ressed  by  contact 
of  the  same.  The  influence  of  the  tongue  in  mastication  and  deg- 
lutition, the  origin,  distribution,  and  general  functions  of  the  chorda 
tvmpani  and  glosso-pharyngeal  nerves  having  l)cen  considered,  it 
onlv  remains  for  us  now  to  point  out  the  manner  in  which  gusta- 
tion is  performed  through  the  parts  just  mentioned.  That  the 
tono-ue  is  the  or^ran  of  (gustation  there  can  be  no  doubt.  It  would 
appear,   however,  from  experiments  such   as    those  pertormed  by 


730     NOSE  AND  OLFACTION;   TONGUE  AND  GUSTATION. 


Longet  ^  and  others,  in  wliicli  different  parts  of  the  mncous  mem- 
brane are  touched  with  a  sponge  soaked  in  a  sapid  sohition,  that 
the  sense  of  taste,  probably  in  man  at  least,  is  limited  to  the  dorsal 
surface  of  the  tongue,  and  from  the  experiments  of  Canierer,"  in 
which  solutions  were  applied  through  tine  glass  tubes,  more  par- 
ticularly to  the  circumvallate  and  fungiform  papillae,  the  parts 
around  the  latter  not  appearing  to  be  impressed  by  sapid  sub- 
stances. The  circumvallate  papilla  (Fig.  421),  so  called  on  ac- 
count of  each  papilla  being  sur- 
rounded by  a  trench  or  fossa, 
from  seven  to  twelve  in  num- 
ber, are  disposed  in  two  rows 
(in  the  form  of  a  V,  the  open 
ano-lc  of  the  latter  being:  di- 
rected  forwards),  on  the  back 
part  of  the  tongue.  Each 
papilla  is  covered  by  numerous 
small    secondary    papilla^,   the 

Vertical  sectiou  of  circumvallate  jiapilla,  from  latter,  llOWCVCr,       bciuff      COU- 

the  calf.     35  diameters.    A.  The  papilla.     B.  The              i     i  i         ,i        ji   •    i  i      j 

surrounding  wall.    The  figure  shows  the  nerves  of  CCalcd  by  tuC  thlCk  aud  Stratl- 

the  papilla  spreading  toward  the  surface,  and  t*     ^  • ,  i     t                  n-ii          r 

•  •      '    •    ■* tied   epithehum,       ihe    lungi- 

form  papillfe,  more  numerous 
than  the  circumvallate,  and 
readily  distinguished  during  life  by  their  deep  red  color,  while 
found  in  the  middle  and  forepart  of  the  dorsum  of  the  tongue,  are 
most  numerous  and  closely  set  together  at  the  apex  and  near  the 
borders.  Each  fungiform  papilla,  while  narrow  at  its  attachment 
(Fig.  422),  at  its  free  extremity  is  blunt  and  rounded,  and,  like 


toward'the  taste-buds^which  are  imbedded  in  the      ficd    epithelium 
epithelium  at  the  sides  ;  iu  the  sulcus  on  the  left 
the  duet  of  a  gland  is  seen  to  open.    (Engelmann.  ) 


Fig.  422. 


Surface  and  seotional  view  of  a  fungiform  papilla.  A.  The  surface  of  a  fungiform  papilla  par- 
tially denuded  of  the  (  pitlielium.  (35  diameters.)  p.  Secondary  papilloe.  n.  Epithelium.  B. 
Section  of  a  fungiform  papilla  with  the  blood  vessels  injected,  a.  Artery,  r.  Vein.  c.  Capillary 
loops  of  simple  papilhe  in  the  neighborhood,  covered  by  the  epithelium.  (From  KOllikek,  after 
Todd  and  Bowman.  ) 

the  circumvallate  })apilhe,  is  covered  with  secondary  papilhe  and 
epithelium.  Imbedded  in  the  epithelium,  and  more  particularly 
in  that  of  the  circumvallate  papillse,  are  found  ovoidal  flask-shaped 

'  Pliysioloiiie,  Tome  iii.,  p.  52.     Paris,  1873. 
^Zfitsclirift  fiir  P.iologie,  1870,  Band  vi.,  s.  440. 


TASTE  BUDS. 


731 


Two  taste-buds  from  the  papilla  foliata  of  the  rabbit.  (450 
diameters.)     (Esgelma>-s.  ) 


bodies  (Fig.  423),  having  a  length  of  the  ^^  of  a  mm.  (g^-g^iy  of  an 
inch),  and  a  diameter  of  the  J^  of  a  mm.  (ygVu  ^^  ^^^  inch),  con- 
sisting apparently  of  modified  epithelial  cells,  which,  w-ith  good 
reason,  are  supposed  to  be  the  special  organs  of  the  sense  of  taste.' 
Each  ovoid  body,  sur- 
rounded by  flattened  epi-  Fig.  423. 
thelial  cells,  consists  of 
a  cortical  and  a  central 
part.  The  former  is  com- 
posed of  long,  flattened, 
tapering  cells,  disposed 
edo;e  to  edge,  and  coming 
to  a  point  at  the  taste- 
pore,  the  latter  of  spin- 
dle -  shaped  taste  cells. 
The  latter  resemble  very 
closely  the  olfactory 
cells ;  the  distal  end  of 
the  cell  projecting  from 

the  orifice  of  the  taste-bud,  and  the  central  beaded,  varicose  end  being 
continuous  with  the  terminal  filament  of  the  gustatory  nerve.  Such 
being  the  disposition  of  the  taste  cells,  it  would  appear  that  the  ter- 
minal filaments  of  the  gustatory  nerves,"  of  which  the  fonner  are  the 
continuation,  are  excited  by  the  flow  of  sapid  solutions  through  the 
taste-pore  into  the  interior  of  the  taste-bud  ;  the  taste  cells  being 
especially  susceptible  to  impressions  made  by  substances  in  solution, 
whence  the  impression  is  transmitted  by  the  chorda  tympani  and 
glosso-pharyngeal  nerves  to  the  centers  of  taste,  localized  in  the 
subiculum  cornu  of  the  hippocampus  (Fig.  37o,  U),  where  they  are 
perceived.  That  the  chorda  tympani  and  the  glosso-pharyngeal 
nerves  are  the  special  nerves  of  the  sense  of  taste,  the  former  more 
particularly  for  the  anterior  two-thirds  of  the  tongue,  the  latter  for 
the  posterior  third,  can  be  shown,  as  already  mentioned,  both  by 
experiments  performed  upon  animals,  and  by  pathological  cases 
observed  in  man,  division  or  disease  of  these  nerves  involving  loss 
of  the  sense  of  taste.  The  glosso-pharyngeal  differs  from  the  chorda 
tympani,  however,  in  this  respect,  in  that  it  is  a  nerve  of  general 
sensibility,  as  well  as  that  of  taste,  the  chorda  tympani  (gustatory 
fibers)  being  a  nerve  of  taste  alone,  the  sensory  fibers  of  the  lingual 
ner^^e  bearing  to  the  chorda  tympani  the  same  relation  that  the 
sensory  fibers  of  the  glosso-pharyngeal  bear  to  its  gustatory  ones. 

It  should  be  mentioned,  however,  that  according  to  Gowers  ^  any 
gustatory  properties  that  the  glosso-pharyngeal  possesses  is  due  to 
fibers  derived  from  the  fifth  nerve  through  the  otic  ganglion,  tym- 
panic plexus,  and  petrous  ganglion. 

It  is  generally  admitted  that  all  gustatory  sensations  are  made 
up  of  four  primary  sensations,  sweet,  bitter,  acid,  and  saline.  It  is 
iRauber,  op.  cit.,  s.  694.         ^Edinger  op.  cit.,  s.  40.         ^Op.  cit.,  Vol.  ii.,  p.  278. 


732     NOSE  AND  OLFACTION ;  TONGUE  AND  GUSTATION. 

also  regarded  as  probable  that  there  are  distinct  nerve  fibers  for  the 
transmission  of  impulses  to  special  cortical  centers,  which  when  re- 
spectively excited,  give  rise  to  the  above  special  sensations.  How- 
ever that  may  be,  it  has  been  shown  as  a  matter  of  fact,^  that 
potassium  chloride  tastes  cool  and  saltish  at  the  anterior  part  of  the 
tongue,  and  sweetish  at  the  posterior  part ;  potassium  nitrate  cool 
and  piquant  at  the  anterior,  and  bitter  and  insipid  at  the  posterior 
end.  Certain  substances,  like  mineral  acids,  ferric  sulphate,  jalap, 
and  colocynth,  while  but  little  appreciated  at  the  anterior  part  of 
the  tongue,  are  appreciated  very  acutely  at  the  posterior  portion. 
On  the  other  hand,  meats,  milk,  and  wines,  are  equally  well  appre- 
ciated at  both  ends  of  the  tongue. 

Fig.  424. 


Filiform  papillif.     (Qi'ain.) 


The  time  which  elapses  between  the  a])plication  of  a  sapid  sub- 
stance and  the  resulting  sensation  varies  with  diiferent  substances. 
Thus  according  to  Van  Vintschgan "  saline  substances  are  tasted 
most  quickly  within  tlie  0.17  sec,  then  sweet,  acid,  and  l)itter  ones; 
the  latter  in  the  case  of  (piininc  within  0.258  sec.  It  is  well  known 
that  the  sense  of  taste  is  much  aided  by  that  of  smell,  the  two  sen- 

'  Lus-tana,  Archives  de  Physiolof^ie,  Tome  ii.,  1869,  j).  20S. 
^Landois,  op.  cit.,  p.  1042. 


FILIFORM  PAPILL.E.  733 

sations  together  giving  rise  often  to  that  of  flavor.  The  sense  of 
taste  is  aided  also  l)y  that  of  sight.  Thus,  for  example,  if  the  eyes 
be  bandaged  and  red  and  white  wine  be  rapidly  tasted  alternately  it 
beeomes  impossible  in  a  short  time  to  distinguish  one  from  the 
other.  The  most  favorable  temperature  for  taste  appears  to  be  be- 
tween 10°  and  35°  C.  (oO"  to  95°  F.),  hot  and  cold  water  paralyz- 
ing taste  at  least  temporarily.  The  sense  of  taste  like  that  of 
smell  is  susceptible  of  great  improvement. 

It  may  be  mentioned  incidentally  that  the  hliform  papillne,  the 
minute  conical  eminences  densely  set  over  the  greater  part  of  the 
dorsum  of  the  tongue  and  disposed  in  lines  diverging  from  the 
raphe,  appear  to  be  tactile  in  function. 


CHAPTER    XXXYIIl. 


THE  EYE  AND  VISION. 


The  organ  of  vision  includes  the  optic  nerve,  the  eye  and  its 
appendages.  The  optic  nerves — consisting  of  medunated  fibers  but 
without  neurilemma,  together  with  some  gray  nerve  fibers — are 
usually  described  as  arising  from  the  optic  chiasma,  or  commissure. 
Eegarded,  however,  as  the  continuation  of  the  optic  tracts,  the  optic 
nerves  in  reality  arise,  as  we  have  seen,  from  the  optic  lobes,  thal- 


FiG.  425. 


Cortical  visual  centers  on  the  outer  sur- 
face of  the  hemisphere.  The  darker  shad- 
ing indicates  the  region  of  the  half  vision 
center  (the  precise  limitation  of  which  is 
not  yet  known);  the  lighter  shading  is  that 
of  the  supposed  higher  visual  center. 

(GOWERS.) 


ami  optici,  corpora  geniculata, 
cuneal  portions  of  the  occipital 
lobes,  and  prol)ably  also  from 
the  angular  gyri.  The  root 
fibers  (438,000  in  number)' 
from  these  different  points  of 
origin,  converging,  form  flat- 
tened bands,  which.  Minding 
obliquely  around  the  under 
surface  of  the  crura  cerebri, 
pass  to  the  temporal  side  of 
one  eye  and  to  the  nasal  side 
of  the  other,  the  decussation 
of  the  fibers  in  the  chiasma 
being  therefore  incomplete 
(Fig.  420),  at  least  such 
is  the  view  held  bv  most  neu- 


Right  homonymous  lateral  hemianopsia,  from 
lesion  of  the  left  visual  center  of  the  cortex  or 
left  optic  tract.  A.  Dark  left  nasal  half  field  from 
blind  temijoral  half  of  retina.  A'.  Dark  right  tem- 
])oral  half  field  from  blind  nasal  half  of  retina. 
B.  Left  eye.  B'.  Right  eye.  f,  C.  Left  and 
right  optic  nerves,  composed  of  the  cross  bundles 
of  fibers.  /J,  I)'.  Left  and  right  crossed  bundles. 
JS,  E'.  Left  and  right  occipital  lobes.  F,  F' .  Left 
and  right  posterior  horns.  Ci,  G'.  Optic  radia- 
tion. //,  y/'.  optic  chiasm.  /, /'.  Angular  gyrus. 
K.  Region  of  optic  thalamus,  geniculate  body  and 
quadrigcrainal  bodies,  collcctivelv  termed  pri- 
mary optic  centers.  M,  M'.  Cuneus.  The  left 
ciineus  and  optic  tract  are  shaded,  to  show  lesion 
of  these  parts  and  the  influence  of  the  lesion  upon 
the  retina.     (Mills.) 


rologists  as  explaining  best  the  facts  of  homonymous  lateral  hemi- 
anopsia.     Nevertheless,  it  must  be  admitted  that  Kolliker^  and 


1  Salzer,  Wiener  Sitzungsberichte,  Band  81,  1880,  s.  3. 


2  Op.  cit.,  s.  563. 


THE  OPTIC  NERVES.  735 

other  liistologists  of  authority  hohl  that  the  decussation  of  the 
fibers  in  the  chiasnui  in  man  is  complete.  The  extent  of  de- 
cussation in  animals,  which  is  variable,  appears  to  depend  upon 
the  amount  of  separation  of  the  fields  of  vision.  Thus  in  man 
and  certain  mammals,  Avhere  the  eyes  are  so  placed  that  tliey  can 
both  be  directed  to  the  same  object,  the  fields  of  vision  overlap 
and  there  is  incomplete  decussation.  On  the  other  hand,  in 
the  lower  mammals,  such  as  the  mouse  and  guinea-pig,  birds 
(with  the  exception  perliaps  of  owls),  reptiles,  amphibia,  and 
fishes,  in  which  the  fields  of  vision  are  distinct  and  do  not  over- 
lap, there  is  a  total  decussation.  It  should  be  mentioned,  how- 
ever, that  the  fibers  constituting  the  anterior  portion  of  the  chiasma 
are  not  derived  from  the  optic  tracts,  but  simply  pass  from  one 
eye  to  the  other,  while  the  fibers  constituting  the  posterior  part — 
and  sometimes  wanting — pass  from  tract  to  tract  without  being 
connected  with  the  eyes.  The  optic  nerves  proper,  arising  from 
the  anterior  and  outer  border  of  the  chiasma,  curved  in  direction 
and  rounded  in  form,  enclosed  in  a  double  fibrous  sheath,  derived 
from  the  dura  mater  and  arachnoid,  pass  into  the  orbit  through  the 
optic  foramina,  piercing  the  sclerotic  coat  of  the  eye  at  its  posterior, 
inferior,  and  internal  portions  ;  the  thin,  but  strong  membrane 
through  which  the  nervous  filaments  pass  into  the  sclerotic,  known 
as  the  lamina  cribrosa,  being  partly  derived  from  the  sclerotic,  and 
partly  from  the  coverings  of  the  nerve  fibers  which  are  lost  at 
this  point.  At  about  5  millimeters  (4  of  an  inch)  behind  the 
globe  of  the  eye,  the  optic  nerve  receives  the  central  artery  and 
vein  of  the  retina,  which,  together  with  a  delicate  filament  from 
the  ophthalmic  ganglion,  is  thence  transmitted  within  the  center  of 
the  nerve  l)y  a  minute  canal,  lined  with  fibrous  tissue.  That  the 
optic  nerves  are  the  special  nerves  of  the  sense  of  sight  there  can 
be  no  doubt,  since  their  injury  or  division  always  involves  impair- 
ment or  loss  of  sight.  While  the  optic  nerves  are  the  avenues  or 
paths  by  which  the  impressions  due  to  the  presence  of  light  are 
transmitted  to  the  cunei  and  angular  gyri,  there  to  become,  as  we 
have  seen,  conscious,  intelligent  vision,  they  are,  hoMever,  abso- 
lutely insensible  to  ordinary  impressions.  Xot  only  have  these 
nerves  been  pinched,  cut,  and  cauterized  in  animals,  without  the 
latter  evincing  any  pain,  but  their  insensiliility  in  man  has  often  been 
observed  also,  as  in  surgical  operations,  for  example,  in  which  the 
nerves  have  been  exposed.  That  the  optic  nerves  are  especially 
susceptible  to  the  impressions  of  the  rays  of  light  is  still  further 
shown  from  the  fact  of  their  excitation,  however  caused,  always 
giving  rise  in  consciousness  to  the  idea  of  liglit — a  severe  blow  on 
the  orbit  making  one  see  stars,  as  often  said,  the  mind  having  asso- 
ciated so  uniformly  the  excitement  of  the  optic  nerve  with  the 
presence  of  light,  that  in  time  it  becomes  impossible  to  disassociate 
the  two  ;  the  excitement  of  the  one  invariably  suggesting  the  pres- 
ence of  the  other. 


736  THE  EYE  AND   VISION. 

The  Eyeball. 

The  eyeball,  a  spheroidal  body,  partly  imbedded  in  a  cushion  of 
fat,  protected  by  the  surrounding  bony  orbit  and  the  eyelids,  mois- 
tened by  the  lachrymal  secretion,  and  moved  by  various  muscles,  is 
composed  of  several  coats,  concentrically  disposed,  and  enclosing 
several  refractive  media.  Were  it  not  for  the  fact  of  the  cornea 
being  set  in  the  sclerotic,  like  a  crystal  into  the  rim  of  the  face  of 
a  watch,  the  eyeball  would  present  the  form  of  a  spheroid.  Owing, 
however,  to  the  cornea  constituting  one-tenth  of  the  outer  circum- 
ference of  the  eye,  and  to  tlie  fact  just  mentioned,  the  longest  diam- 
eter is  in  the  antero-postcrior  direction,  as  shown  by  the  mean 
results  obtained  by  Sappey.^ 

Diameter  of  Eyeball  in  Millimeters. 

Ant.  post.  Tran.sverse.     Vertical.    Oblique. 

Mean  of  12  females  from 

18  to  81  years  of  age,        23.9     (0.96  inch.)     23.4         23.0         23.8 
Mean  of  14  jnales  from 

20  to  79  years  of  age,        24.6     (0.98  inch.)     23.9         23.2         24.1 

It  will  be  observed,  from  the  above,  that  all  the  diameters  are 
less  in  the  female  than  in  the  male.  It  may  be  appropriately  men- 
tioned in  this  connection,  also,  that  all  such  measurements  should 
be  made  as  soon  as  possible  after  death,  within  from  one  to  four 
hours,  owino;  to  the  eveball  losine;  so  soon  its  ncn-mal  form  and 
dimensions. 

The  Sclerotic  and  Cornea. 

The  sclerotic  (Fig.  427,  2),  the  outer  protective  coat  of  the  eye- 
ball, covering  the  posterior  five-sixths  of  the  latter,  varying  in 
thickness  from  1  to  |  mm.  (J^  to  the  -gig-  of  an  inch),  is  a  dense  white, 
opaque  tunic,  composed  of  ordinary  connective  tissue,  mixed  with 
small  elastic  fibers  and  a  few  blood  vessels,  and  yielding,  on  boiling, 
gelatine.  The  cornea,  the  first  of  the  refractive  media,  constituting 
the  anterior  sixth  of  the  outer  circumference  of  the  eyeball,  and 
varying  in  thickness  from  1.1  to  ^L  i^^™-  (o^o  to  the  3^2  of  ^>^  inch), 
is  the  transparent  projecting  tunic  (Fig.  427,  3)  attached  to  the 
periphery  of  the  sclerotic,  of  which,  indeed,  it  may  be  regarded  as 
the  continuation,  consisting,  like  the  latter,  of  layers  of  connective 
tissue,  though  somewhat  modified,  l)oth  structurally  and  chemically, 
since  it  is  transparent,  admitting  light  into  the  interior  of  the  eye, 
and  yielding  chondrine  on  boiling.  The  cornea  may  be  described 
as  consisting  of  three  parts  :  a  stratified  epithelium  anteriorly,  con- 
tinuous W'ith  that  of  the  conjunctiva,  a  middle  portion,  the  cornea 
proper,  continuous  witli  the  sclerotic,  consisting  of  modified  connec- 
tive tissue,  posteriorly,  of  a  homogeneous,  elastic  lamella,  covered 
with  epitlielium-like  cells,  the  membrane  of  Demours  or  Desceraet, 
the  part  of  the  membrane  passing  to  the  anterior  surface  of  the  iris, 

'  Traite  d' Anatomie,  Tome  troisieme,  p.  747.     Paris,  1877. 


THE  CHOROID. 


i6i 


more  uoticeable  iu  the  eyes  of  the  sheep  and  ox  than  in  man,  being 
known  as  the  ligamentum  pectinatum  iridis.  In  a  state  of  health 
in  the  adult,  vessels  are  n(»t  found  in  the  cornea,  except  at  its  cir- 
cumference, where  they  are  disposed  in  capillary  loops,  and   by 


Fig.  427. 


Horizontal  section  of  right  eyeball.  1.  Optic  nerve.  2.  Sclerotic  coat.  3.  Cornea.  4.  Canal  of 
Schlemm.  5.  Choroid  coat.  6.  Ciliary  muscle.  7.  Iris.  8.  Crystalline  lens.  9.  Retina.  10. 
Hyaloid  membrane.    11.  Canal  of  Petit.    12.  Vitreous  body.    1.3.  Aqueous  humor. 

which  nutrition  is  apparently  carried  on.  The  ner\-es  of  the  cornea 
are,  however,  very  numerous,  and  are  derived  from  the  long  and 
short  ciliary  nerves.  Entering  the  sclerotic,  and  crossing  the 
choroid,  they  pass  into  the  cornea,  extending  almost  through  to  its 
free  surface. 

The  Choroid. 

Removing  the  sclerotic  in  the  manner  represented  in  Fig.  428, 
the  second  coat  of  the  eyeball  from  without  inward,  the  choroid 
with  its  anterior  prolongation,  the  ciliary  muscle  will  then  be  ex- 
posed. The  choroid  may  be  regarded  essentially  as  the  vascular 
pigmental  tunic  of  the  eyeball.  Its  inner  or  pigmental  layer 
constitutes,  however,  in  reality,  the  outer  coat  of  the  retina,  being 
developed,  as  we  shall  see  hereafter,  like  the  latter  from  the  invagi- 
nated  portion  of  the  optic  vesicle.  The  choroid,  varying  in  thick- 
ness from  the  ^  mm.  to  1  mm.  (j^  to  the  -^^  of  an  inch),  and 
covering  the  eyeball  to  the  same  extent  as  the  sclerotic,  is  connected 
by  its  outer  surface  with  the  latter  tunic  by  connective  tissues,  ves- 
sels, and  nerves,  the  so-called  .membrana  fusca,  and,  like  the 
sclerotic,  is  traversed  posteriorly  by  the  optic  nerve.  The  arteries 
47 


r38 


THE  EYE  AND   VISION. 


of  the  choroid,  the  short  ciliary,  comparatively  large  after  piercing 
the  sclerotic  close  to  the  optic  nerve,  break  up  into  branches,  which 
pass  forward  and  then  inward  to  end  in  the  capillaries,  the  latter 
being  sometmies  known  as  the  tunic  of  Ruysch.  The  veins  situ- 
ated externally  to  the  other  vessels  are  very  numerousj  and,  being 


Fig.  428. 


Choroid  membrane  and  iris  exposed  by  the  removal  of  the  sclerotic  and  cornea.  Twice  the 
natural  size.  «.  One  of  the  segments  of  the  sclerotic  thrown  back.  /.  Ciliary  muscle,  k.  Iris, 
e.  One  of  the  ciliary  nerves.    /.  One  of  the  vasa  vorticosa  or  choroidal  veins.     (Quain.) 

disposed  in  curves  converging  into  four  trunks,  present  a  peculiar 
appearance,  which  has  given  rise  to  the  name  of  vasa  vorticosa. 
Among  the  vessels  of  the  choroid  are  also  found  elongated  and 
stellated  pigment  cells,  with  branches,  which,  intercommunicating, 
constitute  a  sort  of  network.  The  nerves  supplying  the  choroid 
are  derived  from  the  long  and  short  ciliary.  The  inner  surface  of  the 
choroid  is  smooth  and  is  covered  with  the  hexagonal  pigmental  cells 
of  the  retina,  which  will  be  considered  as  the  outer  layer  of  that 
tunic  rather  than,  as  formerly,  as  the  inner  layer  or  tapetum  nigrum 
of  the  choroid  for  the  reason  just  given. 

Ciliary  Processes. 

It  will  be  observed  from  Fig.  428  that  the  choroid  passes  forward 
into  the  ciliary  muscle,  the  latter  in  turn  passing  into  the  iris,  con- 
stituting, in  fact,  one  continuous  layer — the  second  tunic  of  the 
eyeball.  If,  however,  the  choroid  be  viewed  from  behind,  as  rep- 
resented in  Fig.  429,  in  which  the  eyel)all  is  supposed  to  have 
been  divided  transversely,  it  will  be  seen  that  the  choroid  passes 
forward  and  posteriorly  into  the  ciliary  processes,  just  as  we  have 
seen  it  passes  forward  but  anteriorly  into  the  ciliary  muscle.  Or, 
briefly,  the  relation  of  the  parts  may  be  expressed  by  saying  that 
the  choroid  .splits  at  its  anterior  termination  into  the  ciliary  muscle 


CILIARY  MUSCLE. 


739 


Fig.  429. 


in  front,  and  the  ciliary  processes  behind,  the  ciliary  muscle  being 
continued  into  the  iris,  hence  the  general  term  of  uvea  applied  to 
all  of  these  parts  by  the  older 
anatomists.  The  ciliary  processes 
or  plications,  about  seventy  in 
number,  disposed  radially  behind 
the  ciliary  muscle  and  the  iris, 
and  fitting  posteriorly,  as  we  shall 
see,  into  corresponding  plications 
of  the  suspensory  ligament  of  the 
lens,  more  particularly  into  that 
part  of  it  known  as  the  zone  of 
Zinn,  consists  of  large  and  small 
thickenings  of  the  choroid,  the 
small  folds  alternating,  though  ir- 
regularly, with  the  large  ones,  the 
latter  measuring  about  the  J^-  of 
an  inch  in  length  and  the  -^^  in 

dpnth       nnd      comnOMcd      like      tlip       of  the  ciliary  processes,  of  which  about  sev- 
aeptn,      auu      COmpUbea      lllve       Uie       euty-one  are  represented.    J^.     (Quain.) 

choroid  proper  of  vessels  and  pig- 
ment, the  latter,  though,  being  absent  in  the  rounded  inner  ends. 


Ciliary  processes  as  seeu  from  behind.  1. 
Posterior  surface  of  the  iris,  with  the  sphinc- 
ter muscle  of  the  pupil.    2.  Pupil.    3.  One 


Ciliary  Muscle. 

The  ciliary  muscle  (Fig.  428,  6),  the  continuation  anteriorly 
of  the  choroid,  about  3.1  millimeters  (|  of  an  inch)  wide,  con- 
sisting of  longitudinal  and  circular  fibers,  the  latter,  however, 
present  at  the  periphery  of  the  iris  only,  may  be  regarded  as 
arising  from  the  inner  side  of  the  junction  of  the  sclerotic  and 
cornea,  close  to  the  canal  of  Schlemm,  and  inserted  into  the 
choroid  opposite  the  ciliary  processes.  Such  being  its  disposi- 
tion, it  is  evident  that,  in  contracting,  the  nerves  supplying  it  be- 
ing the  long  and  short  ciliary  nerves,  it  will  draw  the  choroid 
forward,  thereby  compressing  the  vitreous  humor  and  relaxing 
the  suspensory  ligament  of  the  crystalline  lens,  the  significance 
of  which  action  will  be  better  appreciated  when  the  subject  of 
accommodation  has  been  considered. 


The  Iris. 

The  iris  (Fig,  428,  e),  the  circular,  contractile,  and  colored  mem- 
brane seen  through  the  transparent  cornea,  to  which  the  character- 
istic color  of  the  eye  is  due,  is  the  muscular  diaphragm  of  the  eye, 
the  aperture  in  its  center  or  pupil  permitting  and  regulating  the 
passage  of  light  into  the  interior  of  the  eye.  The  iris,  about  as 
thick  as  the  choroid,  is  attached  by  its  circumferential  border  to 
the  line  of  junction  of  the  cornea  and  sclerotic  at  the  origin  of  the 
ciliary  muscle,  and  measures  about  one-half  an  inch  across,  and  in 
a  state  of  rest  about  the  one-fifth  of  an  inch  from  the  circumfer- 


740 


THE  EYE  AND   VISION. 


ence  to  the  pupil.  The  iris  consists  essentially  of  a  stroma  of  con- 
nective tissue  and  muscular  fibers,  the  latter  disposed  as  a  ring  around 
the  pupil,  constituting  the  sphincter,  and  as  a  rays  from  the  center 
to  the  circumference,  the  dilator  muscles  of  the  iris.  The  pupil,  or 
aperture  in  the  iris  regulating  the  amount  of  light  admitted,  varies 
in  size  according  as  the  muscular  fibers  are  contracted  or  relaxed, 
from  the  one-twentieth  to  the  one-third  of  an  inch,  and  during 
foetal  life  is  closed  by  a  delicate  transparent  membrane.  The  iris 
is  supplied  by  the  two  long  ciliary  and  anterior  ciliary  arteries,  the 
latter  being  derived  from  the  muscular  branches  of  the  ophthalmic. 

The  two  long  ciliary  arteries  hav- 
FiG.  430.  ing  pierced  the  sclerotic,  one  on 

each  side  of  the  optic  nerve,  pass 
between  the  latter  tunic  and  the 
choroid  to  the  ciliary  muscle,  and 
each  vessel,  just  before  reaching 
the  iris,  divides  into  an  upper  and 
lower  branch,  which,  anastomos- 
ing with  the  corresponding  ves- 
sels of  the  opposite  side,  and  with 
the  anterior  ciliary  arteries,  forms 
a  vascular  ring,  the  circulus 
major  of  the  ciliary  muscle,  from 
which  small  branches  are  given 
oif,  some  of  which  supply  the 
muscle,  M'hile  others,  converging 
toward  the  pupil,  form  a  second 
vascular  circle  —  the  circulus 
minor  ;  from  the  latter  capillaries 
are  given  oif  which  terminate  in 
veins.  The  veins  of  the  iris 
terminate  in  the  circular  venous 
sinus  known  as  the  canal  of 
Schlemm,  situated  at  the  junc- 
tion of  the  cornea  with  the  scler- 
otic. The  nerves  of  the  iris  are 
the  long  ciliary,  which,  as  we 
have  already  seen,  are  given  off 
from  the  nasal  branch  of  the 
ophthalmic  and  the  short  ciliary 
nerves  derived  from  the  ciliary 
ganglion.  The  ciliary  nerves, 
after  piercing  the  sclerotic,  pass 
forward  on  the  surface  of  the 
choroid,  to  which  tunic  they  give 
branches,  to  the  ciliary  muscle,  in  Avhich  they  form  a  plexus  con- 
tinued forward  into  the  iris  ;  they  apparently  terminate  at  the  pupil 
in  a  plexus  of  uon-medullated  fibers.     The  lenticular  or  ciliary  gan- 


in. 

oc.  m 


V.  optJi. 


Diagrammatic  representation  of  the  nerves 

foverniiig  the  puidl.  //.  Optic  nerve.  /.  <j. 
lenticular  ganglion,  r.  h.  Its  short  root  from 
III.  oc.  m.  Third  or  oculomotor  nerve,  siiru. 
Its  sympathetic  root.  r.  I.  Its  long  root  from 
V.  op/ithm.,  the  nasal  branch  of  the  ophthalmic 
division  of  the  fifth  nerve,  s.  c.  The  short  cil- 
iary nerves  from  the  lenticular  ganglion.  /.  c. 
The  long  ciliary  nerve  from  the  nasal  branch  of 
the  ophthalmic   division    of    the    fifth    nerve. 

(Fo.STER. ) 


THE  IRIS. 


741 


glion  [L  g.,  Fig;.  430)  beiiitr  made  up  of  fibers  derived  from  the  third 
pair,  the  nasal  branch  of  the  ophthahnic  and  the  sympathetic,  it 
mav  be  inferred  that  the  short  ciliary  nerves  consist  of  motor, 
sensory,  and  sympathetic  fibers. 

It  has  already  been  mentioned  that  the  fibers  of  the  third  pair 
of  nerves  and  of  the  sympathetic  exercise  an  antagonistic  in- 
fluence upon  the  pupil ;  division  of  the  third  pair  being  followed 
by  dilation,  and  that  of  the  sympathetic  by  contraction  of  the 
pupil. 

Putting  together  these  facts,  and  further  assuming  that  the  fibers 
of  the  third  pair  and  sympathetic  pass  through  the  ganglion, 
thence,  as  the  ciliary  nerves,  to  terminate  in  the  circular  and  dila- 
tor fibers  of  the  iris  respectively,  it  has  been  supposed  that  the 
pupil  dilates  if  the  third  jiair  be  divided,  since  there  is  noth- 
ing then  to  antagonize  the  dilating  effect  of  the  sympathetic,  and 
that  the  pupil  contracts  if  the  sympathetic  be  divided,  since  then 
there  is  nothing  to  antagonize  the  constricting  eifect  of  the  third 
pair. 

Recent  investigations^  render  it  probable,  however,  that  the  im- 
pulses that  cause  dilation  of  the  pupil  are  transmitted  by  those  fibers 
of  the  sympathetic  that,  pass- 
ing over  the  ganglion  of  Fig.  431. 
Oasser,  run  juxtaposed  with  ^ 
those  of  the  ophthalmic  branch 
of  the  fifth  nerve,  and  thence 
through  the  nasal  branch  of 
the  latter  into  the  long  ciliary 
nerve,  rather  than  by  those 
fibers  that  pass,  as  just  men- 
tioned, into  the  ciliary  gang- 
lion. Such  being  the  disposi- 
tion of  the  nerves  innervating 
the  muscular  fibers  of  the  iris, 
it  may  be  said  that  the  con- 
traction of  the  pupil  due  to  the 
falling  of  light  upon  the  retina 
is  a  reflex  act,  the  optic  being 
the  afferent  nerve,  the  third 
the  efferent  nerve,  the  center 
that  part  of  the  floor  of  the 
aqueduct  beneath  the  anterior 
corpora  quadrigemina.  (Fig. 
431.)  That  this  is  the  case, 
is  shown  by  the  following 
facts  :   When  the  optic  nerve 

is  divided  (it  being  supposed   that  the  observation  is  limited   to 

one  eye),  light  falling  on  the  retina  of  that  eye  no  longer  causes 

1  Langley,  Journal  of  Physiology,  Vol.  xiii.,  p.  575. 


Schema  of  the  nerves  of  the  iris.  B,  C.  Oculo- 
motor center.  D.  Dilator  center.  E.  Iris.  G. 
f)ptic  nerve.  H.  Oculomotor  (contractor)  nerve. 
/.  Sympathetic  (dilator)  nerve.  K,  L.  Anterior 
roots.  M,y.O.  iPosterior  roots.  A.  Seat  of  lesion, 
causing  pupUlary  immobility.  *.  Probable  seat 
of  lesion,  causing  myosis.     (Landois.) 


742  THE  EYE  AND   VISION. 

contraction  of  the  pupil.  When  the  third  nerve  is  divided,  stimu- 
lation of  the  retina,  or  of  the  optic  ners^e,  does  not  cause  contraction 
of  the  pupil,  "whereas  stimulation  of  the  peripheral  end  of  the  di- 
vided third  nerve  may  cause  extreme  contraction.  If  the  center 
beneath  the  corpora  <|uadrigemina  be  stimulated,  the  pupil  will  con- 
tract, even  though  no  light  falls  upon  the  retina  or  after  division  of 
the  optic  nerve,  whereas  after  destruction  of  the  center,  stimula- 
tion of  the  retina  will  not  cause  contraction  of  the  pupil.  Fi- 
nally, the  center  and  its  connections  with  the  optic  and  third 
nerves  being  intact,  light  falling  upon  the  retina  will  still  cause 
contraction,  even  though  all  the  other  parts  of  the  brain  have  been 
removed. 

It  should  be  mentioned,  hoAvever,  in  this  connection,  that  light, 
apart  from  any  nervous  influence,  will  exercise  a  direct  stimu- 
lating effect  upon  the  iris,  causing  the  pupil  to  contract  even 
after  the  eye  has  been  removed  from  the  orbit  several  hours  after 
death. 

This  fact  is  an  important  one,  since  it  offers  an  explanation 
of  the  pupil  contracting  at  times  even  after  division  of  the  third 
nerve.  The  contraction  of  the  pupil  in  response  to  the  direct 
stimulus  of  light  is,  however,  a  very  different  one  from  that  ob- 
served when  the  action  is  a  nervous  reflex  one,  taking  place  only 
after  a  very  long  exposure.  While  there  is  still  some  doubt  as 
to  exactly  how  the  fibers  of  the  optic  nerves  are  connected  with 
the  pupil  constrictor  center,  it  appears  to  have  been  established 
that  the  constricting  impulses  are  transmitted  by  those  fibers  of 
the  third  nerve  that  arise  in  the  anterior  part  of  the  nucleus, 
close  behind  those  influencing  accommodation,  the  fibers  arising 
from  the  posterior  part  innervating  the  ocular  muscles.  While 
contraction  of  the  pupil  in  response  to  the  stimulus  of  light  act- 
ing in  the  manner  just  mentioned,  appears  to  be  understood,  dif- 
ference of  opinion  still  prevails  as  to  how  dilation  of  the  pupil 
is  caused.  According  to  some  physiologists,  the  dilation  of  the 
pupil  is  a  vasomotor  phenomenon,  being  due  to  contraction  of 
the  blood  vessels.  That  such  is  not  the  case,  however,  is  shown 
by  the  following  facts  :  That  stimulation  of  tlie  long  ciliary 
nerves  causes  dilati(ju  of  the  pupil  without  contraction  of  the 
blood  vessels  of  the  iris,  and  that  stimulation  of  the  sympathetic 
after  division  of  the  long  ciliary  nerves,  causes  contraction  of  the 
blood  vessels,  without  dilation  of  the  pupil.  The  fibers  of  the  long 
ciliary  nerves,  which  appear  to  transmit  the  impulses  which  cause 
dilatation  of  the  pupil,  pass  down  the  cervical  sympathetic  (Fig. 
431, 1)  to  the  upper  thoracic  ganglion,  and  by  the  ramus  com- 
municans  and  anterior  root  of  the  second  thoracic  nerve  into  the 
spinal  cord,  and  thence  upwards  to  the  ])upil  dilator  center  (Fig. 
431,  C),  situated  in  the  aqueduct  close  to  the  pupil  constrictor  center. 
A  secondary  pupil  dilator  center,  the  so-called  cilio-spinal  center, 
is  also  supposed  by  some  physiologists  to  exist  in  the  cord  just 


DILATATION  OF  THE  PUPIL.  743 

above  the  level  of  the  second  thoracic  nerve.  The  pupil  dilator 
center  of  the  medulla  appears  to  be  excited  by  emotions  such  as 
fear,  by  the  stimulation  of  sensory  nerves,  dyspnoea,  etc.,  and  as 
contraction  of  the  pupil  follows  nerve  division  of  the  sympathetic, 
the  center  seems  to  be  a  tonic  one  constantly  sending  impulses  to 
the  dilatory  fibers  of  the  iris.  It  appears,  therefore,  that  it  is  by  the 
oculo-motor  mechanism,  that  the  size  of  the  pupil  is  modified  ac- 
cording to  the  amount  of  light,  and  that  by  means  of  the  svmpa- 
thetic  the  pupil  is  influenced  by  other  stimuli.  The  reflex  dilata- 
tion of  the  pupil  follows  a  little  later  than  the  reflex  contraction, 
the  time  intervening  between  the  cutting  off  of  the  light  and 
stimulating  by  the  same  being  0.5  and  0.3  sec.  respectivelv.  The 
pupil  reflex  in  man  and  many  of  the  higher  animals  is  a  bi- 
lateral one,  that  is  to  say,  light  falling  upon  the  retina  of  one 
eye  causes  contractions  of  the  pupils  of  both  eves.  Any  one 
can  convince  himself  that  such  is  the  case  by  illuminating  the 
retina  of  one  eye  by  means  of  light  transmitted  through  a  pin- 
hole in  a  screen  placed  in  the  anterior  focus  and  then  alter- 
nately closing  and  opening  the  other  eye,  the  size  of  the  circle 
of  light  being  increased  or  diminished  accordingly.  The  bi- 
lateral character  of  the  pupil  reflex  appears  to  depend  upon  the 
extent  of  the  decussation  of  the  optic  fibers  in  the  chiasma,  since 
in  those  animals  in  which  decussation  is  complete,  the  contrac- 
tion of  the  pupil  is  confined  to  the  illuminated  eye.  Further, 
as  we  have  just  seen  that  the  extent  of  the  decussation  is  asso- 
ciated with  the  position  of  the  eyes  in  the  head,  it  will  be 
found  that  in  animals  having  binocular  vision  the  pupil  reflex  is 
bilateral.^ 

Of  the  light  that  enters  the  eye  part  is  absorlied  by  the  black 
pigment,  part  reflected  and  in  the  same  direction  in  which  it 
enters.  In  observing  the  eye  of  another  person  the  head  of  the 
observer,  being  an  opaque  object,  cuts  off  the  light  and  as  no  light 
therefore  enters  the  eye,  none  is  reflected  back.  Hence  the  pupil 
of  the  eye  appears  to  one  oliserving  it  as  a  black  circular  spot 
in  the  middle  of  the  colored  iris.  It  is  obvious,  therefore,  that 
in  order  to  see  the  interior  of  the  eye  the  latter  must  be  illumi- 
nated by  lateral  ravs  the  eve  of  the  observer  beino^  in  the  line 
of  vision.  It  is  upon  these  principles  that  is  based  the  con- 
struction of  the  ophthalmoscope  the  nature  of  which  will  l)e  how- 
ever better  understood  after  the  action  of  lenses  upon  light  has 
been  explained. 

AVhile  the  function  of  tlie  iris  is  without  doubt  that  of  a 
diaphragm,  regulating,  through  the  pu])il,  the  amount  of  liglit 
admitted   to   the   interior   of  the  eye,   it   will    be   observed,  from 

^In  the  case  of  oavIs  in  wliich  tlie  visual  axes  arc  parallel,  diflerence  of  ojiinion 
still  prevails  as  to  the  extent  of  the  decussation  of  the  optic  tihei's.  Thus,  wliile 
accordintr  to  Fcrrier  (Croonian  lecture,  1890,  p.  70),  decussjition  is  incomplete,  ac- 
cording to  .Steinach  I  PtKisjer's  Arciuv,  B.  47,  s.  313),  it  is  complete  and  the  pupil 
reflex  unilateral  as  in  otiier  birds. 


744  THE  EYE  AND  VISION. 

Fig.  432,  that  not  only  will  the  light  enter  the  eye  from  a  point 
(a)  in  the  line  of  direct  vision,  l)ut  from  a  point  (6)  outside  that 

Fig.  482. 


Diagrammatic  section  of  the  eyeball,  showing  difFereuce  of  refraction  for  direct  and  indirect 
vision,  a,  x.  Rays  from  a  point  in  the  line  of  direct  vision,  foeussed  at  the  retina.  6,  y,  z.  Rays 
from  a  point  outside  the  line  of  direct  vision,  brought  to  a  focus  and  dispersed  before  reaching 
the  retina.     (Daltos.) 

line,  and  that  the  latter  rays  being  brought  too  soon  to  a  focus, 
are  dispersed  again  before  reaching  the  retina,  and  so  give  rise  to 
confused  vision. 

The  Retina. 

If  the  choroid,  including  the  tapetum  nigrum,  be  removed  under 
water  in  the  same  manner  as  the  sclerotic,  the  third  tunic  of  the 
eye  from  without  inward,  or  the  retina,  will  be  then  exposed  as  a 
very  delicate  and  transparent  membrane,  through  which  will  be 
seen  the  posterior  portion  of  the  underlying  vitreous  humor. 
Within  a  short  time  after  death,  however,  the  retina  loses  its  trans- 
parency and  becomes  opaline,  the  change  being  hastened  by  the 
action  of  water,  alcohol,  and  other  fluids.  The  retina,  varying  in 
thickness  from  J  to  |  of  a  millimeter  (Jg-  to  2^0^  of  <'in  iuch),  ex- 
tends over  the  posterior  portion  of  the  eyeball  to  within  a  distance 
of  about  1.4  millimeters  ( jL  of  aii  inch),  of  the  ciliary  processes, 
and,  if  torn  from  its  anterior  attachment,  presents  a  flnely  indented 
edge,  the  so-called  ora  serrata.  As  a  matter  of  fact,  however,  the 
retina  does  not  terminate,  as  often  said,  at  the  ora  serrata,  but  is 
continuous  forward  as  a  thin  layer  of  transparent  cohimnar  nucleated 
cells,  the  pars  ciliaris  retiuie,  which,  rcacliing  the  tips  of  the  ciliary 
processes,  then  disappears.  The  retina,  the  nervous  tunic  of  the 
eye,  and  that  portion  of  it  susceptil^le  of  being  impressed  by  light, 
may  be  regarded  as  an  expansion  of  the  optic  nerve,  though  it  is 
usually  described  as  being  traversed  l)y  the  latter,  like  the  sclerotic 
and   (jhoroid.     The    optic  nerve   aj)i[)arently,    then,   penetrates  the 


THE  RETINA. 


745 


retina  about  3  millimeters  (|  of  an  inch)  within,  and  1  millimeter 
(1  of  an  inch)  below  the  antero-posterior  axis  of  the  eye.  The 
nerve  fibers  being  at  this  point,  the  porus  opticus,  slightly  elevated, 
gives  rise  to  a  small  eminence  (Fig.  433),  the  colliculus  nervi  optici, 


Jtetifua. 


Fi(i.  433. 
JHembrana  Fusca  Larnina  crihrosa 


Sclerotic 

coat.  ^ 


i  %\ 


^li. 


Section  through  the  middle  of  the  optic  nerve  and  the  tunics  of  the  eye  at  the  place  of  its  passage 

through  them.     (Ecker.) 

between  which  the  central  artery  of  the  retina  appears,  and  spreads 
out  arborescent-like,  over  the  inner  surface  of  the  retina  (Fig.  434), 
and  the  branches  of  the  central  veins  converge  and  disappear.  To  the 
outer  side  of  the  optic  nerve,  about  2.5  milHmeters  (J^  of  an  inch), 
may  be  also  seen  on  the  inner  surface  of  the  retina,  a  yellow  spot, 
somewhat  elliptical  in  shape,  about  3  millimeters  (|  of  an  inch)  long, 
and  0.8  millimeters  (Jg-  of  an  inch)  l)road,  its  long  diameter  being 
horizontal,  the  so-called  macula  lutea  or  limbus  lutens  of  Sommer- 
ing,  presenting  in  its  center  a  depression,  the  fovea  centralis,  which 
is  situated  in  the  axis  of  vision.  As  the  retina  is  so  thin  at  this 
point  that  the  pigmental  layer  can  be  seen  clearly  behind  it,  the  fovea 
centralis  gives  the  impression  that  it  is  a  hole  that  has  been  made 
in  the  retina.  It  is  an  interesting  fact,  that  the  yellow  spot  of  S5m- 
mering  has  only  been  found  in  the  eye  of  the  primates.  The  sensi- 
tiveness of  the  retina  to  light  varies  very  much,  being  greatest  at 
the  yellow  spot,  and  gradually  diminishing  toward  the  periphery. 
The  difference  can  be  determined  experimentally  on  the  same  prin- 
ciple as  the  tactile  sensibility  of  the  skin  was  determined.  Thus, 
if  two  wires  be  placed  close  together,  but  sufficiently  fiir  apart  to 
enable  us  to  distinguish  one  from  the  other,  and  then  the  eye  be  so 
directed  that  the  image  of  the  wires  shall  fall,  first  u})on  tlie  yellow 
spot,  and  then  upon  the  great  circle  of  the  eye  ;    in  the  latter  case, 


746 


TEE  EYE  AND   VISION. 


the  wires,  to  be  seen  distinctly,  must  be  separated  at  a  distance  150 
times  greater  than  in  the  former  one.  It  is  evident,  therefore,  why 
the  movements  of  the  eyeball  all  tend  to  bring  the  image  of  external 
objects  npon  the  yellow  si)ot,  and  as  the  latter  only  constitutes 
about  the  ^i^  of  the  retina,  it  follows  that  but  a  small  portion  of 


Fig.  434. 


Fig.  435. 

Outer  or  choroidal  surftu 


The  posterior  liall  .H  tlic  retina  of  Uie  left 
eye  viewed  from  before.  Twice  its  natural 
size.  *.  Cut  edge  of  the  sclerotic,  ch.  Cho- 
roid, r.  Retina:  in  the  interior  at  the  mid- 
dle the  macula  lutea  witli  the  dcpressi.in  of 
the  fovea  centralis  is  represented  by  a  slight 
oval  shade  ;  toward  the  left  side  the  light 
spot  indicates  the  colliculus  or  eminence  at 
the  entrance  of  the  optic  nerve,  from  the 
center  of  which  the  arteria  centralis  is  seen 
sending  its  branches  into  the  retina,  leaving 
the  part  occupied  by  the  macula  compara- 
tively free.     (Hen'le.) 

the  latter  is  actually  made  use 
of  in  distinct  vision.  As  an 
illustration  may  be  mentioned 
the  familiar  fact  that,  in  read- 
ine;,  we  see  one  or  two  words 
at  a  time,  and  that  the  eye 
must  pass  over  the  whole  line 
in  order  to  read  it. 

The  retina  consists,  micro- 
scopically, of  a  connective  tis- 
sue scaffolding,  so  to  speak, 
supporting  eight  distinct  layers 
disposed  from  without  inward, 
as  follows  (Fig.  4.">5)  :  1,  pig- 
mentary layer  ;  2,  columnar  layer ;  3,  outer  nuclear  layer  ;  4,  outer 
molecular  laver  ;  5,  inner  nuclear  layer  ;  6,  inner  molecular  layer  ; 
7,  ganglionic  layer ;  and  <S,  nerve  layer.  The  first  outer,  or  pig- 
mentary, layer  of  the  retina,  formerly  described  as  the  inner  layer, 
or  tapetum  nigrum  of  the  choroid,  consists  of  a  single  stratum  of 
hexagonal  nucleated  epithelium  cells.     The  outer  surface  of  each 


Inner  surface. 

Diagrammatic  section  of  the  human  retina.  1. 
Layer  of  the  pigment  cells.  2.  Layer  of  rods  and 
cones.  .  .  Membranalimitans  extei  iia.  3.  Outer 
nuclear  layer.  4.  Outer  luuleeular  layer.  .5.  Inner 
nuclear  layer.  6.  Inner  molecular  layer.  7.  Layer 
of  nerve  cells.  8.  Layer  of  nerve  fibers.  .  _J^. 
Membrana  limitaus  interna.     (Schui-tze.) 


BODS  AND  CONES.  747 

cell,  that  lying:  next  to  the  choroid,  is  smooth,  flattened,  and  usually 
free  from  pigment ;  the  inner  portion,  prolonged  as  fine  straight 
filamentous  processes  between  the  rods  and  cones  of  the  second  or 
columnar  layer  is,  however,  loaded  with  pigment.  The  second,  or 
columnar  layer,  also  known  as  the  bacillary  layer,  Jacob's  mem- 
brane, consists  of  millions  of  elongated  bodies,  the  so-called  rods 
and  cones,  disposed,  in  a  ])alisade-like  manner,  between  the  pig- 
mentary layer  and  the  so-called  mendjrana  limitans  externa,  which 
is  not  a  continuous  membrane,  but  is  formed  through  the  connec- 
tive tissue  fibers  of  the  retina  uniting  more  or  less  along  a  definite 
line  at  the  l>oundary  of  the  third,  or  outer  nuclear  layer.  The  rods 
exceed  the  cones  in  number,  the  latter  amounting  to  more  than 
three  millions,  there  being  usually  about  four  rods  to  one  cone, 
except  at  the  macula  lutea,  where  cones  only  are  present ;  they 
have  an  elongated  cylindrical  form  with  a  diameter  of  about  ^^  of 
a  millimeter  {^2'h~oi)  of  an  inch)  and  a  length  of  Jjj  of  a  millimeter 
(^^1.^  of  an  inch).  The  cones  on  the  other  hand,  are  shorter  and 
thicker,  having  a  diameter  of  about  yi^  of  a  millimeter  (^yg  6  ^^ 
an  inch),  bulge  out  at  the  inner  end  or  base,  and  terminate  exter- 
nally by  a  fine  tapering  portion.  The  cones  are  usually  separated 
by  a  distance  of  j^-^  of  a  millimeter  (^^-sVo"  ^^^  ^"  inch),  the  inter- 
vening portion  being  filled  by  rods. 

Through  delicate  fiber-like  prolongations  the  inner  ends  of  the 
rods  and  cones  are  in  relation  with  the  third  or  outer  layer  of  the 
retina,  the  outer  nuclear  layer,  which  consists  of  several  strata  of 
clear,  oval  elliptical  nucleated  cells  from  both  ends  of  which  delicate 
fibers  are  prolonged.  These  outer  cells,  presenting  marked  differ- 
ences, are  of  two  kinds,  known  as  rod  granules  and  cone  cells,  ac- 
cording as  they  are  connected  "vvith  the  rods  or  cones,  respectively. 
While  the  outer  fibers  of  the  outer  nuclear  layer  are  prolonged  into 
the  rods  and  cones,  the  inner  fibers  of  the  same  are  prolonged  into 
the  outer  molecular  layer ;  the  latter  in  turn  appears  to  be  in  rela- 
tion through  fibrils  with  the  cells  of  the  inner  nuclear  layer,  the 
latter  being  in  relation  with  tlie  inner  molecular  layer.^  The 
seventh  layer  of  the  retina  from  without  inward,  the  ganglionic  or 
layer  of  nerve  cells,  consists  of  a  stratum  of  nerve  cells  of  a  sphe- 
roidal or  pyriform  figure,  which  appears  to  be  in  relation  by  fibers 
on  the  one  hand,  with  the  preceding  inner  molecular  layer,  and,  on 
the  other,  with  the  fibers  of  the  optic  nerve.  The  latter,  constitu- 
ting the  eighth  layer  of  the  retina,  appears  to  be  bounded  by  a  dis- 
tinct membrane,  the  membrana  limitans  interna,  which,  however,  is 
not  a  continuous  structure,  as  its  appearance  would  lead  one  to  sup- 
pose, but  is  formed,  like  that  of  the  membrana  limitans  externa,  by 
the  terminal  fibers  of  the  sustenacular  or  connective  tissue  frame- 
work of  the  retina  being  united  together  at  this  point.  From  this 
necessarily  brief  description  of  the  minute  structure  of  the  retina  it 
Avill  be  seen  that  the  layer  of  th.e  rods  and  cones,  or  Jacob's  mem- 
1  Rauber,  op.  cit.,  s.  723.     Gehuohten,  op.  cit.  s.  628. 


748  THE  EYE  AND  VISION. 

brane,  bounded  externally  by  the  pigmentary  layer,  may  be  regarded 
as  the  termination  of  the  optic  nerve  fibers.  It  may  be  mentioned, 
in  this  connection,  that,  as  the  rods  and  cones  far  exceed  the  optic 
nerve  fibers  in  number,  it  is  impossil)]e  that  each  optic  nerve  fiber 
should  be  connected  with  a  rod  or  cone  throughout  the  retina,  though 
such  a  relation  may  exist  at  the  macula  lutea.  It  has  already  been 
mentioned  that  at  the  macula  lutea  the  rods  are  absent,  the  cones 
only  being  present ;  the  latter  are,  further,  nnich  longer  and  nar- 
rower than  elsewhere,  especially  opposite  the  fovea.  At  this  por- 
tion of  the  retina  the  various  layers  of  which  it  consists  are  also 
very  much  thinned.  The  yellow  color  of  the  macula,  deepest  at  the 
center,  is  due  to  a  coloring  matter  diffused  through  all  the  layers 
except  that  of  the  cones  and  tlie  outer  nuclear  layer.  It  might 
naturally  be»supposed  that  tlie  anterior  layer  of  the  retina,  that  fac- 
ing the  light,  would  be  the  sensitive  layer — as  a  matter  of  fact,  of 
all  the  layers  of  the  retina,  however,  that  of  the  rods  and  cones  is 
most  sensitive  to  light,  as  can  be  shown  experimentally  by  so  illu- 
minating the  eye  that  one  is  able  to  perceive 
Fig.  436.  the  shadows  of  the  vessels  of  his  o^vn  retina, 

which  are  cast  upon  the  layer  of  rods  and 
cones.  The  vessels  of  the  retina,  being  situ- 
ated in  its  anterior  layer,  necessarily  cast  their 
shadows  on  one  of  its  posterior  layers,  and 
the  only  reason  that  we  do  not  ordinarily  see 
these  shadows  is  probably  that  we  have  be- 
come so  accustomed  to  them  that  they  no 
B.  A  candle  placed  at  the     longer  attract  our  attention.     If,  however,  the 

side  of  the  eye — that  is,  as  !•  i  •    i  i     i  i  i   •  i 

much  to  the  side  of  the  ceu-  source  ot  light  be  placcd  lu  an  unusuai  posi- 

B'fnterrMum^fuo'i';  tiou,  as  iu  Fig.  436,  thcu  thc  shadows  of  the 

Tiigh'ttre'tritedl/the  vcsscls  falling  ou  au  uuusual  portion  of  the 

crystalline  leus  upon  the  layer  of  rods  and  coucs  wiU   be  perceived, 

extreme  lateral  portion   of  i-iii  ii* 

the  eye.   CD.  Two  vessels     and  wul   bc  sccu  bv  ouc  looking:  at  a  vcrv 

of  the  retina  (the  size  of  the        ,      ,  „  .  ,  •'  ,  ^.  „  •      ,     i 

retina  is  here  greatly  exag-  (lark  surtacc  lu  a  darJc  rooui,  as  it  projcctcd 
fheseTwo  vessels "is^seeu  as  at  T>'  C ,  and  rcscmbliug  cxactlv  the  vessels 
JLl"rSc:?i^RK?;^f-  of  the  retina,  the  picture  of  the  retina  so 
seen  being  known  as  the  vascular  tree  of 
Purkinje.  Now  it  Avas  shown  by  H.  Muller,^  that  the  distance  be- 
tween the  anterior  layer  of  the  retina,  and  the  layer  of  rods  and 
cones  was  about  equal  to  tliat  between  the  retinal  vessels  and  their 
shadows  ;  necessarily,  tlien,  the  layer  of  rods  and  cones  must  be 
sensitive  to  light.  Now,  it  l)cing  remembered  that  the  layer  of 
rods  and  cones  lies  next  to  the  pigmental  layer,  and  that  the  ret- 
ina, with  the  exception  of  the  latter  layer,  is  transparent,  it  follows 
that  a  ray  of  light  passes  through  the  retina  until  it  I'caches  the 
pigmental  layer  wlien  it  ceases  to  be  light,  l)eing  transformed  into 
either  heat,  chemical  or  nervous  force ;  the  latter  exciting  the  rods 
and  cones,  gives  rise  to  an  impression  which  is  then  transmitted 

'  Verhaiid.  der  phy.sik.  med.  Gcfsellscliaft  zu  Wurzburg,  v.,  s.  411. 


VISUAL  PURPLE.  749 

back  to  the  optic  fibers  on  the  anterior  surface  of  the  retina, 
where  it  is  again  reflected  along  tlie  optic  nerve  fibers  to  the  optic 
lobes,  etc. 

It  has  been  shown  more  particularly  by  the  researches  of  Kiihue' 
that  the  outer  ends  of  the  rods  of  the  retina  contain  a  substance 
known  as  "  rhodopsin "  or  "visual  purple"  and  Avhich  is  appa- 
rently elaborated  out  of  the  retinal  epithelium  lying  l)etween  the 
rods  and  cones.  If  an  eye  after  excision  or  in  its  natural  position 
be  protected  from  light  for  a  time,  and  then  the  light  of  a  lamp  or 
a  window,  for  example,  l)e  allowed  to  fall  upon  it,  the  retina  will 
show,  if  examined  under  red  light,  the  image  of  the  object  impressed 
upon  it  by  the  bleaching  of  the  purple.  If  the  retina  be  further 
treated  with  a  4  per  cent,  solution  of  alum-potash  before  the  retinal 
epithelium  has  had  time  to  obliterate  the  bleaching  effects,  the  im- 
age or  "  optogram  "  of  the  external  object  may  be  "  fixed  "  as  the 
photographers  express  it.  Even  if  it  be  admitted  that  the  chem- 
ical changes  undergone  by  the  visual  purple,  due  to  light  act  as  a 
stimulus  to  the  optic  nerve  fibers,  such  changes  cannot  be  essential 
to  vision,  since  vision  is  most  acute  at  the  yellow  spot  just  where 
the  visual  purple  is  absent,  the  rods  not  being  present  in  that  situ- 
ation. INIoreover,  vision  is  fairly  distinct  in  albinos  in  which  the 
visual  purple  is  absent. 

Beyond  the  statement  that  the  rods  and  cones  are  excited  by  the 
heat  or  nerve  energy,  or  whatever  the  form  of  energy  may  be  into 
which  the  light  is  transformed  in  the  pigmental  layer,  little  can  be 
said  as  to  the  special  role  they  play  in  vision.  Such  facts,  however, 
as  that  in  the  bat,  hedge iiog,  and  mole,  nocturnal  animals,  and  night 
birds,  also,  the  retina  consists  solely  of  rods  ;  whereas,  in  day-birds, 
especially  in  those  which  live  on  insects,  of  brilliant  colors,  the  ret- 
ina contains  a  much  larger  number  of  cones  than  the  mammalia, 
would  lead  one  to  suppose  that  the  rods  are  affected  by  differences 
in  the  intensity  of  the  light,  the  cones  by  differences  in  its  quality — 
that  is,  its  color.  AVliile  there  can  be  no  doubt  that  the  fibers  of 
the  optic  nerve  transmit  luminous  impressions,  or  their  modifica- 
tions, in  the  manner  described,  it  can  be  shown  experimentally 
that  the  part  of  the  retina  where  these  fibers  appear  is  insensitive 
to  light,  and  is  called,  for  that  reason,  the  punctum  csecum.  Thus, 
if  two  black  points  (Fig.  437,  A,  B),  on  a  piece  of  paper,  separated 

Fig.  437. 
A  B 

•  • 

by  a  distance  of  two  inches,  be  viewed  at  a  distance  of  six  inches  by 
the  right  eye,  the  left  eye  being  closed,  the  point  B  Avill  be  invis- 
ible, being  then  opposite  the  punctum  caecum,  or  blind  spot. 

1  Centralbl.  f.  d.  med.  Wissensch.,  1877,  s.  19-1.  Hermann,  op.  cit.,  Bd.  3,  1, 
1879,  s.  261. 


750  THE  EYE  AND   VISION. 

The  Vitreous  Humor  and  Hyaloid  Tunic. 

The  vitreous  humor,  whik'  enclosed  l)y  the  retina,  does  not,  how- 
ever, lie  loosely  in  the  cavity  of  the  eyeball,  being  invested  by  a 
delicate  membranous  capsule,  about  .^~\-^  of  a  millimeter  (g  q^q^q^  of 
an  inch)  in  thickness — the  hyaloid  tunic.  The  latter  is  thicker  in 
advance  of  the  retina  than  elsewhere,  and,  as  already  mentioned,  is 
impressed  by  the  ciliary  processes  of  the  choroid,  the  zone  so  formed 
around  the  crystalline  lens,  and  well  defined  by  the  staining  of  the 
processes,  being  known  as  the  zone  of  Zinu.  Anteriorly  the  hyaloid 
tunic  splits  into  two  laminae,  which,  diverging  at  the  border  of  the 
crystalline  lens,  becomes  confluent  Avith  the  anterior  and  posterior 
surfaces  of  its  capsule,  the  two  laminae  adhering  at  intervals  ;  if  the 
space  between  them  be  inflated,  it  will  assume  the  appearance  of  a 
beaded  canal,  surrounding  the  circumference  of  the  lens — the  canal 
of  Petit.  Such  being  the  disposition  of  the  hyaloid  tunic,  it  is  evi- 
dent that  not  only  does  it  support  the  vitreous  humor,  through  in- 
vesting the  latter,  but  acts  also,  from  what  has  just  been  said,  as  the 
suspensory  ligament  of  the  lens.  The  vitreous  humor,  one  of  the 
refractor}^  media  of  the  eye,  occupying  about  the  posterior  two- 
thirds  of  the  globe,  consists  of  a  clear,  glassy,  gelatinous  matter, 
containing  albumin,  a  mucoid,  and  mineral  bodies.  It  is  divided 
into  compartments  by  delicate  membranous  processes,  which,  given 
off  by  the  hyaloid  tunic,  penetrate  its  substance.  The  specks  that 
one  sees  occasionally  floating  about,  as  it  were,  in  the  field  of  vision, 
the  so-called  muscte  volitantes,  are  due  to  the  shadows  cast  upon  the 
retina  by  the  connective  tissue  elements  suspended  in  the  vitreous 
humor. 

The  Crystalline  Lens. 

The  crystalline  lens  (Fig.  427,  8),  the  most  important  of  the  re- 
fracting media  of  the  eye,  transparent  and  very  elastic,  is  situated 
in  the  hyaloid  fossa  of  the  vitreous  humor,  behind  the  pupil,  and  is 
enclosed,  as  already  mentioned,  betAveen  the  laminae  of  the  hyaloid 
tunic,  the  latter  constituting  its  suspensory  ligament.  The  crystal- 
line lens  is  a  double  convex  lens,  the  convexity  of  the  posterior 
surface  being  greater  than  that  of  the  anterior.  The  antero-poste- 
rior  diameter,  6.2  millimeters  (J  of  an  inch),  is,  however,  a  little 
less  than  that  of  the  lateral  one,  8.3  millimeters  (^  of  an  inch). 
With  advance  in  age  the  convexities  diminish,  the  lens  becomes 
harder  and  inelastic,  which  accounts  for  the  gradual  diminution  in 
the  power  of  accommodating  the  eye  to  distances.  If  the  lens  be 
examined  with  a  low  magnifying  power,  there  w^ill  be  observed  on 
each  of  its  surfaces  a  star-like  Ixxly,  nine  or  sixteen  rays  of  which 
extend  from  the  center  to  Avithin  about  two-thirds  of  the  periphery. 
The  l)ody  of  the  stars  and  their  rays  are  not  of  a  fibrous  character, 
like  the  rest  of  the  lens,  but  consist  of  a  homogeneous  substance, 
which  extends  between  the  fibers.  The  latter  are  flattened,  six- 
sided  prisms,  from  yig-  to  -g^g  of  a  millimeter  (^-gVs"  ^^  2Tcnr  ^^  ^^ 


THE  AQUEOUS  HUMOR.  751 

inch)  In'oad,  and  from  -^i^  to  gi^  of  a  millimeter  (yg^oQ-  to  -q-q\jj- 
of  an  inch)  thick.  Their  flat  surfaces  arc  parallel  with  the  surface 
of  the  lens,  and  their  direction  is  from  the  center,  and  from  the  rays 
of  one  star  to  the  periphery,  where  they  turn  and  pass  toward  those 
of  the  other.  Chemically,  the  lens  is  composed  of  a  globulin,  called 
crystalline,  combined  with  inorganic  salts.  The  crystalline  lens  is 
enclosed  within  a  very  thin,  transparent,  elastic  membrane,  the 
capsule,  which  is  lined  anteriorly  with  a  layer  of  delicate  nucleated 
cells. 

The  Aqueous   Humor. 

The  aqueous  humor  (Fig.  427,  13),  the  remaining  of  the  refracting 
media  of  the  eye,  is  a  colorless,  transparent,  almost  watery  fluid, 
filling  the  anterior  chamber  of  the  eye — that  is,  the  space  between 
the  cornea  in  front  and  the  iris  and  crystalline  lens  behind,  and  the 
posterior  chamber,  or  the  space  between  the  posterior  surface  of  the 
iris  and  the  lens,  supposing  that  such  a  place  exists,  which  is  very 
doubtful,  and  in  any  case  must  be  very  small.  That  the  aqueous 
humor  is  secreted  possibly  by  the  blood  vessels  of  the  iris  and 
ciliary  processes,  or  the  internal  layer  of  the  cornea,  is  shown  by 
the  rapidity  with  which  it  is  reproduced  after  it  has  been  evacuated, 
as  in  surgical  operations  performed  upon  the  eye.  The  solids  of 
the  aqueous  humor  amount  to  thirteen  per  thousand,  among  which 
serum  globulin  and  glo1)ulin  are  found  in  traces. 

Intraocular  Pressure. 

The  watery  fluids  filling  the  cavity  of  the  eye  are  during  life 
subjected  to  a  pressure,  the  so-called  intraocular  pressure.  This 
pressure,  depending  upon  that  of  the  blood  pressure  of  the  retina, 
choroid,  etc.,  must  vary  with  the  latter,  rising  and  falling  with  it. 
The  character  of  this  pressure  is  determined  by  pressing  upon  the 
eyeball  and  of  so  learning  whether  it  is  soft,  tense,  or  compressible. 


CHAPTER   XXXIX. 


PHYSIOLOGICAL  OPTICS. 


Refraction  and  Accommodation. 

From  the  necessarily  brief  description  just  given  of  the  eye,  it  is 
ajDparent  that  it  resembles  essentially  in  its  structure  the  camera  of 
the  photographer,  its  refractive  media  being  comparable  to  the  lens, 
the  iris  to  the  diaphragm,  the  choroid  to  the  internal  blackened 
surface,  the  retina  to  the  sensitive  plate,  the  image  of  the  external 
object  being  brought  to  a  focus  on  the  retina  or  sensitive  plate, 
respectively,  through  the  refraction  undergone  by  the  rays  of  light. 
In  order,  however,  to  understand  the  manner  in  which  the  rays  of 
light  are  brought  to  a  focus  on  the  retina  by  the  cornea,  crystalline 
lens,  etc.,  it  will  be  necessary  to  describe  briefly  the  phenomena  of 
refraction  or  the  course  that  rays  of  light  take  in  passing  through 
refractive  media.     Suppose  that  W  W  (Fig.  438)  represent  a  mass 

of  water,  and  C  A  the  direc- 
FiG.  438.  tion  of  a  beam  of  light  pass- 

ing through  the  atmosphere 
L  L,  the  rarer  medium,  it 
will  be  observed  that  as  the 
ray  of  light  passes  through 
the  Avater,  the  denser  me- 
dium, it  is  bent  toward  the 
perpendicular  A  F,  but  that 
as  it  passes  out  of  the  water 
into  the  air  again,  the  rarer 
medium,  it  is  bent  away 
from  the  perpendicular.  Let 
now  the  line  C  A,  repre- 
senting the  direction  of  the 
incident  beam,  be  connected 
with  tlie  perpendicular  B  F 
by  the  line  D  E,  and  the 
line  representing  the  refracted  beam  A  H,  be  connected  witli  the 
perpendicular  by  the  parallel  line  G  H,  and  it  will  be  seen  that  the 
line  G  H  is  three-fourths  as  long  as  the  line  D  E ;  and  further 
that  this  ratio  of  4  to  3,  equal  to  1.33G,  will  be  invariably  the, 
same  whatever  the  angle  may  be  that  the  incident  beam  C  A  makes 
with  the  surface  of  the  water  I K,  except  it  be  a  right  angle,  the 
beam  then  passing  directly  through  the  water  without  being  re- 
fracted at  all. 

The  well-known  fact  of  a  stick  ajipearing  bent  when  obliquely 


Refraction  of  Light. 


REFRACTION. 


753 


thrust  into  water  (Fig.  439)  or  of  a  coin  lying  upon  tlie  bottom  of 
a  vessel  appearing  to  be  at  some  distance  from  the  latter  (Fig.  440), 
are  familiar  illustrations  of  refraction. 


Fig.  439. 


Fig.  440. 


Illustratioa  of  refraction. 


Illustratiou  of  refraetiou. 


If,  however,  with  A  as  a  center,  and  a  radius  A  D,  a  circle  be 
described,  the  line  D  E  becoming  then  trigonometrically  the  sine  of 
the  angle  I)  A  31,  and  the  line  G  H  the  sine  of  the  angle  HA  X, 
the  law  according  to  which  light  is  refracted  as  it  passes  from  air 
through  water,  may  be  expressed  by  saying,  that  the  ratio  of  the 
sines  of  the  angles  of  incidence  and  of  refraction  equals  |  =  1.336 
and  is  constant  for  the  particular  substance  water,  or,  briefly,  that 
the  index  of  refraction  of  water  is  1.33.  That  is  to  say,  if  the  line 
D  E  is  4  inches  in  length,  then  H  G  ^\\\\  be  3  inches,  the  two  being 
always  in  the  same  ratio.  If  now,  for  water,  crown  glass  be  sub- 
stituted, it  will  be  found  that  the  sine  of  the  angle  of  incidence  D  E 
is  to  the  sine  of  the  angle  of  refraction  H  G  not  as  4  is  to  3,  as  in 
the  case  of  air  and  water,  l)ut  as  3  to  2 — that  is,  the  index  of  refrac- 
tion for  the  particular  substance  crown  glass  equals  |-  =  1.5. 

Bearing  in  mind  then,  that  as  the  beam  of  light  passes  from  the 
air,  the  rarer  medium,  through  the  glass  it  is  bent  toward  the  per- 
pendicular, but  away  from  it  as  it  passes  out  of  the  glass,  the 
denser  medium,  and  that  by  the  index  of  refraction  is  meant  the 
ratio  of  the  sines  of  the  angles  of  incidence  and  refraction,  there 
will  be  no  diiliculty  in  compreliending  the  manner  in  which  the 
direction  of  a  beam  of  light  is  altered  in  passing  through  biconvex 
and  biconcave  lenses.  Let  C  (Fig.  441),  for  example,  represent  a 
biconvex  lens  of  crown  glass  in  which  the  radii  of  curvature  are 
nearly  equal — that  is  to  say,  the  two  surfaces  or  curves  of  the  lens 
are  about  equally  distant  from  the  centers  of  the  circles  of  which 
these  curves  form  parts,  and  that  BE,  C  G  be  two  luminous  rays 
parallel  with  the  principal  axis  A  D  passing  through  the  optical 
center  C  of  the  lens,  which  fall  .upon  the  lens  at  the  points  E  and 
G,  respectively.  Then,  according  to  the  law  just  enunciated,  the 
48 


754  PHYSIOLOGICAL  OPTICS. 

ray  B  E  being  first  bent  toward  the  perpendicular,  and  then  away 
from  the  perpendicular,  and  the  ray  G  G  being  in  the  same  manner 
bent  first  toward  and  then  away  from  the  perpendicular,  and  the 
ray  A  G  being  in  the  direction  of  the  optical  axis,  and  consequently 


Effect  of  bicouvex  lens  ujMjn  rays  of  light. 

passing  through  the  lens  perpendicularly,  and,  therefore,  unre- 
fracted,  it  follows  that  the  three  rays,  and  all  others  parallel  with 
them,  will  meet  at  a  point  F,  known  as  the  principal  real  focus, 
and  situated  in  the  principal  axis  of  the  lens  at  a  distance  from  the 
latter  (^F  H)  which  will  be  determined  presently,  and  known  as 
the  principal  focal  distance.  The  eifect  of  a  biconvex  lens  is  then 
to  bring  parallel  rays  of  light  to  a  focus  on  the  side  of  the  lens 
opposite  to  the  source  of  light,  the  amount  of  convergence  depend- 
ing upon  the  radius  of  curvature  of  the  lens  and  its  index  of  re- 
fraction, which  in  this  particular  case,  as  w^e  have  seen,  is  1.5.  The 
converse  of  this  is  also  true,  since  if  the  source  of  light  be  at  the 
principal  focus  F,  then  the  divergent  rays  after  leaving  the  lens 
will  be  brought  parallel  with  each  other,  and  with  the  principal 
axis.  Such  being  the  action  of  a  biconvex  lens,  it  will  be  seen 
from  a  comparison  of  Fig.  441  with  Fig.  442,  that  the  action  of  a 

Fig.  442. 


A*^ 


3/ 


Effect  of  biconcave  lens  upon  rays  of  light. 


biconcave  lens  is  exactly  the  opposite  of  a  biconvex  one,  since  the 
rays  of  light  {B  E,  G  G,  Fig.  441),  after  being  bent  toward  their 
respective  perpendiculars  and  then  away  from  them,  according  to 


CONJUGATE  FOCI.  755 

the  law  of  refraction,  will  diverge  from  the  princi])al  axis  A  D, 
instead  of  converging  tOAvard  it,  and  the  rays  of  light  B  E,  C  G, 
and  all  others  parallel  with  them,  will  diverge  as  K L,  31 N,  instead 
of  being  bronght  to  a  focus,  on  the  side  of  the  lens  opposite  to  that 
of  the  light.  In  the  case  of  a  biconcave  lens  the  focus  is  negative, 
virtual,  that  is  to  say,  it  is  upon  the  same  side  of  the  lens  as  the 
light,  and  its  position  is  found  by  prolonging  backward  the  rays 
L  K  and  N  31  until  they  meet  in  the  principal  axis  A  D.  It  will 
be  also  observed  that  the  converp-ing;  ravs  L  K,  N  31  are  brought 
parallel  with  each  other  on  the  same  side  of  the  lens  as  that  where 
the  light  is  now  supposed  to  be. 

Let  us  now  consider  the  case  in  which  the  luminous  object  L  is 
beyond  the  principal  focus  F  (Fig.  443),  but  so  near  that  all  the 
incident  rays  L  E,  L  F  form  a  divergent  cone,  then,  according  to 
the  law  of  refraction,  the  rays,  after  leaving  the  lens,  will  be  found 
to  come  to  a  focus  at  /,  and  the  converse  of  this  will  be  found  to  be 
true,  since,  if  the  luminous  object  be  placed  at  I,  the  focus  will  then 
be  at  i,  hence  /  and  X  are  conjugate  foci.  Further,  it  will  be  found 
by  experimentation,  or  by  calculation,  that  if  the  distance  between 
the  luminous  object  I  and  the  lens  be  twice  the  focal  distance — that 
is,  twice  H  F  equals  H I — then  the  focus  I  will  be  situated  on  the 
other  side  of  the  lens  at  the  same  distance,  or  twice  H  F,  as  at  the 
point  A,  on  the  axis  A  D.  If,  however,  the  distance  between  the 
lens  and  the  luminous  object  be  less  than  twice  the  fo.cal  distance, 
the  focus  will  be  situated  beyond  the  point  A,  and  if  more  than 
twice  the  focal  distance,  then  the  focus  will  be  situated  within 
the  point  A — that  is,  between  the  point  A  and  the  lens.      After 


Coujugate  foci  of  leus. 

what  has  just  been  said,  with  reference  to  the  manner  in  which 
the  rays  of  light  are  brought  to  a  focus  by  biconvex  lenses, 
etc.,  it  will  be  readily  seen  from  Fig.  444  how  the  image  of 
an  object,  as  of  an  illuminated  arrow,  for  example,  is  formed  if  a 
biconvex  lens  be  placed  between  the  latter  and  a  screen.  It  will 
be  observed,  however,  that  the  part  of  the  arrow  at  a  being  brought 
to  a  focus  at  x,  that  at  h  at  y,  that  the  image  of  the  arrow  is  neces- 


756  PHYSIOLOGICAL  OPTICS. 

sarily  reversed,  and  that  if  the  luminous  object  approaches  the  lens 
its  image  recedes  and  becomes  larger,  and  if  it  recedes  from  the 
lens  its  image  approaches  and  becomes  smaller,  and  that  if  the 
luminous  object  be  situated  at  twice  the  focal  distance  from  the 
lens  its  image  will  be  of  the  same  size  and  situated  at  the  same 
distance  from  the  lens.  The  distance  at  which  the  image  is  formed 
l)ehind  the  lens  can  be  readily  calculated  in  any  case  by  formulse  to 
be  found  in  any  standard  work  on  physics. 

Fig.  444.  Fif4.  445. 


Paths  of  rays  of  light  through  lens  with 

foniiatiou  of  image.  Paths  of  rays  of  light  witliout  lens. 

It  need  hardly  be  added  that  in  the  absence  of  a  lens,  the  rays  of 
light  will  follow  the  paths  indicated  in  Fig.  445,  and  as  the  light 
from  a  will  meet  at  4  that  from  b,  and  the  light  from  6  at  1  that 
from  rt,  no  image  of  the  arrow  will  be  formed  upon  the  screen. 
Having  considered  now  the  properties  of  lenses,  let  ns  apply  what 
has  been  established  of  the  same  to  the  elucidation  of  vision,  and 
show  how  the  rays  of  light,  passing  successively  through  the  cornea, 
aqueous  humor,  crystalline  lens,  and  vitreous  humor  are  finally 
brought  to  a  focus  on  the  retina. 

In  considering  the  paths  of  the  rays  of  light  through  the  refractive 
media  of  the  eye  ])hysicists  make  use  of  a  normal  schematic  eye,  a 
standard  eye,  so  to  speak,  in  which  certain  cardinal  points  have  been 
established,  and  by  which  the  course  of  the  rays  of  light  through  the 
eye  can  be  readily  constructed,  the  position  of  the  focus  determined, 
and  the  size  of  tlie  image  estimated.  Let  ns  endeavor,  therefore,  to 
explain  the  method  by  which  the  cardinal  points  are  determined. 
Let  M,  M^  be  two  refractive  media  separated  from  each  other  by 
a  spherical  surface  B  C  (Fig.  446),  constituting  what  is  known  op- 
tically as  a  simple  collecting  system,  and  N  the  center  of  curvature 
— that  is,  the  center  of  a  circle,  of  which  B  C  forms  a  part.  All 
the  radii  drawn  from  the  center  N  to  B  C,  such  as  N  B,  IST  x,  N  Y, 
being  perpendicular  rays  of  light  falling  in  the  direction  of  the  radii, 
must  pass  unrefracted  through  N  as  L  D,  I^  d',  for  example,  and 
are  called,  therefore,  lines  of  direction,  while  N,  the  point  of  inter- 
section of  all  such  lines,  is  called  the  nodal  ])oint.  The  line  O  A, 
connecting  N,  the  center  of  cur\aturc,  with  the  vertex  I,  and  pro- 
longed in  both  directions,  is  known  as  the  optic  axis,  the  plane  H  E, 
perpendicular  to  the  optic  axis  at  I,  being  called  the  principal 
plane,  and  the  point  I,  within  the  latter,  the  })rincipal  point.     Such 


SIMPLE  COLLECTIVE  SYSTEM. 


757 


being  prcsuppixscd,  it  can  be  shown  that  all  rays  jiarallel  with  each 
other,  and  with  the  optic  axis  in  the  medium  M,  such  as  f  H,  p  E, 
falling  upon  B  C,  come  to  a  focus  at  F^  in  the  second  medium, 
called  the  second  principal  focus,  or  second  focal  point,  the  plane 
S  F-  P,  perpendicular  to  the  optic  axis  O  A,  at  this  point,  being  the 


Fig.  440. 


Simple  collective  system  of  refracting  media. 

second  focal  plane.  Of  course,  the  converse  of  the  above  is  true — 
that  is,  rays  diverging  from  F',  such  as  F^  B,  F"  C,  pass  into  the 
first  medium  ])arallel  with  each  other,  and  with  the  optic  axis. 
Further,  it  will  lie  seen  from  an  inspection  of  Fig.  446,  that  rays 
which  are  parallel  t(^  each  other  in  the  first  medium,  but  not  paral- 
lel with  the  optic  axis,  such  as  Q  T,  U  Z,  come  to  a  focus  in  the  sec- 
ond medium  in  the  point  D  of  the  second  focal  plane,  where  the  non- 
refracted  directive  ray  L  D  meets  the  latter,  and  that  rays  diverging 
from  D  pass  through  the  first  medium  parallel  with  each  other, 
but  not  parallel  with  the  optic  axis.  It  is  also  evident  that  all  rays, 
which,  in  the  second  medium  are  parallel  with  each  other,  and  with 
the  optic  axis,  such  as  S  B,  P  C,  come  to  a  focus  (F^)  in  the  first 
medium,  called  the  first  focal  point,  or  first  principal  focus,  the 
plane  of  f  F^  p,  perpendicular  to  the  optic  axis  at  this  point,  being 
known  as  the  first  focal  plane.  Of  course,  the  converse  of  the 
above  is  true,  viz.,  tliat  rays  diverging  from  F^  pass  through  the 
second  medium  parallel  with  each  other  and  with  the  optic  axis. 

Finally  it  follows  that  the  radius  of  the  spherical  surface  X  I  is 
equal  to  the  difierence  of  the  distance  of  the  focal  points  F',  F-, 
from  the  principal  point  I — that  is,  that  X  I  =  F'  I  —  F^  I.  Such 
being  admitted,  it  will  be  seen  that  an  incident  ray  (Q  T)  comes  to 
a  focus  in  the  second  focal  plane  in  the  point  D,  where  the  non- 
refracted  directive  ray  L  D  meets  the  latter,  and  that  a  reversed 
image  |  of  an  external  object  like  an  arrow  |  situated  in  the  first 
meclium  is  formed  in  the  second  medium  at  the  point  where  the 
prolonged  ray  BF"  meets  the  non-refracted  directive  ray  I'd'. 
Now  did  the  eye  consist  simply  of  two  refractive  media,  separated 


758 


PHYSIOLOGICAL  OPTICS. 


by  a  spherical  surface,  as  in  the  simple  collecting  system  just  de- 
scribed, the  construction  of  the  refracted  ray  and  of  the  image  of 
the  object  would  be  essentially  the  same  and  equally  simple.  In- 
asmuch, however,  as  the  eye  consists  of  four  refractive  media, 
cornea,  aqueous  humor,  crystalline  lens,  and  vitreous  humor,  the 
cornea  and  aqueous  humor  constituting  a  concavo-convex  lens,  the 
crystalline  a  biconvex  lens,  and  the  vitreous  humor  a  concavo-con- 
vex lens,  to  apply  to  the  eye  what  has  just  been  established  would 
involve  proceeding  from  medium  to  medium,  which  would  be  a 
tedious  operation.  If,  however,  the  several  media  are  centered, 
that  is,  if  they  have  the  same  optic  axis,  which  is  pretty  nearly 
the  case  in  the  eye,  then,  as  shown  by  Gauss,^  the  refractive  media 
of  such  a  system  may  be  represented  by  two  imaginary  equally 
strong  refractive  surfaces  (Fig.  447,  F  P'),  the  rays  falling  upon 
the  first  system  not  being  refracted,  but  projected,  so  to  speak, 
parallel  with  themselves  to  the  second  surface  as  at  x  x' ,  y  y' , 
refraction  taking  place  at  the  latter  just  as  if  that  surface  alone 
was  present,  and  that  the  data  required  in  determining  the  situa- 
tion of  the  tAvo  refractive  surfaces  are  the  refractive  indices  of 
the  media,  the  radii  of  the  refractive  surfaces,  and  the  distances 
of  the  latter  from  each  other,  which  can  be  experimentallv  de- 
termined.    Let  J/',  ]\P,  M\  and  31^  (Fig.  447)  be  four  media, 


System  of  refractive  media  liaving  the  same  optic  axis. 

for  example,  such  as  the  air,  aqueous  humor,  crystalline  lens,  and 
vitreous  humor  ;  B  C  ii  spherical  surface  like  the  cornea,  sep- 
arating the  air  from  the  aqueous  humor  ;  L I  the  anterior  surface 
of  a  biconvex  lens  like  the  crystalline  lens,  a  spherical  surface 
separating  the  aqueous  humor  from  the  substance  of  the  lens  ; 
and  Vv  the  posterior  surface  of  tlie  lens,  also  a  spherical  surface, 
reversely  disj)osed,  however,  with  reference  to  the  cornea  and  an- 
terior surface  of  the  lens,  and  separating  the  substance  of  the  lens 
from  that  of  the  vitreous  humor.  Such  being  the  relation  of  the 
refractive  media,  and  the  spherical  surfaces  separating  them,  the 
cardinal  points  of  such  a  system,  six  in  number,  are  as  follows  :  two 

'  Dioptrische  Untersuchungen  AblKiiid.     Giittingcii  Gesells.,  1841. 


CABDIXAL  FOIXTS.  759 

focal  points  (F'  F'-),  two  principal  points  (P  P'),  two  nodal  points 
(N N').  Inasmnch  as  the  properties  of  the  two  foci  F'  F-,  as  re- 
gards the  rays  of  light  diverging  from  or  converging  toward  them 
respectively,  and  of  the  anterior  and  posterior  focal  \Aanesfp,  S  P, 
are  essentially  the  same  as  already  described,  it  Avill  not  be  neces- 
sary to  consider  them  again  in  detail  in  this  connection.  As  re- 
gards the  principal  points  P P' ,  they  being  conjugate  foci  like  LI 
(Fig.  443),  rays  of  light  passing  through  one  point  will  pass 
through  the  other  also  ;  P  P'  being  the  principal  points,  HF  and 
H'  F'  will  be  principal  planes,  and  each  point  of  the  one  plane 
having  a  conjugate  focus  in  the  otlier,  a  ray  of  light  passing  through 
a  point  on  one  plane  will  pass  through  a  corresponding  point  on  the 
other  at  the  same  distance  from  the  axis  and  on  the  same  side,  the 
distance  F '  P  being  the  anterior  focal  length,  and  the  distance 
F'  P'  the  posterior  focal  length.  In  fact,  either  plane  may  be  re- 
garded as  the  image,  the  other  being  the  object.  It  will  be  ob- 
served that  the  nodal  points  X3''  are  so  disposed  that  if  the  incident 
ray  a  N  were  prolonged,  it  would  emerge  parallel  with  the  emergent 
ray  N'  a' ,  and  vice  versa.  Such  being  the  position  of  the  cardinal 
points  in  the  system  of  refractive  media  and  spherical  surfaces  rep- 
resented in  Fig.  447,  let  a  6  be  an  object,  an  illuminated  arrow,  for 
example,  from  which  rays  pass  through  the  above  ;  its  image  will 
be  formed  at  b'  a'.  That  this  must  be  the  case  can  be' at  once 
shown  by  construction,  for  the  ray  af,  after  cutting  the  two  princi- 
pal planes  in  .r.i"',  and  passing  through  the  posterior  focal  points 
F'-,  Avill  meet  the  line  X'  a',  emerging  from  the  lens  parallel  with 
aX,  uniting  with  the  latter  at  the  point  a',  the  same  point  where 
the  ray  «  F\  after  passing  through  the  anterior  focal  point  and  cut- 
ting the  principal  planes  in  i/ 1/' ,  meets  X'  a'.  In  precisely  the  same 
manner  it  can  be  shown  by  construction  that  the  point  b  of  the  ar- 
row will  be  brought  to  a  focus  at  b'.  It  need  hardly  be  observed 
that  the  image  of  the  arrow  will  be,  of  course,  reversed.  Let  us 
suppose  now  that  the  index  of  refraction  for  air  being  taken  as 
unity,  that  with  Listing  ^  the  index  of  refraction  for  the  aqueous 
and  vitreous  humors  has  been  determined  to  be  equal  to  1.3379 
(i-P_3.)^  that  of  the  crystalline  lens  to  be  1.4545  (if),  the  radius  of 
curvature  of  cornea  8  mm.  (t/^  of  an  inch),  the  radius  of  curvature 
of  the  anterior  surfoee  of  the  crystalline  lens  10  mm.,  that  of  the 
posterior  surface  6  mm.,  the  distance  of  the  anterior  face  of  the 
cornea  from  the  anterior  surface  of  the  crystalline  lens  to  be 
equal  to  4  mm.,  the  distance  from  the  anterior  surface  of  the  lens 
to  the  posterior  surface,  or  the  thickness  of  the  lens,  4  mm., 
then  by  means  of  appropriate  formula?,  developed  by  mathe- 
matical methods  ^  from   the  relations    existing  between    the  radii 

'  Dioptrik  des  Auges.     Wagner,  Physiology,  Baudiv. ,  s.  4ol. 

2  Helniholtz,  Optique  Physiologique,  trans,  by  Javal  and  Klein,  1867,  p.  70. 
Bonders.  On  the  Anomalies  of  Accommodation  and  Kefraction  of  the  Eve,  trans, 
by  W.  D.  Moore,  1864,  p.  38. 


760 


PHYSIOLOGICAL  OPTICS. 


of  curvature,  the  indices  of  refraction,  etc.,  and  the  six  cardinal 
points,  the  exact  position  of  the  latter  in  the  human  eye  can  be 
shown  to  be  as  follows  : 

The  anterior  principal  focus  12.8326  mm.  in  front  of  the  cornea, 
the  posterior  principal  focus  22.<j470  mm.,  the  anterior  principal 
point  2.1746  mm.,  the  posterior  principal  point  2.5724  mm.,  the 
first  nodal  point  7.2420  mm.,  the  second  nodal  point  7.6398  mm. 
behind  the  cornea.  The  distance  between  the  anterior  principal 
focus  and  the  anterior  principal  point — that  is,  the  anterior  focal 
length  being  then  15.0072  mm.  =  12.8326  +  2.1746,  and  the  dis- 
tance between  the  posterior  principal  focus  and  the  posterior  prin- 
cipal point — that  is,  the  posterior  focal  length  being  20.0746  mm.  = 
22.6470  —  2.5724,  and  the  distance  between  the  two  principal 
points  0.3978  mm.,  and  the  nodal  points  0.3978  mm.  The  two 
nodal  points  and  two  principal  points  separated  by  only  a  distance 
of  0.39  mm.  (about  the  -gL  of  an  inch)  may  be  regarded  practically 
as  coinciding,  and  we  may  assume,  therefore,  for  tlie  sake  of  sim- 
plicity, without  introducing  any  very  sensible  error  in  the  construc- 
tion, that  there  is  but  one  principal  point  lying  in  the  aqueous 
humor,  2.34  mm.  behind  the  anterior  surface  of  the  cornea,  and 
one  nodal  point  lying  in  the  back  part  of  the  lens,  0.47  mm.  in' 
front  of  the  posterior  surface  of  the  lens,  and,  therefore,  but  one 
refractive  surface,  separating  air  on  one  side  and  water  on  the  other. 

Fig.  448. 


Sdieiua  of  reduced  eye  of  Listing. 


The  eye  so  simplified,  and  constituting  the  so-called  rcchiccd  eye 
of  Listing,  enables  us  to  determine  very  readily  the  position  and 
size  of  the  inverted  image  of  an  external  object  formed  upon  the 
retina.  Thus,  let  A  B  represent  an  object,  an  illuminated  arrow, 
for  example,  placed  vertically  in  front  of  the  eye,  then  Ad,  Be,  be- 
ing rays  of  direction,  will  ])ass  unrefracted  through  the  nodal  point 
K,  while  the  rays  from  A  that  are  refracted  will  come  to  a  focus  at 
d,  and  those  from  B  to  a  focus  at  c,  intermediate  rays  at  some  in- 
termediate point  (G).     The  rays  of  light  taking  this  course  through 


SIZE  OF  IMAGE.  761 

the  media  of  the  eye,  the  inverted  image  of  the  external  object  will 
be  found  on  the  retina  at  D  C.  Further,  since  in  simple  lenses  the 
size  of  tlie  image  is  to  the  size  of  the  object  as  the  distance  of  the 
image  from  the  lens  is  to  the  distance  of  the  object  from  the  lens, 
or,  as  in  the  case  of  the  crystalline  lens  which  we  are  now  consid- 
ering, as  the  distance  of  the  image  from  the  nodal  point  n  k  is  to 
the  distance  of  the  object  from  the  nodal  point  M  k,  it  follows  that 
the  size  of  the  image 

size  of  the  object  X  distance  of  image  from  nodal  point 

distance  of  object  from  nodal  point. 

The  distance  of  the  image  from  the  nodal  point  being,  however,  the 
posterior  focal  distance  may  be  regarded  as  equal  to  the  distance  of 
the  retina  from  the  cornea  (P'),  minus  the  distance  of  the  nodal 
point  from  the  cornea  (i?),  the  distance  of  the  object  from  the  nodal 
point  being  equal  to  the  distance  of  the  object  from  the  cornea  (P), 
plus  the  distance  of  the  cornea  from  the  nodal  point  (P).  Such 
being  the  case,  and  further  calling  the  size  of  the  image  I  and  that 
of  the  object  0,  the  formula  for  the  size  of  the  image  may  be  con- 
veniently expressed  as  follows  : 

P+  R     ' 

Supposing  that  the  object  0  be  1000  mm.  high,  P'  =  22.6470  mm., 
R  =  7.4  mm.,  P=  15.2396  meters,  then 

1000X15-247 
~  15.2396  +  7.4  • 

That  is  to  say,  that  the  image  of  an  object  1000  mm.  (39.3  in.)  in 
height  seen  at  a  distance  of  15.2396  meters  (50  feet)  is  1  mm.  (Jg- 
of  an  inch)  in  height,  or  a  thousand  times  smaller.  It  will  be  ob- 
served also  from  Fig.  448  that  the  visual  angle  A  k  B — that  is,  the 
angle  under  which  A  B  is  seen — being  the  same  as  the  angle  under 
which  the  objects  x  y,  r  s,  are  seen,  that  the  image  of  all  three 
objects  formed  on  the  retina  must  be  the  same,  and  that,  there- 
fore, the  apparent  size  of  all  three  objects,  though  diifering  in  size, 
will  be  the  same.  It  is  also  obvious  that  the  size  of  the  visual 
angle  depends  on  the  size  of  the  object  and  distance  of  the  latter 
from  the  eye.  From  the  fact  of  the  smaller  the  visual  aiigl(>  under 
which  distinct  vision  is  possible  the  more  acute  the  vision,  the 
latter  is  evidently  inversely  as  the  size  of  the  visual  angle.  The 
measure  of  the  acuteness  of  vision  in  general  use  among  physiolo- 
gists, based  upon  this  principle  is  a  series  of  letters,  C  G  B,  the 
thickness  of  which  is  one-fifth  of  their  height,  and  made  of  such  a 
size  that  at  a  distance  of  twenty  feet  they  subtend  an  angle  of  5 
minutes,  the  acuteness  of  vision  being  expressed  by  the  ratio  of  the 
distance  at  which  such  letters  are  still  distinctly  recognized  to  the 
distance  D,  at  which  they  subtend  an  angle  of  5  minutes — that  is 


762 


PHYSIOLOGICAL  OPTICS. 


to  say  F  =  ^  •  Suppose,  for  example,  that  the  person  whose  vision 
is  being  tested  can  recognize  a  letter  at  ten  feet,  then  his  acuteness 
of  vision  will  be  V  =  y  =  y^  =  y,  that  of  one  whose  vision  is  per- 


.      ^/       20 
feet — that  is  in  whom  T  =  y  =  ^^     =  1. 


Practicallv,  the  smallest 


Fig.  449. 


visual  angle  permitting  distinct  vision  is  about  60  seconds, 
and,  corresponding,  as  it  does,  to  a  retinal  image  of  about 
2"^^  of  a  millimeter  (g  sVir  ^^  ^^^  inch),  it  will  just  about  cover 
one  of  the  cones  of  the  retina.  Two  points 
seen  under  such  a  small  visual  angle  would, 
therefore,  appear  as  one.  It  has  already 
been  mentioned  that  the  cardinal  points, 
by  means  of  which  ^\e  follow  the  rays 
of  light  as  they  pass  through  the  media 
of  the  eye  and  determine  the  position  and 
size  of  the  retinal  image,  are  deduced  from 
the  indices  of  refraction  of  the  aqueous  and 
vitreous  humors,  lens,  radius  of  curvature  of 
cornea,  etc.,  experimentally  determined.  In- 
asmuch as  the  methods  by  which  the  in- 
dices of  refraction  of  the  media  of  the  eye 
are  determined  are  essentially  the  same  as  in 
the  case  of  water  or  glass,  it  need  not  in  this 
connection  be  described  again.  The  radius 
of  curvature  of  the  cornea  and  crystalline, 
however,  being  deduced  by  formulae  from  the 
size  of  their  reflected  images,  and  the  latter 
being  measured  by  the  ophthalmometer,  this 
instrument  merits  at  least  a  V)ricf  description. 
The  principle  upon  which  the  ophthalmom- 
eter, invented  by  Helmholtz,^  is  constructed 
is,  that  if  an  image  of  an  object  a  be  viewed 
through  two  piano-parallel  glass  plates  (Fig.  449)  the  image, 
through  refraction,  will  a[)per  double,  a'  <i",  and  that  if  the  plates 
be  so  approximated  that  the  inner  edges  of  the  two  images  are 


«■  «* 


Object  viewed  through  two 
glass  plates. 


Fia.  450. 


<^ 


W=3 


X 


a 


Clk 


Schema  of  ophthalmometer. 


brought  in  contact,  then  the  distance  between  the  outer  edges  of 
the  two  images  will  be  twice  the  size  of  the  single  image.     To 

'Op.  cit.,  p.  11. 


SPHERICAL  ABERBATIOX.  763 

measure  the  size  of  an  image  a  h  (Fig.  450)  by  the  ophthalmom- 
eter it  is  only  necessary,  then,  to  determine  the  lateral  displacement 
of  the  images  a'  h'  cr  b~,  which  is  accomplished  by  observing  the 
angle  made  by  the  glass  plates  P  P,  with  tlie  axis  X  of  the  tele- 
scope, through  which  the  image  is  viewed. 

The  size  of  the  corneal  image  having  been  determined  by  means 
of  the  ophthalmometer,  the  radius  of  curvature  of  the  cornea  can  be 
readily  deduced  from  a  well-known  formula  and  was  found  by  the 
author  and  Dr.  Brubaker  to  be  on  the  averao^e  in  the  horizontal 
meridian  7.797  millimeters  and  in  the  vertical  meridian  7.552 
millimeters,  fifty  persons  being  examined.^  It  may  be  men- 
tioned in  this  connection  that  the  radius  of  curvature  of  the 
lens  is  also  determined  by  the  ophthalmometer,  though  in  a  slightly 
modified   manner.      AVhile   it  is    true   that   rays   of    light    falling 

Fig.  451. 


K 

Diagram  ilhistratiDg  spherit'al  aberratiuu.     (McKkndrick.  ) 

upon  a  refracting  surface  are  brought  to  a  focus  in  essentially  the 
manner  we  have  described  in  treating  of  such  surfaces,  it  must 
be  mentioned  in  this  connection  that  of  rays  impinging  upon  a  re- 
fractive surface,  the  peripheral  ones  being  more  refracted  than  the 
central  ones  are  not  brought  to  exactly  the  same  focus  as  that  of 
the  latter,  there  being,  in  fact,  many  foci,  and  the  image  of  the 
object  consequently  blurred  and  ill-defined.  This  condition,  known 
as  the  aberration  of  sphericity  (Fig.  451),  and  corrected  in  the 
making  of  lenses  for  microscopes,  etc.,  by  appropriate  means,  ob- 
tains also  in  the  eye,  though  not  to  any  marked  extent,  on  account 
of  the  following  circumstances  :  1st,  that  the  lateral  most  refracted 
rays  are  cut  off  by  the  iris,  the  latter  acting  precisely  like  the  dia- 
phragm of  optical  instruments  ;  2d,  that  the  curvature  of  the  cornea 
being  ellipsoidal  the  lateral  rays  are  less  deviated  than  if  the  curva- 
ture was  spherical ;  ."3d,  that  the  anterior  and  posterior  surfaces  of 
the  crystalline  lens  are  so  disposed  that  the  one  corrects,  to  a  certain 

'  For  a  detailed  account  of  the  construction  of  the  oplithalmomoter,  method  of 
using  it  and  results  obtained  by  it,  see  "  Measurement  of  Kadius  of  Cornea,"  by 
H.  C".  Chapman  and  A.  P.  Brubaker,  Proc.  Acad.  Xat.  Sciences,  1893,  p.  349. 
Also,  "History  and  Principles  of  Keratometry,"  by  C.  AVeiland,  Archives  of 
Ophthalmology,  Vol.  xxii.,  1893. 


764 


PHYSIOLOGICAL  OPTICS. 


Decomposition  of  white  light  by  jirisiii. 


extent,  the  action  of  the  other ;  4th,  from  the  fact  that  the  refrac- 
tive power  of  the  lens,  diminishing  from  the  center  to  the  circum- 
ference, the  Lateral  rays  are  but  little  refracted.  Inasmuch  as  a 
refracting  medium  does  not  act  equally  upon  the  different  colored 
rays  of  which  wdiite  light  is  composed,  a  ray  of  white  light  (Fig. 
452,  W)  in  passing  through    a  prism  (P)  is  not  only  bent,  but 

decomposed  into  the  colors  of 
Fig.  452.  the    spectrum,    the   condition 

so  produced,  that  of  chro- 
matic aberration,  giving  rise 
to  the  formation  of  a  colored 
image,  white  at  the  center, 
but  surrounded  at  the  borders 
by  a  circle  of  colors,  like 
those  of  the  rainbow.  In  the 
construction  of  optical  in- 
struments the  chromatic  aber- 
ration, or  aberration  of  re- 
frangibility,  is  corrected  by 
combining  lenses  having  a 
different  dispersive  power,  as  when  a  convex  lens  of  crown  glass 
is  combined  with  a  concave  lens  of  flint  glass,  so,  in  the  case 
of  the  eye,  the  chromatic  aberration  is,  to  a  considerable  extent, 
corrected  through  the  crystalline  lens,  being  composed  of  various 
layers  of  different  consistence  and  of  different  refractive  power. 
As  a  general  rule,  indeed,  we  are  iniaware  that  our  eyes  are  not 
achromatic,  like  the  lenses  of  microscopes  and  telescopes,  but,  under 
certain  circumstances,  our  attention  is  very  forcibly  called  to  the 
fact.  Thus,  if,  after  looking  at  the  cross  hairs  of  an  astronomical 
glass  by  a  red  light,  we  try  to  see  them  with  another  colored  light, 
violet,  for  example,  the  eye  must  be  changed,  the  eye,  when  adapted 
to  see  by  a  red  light,  not  being  able  to  see  by  the  violet.  Again, 
if  we  look  at  a  candle-flame  through  cobalt  blue  glass,  which  trans- 
mits only  the  red  and  blue  rays,  the  flame  may  appear  blue,  sur- 
rounded by  violet,  or  vice  versa,  according  as  the  eye  has  been  ac- 
commodated for  different  distances.  It  may  be  also  mentioned  that 
red  surfaces  always  appear  nearer  than  violet  ones,  since  the  eye, 
having  to  be  accommc^dated  more  for  the  red  than  for  the  violet 
one,  imagines  tlie  former  surfaces  to  be  nearer  than  the  latter.  In 
addition  to  the  aberration  of  sphericity  aud  of  refrangibility,  more 
or  less  present  in  the  eye,  from  the  fact  of  the  focal  length  of  the 
vertical  meridian  of  tlie  cornea  being  shorter  than  the  horizontal 
meridian  rays  of  light  emanating  from  a  })oint,  do  not  converge  to 
one.  The  condition  so  caused,  and  constituting  astigmatism,  is  a 
defect  from  Avhicli  few  eyes,  if  any,  are  free.  That  the  eyes  are 
astigmatic  one  can  readily  convince  himself  by  simply  looking 
(Fig.  453)  at  two  threads  crossing  eacli  other  at  right  angles  in  the 
same  plane,  or  at  two  lines  drawn  in  ink  on  a  sheet  of  wliitc  paper 


ASTIGMATISM. 


705 


disposed  in  a  similar  manner,  when  it  will  be  observed  at  the  point 
of  distinct  vision  that  it  is  inij)()ssil)le  to  see  both  threads,  or  lines, 
with  equal  distinctness  at  the  same  time;  that  to  see  the  horizontal 
line  distinctly,  for  example,  the  paper  must  be  brought  near  the  eye, 
and  removed  from  it,  to  see  the  vertical  line. 


Fig.  453. 


Diagram  illustratiug  astigmatism.    Lower  figures  illustrate  appearance  of  rays,  eye  being  at  G 
II  I,  respectively.     (McKesdrick.) 

While  the  detailed  consideration  of  the  subject  of  astigmatism 
belongs  .rather  to  the  ophthalmologist  than  physiologist,  it  may  be 
incidentally  mentioned  that  the  astigmatism  of  the  cornea  is,  to  a 
certain  extent,  naturally  corrected  by  that  of  the 
lens,  since  the  focal  length  of  the  vertical  meridian 
of  the  latter  differs  from  that  of  the  horizontal, 
but  in  the  reverse  sense  from  that  of  the  cornea. 

Astigmatism  can  be  corrected  by  the  use  of  a 
cylindrical  glass  (that  is  a  lens  so  cut  as  to  be 
without  curvature  in  one  direction),  the  curvature 
of  which  is  such  that  if  added  to  that  of  the  hori- 
zontal meridian  will  make  its  focal  length  equal  to 
that  of  the  vertical  one.  The  defects  of  the  eye 
due  to  aberration  of  sphericity  and  refrangibility, 
or  astigmatism,  are  so  slight,  usually,  as  not  to 
attract  attention  ;  near-sightedness  and  far-sight- 
edness are,  however,  unfortunately  so  common, 
and  interfere  to  such  an  extent  with  vision,  as  to 
necessitate  tiie  wearing  of  glasses.  The  cause  of 
myopia  and  hypermetropia,  and  their  treatment 
constituting,  like  astigmatism,  one  of  the  most 
important  subjects  of  oplithalmology,  do  not  de- 
mand in  this  connection  special  consideration. 
As  still  further  illustrating,  however,  the  manner  in  Avhich  the  rays 


\c 


Cylindrical  glasse.s 
for  :isti>;iiiati.<ui.  The 
sett  inn  <'  II  li  i:  <iof  the 
eylinilrical  leus  (Fig. 
4.')4 )  represents  a  pla- 
ni>couvex,  the  sec- 
tion C  a  /3  y  5,  a 
concavo-convex  lens. 

(L.VXDOIS.) 


766 


PHYSIOLOGICAL  OPTICS. 


of  light  are  lironglit  to  a  focus  in  the  eye,  and  serving  in  a  measure 
also  to  elucidate  the  manner  in  which  the  eye  is  accommodated  for 
diiferent  distances,  a  brief  description  of  these  abnormal  conditions 
does  not  appear  superfluous.  Let  us  suppose,  for  example,  that 
either  through  elongation  of  the  whole  eye  or  through  the  con- 
verging power  of  the  lens  being  too  great,  that  parallel  rays  of  light 
are  brought  to  a  focus,  not  on  the  retina,  but  in  front  of  it,  at  B 
(Fig.  455),  circles  of  diffusion  being  formed,  the  image  will  be  in- 
distinct, blurred. 

Obviously,  in  order  to  see  distinctly  under  such  circumstances, 
the  object  must  be  brought  closer  to  the  eye,  so  that  the  rays  of  light 
may  be  brought  to  a  focus  on  the  retina,  hence  the  eye  is  said  to 
be  short-sighted  or  myopic.  Such  a  condition  can  be,  however, 
remedied  by  placing  a  suitable  concave  glass  (C)  in  front  of  the 
myopic  eye.  The  rays  of  light  wall  then  be  diverged  to  such  an 
extent  that  they  will  come  to  a  focus  upon  the  retina. 


Fig.  455. 


Fig.  450. 


Myopic  t've. 


Hypermetropic  eye. 


Fig.  457. 


On  the  other  hand,  let  us  suppose  that,  owing  to  the  whole  eye 
being  too  short  or  through  the  converging  power  of  the  lens  being 
too  small,  parallel  i^ays  of  light  come  to  a  focus  behind  the  ret- 
ina (Fig.  456  A),  circles  of  diffusion  being  formed  the  image  will 

be  blurred  and  indistinct.  In  order 
to  see  distinctly  with  such  an  eye 
the  so-called  hypermetropic  or  far- 
sighted  eye,  parallel  rays  of  light 
must  converge  sufficiently  to  come 
to  a  focus  upon  the  retina.  Inas- 
much, however,  as  convergent  rays 
of  light  do  not  exist  in  nature,  the 
defect  can  only  be  remedied  in  such 
an  eye,  the  latter  being  passive,  by 
placing  in  front  of  the  eye  a  suitable 
c  1,  ■     ,  f     ■*!  T-v.         ,     convex  glass  bv  which  the  parallel 

Schemer  .s  experiment  with  Thomsoii'.s  ,"  "  |   . 

moditication.   ,1.  Source  of  light,  j^.  Posi-    ravs  will  bc  converjjcd  Sufficiently 

tion  of  retin.a  iu  regard  to  the  focus  c  of  the  ''  „  ^  •  •         i        a 

ray.s  entering  through  two  apertures  in  a  tO  COUIC  tO  a  toCUS  OU  thc  rctuia.        A 
card,  one  of  which  is  covered  with  a  colored  i  -i     •  •  ,  i       i 

gla.ss  9  in  an  emmetropic  eve.     7/.  Position  VCry    ready    and     ingCUlOUS    nicthod 

M'^^^J'^rinJ]^ll^T^;:S^t^.    for  determining  whether  an  eye  is 

enimctroiiie — that  is,  normal,  my- 

'  In  explaining  to  an  audience  the  manner  in  wliich  astigmatism,  myopia,  and 
hyperruetropia,  circles  of  difiiision,  etc.,  are  produced  tlie  autlior  lias  found  the  arti- 
ficial eye  of  Kuline  a  very  usefid  adjunct. 


A  CCOMMODA  TION.  767 

opic,  or  hypermetropic  consists  in  placini>'  a  piece  of  colored  *i^luss  g, 
red,  for  example,  over  one  of  the  openings  in  the  card  nsed  in 
Scheiner's  experiment,  as  represented  in  Fig.  457.  Supposing  the 
eye  to  be  emmetropic,  it  is  evident  that  the  colored  red  ray  and 
white  ray  falling  upon  the  retina  at  the  same  spot,  but  one  image,  a 
red  one,  will  be  observed.  If  the  eye  be  myopic,  however — that 
is,  the  retina  is  too  far  back,  then  through  the  crossing  of  the  rays 
of  light  two  images  will  be  seen,  a  red  one  below  and  a  white  one 
above.  On  the  other  hand,  if  the  eye  be  hypermetropic  the  two 
images  will  be  seen,  but  the  red  one  will  be  above,  the  white  one 
below. 

Accommodation. 

In  considering  the  manner  in  which  the  rays  of  light  are  refracted 
as  they  pass  through  the  media  of  the  eye,  and  the  image  of  an  ex- 
ternal object  formed  upon  the  retina,  we  have  supposed  heretofore 
that  both  the  eye  and  the  object  were  at  rest.  Every  one  is  familiar 
with  the  fact,  however,  that,  notwithstanding  that  an  object  may 
approach  or  recede  from  the  eye,  in  either  case,  at  least  within  cer- 
tain limits,  it  is  as  clearly  seen  in  the  first,  as  in  the  second  po- 
sition. Such  being  the  case,  evidently  then  the  eye  must  undergo 
some  change,  otherwise,  as  the  object  approached  the  eye,  the  image 
would  recede  from  the  retina,  being  formed  behind  it,  and  as  the 
object  receded  from  the  eye  the  image  \vould  recede  from  the  retina 
in  the  opposite  direction,  being  formed  in  front  of  it.  Thus,  let  us 
suppose  that  the  object  being  at  ^  i^  (Fig.  448),  and  its  image  at 
d  c,  that  the  object  is  moved  to  H,  its  focus  would  then  be  formed 
behind  the  retina  at  H' ,  and  the  condition  of  the  eye  would  be 
hypermetropic,  as  in  the  case  of  Scheiner's  experiments  just  de- 
scribed, unless  simultaneously  with  the  movement  of  the  object 
toward  the  eye  some  change  was  induced  in  the  latter,  by  which  the 
focus  was  kept  upon  the  retina  at  d  c.  On  the  other  hand,  if  the 
object  be  moved  to  31,  then  the  focus  would  be  formed  in  front  of 
the  retina,  as  at  31' ,  and  the  condition  of  the  eye  would  be  myopic, 
unless  simultaneously  with  the  movement  of  the  object  from  the 
eye,  by  some  change  in  the  latter,  the  focus  was  kept  upon  the 
retina  at  d  c.  The  change  undergone  by  the  eye,  and  by  which  the 
image  of  the  object  is  kept  upon  the  retina,  whether  the  object 
approaches  or  recedes,  is  known  as  the  power  of  accommodation, 
and  is  without  doubt  due  to  a  change  in  the  shape  of  the  lens  ;  the 
latter  becoming  more  convex  as  the  object  approaches  the  eye,  less 
so  as  the  object  recedes  from  it.  As  the  object  ap]>roaches  the  eye, 
the  image  tends  to  recede  behind  the  retina,  toward  //',  but  as  the 
lens  becomes  more  convex  at  the  same  time,  the  image  tends  to  ad- 
vance equally  in  front  of  the  retina  toward  31' ,  the  result  of  the 
antagonizing  influences  being  such  that  the  image  neither  recedes  nor 
advances,  but  remains  upon  the  retina.  On  the  other  hand,  as  the 
object  recedes  from  the  eye,  the  image  tends  to  advance  in  front  of 


7(38  PHYSIOLOGICAL  OPTICS. 

the  retina,  toward  J/',  but  as  the  lens  becomes  less  convex  at  the 
same  time,  the  image  tends  to  recede  behind  the  retina,  toward  H'; 
the  image  consequently  remains  as  before  upon  the  retina. 

Before  considering  the  means  by  which  this  change  in  the  shape 
of  the  lens  is  effected,  and  throuo^h  which  the  eve  accommodates  it- 
self  to  different  distances,  let  ns  first  show  how  it  can  be  experi- 
mentally demonstrated  that  such  a  change  in  the  shape  of  the  lens 
as  tliat  just  described  does  actually  occur  during  accommodation. 
With  that  object  let  the  person  whose  eye  is  to  be  examined  be 
requested  to  look  at  some  distant  object,  and  while  so  doing  let  the 
light  from  the  flame  of  a  candle  (B,  Fig.  458)  fall  upon  the  eye 
(C  C)  at  about  the  angle  represented  in  the  figure;  if  the  eye  of 
the  observer  be  situated  at  E  three  images  will  be  seen  (Fig.  459) ; 
the  first  (b)  an  erect  virtual  image,  due  to  the  reflection  of  the  light 
from  the  cornea  (b,  Fig.  458)  to  the  eye  of  the  observer  at  E;  the 

Fig.  458. 


Change  in  the  form  of  the  leus  during  accomuiodation. 

second  (a)  also  a  virtual  erect  image  due  to  the  reflection  of  the 
light  from  the  anterior  convex  surface  of  the  crystalline  lens  («) ; 
the  third  (c)  ;  a  real  reversed  image  due  to  the  reflection  of  the  light 
from  the  posterior  concave  surface  of  the  crystalline  lens  formed  in 
the  manner  represented  in  Fig.  460. 

The  three  images  being  observed,  let  now  the  individual  whose 
eye  is  being  examined  look  at  a  near  object,  and  at  once  the  observer 
at  E  will  notice  that,  while  the  position  of  the  images  (Fig.  459) 
a  and  e  due  to  the  reflection  of  the  light  of  the  candle  B  from  the 
cornea  and  posterior  surface  of  the  lens  remains  unchanged,  that  of 
the  image  6  due  to  the  reflection  of  the  light  from  the  anterior  sur- 
face of  the  lens  is  very  much  changed,  it  Ix'ing  now  much  closer 
to  a,  and  also  that  it  is  smaller  than  wlien  tlie  individual  w4iose 
eye  is  being  observed  looked  at  a  distant  object,  which  can  only  be 
accounted  for  on  the  supposition  that  the  anterior  surface  of  the 
lens  increases  in  convexity,  the  light  falling  upon  e  instead  of  a 


PHAKOSCOFE. 


Ti9 


(Fig.  458),  and  whicli  is  the  case  for  llio  radius  of  curvature  of  the 
anterior  surfoce  of  the  lens  when  the  eye  is  aeconunodated  for  far 
objects,  being  10  mm.,  but  for  near  ones  <)  mm.  In  performing 
this  experiment  the  phakoscope  of  Helmholtz  Avill  be  found  a  use- 
ful instrument.     It  consists  (Fig.  461)  essentially  of  a  l)lack  trian- 


Fin.  4.-)9. 


Fi.;.   4(;i. 


a      b      (■ 
ReHeeted  iinaKe^^  i"  the  eye. 


Real  reversed  image  of  comave  mirror. 


Pliakosfope  of  Jlrliiilinltz.     iM(  Kp:ndrick.) 


gular  box  Avith  four  openings  :  the  first  opening  in  the  base  of  the 
triangle  supports  a  needle  point,  which  constitutes  the  near  object ; 
the  second  opening,  directly  op])osite  to  the  first,  receives  the  eye 
to  be  observed  ;  while  of  the  two  remaining  lateral  openings,  one 
containing  prisms  transmits  the  light,  the  other  receives  the  eye  of 
the  observer.  In  using  the  phakoscope  the  individnal  looks  first 
through  tlie  window  at  a  distant  object,  and  then  at  the  middle 
point.  It  having  been  shown,  then,  that  the  lens  becomes  more 
convex — accommodates  itself  to  see  near  objects — it  only  remains 
now  to  account  for  this  change  in  the  shape  of  the  anterior  surface 
of  the  lens.  It  will  be  remembered,  in  speaking  of  the  action  of 
the  ciliary  muscle,  it  was  mentioned  that,  owing  to  its  disposition 
with  reference  to  the  sclerotic  and  choroid,  that  in  contracting  it 
would  draw  the  choroid  forward,  thereby  relaxing  the  suspensory 
ligament  of  the  lens,  the  effect  of  which  Avould  be  that  the  lens, 
o\\'ing  to  its  elasticity,  would  change  its  shajie. 

It  would  appear,  therefore,  that  the  change  in  the  convexity  of 
the  lens,  through  which  the  eye  accommodates  itself  to  see  near  ob- 
jects, is  brought  about  by  the  contraction  of  the  ciliary  muscle.  If 
such  be  the  case,  of  which  there  can  be  but  little  doubt,  the  sense 
of  effort  which  we  experience  in  looking  at  near  objects  must  arise 
from  the  contraction  of  the  ciliary  muscle.  Accommodation  can 
49 


770  PHYSIOLOGICAL  OPTICS. 

only  take  place  within  a  certain  range,  marked  variation  being  ob- 
served however  in  this  respect  according  to  individnal  pccnliarities. 
As  a  rnle,  objects  sitnated  at  a  distance  of  62  meters  (200  feet) 
and  beyond  to  infinity,  that  is,  at  the  punetnm  remotnm  or  far 
point,  to  be  seen,  do  not  necessitate  accommodation,  as  the  rays  of 
light,  coming  from  snch  a  distance,  being  parallel,  come  to  a  focns 
npon  the  retina ;  the  nearer,  however,  the  object  approaches  within 
this  limit  the  eye,  the  more  accommodating  power  is  exercised,  until 
a  point  is  reached  about  12.5  cm.  (5  inches)  from  the  eye,  the  punc- 
tmn  proximum  or  near  point,  which  if  exceeded  by  the  object,  can- 
not be  compensated  by  any  further  change  in  the  shape  of  the  lens. 
The  accommodation  being  then  strained  to  its  uttermost  if  the  object 
comes  still  nearer  the  eye,  the  rays  of  light  will  not  be  focussed  upon 
the  retina.  The  range  of  accommodation  of  the  eye  for  distance 
lies  then  between  these  two  limits,  that  of  the  punctum  remotum 
and  punctum  proximum.  The  power  of  accommodation  of  the  eye 
can  be  measured  by  the  converging  power  of  a  lens,  which  gives  dis- 
tinct vision  of  an  object  placed  at  the  punctum  proximum  without 
necessitating  any  accommodation  in  the  eye — that  is,  of  a  lens  M'hich 
brings  the  diverging  rays  of  light  from  the  punctum  proximum 
to  a  focus  on  the  retina,  just  as  if  they  had  come  parallel  from  the 
punctum  remotum,  for  which  accommodation  is  not  required  in  the 
normal  eye.  Indeed,  that  is  exactly  the  effect  of  the  change  in  the 
shape  of  the  crystalline  lens  in  accommodation,  viz.,  that  of  retain- 
ing on  the  retina  (Fig.  462,  r),  the  focus  of  the  rays  of  light  diverg- 
ing from  t]ie  near  point  p,  just  as  if  they  came  parallel  from  the 
far  point  r  r. 

Fk;.  462. 


R*^ 


Condition  of  Ions  in  the  wnvmaX  passive  eye  and  during  accniiniiodd/ifm. 

As  the  elasticity  of  the  lens  diminislies  as  a  result  of  age  and  as 
further  it  becomes  more  flattened,  the  lens  gradually  loses  the  power 
of  changing  its  shape,  of  becoming  more  convex  as  an  object  ap- 
proaches the  eye,  and  consequently  the  punctum  proximum  recedes 
further  and  furtlier  from  the  latter.     The  diminution  in  the  range 


PRESBYOPIA. 


771 


of  accommodation  so  produced  is  known  as  presbyopia,  which,  it 
Avill  be  observed,  is  an  anomaly  of  acommodation,  differing  there- 
fore from  myopia  and  hypermetropia,  which  are  anomalies  of  re- 
fraction. While  the  treatment  of  presbyopia  belongs  rather  to  the 
ophthalmologist  than  to  the  physiologist,  it  may  be  mentioned  that 
it  can  be  corrected  by  ])lacing  a  lens  before  the  eye,  such  as  would 
give  the  rays  the  direction  they  would  have  if  they  came  from  the 
normal  punctum  proximum. 

Fig.  463. 


Action  of  a  concave  lens  in  front  of  the  eye,  causing  parallel  rays  to  enter  the  eye  as  if  pro- 
ceeding from  a  finite  point  in  front  of  the  eye.    (Berry.) 

It  may  be  mentioned  also  in  this  connection  as  regards  accom- 
modation that  the  myopic  differs  from  the  emmetropic  eye  in  that 
the  punctum  remotum,  or  far  point,  is  that  point  from  which  di- 
vergent rays  of  light  come  to  a  focus  on  the  retina,  the  eye  being 
passive  (Fig.  463).  While  the  far  point  in  the  myopic  eye  may 
be  situated  at  a  distance  varying  from  150  to  300  centimeters 
(60-120  inches)  the  punctum  proximum,  or  near  point,  may  be  only 
10  to  5  centimeters  (4  to  2  inches)  from  the  eye,  the  range  of  ac- 
commodation in  the  myopic  eye  is  therefore  limited.  On  the  other 
hand,  in  the  hypermetropic  eye  there  is  no  punctum  remotum,  or  far 
point,  since  neither  divergent  nor  parallel  rays  come  to  a  focus  in 
such  an  eye  when  non-accommodated  or  passive.  Inasmuch,  how- 
ever, as  convergent  rays  falling  upon  the  eye  and  directed,  say  to 
a  point /(Fig.  464),  will  come  to  a  focus  on  the  retina,  when  still 


Fig.  464. 


Action  of  a  convex  lens  placed  in  front  of  the  eye,  causing  parallel  rays  to  enter  the  eye,  as  if 
directed  to  a  point  at  a  finite  distance  behind  the  eye.     (Berry.) 

further  refracted  by  passing  through  the  cornea  and  crystalline 
lens  that  point  is  often  said  to  .be  the  punctum  remotum,  or  for 
pomt,  and  negative,  the  converging  rays  being  directed  to  that  point 


772  PHYSIOLOGICAL  OPTICS. 

in  the  same  sense  as  the  diverging  rays  of  the  myopic  eye  are  di- 
rected to  or  appear  to  come  from  the  punctum  remotum,  or  far  point 
(Fig.  463),  which  in  tliat  case  is  positive.  The  punctum  proximum, 
or  near  point,  in  the  hypermetropic  eye  varies  from  20  to  200  cent. 
(8  to  80  inches).  The  range  of  accommodation  is,  therefore,  in- 
finitely great.  The  ciliary  muscle,  by  the  contraction  of  which  ac- 
commodation is  accomplished,  is  innervated  by  nerve  fibers  that  arise, 
as  already  mentioned,  in  the  anterior  part  of  the  nucleus  of  the  third 
nerve  and  pass  thence  to  the  eye  by  the  ciliary  ganglion  and  short 
ciliary  nerves.  That  such  is  the  case  is  sho^yn  by  the  fact  that 
stimulation  of  this  center  is  followed  by  contraction  and  the  accom- 
modation of  the  eye  to  near  objects.  Accommodation  appears  to  be  a 
voluntary  act  in  response  to  visual  sensations  ;  at  least  we  are  led 
to  accommodate  simply  by  the  desire  to  see  distinctly  near  or  far  ob- 
jects. In  passing  from  accommodation  for  a  near  object  to  that  for 
a  far  one  it  can  hardly  be  said  that  we  accommodate  actively  since 
the  action  is  due  simply  to  the  relaxation  of  the  ciliary  muscle  to 
the  return  to  a  condition  more  or  less  of  equilibrium.  In  this  re- 
spect the  ciliary  muscle  diflPers  from  the  iris,  the  muscle  fibers  of 
the  latter  being  influenced,  as  we  have  seen,  by  two  sets  of  nerve 
fibers,  contractor  and  dilator.  It  should  be  mentioned,  neverthe- 
less, that  atropin  not  only  paralyzes  the  accommodation,  rendering 
the  eye  hypermetropic,  but  dilates  the  pupil  and  that  physostigmin 
renders  the  eye  myopic  and  contracts  the  pupil.  We  shall  see 
presently  that  in  the  converging  of  the  axis  of  the  eyes  for  the  pur- 
pose of  viewing  near  objects  as  in  the  accommodating  of  the  eye  for 
the  same  purpose  the  pupil  contracts,  just  as  we  have  seen  is  the  case 
when  the  eye  is  exposed  to  light.  This  is  an  instance  of  what  is  called 
an  "  associated  movement,"  and  appears  to  be  due  to  the  fact  that  the 
will  center,  accommodating  center,  and  pupil  constrictor  center  are 
so  intimately  connected  by  nervous  ties  that  when  an  impulse  from 
the  will  center  stimulates  the  accommodating  center  it  stimulates  at 
the  same  the  pupil  constrictor  center.  While  in  the  case  of  most 
persons,  in  order  to  accommodate,  the  attention  must  be  directed  to 
some  near  or  far  object,  it  is  said  that  by  practice  the  aid  of  exter- 
nal objects  may  be  dispensed  with,  and  it  is  when  this  is  accom- 
plished that  the  pupil  may  appear  to  contract  or  dilate  voluntarily, 
the  effect  being  due  to  accommodation,  as  just  explained. 

The  so-called  Argyll  Robertson  pupil,  frequently  occurring  in 
locomotor  ataxia  and  progressive  i)aralysis  of  the  insane,  is  a 
further  illustration  of  the  intimate  association  existing  between  the 
voluntary  accommodating  and  pupil  constrictor  centers.  In  this 
condition,  Avliile  the  pupil  docs  not  contract  in  response  to  light,  a 
lesion  existing  in  the  nervous  tie  connecting  the  corpora  quadri- 
gemina  and  oculo-motor  center,  it  does  contract  when  the  eye 
is  accommodated  for  a  near  object,  the  centers  causing  contraction 
and  accommodation  being  stimulated  simultimeously  by  the  will. 
In  concluding  the  subjects  of  refraction  and   accommodation,  it  is 


OPHTHALMOSCOPE. 


773 


hoped  that  it  will  not  be  deemed  sujierfluous  if  a  ])rief  account  of 
the  ophthalmoscope  is  oifered  by  which  the  fundus  of  the  normal  and 
diseased  eye  is  examined,  and  through  which,  in  the  hands  of  Bon- 
ders, Graefe,  and  others,  ophthalmic  medicine  was  revolutionized. 


Fig.  465. 


Arrangement  for  examining  the  eye  of  5.    ^ ,  eye  of  observer,   j-.  Source  of  light.    .S",  5,  plate  of 
glass  directed  obliquely,  reflecting  light  into  B. 

The  interior  of  the  eye  under  ordinary  circumstances  appears 
dark,  since  the  observer  being  between  the  eye  to  be  observed  and 
the  source  of  light  intercepts  the  very  rays  whose  reflection  from 
the  interior  of  the  eye  would  form  the  image  that  it  is  desired  to 
see.     Further,  the  diverging  rays  from  the  interior  of  the  eye,  con- 


FiG.  466. 


OphthalnioscoiH'  with  convex  lens. 


verging  as  they  pass  through  its  media,  are  brought  to  a  conjugate 
focus  outside  of  the  eye,  which,  to  be  seen,  would  have  to  be  viewed 
by  the  observing  eye  at  a  distance  so  far  from  the  observed  eye, 


774 


PHYSIOLOGICAL  OPTICS. 


that  little  or  nothing  could  be  distinguished.  If,  hoAvever,  the  in- 
terior of  the  eye  be  illuminated  by  light  reflected  from  an  obliquely 
placed  glass  (Fig,  465),  or  a  concave  mirror,  the  center  of  which  is 
perforated,  and  through  and  behind  which  the  observer  can  view 
the  eye,  then  the  conjugate  focus  formed  as  just  described  by  the 
rays  reflected  from  the  interior  of  the  eye,  can  be  more  or  less  dis- 
tinctly seen. 

The  image  of  the  retina,  entrance  of  the  oj^tic  nerve,  etc.,  as 
viewed  by  such  a  mirror  as  that  just  described,  and  constituting 
the  original  ophthalmoscope,  become,  however,  much  more  distinct, 
if  in  addition  to  the  mirror  the  observed  eye  be  viewed  through  a 
lens.  Suppose  the  lens  used  be  a  convex  one  (Fig.  466,  6),  then 
the  rays  of  light  from  the  retina  A  of  the  obsers'ed  eye  which  would 
otherwise  be   brought  to  a  focus  rather  near  the  observing  eve 


Fig.  467. 


j;-« 


Ophthalmoscope  with  concave  lens. 

through  the  converging  effect  of  the  lens  are  l^rought  to  a  focus  at 
B,  the  image  being  real,  inverted,  and  magnified.  On  the  other 
hand,  suppose  that  a  concave  lens  be  used,  then  the  rays  emanating 
from  Sq  (Fig.  467),  which  would  come  to  a  focus  at  r  were  it  not 
for  the  lens,  on  account  of  being  diverged  by  tlie  latter,  are  pro- 
jected back  to  B,  the  image  being  virtual,  erect,  and  more  magnified 
than  wlien  a  convex  glass  is  used. 


CHAPTER    XL. 


BINOCULAR  VISION.    SENSATION  AND  PERCEPTION  OF  SIGHT. 
PROTECTIVE  APPENDAGES  OF  THE  EYE. 

Ix  describing  the  manner  in  wliich  vision  is  eifccted  we  have 
liitherto  supposed  it  as  being;  accomplished  by  a  single  eye ;  it  re- 
mains for  us  now  to  consider  how  both  eyes  act  in  viewing  objects, 
or  binocular  vision.  It  might  be  naturally  supposed  from  seeing 
an  object  single,  when  viewed  with  one  eye,  that  it  would  appear 
double  when  viewed  with  both  eyes.  A  little  observation  will, 
however,  make  it  clear  that  with  one  eye  Ave  see  but  one  side,  so  to 
speak,  of  an  object,  the  right  side,  for  example,  with  the  right  eye, 
the  left  side  with  the  left  eye,  and  that  in  order  to  obtain  a  percep- 
tion of  the  entire  object  we  must  see  the  two  sides  of  the  oljject 
simultaneously.  Thus,  for  example,  wlien  we  look  at  a  truncated 
pyramid  (Fig.   468,  B)  placed   in  the  middle  line   before   us,  the 

Fig.  468. 


/ 

\  _/ 

\ 
\ 

// 

B 

/ 

\ 

/ 

\ 

/ 

\. 

Illustrating  the  piiuciplc  of  the  stereoscope  and  binocular  vision. 

image  falling  upon  the  right  eye  is  such  as  represented  at  R,  that 
upon  the  left  eye  at  L,  the  perception  of  the  form  of  B  being  only 
obtained  when  the  object  is  viewed  by  both  eyes  simultaneously. 
When  two  dissimilar  images,  one  of  the  one  eye,  and  the  other  of 
the  other,  are  thus  fused  into  one  perception,  the  inference  by  the 
mind  is  that  the  object  giving  rise  to  the  images  is  solid.  Such, 
indeed,  is  the  principle  of  the  stereoscope,  in  Avhich  two  slightly 
dissimilar  pictures,  such  as  would  correspond  to  the  images  of  two 
objects  as  seen  by  each  eye  respectively,  are  by  means  of  mirrors  or 
prisms  cast  upon  the  retina  so  as  to  give  rise  to  a  single  perception, 
that  of  solidity,  or  of  three  dimensions,  though  each  picture  has  a 
surface  .of  but  two  dimensions.  In  order,  however,  that  the  two 
retinal  images  shall  be  fused  into  the  one  mental  perception,  it  is 
essential  that  the  two  images  shall  fill  on  corresponding  points  of 
the  retina,  at  a  a,  c  c  (Fig.  469),  otherwise  there  will  be  double 
vision — hence,  in  viewing  an  object  with  both  eyes  the  latter  are 
converged,  the  angle  made  by  tlie  axes  of  the  two  eyes  being  large 
if  the  object  is  near,  and  small  if  the  latter  be  distant. 


776 


BINOCULAR   VISION. 


As  it  can  be  shown,  however,  that  the  angles  a  A  a  and  c  C  c 
are  equal,  it  follows  that  the  points  A  C  can  not  lie  in  a  straight 
line,  but  in  a  circle,  it  being  the  property  of  a  circle  only,  that  tri- 
angles erected  on  the  same  chord  and  reaching  the  periphery  have 
at  the  latter  equal  angles.  The  line  joining  the  points  A  C  (Fig. 
469),  must,  therefore,  be  a  circle  of  which  the  chord  is  equal  to  the 
distance  between  the  points  of  decussation  {K  K)  of  the  rays  of 
light  in  the  eye.  Such  a  circle  is  known  as  the  "  horopter,"  and  all 
objects  not  lying  in  it  are  seen  double,  their  images  not  falling  upon 

corresponding  points  of  the  retina. 
Standing  upright,  and  looking  at 
the  distant  horizon,  the  "  horopter  " 
would  be  approximately  for  normal 
long-sighted  persons,  a  plane  drawn 
through  the  feet — that  is  to  say, 
the  ground  on  which  they  stand. 

The  eyeball  nearly  tilling  the 
cavity  of  the  orbit,  and  resting 
posteriorly  upon  a  bed  or  cushion 
of  adipose  tissue,  is  moved  by  six 
muscles,  the  recti  superior  and  in- 
ferior, externus  and  internus,  and 
the  obliqui  superior  and  inferior. 
The  eifect  of  these  muscles  when 
acting  separately  is  quite  apparent 
from  their  origin  and  insertion. 
The  four  recti  in  the  order  named,  arising  from  the  apex  of  the 
orbit  around  the  margin  of  the  optic  foramen,  pass  straight  forward, 
piercing  the  capsule  of  Tenon  or  the  fibrous  membrane  surrounding 
the  sclerotic,  to  be  inserted  into  the  latter  tunic  at  about  the  third 
or  fourth  of  an  inch  behind  the  margin  of  the  cornea,  move  the  eye 
upward,  downward,  outward,  and  inward.  The  superior  oblique 
muscle,  arising  from  the  optic  foramen,  proceeds  toward  the  internal 
angle  of  the  orbit  and  terminates  in  a  round  tendon,  which,  passing- 
through  a  fibro-cartilaginous  ring  or  pulley,  is  thence  reflected  back- 
ward and  outward  to  be  inserted  into  the  sclerotic  between  the 
superior  and  external  recti  muscles.  Its  action  is  to  rotate  the  eye- 
ball downward  and  outward.  The  inferior  oblique  muscle  arising 
from  the  orbital  plate  of  the  superior  maxillary  bone  close  to  the 
external  border  of  the  lachrymal  groove  passes  outward  and  back- 
ward between  the  inferior  rectus  and  the  floor  of  the  orbit  to  be 
inserted  into  the  external  and  posterior  part  of  the  sclerotic.  Its 
action  is  to  rotate  the  eyeball  upAvard  and  outward.  It  can  be 
shown,  however,  theoretically,  as  well  as  by  actual  observation, 
that  the  six  muscles  whose  actions  have  just  been  described  may  be 
regarded  as  consisting  of  three  pairs,  each  of  which  rotates  the  eye 
round  a  particular  axis.  Thus  the  recti  superior  and  inferior  rotate 
the  eye  up  and  down  round  a  horizontal  axis  directed  from  the  upper 


Diagram  to  illustrate  the  horopter. 
(McKendrick.) 


LISTING'S  LA  W.  <  i  i 

end  of  the  ^nose  to  the  temple;  the  obli([ui  su])orior  and  inferior 
obhquely  round  a  horizontal  axis  directed  from  the  center  of  the 
eyeball  to  the  occiput  ;  the  recti  internus  and  externus  from  side 
to  side  round  a  vertical  axis  passing  through  the  center  of  rotation 
of  the  eyeball  situated  a  little  behind  the  center  of  the  optic  axis, 
parallel  to  the  median  plane  of  the  head,  the  latter  being  vertical. 
The  different  muscular  actions  just  described  may  be  briefly  sum- 
marized as  follows  : 


Action  of  Ocular  Muscles. 


Number  of  muscles  acting. 

Oue      .     .     . 
Two     .     .     . 


Three 


Direction. 
Inward, 
Outward, 
Upward, 


Downward, 
Inward  and  upward, 

Inward  aud  downward, 

Outward  and  upward, 

Outward  and  downward. 


Muscles  acting. 
Internal  rectus. 
External  rectus. 
Superior  rectus. 
Inferior  oblique. 
Inferior  rectus. 
Superior  oblique. 
Internal  rectus. 
Superior  rectus. 
Inferior  oblique. 
Internal  rectu.s. 
Inferior  rectus. 
Superior  oblique. 
External  rectus. 
Superior  rectus. 
Inferior  oblique. 
External  rectus. 
Inferior  rectus. 
Superior  oblique. 


The  various  movements  of  the  eyeballs,  as  ju.st  described,  con- 
form to  a  general  law,  the  so-called  "  Listing's  law,"  which  may 
be  briefly  described  as  follows  :  Let  us  suppose  that  the  position 
of  the  eyeball  is  the  primary  one — that  is,  such  in  which  the  head 
is  erect  and  vertical,  and  we  look  straight  forward  to  a  distant  hori- 
zon, aud  that  the  visual  axes,  or  the  lines  from  the  fixed  point  of 
vision  to  the  center  of  rotation  in  the  vitreous  humor,  13.5  mm. 
from  the  anterior  surface  of  the  cornea,  are  parallel.  Such  being 
the  case,  it  would  appear  that  all  movements  of  the  eyel)alls  are 
around  either  a  vertical  axis  from  side  to  side,  or  a  horizontal  axis 
up  aud  down,  or  an  oblique  axis,  the  latter  situated  in  the  same 
plane  with  the  other  two.  In  no  case,  however,  does  the  eyeball 
rotate  around  the  visual  axis  itself  in  a  swivel-like  movement — that 
is,  such  that  the  pupil  would  turn  around  like  a  wheel,  since,  if  the 
eye  were  to  so  rotate,  the  rays  of  light  would  not  fall  upon  corre- 
sponding points  of  the  retina.^  It  may  be  also  mentioned  in  this 
connection  that  while  we  can  converge  or  make  parallel  the  visual 
axes  we  cannot,  at  least  without  assistance  of  some  kind,  diverge 

1  It  should  be  mentioned,  however,  that  recent  researches  render  it  hiijhly  prob- 
able that  the  views  generally  prevailing  as  to  the  mechanism  of  the  eye  movements 
are  not  mathematically  correct.  See  an  interesting  paper  on  tliat  subject  by  Carl 
Weiland,  Archives  of  Ophthalmology,  Vol.  xxvii.,  No.  1,  1898. 


778  SENSATIOX  OF  SIGHT. 

them,  since,  if  we  do  so,  tlie  rays  of  light  do  not  fall  upon  corre- 
sponding points  of  the  retina. 

It  will  be  observed,  from  what  has  just  been  said  of  the  action 
of  the  ocular  muscles,  that  even  in  viewing  an  object  with  a  single 
eye,  that  a  considerable  amount  of  muscular  coordination  must  take 
place,  since  when  the  eye  is  moved  in  any  other  than  the  vertical 
or  horizontal  meridian  three  muscles  at  least  must  be  stimulated, 
relatively  to  the  amount  of  inclination  of  the  visual  axis  needed. 
Such  being  the  case  in  single  ^•ision,  necessarily,  then,  the  amount 
of  muscular  coordination  required  in  binocular  vision  must  be  much 
greater.  If  the  eyes  of  any  person  be  observed,  it  will  be  noticed 
that  the  two  eyes  move  alike,  when  the  right  eye  moves  to  the  right 
so  does  the  left,  and  to  the  same  extent  if  the  object  looked  at  be 
distant,  if  the  right  eye  looks  up  so  does  the  left,  and  so  in  every 
other  direction.  Briefly,  then,  the  eyes  move  in  such  a  manner  that 
the  images  of  an  object  always  fall  upon  corresponding  points  of 
the  retina,  the  essential  condition,  as  we  have  seen,  for  the  produc- 
tion of  single  vision,  the  movements  of  the  two  eyes  ceasing  to  agree 
Avith  each  other  only  when  the  power  of  coordination  is  lost,  through 
disease  or  by  alcoholic  or  other  poisoning. 

It  must  be  admitted,  however,  that  the  nervous  mechanism,  by 
which  the  coordination  of  the  ocular  muscles  is  accomplished,  is  as 
yet  but  imperfectly  understood.  That  is  to  say,  it  has  not  been 
definitely  shown  exactly  how  the  centers  for  the  visual  paths  termi- 
nating in  the  occipital  cortex  and  the  centers  from  which  arise  the 
third,  fourth,  and  six  nerves  are  connected  Mith  the  will  center, 
supposed  to  be  situated  in  the  frontal  lobe,  in  the  front  of  the  pre- 
central  fissure. 

By  movements  of  the  eyes,  apart  from  those  of  the  head,  the  ex- 
tent of  the  field  of  vision  may  amount  to  as  much  as  200  degrees 
in  the  horizontal  and  200  degrees  in  the  vertical  meridian,  that  of 
a  single  eye  being  about  145  degrees  for  the  horizontal  and  100  de- 
grees for  the  vertical  meridian. 

Sensation  of  Sight. 

Regarding  the  sensation  of  sight  as  due  to  the  stimulation  of  the 
retina  by  light,  observation  teaches,  as  might  be  supposed,  that  the 
intensity  and  duration  of  the  sensation  will  vary  according  to  the 
strength  of  the  luminous  vibrations  and  the  length  of  time  during 
which  the  latter  continue  to  fall  upon  the  retina.  That  the  in- 
tensity of  the  sensation  varies  with  that  of  the  luminous  object  is  a 
matter  of  daily  experience,  a  wax  candle,  for  example,  appearing 
brighter  than  a  rushlight.  With  a  little  experimentation  it  becomes 
soon  apparent,  however,  that  the  ratio  of  the  sensation  to  the 
stimulus  is  not  a  simple  one,  since  Avhilc  the  sensations  increase  as 
the  luminosity  of  the  object  increases,  the  sensations  increase  less 
and  less,  until  finally  there  is  no  appreciable  increase  of  sensation, 
however  much  the  luminosity  may  be  increased — that  is  to  say. 


DURATION  OF  SENSATION  OF  SIGHT.  779 

when  a  light  reaches  a  given  brightness  it  appears  so  briglit  to  us 
that  "vve  cannot  tell  when  it  becomes  anv  briohter.  It  is  mnch 
easier,  therefore,  to  distinguish  the  difference  between  two  feeble 
lights  than  the  same  difference  between  two  bright  lights — in  fact, 
if  the  latter  be  very  bright  it  becomes  then  impossible.  Thus,  for 
example,  while  there  is  no  difficulty  in  distinguishing  between  the 
light  of  a  candle  and  that  of  a  rushlight,  it  would  be  impossible  to 
distinguish  such  a  difference  between  the  light  of  two  suns,  suppos- 
ing the  light  of  the  one  to  be  in  excess  of  that  of  the  other  in  the 
same  ratio  as  that  of  the  candle  over  that  of  the  rushlight,  just  as 
an  addition  of  half  an  ounce  to  twenty  pounds  will  not  be  appre- 
ciated by  the  sense  of  weight.  Further,  it  will  be  found  that  if  we 
let  the  shadows  of  two  rushlights,  for  example,  fall  upon  white 
paper,  and  then  move  one  of  the  lights  away  until  the  shadow 
ceases  to  be  visible,  that  in  performing  the  same  experiment  with 
two  wax  candles  the  candle  ^\\\\  have  to  be  moved  through  the  same 
distance  as  that  of  the  rushlight  before  its  shadow  ceases  to  be  seen, 
the  smallest  increment  in  light  in  both  cases  appreciable  being  in- 
variable, about  the  yl^  of  the  total  luminosity  made  use  of.  It  is 
also  evident  that  the  duration  of  the  sensation  is  long-er  than  that  of 
the  stimulus,  the  sensation  of  sight  and  the  stimulus  of  light  being 
comparable,  in  this  respect,  to  a  muscular  contraction,  as  induced  by 
a  single  induction  shock.  It  is  for  this  reason  that  if  two  flashes  of 
light  follow  each  other  sufficiently  quickly,  within  the  one-tenth  of 
a  second  for  a  faint  light,  and  the  one-thirtieth  of  a  second  for  a 
strong  one,  the  two  sensations  arising  are  fused  into  one.  Hence, 
the  fact  of  a  luminous  point  moving  rapidly  around  in  a  circle  giv- 
ing rise  to  the  sensation  of  a  continuous  circle  of  light,  which  re- 
minds one  of  the  production  of  muscular  tetanus.  That  the  dura- 
tion of  the  stimulus  of  light  necessary  to  give  rise  to  the  sensation 
of  sight  must  be  very  short,  is  shown  from  the  fact  of  the  electric 
spark  being  seen,  though  the  latter  is  known  to  last  but  the 
2"'5' o~oVo  TTo  ^^^  second.  When  a  large  portion  of  the  retina  is  af- 
fected by  light  the  total  sensation  experienced  is  greater  in  amount 
than  when  a  small  })ortion  is  so  affected,  a  large  piece  of  Avhite 
paper,  for  example,  affecting  our  consciousness  more  than  a  small 
piece.  If,  however,  the  surfaces  of  the  papers  be  equally  and  uni- 
formly illuminated,  the  small  piece  Avill  appear  as  bright,  or  white, 
as  the  large  one,  the  intensity  being  the  same  in  both  cases. 
Fiirther,  as  might  be  expected,  if  the  images  of  the  two  papers  be 
situated  upon  the  retina  at  sufficient  distance  apart,  the  two  sensa- 
tions will  be  distinct,  the  relative  intensity  of  the  same  depending 
upon  the  brightness  of  the  objects,  while,  if  the  images  arc  so  close 
to  each  other  that  the  sensation  fuses  into  one,  then  the  total  sensa- 
tion experienced  will  be  greater  than  that  due  to  cither  one  of  the 
images,  though  not  equal  to  tlie  sum  of  the  single  sensations.  As  a 
general  rule,  the  best  eyes  fail  to  distinguish  two  })nrallc'l  white 
streaks  when  the  distance  separating  them,  as  measured  from  the 


780  SENSATIOX  OF  SIGHT. 

middle  of  each,  subtends  an  angle  of  less  than  73  seconds,  though 
some  individuals  can  distinguish  objects  so  close  to  each  other  that 
the  distance  separating  them  does  not  subtend  an  angle  of  more 
than  50  seconds.  Xow,  as  the  retinal  image  corresponding  to  an 
angle  of  73  seconds  would  measure  in  the  schematic  eye  about 
0.00536  mm.,  and  that  corresponding  to  an  angle  of  50  seconds, 
about  0.00365  mm.,  and  as  the  average  diameter  of  a  retinal  cone 
measures  at  its  widest  part  about  0.004  mm.,  it  is  evident  that  the 
visual  sensory  area  has  a  corresponding  physical  Ijasis  in  the  retinal 
anatomical  area,  which  renders  it  highly  probable  that  there  is  still 
another  corresponding  cerebral  or  perceptive  area. 

It  has  already  been  mentioned  that,  owing  to  the  unequal  re- 
frangibility  of  different  kinds  of  light,  that  white  light  in  passing 
through  a  prism  is  not  only  refracted,  but  is  decomposed  into  the 
seven  kinds  of  light  of  which  white  light  is  composed,  viz.,  violet, 
indigo,  blue,  green,  yellow,  orange,  and  red,  or  the  colors  of  the 
spectrum.  In  considering,  however,  the  manner  in  Avhich  we  be- 
come conscious  of  the  ditferent  colors  of  which  the  spectrum  is 
composed,  or  of  any  colors  or  color,  we  must  disabuse  ourselves  at 
once  of  the  idea  that  what  we  call  color  exists  outside  of  our  own 
consciousness  objectively  as  such,  since  what  we  call  color  in  our- 
selves subjectively,  can  be  shown  experimentally  to  be  due  objec- 
tively to  a  vibration,  an  oscillatory  movement,  a  wave  of  a  definite 
length  passing  into  tlie  eye  at  a  certain  velocity,  all  kinds  of  light 
being  so  propagated.  In  fact,  color  objectively  is  to  the  eye  what 
we  shall  see  pitch  in  the  case  of  sound  is  to  the  ear,  the  latter  de- 
pending solely  upon  the  number  of  vil)rations  striking  the  ear  in  a 
second.  In  other  words,  a  wave  of  a  certain  length,  propagated  at 
a  definite  rate,  in  falling  upon  the  retina,  gives  rise  in  us  to  a  sensa- 
tion of  a  particular  color.  Thus,  the  color  red  is  due  to  the  im- 
pinging upon  the  retina  of  a  wave  about  y 5^17  *»f  ^^  millimeter  (g-gl^oo- 
of  an  inch)  in  length,  travelling  at  such  a  velocity  that  about  474,- 
439,680,000,000  such  waves  enter  the  eye  in  a  second ;  the  color 
violet  to  a  wave  about  o-jQ-g  of  a  millimeter  (-^yz1)1)  ^^^^^  inch),  about 
690,000,000,000,000  "such  waves  entering  the  eye  in  a  second,  the 
waves  giving  rise  to  the  violet  color  being  shorter  than  those  to 
which  the  red  color  is  due,  but  following  each  other  into  the  eye 
more  rapidly  than  the  latter,  the  waves  to  which  the  other  colors 
of  the  spectrum  are  due  with  reference  to  their  length  and  velocity 
lying  between  the  extremes  just  mentioned.  The  sensation  of  color 
depending  then  upon  the  successive  impulses  imparted  to  the  fibers 
of  the  optic  nerve  by  waves  of  different  length  travelling  at  different 
velocities,  it  is  obvious  that  it  would  be  useless  to  look  into  the 
external  world  for  any  attribute  or  quality  that  would  correspond 
objectively  to  what  we  call  in  ourselves  the  sensation  of  color.  In 
■other  words,  the  color  red  of  an  object  is  in  ourselves,  not  in 
the  object  looking  red,  because  tlie  wave  giving  rise  to  red  is  re- 
flected from  the  object  into  our  eyes,  the  remaining  waves  being 


SEXSATIOX  OF  COLOR.  ">^I 

absorbed  by  tlie  object ;  similarly  surroiiiKling  ol^jccts  look  red  when 
viewed  tliroiiirh  a  red  glass,  the  wave  giving  rise  to  red  being  alone 
transmitted  through  the  glass  to  our  eye,  the  remaining  waves  being 
absorbed  by  the  glass,  and  so  with  all  other  colors.  Our  knowledge 
of  color  depending  then  upon  the  impression  made  upon  the  sen- 
sorium  by  the  waves  of  light  is  not  absolute,  but  only  relative. 
In  other  words,  we  do  not  know  the  light  in  itself — the  thing 
itself,  as  Kant^  expressed  it — but  only  by  just  so  much  as  the 
light  or  thing  affects  our  consciousness.  The  extent  to  which  sen- 
sation is  dependent  upon  the  susceptibility  of  the  organism  of  being 
impressed  by  the  external  world,  is  shown  by  the  fact  that,  not- 
withstanding the  solar  spectrum  extends  beyond  the  violet  in  one 
direction  and  beyond  the  red  in  another,  the  eye  under  ordinary 
circumstances  is  unconscious  of  the  existence  of  these  extremes, 
being  so  organized  as  not  to  be  affected  by  the  ultra  violet  or  chem- 
ical rays,  or  the  ultra  red  or  heat  rays.  Our  knowledge  being  due 
to  sensations  arising  from  impressions  made  by  the  environment 
upon  the  organism,  cannot  then  be  innate,  but  must  have  been  ulti- 
mately derived  from  experience,  and  therefore  relative,  as  held  by 
Locke.^  After  what  has  just  been  said,  it  is  evident  that  no  phys- 
ical or  chemical  chang-es  in  the  retina  will  account  for  our  sensation 
of  color,  since  the  cause  of  the  latter  lies  not  in  the  retina,  which 
is  simply  an  intermediate  organ,  correlating  the  physical  with  the 
psychical,  Init  in  that  part  of  the  cerebrum  where  the  still  ])hysical 
vibration  gives  rise  to  sensation.  Indeed,  the  cause  of  the  sensa- 
tion of  color,  as  might  be  premised  from  the  present  imperfect  state 
of  physiological  psychology,  is  not  yet  understood,  although  a  great 
number  of  interesting  observations  have  been  made  with  reference 
to  the  effect  of  fusing  colors,  of  complementary  colors,  of  which  a 
brief  account  at  least  in  this  connection  must  be  given. 

Though  we  have  spoken  of  the  solar  spectrum  consisting  of  seven 
colors,  as  a  matter  of  fact,  it  is  made  up  not  only  of  such,  but  also 
of  a  great  number  of  intermediate  tints  as  well.  External  nature 
presents  the  same  tints,  and  also  a  number  of  others  like  those  of 
purple,  brown,  gray,  etc.,  which,  however,  are  not  present  in  any 
part  of  the  spectrum.  While  such  tints  are  apparently  due  to  dis- 
tinct simple  sensations,  it  can  be  shown  experimentally  that  in 
reality  they  are  compound  ones,  being  obtainable  l)y  the  fusion  of 
two  or  more  color  sensations.  Thus,  purple,  which,  as  just  men- 
tioned, is  not  present  in  the  spectrum,  may  be  readily  produced  by 
the  fusion  of  red  and  blue,  as,  for  example,  by  so  placing  a  red  and 
blue  wafer  and  a  glass  (Fig.  470)  that  the  light  will  be  reflected 
from  the  red  wafer  (R)  in  the  same  direction  as  that  coming  from 
the  blue  wafer  (B).  In  the  same  way  the  various  tints  of  nature 
may  be  obtained  by  fusing  different  colors,  sensations  with  that  of 

Uritiquo  of  Pure  Eeason,  trans,  by  Max  Miiller.  Second  Part,  p.  ^9.  Lon- 
don, ISSl. 

2 Of  Human  Undei-standing,  Locke's  Works.   Chap,  ii.,  Vol.  i.     London,  1883. 


782 


SENSATION  OF  SIGHT. 


white  or  black,  different  kinds  of  brown  resulting  from  mixtures  of 
yellow,  red,  white  and  black,  grays  from  white  and  black,  as  can 
be  shown  by  making  use  of  a  rotating  disk,  on  the  surface  of  which 
colored  sectors  are  painted,  the  resulting  color  being  white,  for  ex- 
ample, in  that  of  the  instance  represented  in   Fig.  471.      Experi- 


FiG.  470. 


Fig.  471. 


_^ML 


■^ 


X,ambert's  method  of  studying  combinations 
of  colors. 


Rotating  disk  of  Sir  Isaac  Xewtiin  fur  mixing 
colors. 


menting  in  this  way,  it  can  be  shown  that  the  (juality  of  a  color 
depends  on  the  wave-length  of  its  constituent  waves  and  on  the 
relative  amount  of  colored  and  white  light  falling  upon  the  retina 
in  a  given  time,  a  color  being  saturated  when  unmixed  with  white 
light,  as  in  the  case  of  the  colors  of  the  spectrum. 

As  regards  the  fusion  of  colors,  it  is  evident,  fnnu  what  has  been 
said  of  the  subject  of  color,  that  in  mixing  red  and  yelloAV  to  pro- 
duce an  orange,  for  example,  undistinguishablc  from  the  orange  of 
the  spectrum,  that  the  sensation  of  orange  cannot  be  due  to  the 
uniting  of  the  red  and  yellow  waves  differing  in  length  from  each 
•other  to  form  an  orange  wave  differing  in  length  from  either,  but 
that  it  is  the  mixture  of  the  sensation  of  red  and  yellow  that  gives 
rise  to  the  sensation  of  orange.  In  other  words,  the  mixture  is 
psychical,  not  physical.  It  is  an  interesting  fact  that  certain  colors, 
when  mixed  together  in  pairs  in  certain  definite  proportions,  give 
rise  to  the  sen.sation  of  white,  as,  for  example,  red  and  blue-green, 
orange  and  blue,  yellow  and  indigo-blue,  green-yellow  and  violet ; 
such  colors  are  said  to  be  complementary  colors,  since  given  the 
color  of  one  of  the  pairs,  say  red,  all  that  is  necessary  or  comple- 
mentary to  produce  white  is  the  other  color  of  the  pair,  or  green. 
It  can  be  also  experimentally  shown,  by  means  of  the  rotating  disk, 
that  the  mixture  in  proper  proportions  of  any  three  distinct  colors 
of  the  spectrum  arbitrarily  selected,  but  sufficiently  far  apart,  as, 
for  example,  red,  green  and  violet,  Avill  produce  white,  and  that  by 
the  further  addition  of  white  the  sensations  of  all  the  other  colors 
can  be  obtained.  In  order  to  avoid  any  misunderstanding  as  re- 
gards the  production  oi  the  sensation  of  white,  it  should  be  men- 


THEORY  OF  COLOR.  783 

tioned  that  the  mixture  of  red,  green,  and  violet  pigments,  unless 
they  are  perfectly  pure,  will  not  produce  white ;  a  mixture  of  ])ig- 
ments  being  totally  different  from  a  mixture  of  sensations  of  colors, 
since  the  color  produced  l)y  the  mixing  of  pigments  is  due  to  the 
light  -which  has  escaped  absorjition  by  the  same  rather  than  the 
color  due  to  a  mixture  of  the  colors.  For  example,  the  sensations 
of  indigo  and  gamboge  when  mixed  give  rise  to  the  sensation  of 
white,  the  sensation  due  to  a  mixture,  however,  of  indigo  and  gam- 
boge pigments  is  green  because  the  gamboge  absorbs  the  blue,  and 
the  indigo  absorbs  the  red  and  the  yellow,  while  both  reflect  green. 
Facts  like  those  just  mentioned  with  reference  to  the  fusion  of 
colors,  their  complementary  relation,  the  composition  of  white  light, 
€tc.,  led  the  celebrated  Young,^  in  the  beginning  of  the  century, 
and  Helmholtz,^  in  recent  times,  to  advocate  the  view  that  all  of 
our  sensations  of  color  are  compounds  of  three  primary  color  sen- 
sations, red,  green,  and  violet,  and  that  waves  of  different  lengths 
give  rise  to  all  three  of  these  sensations  according  to  their  particular 
length — that  is  to  say  (Fig.  472),  the  orange  wave  gives  rise  to 


Diagram  of  three  primary  color  sensations.  1  is  the  so-called  "  red,"  2  "  green,"  and  3  "  violet  ' 
primary  color  sensation.  R,  O,  Y,  etc.,  represent  the  red,  orange,  yellow,  etc.,  color  of  the  spec- 
trum, and  the  diagram  shows,  by  the  height  of  the  curve  in  each  case,  to  what  extent  the  several 
primary  color  sensations  are  respectively  excited  by  vibrations  of  ditferent  wave-lengths. 
(Foster.) 


much  of  the  first  sensation,  or  red,  less  of  the  second,  or  green,  and 
to  little  of  the  third,  or  violet ;  on  the  other  hand,  the  blue  wave 
gives  rise  to  little  of  the  red  sensation,  to  more  of  the  green,  and 
to  much  of  the  violet,  etc.  The  anatomical  basis  for  the  above  is 
the  assumption  that  three  kinds  of  nerve  fibers  exist  in  the  retina, 
the  excitation  of  which  gives  rise  respectively  to  the  sensations  of 
red,  green,  and  violet — homogeneous  light — all  three  of  these  so- 
called  fundamental  sensations,  but  with  different  intensities  accord- 
ing to  the  length  of  the  wave ;  long  waves  exciting  most  power- 
fully the  fibers  who.se  stimulation  give  rise  to  the  sensation  of 
red,  medium  waves  those  causing  the  sensation  of  green,  short 
waves  those  causing  the  sensation  of  violet.  Accepting  pro- 
visionally   the    Young-Helmholtz    theory  of  color    sensation,    it 

'Lectuies  on  Natural  Philosophy.     London,  1807.  ^Op.  cit.,  p.  382. 


784  SENSATION  OF  SIGHT. 

serves  to  explain  some  of  the  phenomena  of  color-bliucluess,  after- 
images, etc.  AVhile  almost  all  individuals  are  able  to  appreciate 
differences  of  color,  there  are  some,  and  the  number  is  far  greater 
than  usually  supposed,  who  are  unaffected  by  certain  colors,  the 
most  common  defect  being  an  insensibility  to  red,  blindness  to 
green  and  violet  being  rare.  Thus,  for  example,  in  Daltonism,  or 
blindness  to  red,  so  called  on  account  of  its  having  been  observed 
in  the  celebrated  Dalton,  the  red  end  of  the  spectrum  appears  dark, 
a  red  gown  lying  on  a  green  grass  plot,  a  red  cherry  among  green 
leaves,  are  distinguished,  not  by  their  color,  but  by  their  form,  the 
color  of  the  gown  or  the  fruit  appearing  to  such  an  eye  not  red,  but 
green  like  that  of  the  grass  or  leaves.  Remembering  that  green 
is  the  complementary  color  to  red,  and  supposing  that  in  a  daltonic 
eye  the  fibers  whose  stimulation  in  an  ordinary  eye  would  give  rise 
to  the  color  of  red  are  either  absent,  diseased,  or  paralyzed,  the 
phenomenon  just  referred  to  can  be  accounted  for.  Similarly, 
if,  after  a  red  patch  has  been  looked  at  steadily  for  some  time  until 
the  eye  becomes  fatigued,  a  white  surface  be  looked  at,  a  green 
patch  will  be  seen  instead  of  the  red  one,  the  green  fibers  of  the 
retina,  so  to  speak,  being  fresh,  are  susceptible  of  being  excited  by 
the  green  color  (or  wave  giving  rise  to  it)  of  the  white  light  re- 
flected from  the  paper,  the  red  fibers  being,  however,  exhausted,  are 
no  longer  susceptible  of  being  excited  by  the  red  color  (or  the  wave 
giving  rise  to  it)  of  the  white  light.  In  the  same  manner  many 
other  negative  after-images  can  be  explained,  so  called  as  contrasted 
with  positive  after-images  which  are  simply  due  to  a  sensation,  being 
continued  even  after  the  object  giving  rise  to  it  has  been  removed 
from  the  field  of  vision.  Thus,  for  example,  if  the  eye  be  directed 
momentarily  to  the  sun  the  image  of  the  latter  will  be  present  for 
some  time  after,  or  if  a  window  be  looked  at  for  an  instant  on  early 
M'aking,  and  the  eye  then  closed,  an  image  of  the  same  with  its 
bright  panes  and  darker  sashes  will  persist  for  some  time.  While 
the  Young-Helmholtz  theory  of  color  sensation  is  accepted  by  many 
physiologists,  another  theory  has  been  advanced  by  Aubert  ^  and 
Hering  -  among  others,  the  latter  of  whom  maintain  that  the  pri- 
mary color  sensations  are  white,  black,  red,  yellow,  green,  and  blue, 
and  that  these  different  sensations  are  due  to  the  changes  in  the  so- 
called  visual  substance  of  the  visual  apparatus,  the  changes  giving 
rise  to  the  sensations  of  black,  green,  and  blue  being  processes  of  a 
constructive-assimilating  kind,  those  giving  rise  to  the  sensations  of 
Avhite,  red,  and  yellow,  of  a  destructive-assimilating  kind.  If  Her- 
ing's  view  be  accepted,  then  black  and  white,  green  and  red,  blue 
and  yellow,  far  from  being  complementary,  must  be  regarded  as 
antagonistic  to  each  other,  and  the  visual  substance  assumed  to  be 
always  undergoing  changes,  never  in  a  state  of  rest.  The  limits 
of  this  Avork  will  not  permit  of  further  illustration  or  discussion  of 

1  Physioloffii-  der  Netzhaiit,  ISGfi. 

^Wien.  Sitzberich,  Lxvi.  (1872),  Iviii.,  Ixix.,  ixx. 


PERCEPTION  OF  SIGHT.  785 

the  relative  merits  of  the  Helmholtz  and  Hering  theories  of  the 
sensations  of  color ;  it  may  be  pointed  out,  however,  once  more, 
that  whether  the  one  or  the  other  theory  be  accepted,  we  are  not  a 
whit  nearer  the  explanation  of  the  sensation  of  color,  since  the 
transformation  of  the  ultimate  physical  vibration  or  wave  into  the 
psychical  color  sensation  takes  place  not  in  the  retina  but  in  the 
cerebrum. 

Perception  of  Sight. 

It  has  already  been  mentioned  that  as  the  apparent  size  of  an  ob- 
ject depends  upon  the  visual  angle,  if  two  objects,  though  of  different 
size,  subtend  with  the  eye  equal  angles — that  is,  if  their  visual 
angles  are  the  same — the  apparent  size  of  the  objects  will  be  the 
same.  The  real  size  of  an  object  is  therefore  not  determined  by  the 
sense  of  sight,  the  latter  only  giving  rise  to  the  sensation  of  its 
apparent  size.  The  estimate  of  the  real  size  of  an  object  is  really 
an  inference  based  upon  its  apparent  size,  but  modified  by  the 
knowledge  of  its  distance  from  the  eye.  In  other  words,  it  is  not 
a  simple  sensation,  but  a  judgment  based  upon  the  sensations  of 
touch,  as  well  as  those  of  sight.  Knowing  the  distance  of  an  object 
from  us,  we  infer  from  its  apparent  size  its  real  size  ;  and  con- 
versely, knowing  the  size  of  the  object,  we  infer  its  distance.  Thus, 
if  the  image  of  some  well-known  object,  a  man,  for  example,  appear 
in  our  field  of  vision,  and  we  know  how  far  off  the  man  is,  we  infer 
his  size  from  that  of  our  retinal  image  ;  and,  conversely,  knowing 
the  size  of  the  man,  if  his  retinal  image  be  very  small,  "\ve  infer 
that  the  man  is  very  fir  off.  That  our  estimate  of  the  size  of  an 
object  is  dependent  upon  the  knowledge  of  its  distance  from  us,  is 
shown  from  the  fact  that  if  we  have  no  means  of  even  approxi- 
mately estimating  the  latter  it  is  impossible  to  obtain  any  idea  of 
its  size.  Thus  the  sun,  though  about  four  hundred  times  the  dis- 
tance of  the  moon,  is  apparently  of  the  same  size  as  the  latter,  but 
we  infer  from  that  very  reason  that  the  one  body  is  larger  than  the 
other ;  did  we  not  know,  however,  their  relative  distance  from  the 
earth  it  would  be  impossible  to  say  which  of  the  two,  the  sun  or 
the  moon,  was  the  larger  body.  Our  estimate  of  the  distance  of 
objects  is  not  only  based  upon  their  size,  but  largely  upon  the 
presence  of  surrounding  and  intermediate  objects,  it  being  difficult 
to  estimate  the  distance  of  an  object  entirely  isolated,  as  in  looking 
at  a  single  distant  object  at  sea.  The  muscular  sensations  arising 
through  the  contraction  of  the  ocular  muscles  in  converging  the 
visual  axis  for  near  objects,  and  making  them  parallel  for  distant 
ones,  aid  us  very  much  in  forming  a  correct  judgment  as  to  the 
distance  of  objects.  As  with  our  estimate  of  the  distance  of  objects, 
so  with  that  of  the  idea  of  solidity,  which  is  essentially  an  estimate 
of  the  distance  of  the  diftcreut  parts  of  an  object,  the  idea  being  a 
judgment,  a  mental  combination,  of  the  two  dissimilar  pictures 
formed  upon  the  retina,  the  image  of  the  object  as  viewed  by  the 
50 


786  PERCEPTION  OF  SOLIDITY,  ETC. 

right  eye  being,  as  already  mentioned,  diiferent  from  that  as  viewed 
by  the  left  eye,  the  resultant  image  being  seen  in  relief,  and  giving 
rise  to  the  idea  of  solidity.  The  fact  that  we  see  objects  erect, 
though  their  images  are  reversed  upon  the  retina,  as  already  men- 
tioned, is  due  to  the  fact  of  the  sensation  of  the  image  derived  from 
the  sense  of  sight  being  modified  by  the  sensation  of  the  object 
derived  from  the  sense  of  touch.  The  mind  associating  images 
situated  at  the  upper  and  inner  part  of  the  retina  with  the  objects 
giving  rise  to  them  but  situated  below  and  to  the  outer  side  of  the 
eye,  and  images  at  the  upper  and  outer  part  of  the  retina  with 
objects  situated  below  and  to  the  inner  side  of  the  eye,  and  project- 
ing outward,  the  images  or  the  luminous  sensation  back  to  the 
object  giving  rise  to  them,  finally  perceives  the  objects  erect.  In 
the  same  w^ay,  but  conversely,  wdien  a  phosphene  or  luminous 
image  is  created  by  pressing,  say  on  the  outer  or  lower  side  of  the 
eyeball,  the  image  appears  to  lie  above  and  to  the  inner  side  of  the 
eye.  Indeed,  the  association  of  the  sense  of  sight  with  that  of  touch 
in  obtaining  the  ideas  of  the  size,  distance,  solidity,  position  of  ob- 
jects, etc.,  is  so  intimate  that  w^ere  our  knowledge  of  the  same 
derived  through  the  sense  of  sight  alone  it  would  be  of  the  most 
inexact  and  unreliable  character.  That  such  is  the  fact  has  been 
shown  by  cases  like  those  of  the  youth  reported  by  Cheselden,^  who 
for  some  time  after  the  sense  of  sight  was  given  him,  he  having 
been  born  blind,  saw  everything  flat,  as  in  a  picture,  and  supposed 
that  objects  when  seen  touched  his  eyes,  as  objects  when  felt 
touched  his  fingers.  The  newly  acquired  sense  of  sight  at  first 
rather  hindered  him  in  finding  his  way  about  the  house,  which  he 
could  do  perfectly  well  by  the  sense  of  touch  alone.  The  fact  that 
the  youth  could  not  tell  of  his  two  pets  which  was  the  cat,  and 
which  was  the  dog,  by  the  sense  of  sight  alone,  though  he  could  at 
once  distinguish  them  by  feeling  them,  led  him  one  day  to  feel  the 
cat  and  at  once  look  at  her,  and  then  setting  her  down,  said,  "  So 
puss,  I  shall  know  you,  another  time."  AVhat  has  just  been  said 
renders  it  very  probable,  as  held  by  Locke,^  that  a  person  born 
blind,  on  suddenly  obtaining  his  sight,  would  be  unable  by  sight 
alone  to  distinguish  a  cube  from  a  sphere — that  is,  to  be  able  to 
say  w^hich  was  the  sphere,  which  the  cube,  for  though  he  knows 
how  the  sphere  or  the  cube  affects  his  touch,  he  has  not  learned  by 
experience,  as  yet,  that  if  the  cube,  etc.,  affects  his  touch  so  and  so, 
it  will  affect  his  sight  so  and  so,  and  enable  him  by  sight  alone  to 
distinguish  it  from  the  sphere.  Since  our  perception  of  external 
objects  is  elaborated  out  of  the  sensations  that  the  retinal  images  give 
rise  to,  it  might  be  supposed  that  the  perception  would  invariably 
correspond  to  the  sensation,  just  as  the  latter  would  correspond  to 
the  retinal  image  causing  it.  As  a  matter  of  fact,  however,  such  is 
not  invariably  the  case,  discrepancies  arising  between  the  retinal 
image  and  the  perception,  some  of  cerebral,  others  of  retinal  origin, 
iPhil.  Trans.,  1728,  p.  477.  ^Op.  cit,  Book  II.,  chap,  ix.,  p.  256. 


PERCEPTION  OF  SIGHT. 


787 


the  effect  of  Avhicli  is  so  to  modify  the  perception  that  the  usually 
reliable  judgment  as  to  the  size,  distance,  etc.,  of  objects  is  per- 
verted. Thus,  for  example,  the  white  square  (Fig.  478)  on  the 
black  ground  appears  larger,  and  the  black  square  on  the  white 


Fig.  473. 


Fig.  474. 


Illustration  of  irradiation.     (McKendrick.  ) 


Illusions  of  size. 


ground  smaller,  than  it  really  is,  the  over-lapping  of  the  white  light 
in  either  case,  or  the  irradiation,  being  due,  as  it  were,  to  retinal  or 
cerebral  fibers  other  than  those  directly  stimulated  by  the  light 
being  thrown  into  sympathetic  vibration.  If  a  white  strip  be 
placed  between  two  black  ones  the  inner  edges  of  the  former — that 
is,  the  edges  nearest  the  black — will  appear  by  contrast  whiter  than 
the  median  portions.  In  the  same  manner,  the  center  of  a  white 
cross  placed  upon  a  black  background  will  often  appear  shaded,  as 
compared  with  the  remaining  parts.  The  judgment  may  also  be  at 
fault  with  reference  to  size,  as  in  Fig.  474,  when  though  the  dis- 

FiG.  475. 


s  Y/  ^ 


^7 


N  C  ^ 


r 
.      / 

/ 
/ 
/ 
/ 
/ 
/ 
/ 
/ 
/ 
/ 
/ 
/ 
/ 
/ 
/ 
/ 


< 


^^ 


Zoellner's  figure,  showing  an  illusion  of  direction.     (McKexdrick.) 


tance  A  B  is  equal  to  the  distance  B  C,  the  former  appears  to  be 
the  greater ;  or  with  reference  to  direction,  as  in  the  case  of 
Zoellner's  (Fig.  475)  lines,  which,  if  looked  at  obliquely,  will  give 


788        PROTECTIVE  APPENDAGES,  ETC.,   OF  THE  EYE. 

the  impression  that  the  vertical  lines,  though  parallel,  converge  or 
diverge,  and  the  oblique  lines,  though  continuous  across  them,  are 
not  exactly  opposed  to  each  other.  That  the  above  effect  is  due  to 
an  error  of  judgment,  is  shown  by  the  fact  that  by  an  eifort  it  may 
be  controlled,  the  lines  being  then  seen  as  they  really  are.  If  two 
equal  squares  be  marked,  one  with  vertical,  and  the  other  with  hori- 
zontal, alternate  dark  and  light  bands,  the  former  will  appear 
broader,  and  the  latter  higher  than  it  really  is.  Short  persons 
should  therefore  wear  dresses  horizontally  striped  if  they  wish  to 
increase  their  apparent  height,  and  stout  persons  avoid  wearing 
longitudinally  striped  ones.  Many  other  such  examples  might  be 
given,  but  the  above  will  sulhce  to  illustrate  the  errors  of  judgment 
that  the  sense  of  siffht  alone  mav  lead  one  into. 

Protective  Appendages,   etc.,   of  the  Eye. 

The  eyeljall,  with  its  muscles,  etc.,  is  protected  by  the  bony  orbit, 
the  outer  wall  of  which  is  stronger  than  the  inner  one,  the  eye  being 
more  exposed  to  injury  from  the  outer  than  the  inner  side  ;  the  inner 
wall  of  the  orbit  projecting,  however,  considerably  beyond  the  outer 
wall,  the  extent  of  vision  is  far  greater  in  the  outward  than  in  the 
inner  direction.  The  upper  semi-circumference  of  the  orbit  and 
the  superciliary  ridge  is  provided  with  short,  stiff  hairs,  the  eye- 
brows, which  serve  to  protect  the  eyelids  from  the  perspiration  of 
the  forehead,  and  to  shade  the  eye  from  excessive  light.  The  eye- 
lids consist  of  folds  of  very  thin  integument  lined  by  mucous  mem- 
brane, the  conjunctiva,  the  subcutaneous  connective  tissue  being 
thin,  loose,  and  free  from  fat,  and  containing  small  papilla,  and 
sudoriferous  glands.  The  eyelashes,  the  short,  stiff,  curved  hairs 
projecting  from  the  borders  of  the  lids  in  two  or  more  rows,  serve  to 
protect  the  eye  from  dust,  and,  to  a  certain  extent,  also,  to  shade  it. 
The  palpebral  cartilages,  extending  from  the  edges  of  the  lids,  which 
they  support,  to  the  margin  of  the  orbit,  are  small,  elongated,  semi- 
lunar plates,  attached  internally  by  the  tendo-palpebrarum  to  the 
lachrymal  groove,  externally  by  the  external  tarsal  ligament  to  the 
malar  bone,  and  supported  by  the  palpebral  ligament.  On  the  pos- 
terior surface  of  the  tarsal  cartilages,  lying  just  beneath  the  con- 
junctiva, are  found  the  Meibomian  glands,  wdiich,  in  structure,  are 
modified  sebaceous  glands,  whose  secretion,  an  oily  fluid,  in  smear- 
ing the  edges  of  the  eyelids,  prevents  the  overflow  of  the  tears. 
The  eyelids  serve  to  protect  the  eyeball,  their  movements  constitut- 
ing, respectively,  the  opening  and  closing  of  the  eye,  the  act  of 
Mdnking  favoring  the  passage  of  tears  over  the  globe  and  through 
the  lachrymal  canals  into  the  nasal  sac  ;  and  hence,  when  the  orbicu- 
laris palpebrarum  is  paralyzed,  by  the  contraction  of  M'hich  muscle 
the  eye  is  closed,  the  tears  do  not,  as  readily  as  usual,  pass  into  the 
nose.  The  eye  is  principally  opened  by  the  raising  of  the  upper 
eyelid  through  the  contraction  of  the  levator  palpebrarum,  though 
it  is  also  opened  through  the  elevation  of  the  upper  and  depression 


THE  TEARS.  789 

of  the  lower  eyelids,  respectively,  through  the  action  of  the  plain 
muscular  fibers  existing  in  both  eyelids,  and  which  are  innervated 
by  the  sympathetic,  the  orbicularis  palpebrarum  being  supplied,  as 
has  already  been  mentioned,  by  the  facial  and  the  levator  palpebrae 
by  the  third  nerve. 

The  eyes  are  usually  kept  open,  almost  involuntarily,  though  we 
can  close  or  open  them  at  will ;  the  action  of  the  orbicularis  muscle  is, 
however,  to  such  an  extent  of  a  reflex  character  that  if  the  globe  of 
the  eye  be  touched  or  irritated,  or  if  the  impression  of  light  produces 
pain,  it  is  then  impossible  to  keep  the  eye  open.  It  has  already 
been  mentioned  that  the  inner  surface  of  the  upper  and  lower  eye- 
lids is  lined  by  a  mucous  membrane,  the  conjunctiva.  The  con- 
junctiva, continuous  with  the  membrane  lining  the  puncta  lach- 
rymalis,  and  the  lachrymal  ducts,  is  reflected  forward  from  the 
inner  periphery  of  the  lids  over  the  eyeball,  that  lining  the  lids 
being  called  the  palpebral,  that  covering  the  eyeball  the  ocular  con- 
junctiva ;  the  latter  differing,  further,  in  its  sclerotic  and  corneal 
portions.  At  the  point  where  the  membrane  is  reflected  upon  the 
globe  it  presents  a  superior  and  inferior  fold,  the  former  containing 
numerous  glandular  follicles  and  minute  lachrymal  glands.  At  the 
inner  canthus  there  is  a  vertical  fold,  the  so-called  plica  semilunaris, 
w^hich,  morphologically,  corresponds  to  the  inner  and  third  eyelid, 
or  the  nictitating  membrane  present  in  many  of  the  lower  animals,  as 
in  sharks,  birds,  and  some  mammals.  The  caruncula  lachrymalis, 
the  reddish,  spongy  elevation  situated  at  the  inner  portion  of  the 
plica  just  mentioned,  consists  of  a  collection  of  follicular  glands  with 
a  few  delicate  hairs  on  its  surface.  The  eye  is  kept  continually 
moist  by  a  thin,  watery  fluid  secreted  by  the  lachrymal  gland, 
which,  after  being  spread  over  the  globe  by  the  movement  of  the 
lids  and  of  the  eyeball,  passes  into  the  lachrymal  apparatus,  any 
overflow  upon  the  cheek,  constituting  the  tears,  being  prevented 
ordinarily  by  the  secreting  of  the  ]Meibomian  glands.  The  lach- 
rymal gland,  about  the  size  of  an  almond,  ovoid  in  form,  and  of  a 
racemose  type  of  structure,  is  situated  at  the  upper  and  outer  por- 
tion of  the  orbit.  It  presents  six  to  eight  ducts,  five  or  six  of 
which  open  above,  and  two  or  three  below  the  outer  canthus  of  the 
eye.  The  tears  consist  largely  of  water,  which  amounts  to  over  90 
per  cent.,  the  remaining  elements  being  made  up  of  small  quantities 
of  epithelium,  albumin,  sodium  chloride,  alkaline  and  earthy  phos- 
phates, mucus,  and  fat.  The  actual  amount  of  the  lachrymal  se- 
cretion has  not  been  determined.  Every  one  is  fiimiliar  with  the 
fact  that  the  secretion  of  tears  is  very  much  increased  by  emotion  ; 
hypersecretion  may  be  also  readily  induced  through  reflex  action 
by  irritation  of  the  conjunctiva,  nasal  mucous  membrane,  muscular 
effort,  laughing,  coughing,  and  sneezing,  the  efferent  nerves  Involved 
being  the  lachrymal  and  orbital  branches  of  the  fifth  nerve,  branches 
of  the  cervical  sympathetic  ;  the  afferent  nerves  varying  according 
to  the  exciting  cause.     The  lachrymal  apparatus,  through  which 


790       PROTECTIVE  APPENDAGES,  ETC.,   OF  THE  EYE. 

the  tears  usually  flow  into  the  nose,  begins  by  two  little  points  or 
orifices,  the  puncta  lachrymale  of  the  eyelids,  which  leads  into 
the  upper  and  lower  lachrymal  canals,  the  latter  surrounding  the 
caruncula  lachrymalis.  Just  beyond  the  caruncula  the  canals  unite 
and  pass  then  into  the  lachrymal  sac  or  the  upper  dilated  portion  of 
the  nasal  duct.  The  duct  being  about  half  an  inch  in  length,  fibrous 
in  structure,  and  lined  with  ciliated  epithelium,  empties  into  the 
inferior  meatus  of  the  nose.  Reflux  of  the  tears  from  the  nose  to 
the  eye  is  prevented  by  the  folds  of  mucous  membrane,  present  in 
the  lachrymal  canals,  and  at  the  opening  of  the  duct  into  the  nose, 
acting  as  valves,  the  latter  one  being,  in  this  respect,  much  more 
efficient  than  the  former. 


CHAPTER    XLI. 

PHYSIOLOGICAL   ACOUSTICS. 

Just  as  we  have  seen  that  in  order  to  understand  how  vision  is 
accomplished,  some  knowledge  of  optics  is  absolutely  essential,  so 
for  the  comprehension  of  the  manner  in  which  the  voice  is  produced 
and  sound  is  heard,  a  knowledge  of  acoustics  is  equally  indispen- 
sable. Similarly  as  in  the  case  of  vision,  attention  was  continually 
being  called  to  the  distinction  between  the  sensation  of  sight  and 
the  waves  of  light  giving  rise  to  it,  so  in  case  of  sound  the  sensation 
of  hearing  must  be  distinguished  from  the  waves  of  sound  giving 
rise  to  it,  for  what  constitutes  in  us  subjectively  hearing  is  out 
of  us  objectively  vibration.  Our  knowledge  of  sound  is  then 
like  that  of  light,  etc.,  of  all  knowledge,  only  relative,  depending 
upon  the  vibrations  and  the  extent  of  the  susceptibility  of  the  audi- 
tory apparatus  being  impressed  by  the  same.  Let  us  consider  first, 
then,  how  sound  is  produced  in  general,  and  more  especially  by  the 
larynx,  and  then  turn  to  the  consideration  of  how  it  is  appreciated 
by  the  brain,  through  the  ear  and  auditory  nerve.  The  sensation 
of  sound,  or  more  properly  of  musical  sound  as  contrasted  with 
mere  noise,  is  due,  as  we  shall  see  presently,  to  the  periodic  rhythmic 
vibratory  wave-like  oscillation  of  the  sounding  or  sonorous  body, 
being  transmitted  by  an  elastic  medium,  usually  the  air,  to  the  ear, 
noise  being  due  to  the  oscillations  being  transmitted  in  an  unperiodic, 
irregular  manner.  The  drawing  of  the  bow  across  the  strings  of  a 
violin  gives  rise  in  us  to  what  we  call  music,  the  shaking  of  a  box 
containing  nails,  chisels,  files,  etc.,  to  noise,  the  auditory  nerve  be- 
ing affected  in  the  one  case  by  oscillations  following  each  other  in  a 
regular,  orderly  sequence,  and  in  the  other  by  irregular,  disorderly 
oscillations  following  each  other  in  no  sequence  at  all.  The  effect 
of  noise  upon  the  ear  has  often  been  compared  to  that  of  flickering 
light  upon  the  eye,  the  painful  experience  in  both  cases  being  due 
to  the  sudden,  abrupt,  and  irregular  stimulation  of  the  auditory 
and  optic  nerves  respectively.  Nevertheless,  the  difference  be- 
tween noise  and  sound  is  not  an  absolute  one,  being  rather  one  of 
degree  than  of  kind,  as  shown  by  the  noise  due  to  the  rattling  of  a 
carriage  over  stones,  becoming  a  musical  sound  as  soon  as  the  oscil- 
lations become  rhythmical  and  regular  in  character.  Let  us  en- 
deavor to  explain  now,  by  a  few  simple  illustrations,  what  is  meant 
by  periodical  rhythmical  vibrations,  to  which  the  sensation  of  sound 
has  just  been  said  to  be  due.  Let  us  suppose,  for  example,  that  a 
number  of  persons  are  standing  in  a  row,  one  behind  the  other,  each 
individual's  hands  restins:  against  the  back  of  the  one  in  front  of 


792  PHYSIOLOGICAL  ACOUSTICS. 

liira,  and  that  the  individual  at  the  one  end  of  the  row  be  suddenly 
pushed  from  behind,  forward  against  the  individual  standing  in 
front  of  liim,  the  latter  in  turn  will  be  pushed  against  the  individual 
standing  in  front  of  liim,  and  so  through  the  whole  row  until  the 
last  individual  will  be  pushed  forward.  Further,  let  us  suppose 
that  the  push  be  not  very  violent,  and  that  the  individual  at  the 
one  end  of  the  row  first  pushed  forward  regains  his  erect  position, 
and  then  the  second  regains  his,  and  so  on  through  the  whole  row 
until  the  last  man  at  the  other  end  of  the  row  regains  his  position, 
it  is  evident  that  though  each  individual  person  may  have  swayed 
to  and  fro,  oscillated  pendulum-like  through  a  very  small  fractional 
part  of  the  distance  through  which  the  push  has  passed,  the  push 
itself  or  the  wave  may  have  been  transmitted  through  a  long  row 
of  individuals,  a  hundred  or  more.  Conceive  the  last  individual 
body,  the  last  individual  of  the  row,  to  be  the  tympanic  membrane 
of  the  ear,  the  intermediate  individuals  of  the  row,  laminae  of  air  or 
of  any  other  elastic  medium,  and  we  can  readily  picture  to  ourselves 
what  is  taking  place  in  the  air,  as  the  wave  giving  rise  to  the  sensa- 
tion of  sound  passes  from  the  sounding  body  to  the  ear.  The  condi- 
tions being  strictly  analogous  in  both  cases,  each  lamina  of  air  being 
pushed  forward  against  its  neighbor,  through  the  elasticity  of  the  air, 
after  giving  up  its  motion  to  the  next  lamina  will  recoil  again,  and 
just  as  in  the  case  of  the  individuals  in  the  row,  the  more  rapid  the 
to-and-fro  motion  of  the  laminte  of  the  air,  the  greater  the  velocity 
of  the  push  transmitted  through  the  row  and  of  the  sound  wave 
through  the  air.  On  account  of  the  importance  of  thoroughly  un- 
derstanding the  manner  in  which  the  sound  is  propagated  in  air, 
let  us  consider  a  little  more  particularly  the  case  in  which  it  is 
propagated  through  a  tube  of  indefinite  length.  Let  A  B  (Fig. 
476)  be  a  tube  filled  with  air,  the  temperature  and  pressure  being 


H 

G 

Fig.  476. 

F 

E           D 

C 

B 

1  P 

1    A 

To  illustrate  propagation  of  sound  in  air. 

constant,  and  let  us  suppose  that  P  be  a  piston,  oscillating  rapidly 
from  C  to  D,  then  as  the  piston  passes  from  C  to  D,  it  condenses  the 
air  in  the  tube,  the  condensation,  however,  not  extending  at  once 
throughout  the  whole  tube,  but  on  account  of  the  great  compressi- 
bility of  the  air  only  to  the  extent  D  E.  As  the  piston,  however, 
then  passes  from  D  back  to  C,  the  air  in  contact  with  its  anterior 
face  expands  and  becomes  rarefied,  and  by  the  time  that  the  piston 
reaches  C  the  air  has  become  rarefied  to  an  extent  (E  D)  exactly 
equal,  but  opposite  in  direction  to  that  of  the  previous  condensation 
(I)  E).     Supposing  the  tube  A  B  to  be  divided  into  equal  parts 


PROPAGATION  OF  SOUND  IN  AIR.  793 

(D  E,  E  F,  EG,  GH),  etc,  it  is  also  evident  that  by  the  time  the 
condensation  beginning  at  say  E  reaches  F,  due  to  the  forward 
movement  of  the  piston  from  C  D,  condensing  D  E,  that  the  rarefac- 
tion beginning  at  E  due  to  the  backward  motion  of  the  piston  from 
D  to  C  Avill  reach  D,  and  that  the  forward  condensation  p]  F  and 
backward  rarefaction  E  D  are  equal  and  opposite  in  direction. 
The  condensed  and  rarefied  laminte  of  air  {Y,  F,  E  D),  so  produced 
during  the  forward  and  backward  movements  of  the  piston,  consti- 
tute a  wave,  a  vibration,  an  undulation,  just  as  the  to-and-fro 
motion  of  a  pendulum  constitutes  a  vibration,  the  length  of  the 
sonorous  wave  or  vibration  being  the  distance  traversed  by  the 
sound  during  the  complete  vibration,  or  to-and-fro  movement  of 
the  vibrating  body  causing  it.  In  France,  however,  a  vibration  is 
considered  as  being  either  the  to  or  fro  movement,  not  both,  that  is  to 
say,  each  English  vibration  is  equal  to  two  French  ones.  By  a  vibra- 
tion we  shall  always  mean  the  double  vibration  e({ual  to  two  single 
French  ones.  That  is  to  say,  as  the  piston  passes  from  C  to  D,  the 
sound  travels  from  D  to  E,  and  as  the  piston  passes  back  from  D 
to  C,  the  sound  passes  on  from  E  to  F.  It  need  hardly  be  added 
that  the  length  of  the  undulations  will  be  less  in  proportion  to  the 
rapidity  with  which  they  follow  each  other,  and  that  though  the  to- 
and-fro  movements  of  the  individual  particles  of  the  air  giving  rise 
to  the  condensations  and  rarefactions  may  be  very  slight,  and  the 
undulations  long  or  short,  few  or  many  in  a  given  time,  the  sound 
wave  itself  may  be  transmitted  to  a  great  distance. 

Such  being  the  manner  in  which  a  sound  wave  is  propagated  in 
a  cylindrical  tube,  there  will  be  no  difficulty  in  comprehending  how 
sound  waves  are  propagated  in  an  uninclosed  medium,  if  we  only 
conceive  each  molecule  of  the  vibrating  body  as  acting  as  the  pis- 
ton in  the  tube,  a  series  of  waves  alternately  condensed  and  rare- 
fied being  then  generated  around  each  center  of  vibration,  the  sound 
radiating  in  all  directions,  like  the  waves  of  water  spreading  out 
upon  the  surface  from  some  point  of  disturbance — the  intensity  of 
the  same  gradually,  therefore,  in  both  instances  diminishing.  That 
sounding  bodies  are  actually  vibrating  can  be  readily  demonstrated. 
In  the  case  of  strings  it  is  a  mere  matter  of  observation,  the  vibra- 
tions being  so  apparent  as  to  be  visible  to  the  naked  eye.  It  will 
be  remembered,  also,  that  we  maide  use  of  the  traces  due  to  the  vi- 
bration of  a  reed  or  tuning  fork  to  determine  small  intervals  of 
time,  and,  indeed,  by  such  graphic  methods  we  are  accustomed  to 
test  the  accuracy  of  our  standard  tuning  forks.  Apart,  also,  from 
the  thrill  experienced  when  a  sounding  bell  is  touched,  its  vibra- 
tions are  made  visible  indirectly  at  least  by  the  brisk  to-and-fro 
movement  of  pith  balls  placed  in  contact  with  it.  The  vibrations 
of  a  sounding  glass  plate  can  also  be  rendered  visible,  as  first  shown 
by  the  celebrated  Chladni  ^  by  sprinkling  sand  upon  its  surface,  the 
sand  only  remaining  at  rest  upon  the  part  of  the  plate  not  in  vibra- 

iDie  Akustik,  Leipzig,  1802,  s.  xvi. 


794  PHYSIOLOGICAL  ACOUSTICS. 

tion,  and  disposing  itself  in  characteristic  lines  according  to  the 
shape  of  the  plate  and  the  character  of  the  sound.  It  has  already 
been  mentioned  that  the  vibrations  of  sonorous  bodies  can  only  give 
rise  to  the  sensation  of  sound  in  us  by  the  intervention  of  an  elas- 
tic medium  interposed  between  the  ear  and  the  vibrating  body,  and 
vibrating  with  the  latter.  While  this  medium  is  usually  the  air, 
the  waves  of  sound  are  also  transmitted  through  gases,  vaporous 
liquids,  and  solids.  A  diver  at  the  bottom  of  the  water  can  hear 
the  sound  of  voices  on  the  bank  ;  the  scratching  of  a  pen  at  one 
end  of  a  piece  of  wood  is  heard  at  the  other  end  ;  while  the  earth 
conducts  sound  so  well  that  if  at  night  the  ear  be  placed  upon  the 
ground  the  steps  of  horses  or  other  sounds  or  noise  can  be  heard 
at  a  great  distance  off.  That  the  waves  of  sound  are  not  propa- 
gated in  vacuo,  as  first  shown  by  Hawksbee,^  can  be  very  easily 
demonstrated  by  means  of  an  apparatus  which  consists  of  an  air- 
pump  and  receiver  standing  upon  wadding,  and  a  bell,  the  hammer 
of  which  is  made  to  strike  by  clock-work  set  going  by  the  raising 
of  a  detent  passing  through  the  top  of  the  receiver.  The  bell,  etc., 
having  been  placed  within  the  receiver,  the  air  from  the  latter  ex- 
hausted by  the  pump,  and  the  hammer  made  to  strike,  no  appreci- 
able sound  will  be  heard  until  the  air  is  allowed  to  pass  into  the 
receiver.  By  allowing  hydrogen  gas,  which  is  fourteen  times  lighter 
than  air,  to  pass  into  the  receiver,  and  by  which  the  air  is  rendered 
very  much  more  attenuated,  such  a  perfect  vacuum  is  obtained  that 
not  the  slightest  sound  is  heard,  even  though  the  ear  be  placed 
against  the  bell  itself.  The  experiment  just  described  is  not  only  a 
very  striking  one,  as  proving  that  sound  is  not  transmitted  in  vacuo, 
or  a  very  attenuated  atmosphere,  but  it  illustrates  the  difference 
between  the  cause  of  sound  and  the  sensation  of  sound,  since,  though 
the  hammer  may  be  seen  striking  the  bell  and  causing  it  to  vibrate, 
no  sound  is  heard  as  long  as  the  vacuum  is  maintained,  there  being 
no  intermediate  medium  to  transmit  the  vibrations  of  the  bell  to  the 
ear.  Sounds,  however  produced,  whether  by  strings,  reeds,  tuning 
forks,  bells,  plates,  etc.,  are  distinguished  by  their  intensity,  pitch, 
and  quality,  and  as  these  differences  in  the  character  of  sounds  must 
be  thoroughly  appreciated  in  order  to  understand  how  the  voice  is 
produced,  and  sounds  are  heard,  let  us  endeavor,  therefore,  to  explain 
them  now  a  little  in  detail. 

Intensity  of  Sound. 

By  the  intensity  of  sound  is  meant  the  loudness  of  sound.  We 
hear  one  sound  louder  than  others  because  the  particles  of  air  set  in 
motion  by  the  sounding  body  strike  the  tymj^anic  membrane  of  the 
ear  harder  in  the  one  case  than  another.  Just  as  the  force  with 
which  a  ball  strikes  a  target  can  be  shown  on  mechanical  principles 
to  be  proportional  to  its  weight  and  the  square  of  the  velocity  with 
Mhich  it  is  moving,  so  the  force  with  which  the  air  particles  strike 
'Phil.  Trans.,  Vol.  xxiv.,  p.  100-4. 


INTENSITY  OF  SOUND.  795 

the  tympanic  membrane  can  be  shown  to  be  proportional  to  the 
square  of  the  maximum  velocity  with  which  it  is  moving.  The 
intensity  of  a  sound  depends,  however,  on  the  density  of  the  air  in 
which  the  sound  is  generated,  and  not  on  that  of  the  air  in  which 
it  is  heard.  Thus,  while  a  cannon  fired  in  a  valley  may  be  heard 
at  the  top  of  a  high  mountain  above,  the  same  cannon  fired  at  the 
top  of  the  mountain  will  not  be  heard  in  the  valley  below,  the  sound 
generated  in  the  dense  air  of  the  valley  being  louder  than  that  gen- 
erated in  the  rare  air  on  the  top  of  the  mountain.  The  intensity 
of  the  sound  is  also  proportional  to  the  square  of  the  amplitude  of 
the  vibration,  the  amplitude  being  the  width  of  swing,  the  distance 
through  which  the  air  particle  moves  to  and  fro  when  the  sound 
wave  passes  it. 

That  such  is  the  case  can  be  readily  shown  by  means  of  vibrat- 
ing cords  ;  for  if  the  latter  are  long,  the  oscillations  being  visible 
to  the  eye,  it  will  be  seen  that  the  sound  becomes  feebler  in  propor- 
tion as  the  amplitude  of  the  oscillation  decreases.     The  intensity 
of  sound  is  modified  by  the  distance  of  the  sonorous  body  from  the 
ear,  varying  inversely  as  the  square  of  the  distance  ;  that  is  to  say, 
for  example,  the  intensity  of  the  sound  of  a  bell,  situated  at  a  dis- 
tance of  20  yards  from  the  ear,  would  be  only  one-fourth  of  the 
intensity  of  the  same  bell  if  situated  at  10  yards  from  the  ear,  or 
half  the  distance ;  or  what  is  the  same  thing,  the  intensity  of  four 
bells,  situated  at  a  distance  of  20  yards,  is  the  same  as  that  of  one 
bell  situated  at  a  distance  of  10  yards  from  the  ear,  supposing,  of 
course,  that  the  bells  are  all  of  the  same  size,  and  other  conditions 
equal.     That  the  intensity  of  the  sound  must  diminish  in  the  above 
ratio — that  is,  as  the  square  of  the  distance — will  become  evident 
when  it  is   borne  in  mind  that,  as  the  spherical  Avaves  of  sound 
radiate  outward  from  the  center  of  disturbance  toward  the  periph- 
ery, the  mass  of  air  set  in  motion  must  be  continually  augmented 
as' the  squares  of  the  distance  from  the  center,  the  areas  of  circles 
being  to  each  other  as  the  squares  of  their  radii.     The  matter 
affected  increasing  then  as  the  square  of  the  distance,  the  intensity 
of  the  sound  must  diminish  in  the  same  ratio.     If,  however,  the 
wave  of  sound  be  propagated  in  a  tube,  lateral  diffusion  being  pre- 
vented, as  in  Fig.  47(5,  then  the  sound  can  be  transmitted  through 
great  distances  with  very  little  diminution  in  intensity  ;  thus  Biot 
found  that  a  person  whispering  at  one  end  of  one  of  the  empty 
water-pipes  of  Paris,  a  tube  3,120  feet  in  length,  could  be  heard  at 
the  other  end,  and  that  the  firing  of  a  pistol  at  one  end  of  the  tube 
put  out  a  lighted  candle  at  the  other.     The  intensity  of  sound  is 
modified   by  the  condition  of  the   atmosphere,  sound  being  better 
propagated'in  calm  than  in  windy  weather  ;  in  the  latter  case,  how- 
ever, sound  is  better  heard  when  transmitted  in  the  direction  of  the 
wind   than  in   the   opposite   direction.     Finally,  the   intensity  of 
sound  is  very  much  increased  by  the  proximity  of  a  sonorous  body. 
Hence,  the  association  of  sounding-boxes  with  strings,  as  in  the  case 


790 


PHYSIOLOGICAL  A  CO  USTICS. 


of  the  violin,  guitar,  etc.,  the  increase  in  the  loudness  of  the  sound 
being  then  due  to  the  fact  that  the  box  and  air  Avithin  it  vil^rate 
in  unison  with  the  strings  as  we  shall  endeavor  presently  to  explain. 
The  distance  at  which  sounds  are  heard,  depending  upon  their  in- 
tensity, may  be  very  great ;  thus,  it  is  said  that  the  report  of  the 
volcano  at  St.  Vincent  was  heard  at  Domerara,  300  miles  oflP,  and 
the  firine;  at  Waterloo  at  Dover.' 


Pitch  of  Sound. 

Sounds  are  distinguished,  as  already  mentioned,  not  only  by  their 
intensity  or  loudness,  but  by  their  pitch  or  height.  The  pitch  of  a 
sound  can  be  shown  to  depend  upon  the  number  of  vibrations  made 
by  a  sounding  body  in  a  given  time — a  second,  for  example — 
sounds  of  low  pitch  being  due  to  the  aerial  vibrations  impinging 
upon  the  tympanic  membrane  following  each  other  slowly,  those  of 
high  pitch  to  the  aerial  vibrations  following  each  other  rapidly. 
Thus,  for  example,  the  pitch  of  the  sound  of  a  string  four  feet  in 
length,  sufficiently  tensed,  and  of  a  given  density  and  thickness 
vibrating    128   times  in  a  second    (Do",Ut^,  C^  of   piano),  is  low 

as  compared  with  that  of  one  two  feet  in  length,  vibrat-     ^ 

ing  256  times  in  a  second  (Do^,Ut^,C^),  or  an  octavo  Fg^zEiq3 
.'e.^     In  the  same  way,  the  pitch  of  the  sound  of  ^r     ^i^ 


abov 


an  organ-pipe  four  feet  in  length  due  to  128  vibrations  per  second 
(Do^t-)  is  low  as  compared  with  that  of  the  sound  of  one  two 


Fig.  47 


Fig.  47i 


Vibration  of  string. 

feet  in  length,  due  to  256  vibrations  per  second  (Do^Ut^) 
or  the  octave  above.  It  may  be  mentioned  in  this  con- 
nection that,  while  in  the  case  of  the  string  it  is  the  "^ 
vibrations  of  the  latter  (Fig.  477)  that  give  rise  to  the  '"^''""^'p''- 
aerial  vibrations  affecting  the  auditory  apparatus,  in  the  case  of 
the  organ-pipe  it  is  to  the  vibrations  of  the  enclosed  column  of 
air  that  the  aerial  vibrations  are  due,  as  the  current  of  air  forced 
by  the  bellows  through  the  mouth  P  B  of  Fig.  478  of  the  pipe 
in  striking  against  the  upper  bevelled  lip  B,  produces  a  shock,  the 
air  issues  from  the  eml)ouchure  or  space  between  the  lips  in  an 
intermittent  manner,  the  pulsations  so  produced  in  being  trans- 
mitted to  the  air  enclosed  within  the  ]Mpe  in  turn  .set  it  into  vibra- 
tion, which  causes  the  sound.     It  will  l:)e  observed,  also,  as  might 

Kianot,  Physios,  Trans,  by  Atkinson,  p.  175.     London,  1870. 

2  If  the  5th  A  of  the  piano  he  turned  to  vibrate  440  vibrations  per  second,  in- 
stead of  426  times  a.s  a.ssumed  in  text,  then  the  middle  C  or  Ut='  will  vibrate  264 
times,  and  the  lowest  C  33  times  per  second. 


PITCH  OF  SOUND. 


797 


Fig.  479. 


have  been  anticipated  on  mechanical  principles,  that  the  number  of 
vibrations,  both  in  the  case  of  the  strin*.::  and  pipe,  are  inversely 
as  the  length,  the  number  of  vibrations  in  both  eases  being  doubled 
by  having  the  lengths,  since,  in  the  latter  case,  the  amount  of  work 
to  be  done  being  one-half,  it  can  be  done  in  half  the  time,  or  double 
the  work  can  be  done  in  the  same 
time.  The  distinction  between  in- 
tensity or  loudness  and  pitch  or 
height  must  be  carefully  borne  in 
mind,  being,  as  just  shown,  due  to 
entirely  diiferent  causes  ;  a  sound, 
therefore,  may  be  a  loud  one,  and 
yet  be  low  in  pitch  ;  and,  on  the 
other  hand,  a  sound  may  not  be  a 
loud  one,  and  yet  be  high  in  pitch. 
In  sounding;  the  long;  stringy  and 
long  organ-pipe,  apart  from  the 
intensity  of  the  sound,  and  from 
the  pitch  of  the  note  Do-Ut",  128 
vibrations  per  second,  the  same, 
therefore,  in  both  cases,  another 
and  very  marked  difference  is  ap- 
preciable, and  that  by  not  especi- 
ally musical  ears,  viz.,  the  character 
or  quality  of  the  sound.  Before 
considering,  however,  the  quality 
of  sound,  or  that  in  which  the 
sound  of  a  violin,  for  example, 
differs  from  that  of  a  piano,  and 
the  sound  of  the  latter  from  the 
sound  of  the  organ-pipe,  or,  in  general,  that  which  distinguished 
the  sounds  of  different  kinds  of  musical  instruments,  let  us  first 
endeavor  to  explain  how,  by  means  of  the  siren,  we  are  able 
to  determine  the  number  of  vibrations  to  which  the  pitch  of  a 
sound  is  due.  The  siren — so  called  on  account  of  its  emitting 
sounds  when  under  water  in  its  original  form  as  invented  by 
Cagniard  de  la  Tour — is  a  much  more  simple  instrument  than 
that  we  shall  make  use  of,  or  the  double  siren  of  Helmholtz 
(Fig.  479).  The  principle  upon  which  both  instruments  are  con- 
structed is,  however,  the  same,  since  the  siren  of  Helmlioltz  con- 
sists of  two  Dove  sirens,  the  Dove  .siren  in  turn  differing  from  that 
of  Cagniard  de  la  Tour  (Fig.  481)  in  being  provided  with  four 
series  of  orifices  instead  of  one.  Such  being  the  case,  let  us  begin 
our  description  of  a  double  siren  with  that  of  a  single  Dove  siren. 
Suppose,  for  example,  that  the  lower  Dove  siren  (Fig.  479)  be 
taken  apart,  it  will  he  seen  that  the  tube  B  leads  into  the  brass 
cylinder  C,  the  top  of  which  is  closed  by  a  brass  2)late,  perforated 
with   four   series  of  holes  disposed   concentrically,  the   outermost 


Helmholtz's  double  siren. 


798 


PHYSIOLOGICAL  ACOUSTICS. 


series  containing  16,  the  next  12,  the  next  10,  the  next  8  orifices, 
the  latter  being  opened  or  closed,  respectively,  by  pressing  in  or 
pulling  out  the  keys  numbered  correspondingly.  It  will  also  be 
seen  that  the  brass  disk,  receiving  in  its  center  the  steel  axis  x,  is 


Fig.  481. 


Siren  of  Cagniard  de  la  Tour. 


Showing  oblique  opening  in  siren 
of  C'agniard  de  la  Tour. 


also  perforated  with  16,  12,  10,  and 
8  orifices,  disposed  concentrically  at 
the  same  distance  from  the  center, 
and  with  the  same  intervals  between 
them  as  those  on  the  top  of  the 
cylinder  C,  the  only  difference  be- 
tween the  two  sets  being  that  those  passing  through  tlie  top  of  the 
cylinder  C,  while  oblique  in  direction  (Fig.  480),  arc  oppositely 
inclined  to  those  passing  also  obliquely  through  the  brass  disk. 

The  two  sets  of  orifices  being  so  disposed  to  each  other  if  air  be 
forced  by  a  pair  of  bellows  through  the  tube  B  into  the  cylinder  C, 
the  air  will  issue  from  the  latter  not  vertically  but  in  side  currents, 
which  in  impinging  against  the  sides  of  the  orifices  of  the  disk  will 
drive  the  disk  around  the  axis  .v,  held  upright  by  means  of  a  steel 
cap  brought  down  on  its  upper  end.  As  the  disk  turns  around,  its 
orifices,  coming  alternately  over  the  orifice  of  the  cylinder  C  and 
over  the  intervening  spaces,  the  continuous  current  of  air  passing 
through  the  cylinder  C  is  carved  into  discontinuous  puffs,  which  at 
first  follow  each  other  so  slowly  that  they  may  be  counted.  As  the 
motion  of  the  disk,  however,  increases  the  puffs  of  air  succeed  each 
other  so  rapidly  that  the  air  links  them  together  as  continuous  mu- 
sical notes,  whose  pitch  can  then  be  at  once  shown  to  depend  upon 
the  number  of  puffs  of  air  or  vibrations,  by  simply  increasing  or 
diminishing  the  rapidity  of  the  rotation  of  the  disk,  the  pitch  of  the 
note  rising  or  falling  accordingly.  In  order,  however,  to  determine 
the  number  of  puffs  issuing  from  the  orifices  in  a  given  time,  a  sec- 
ond, for  example,  they  must  be  recorded.  This  is  accomplished  by 
providing  the  axis  x  at  its  upper  part  with  a  screw  .s>  (Fig.  482) 
which  works  into  a  pair  of  toothed  wheels,  the  latter  rotating  as  the 
disk  and  its  axis  turn,  the  number  of  rotations  being  indicated  by 


PITCH  OF  SOUND.  799 

the  hands  on  the  dial  plates  (omitted  in  Fig.  479,  but  represented 
in  Fig.  481),  the  hand  of  one  dial  plate  making  an  entire  revo- 
lution while  that  of  the  other  passes  over  but  one  division  of  the 
graduated  circumference.  The  process  of  recording  can  be  started 
or  stopped  by  simply  pushing  a  button,  which  throws  the  wheel- 
work  just  mentioned  into  or  out  of  action.  In  order,  now,  to 
show  how  by  means  of  the  siren  we  determine  that  the  note  Do\ 
emitted  by  the  string  or  organ-pipe  two  feet  long,  is  due  to  the  vi- 
brations following  each  other  at  the  rate  of  25(3  vibrations  a  second, 
we  force  the  air  from  the  bellows  through  the  cylinder  C,  the  outer- 
most series  of  1 6  orifices  being  open  until  the  disk  rotates  so  rapidly 
that  the  sound  produced  by  the  siren  is  in  unison  with  that  emitted 
by  the  string  or  organ-pipe  soiuided  at  the  same  time.  The  sound 
of  the  siren  and  the  string  or  pipe  being  then  in  perfect  unison,  we 
push  the  button  and  so  set  going  the  recording  mechanism  and  let 
the  siren  sing  for  just  one  minute,  then  instantly  stopping  the  record- 
ing, we  observe  by  the  hands  of  the  dial  plate  the  number  of  rota- 
tions the  disk  d  e  has  made  in  that  time.  It  will  be  found  that  the 
niunber  is  just  960  ;  dividing  this  by  60  the  quotient,  or  16,  will  be 
the  nimiber  of  times  that  the  disk  has  rotated  in  one  second,  but  since 
16  orifices  were  open  in  one  rotation  of  the  disk  16  puffs  of  air 
issued  in  succession  from  the  siren,  and  consequently  during  16 
rotations  256  puffs  of  air.  As  the  note  Do'^,  produced  by  the 
siren  was  due  to  the  number  of  puffs  or  vibrations  of  air,  and  as  the 
note  of  the  siren  was  in  unison  with  that  due  to  the  sounding  of 
the  string  or  pipe,  the  latter,  or  Do\  must  be  also  due  to  the  same 
number  of  vibrations,  viz.,  256  vibrations  per  second.  It  will  be 
remembered  that  while  the  outermost  series  of  orifices,  those  whicli 
in  the  preceding  experiment  Avere  supposed  to  be  open,  are  16  in 
number,  the  innermost  series  of  orifices  are  only  8  in  number.  If 
the  latter  now  be  opened  as  well  as  the  former  by  pushing  in  the  key 
numbered  8,  then  two  sounds  will  be  simultaneously  emitted  by  the 
siren,  one  of  which,  Do\  is  due,  as  before,  to  the  rate  of  vibration 
being  256  per  second,  the  other  Do"  an  octave  below,  the  rate  being 
just  half,  or  128  vibrations  per  second,  the  air  issuing  from  8  orifices 
during  one  rotation  of  the  disk,  instead  of  from  16,  as  in  the  former 
case.  The  innermost  and  outermost  series  of  orifices  being  open, 
then  the  rate  of  vibration  of  the  two  sounds  is  as  1  to  2.  From 
what  has  just  been  said,  it  is  evident,  without  further  explanation, 
that  if  the  innermost  series  of  8  orifices  and  the  next  series  to  it  of 
10  orifices  be  open,  then  the  rate  of  vibration  will  be  as  4  to  5 — 
that  is  to  say,  of  the  two  notes  produced  by  the  siren  simultaneously, 
if  one  be  Do',  due  to  128  vibrations  per  second,  the  other  note  will 
be  Mi-  E-,  due  to  160  vibrations  per  second,  and  if  the  innermost 
series  of  8  orifices  and  the  third  series  from  within  outward,  that  of 
12  orifices,  be  both  open,  then  the  rate  of  vibration  of  the  two 
sounds  will  be  as  2  to  3 — that  is,  if  Do-  be  one  of  the  two  notes 
heard  simultaneously  the  other  note  will  be  SoP  G"',  due  to  192  vi- 


800  PHYSIOLOGICAL  ACOUSTICS. 

bratious  per  second.  It  follows,  therefore,  that  if  the  three  inner- 
most series  of  orifices,  8,  10,  and  12,  be  open  we  will  obtain  the 
major  chord  C"  E-  G^,  Do^  Mi"  SoP,  and  if  in  addition  at  the  same 
time  the  outermost  series  of  1(3  orifices  be  open  C^  E^  G^  C^,  which, 
as  produced  by  the  siren,  is  quite  musical.  The  construction  and 
manner  of  using  a  single  Dove  siren  being  now  understood,  there 
will  be  no  difficulty  in  comprehending  that  of  Helmholtz,  it  con- 
sisting, as  already  mentioned,  of  two  Dove  sirens.  It  must  be  men- 
tioned, however,  that  the  outermost  series  of  orifices  in  the  lower  of 
the  two  sirens  are  18  in  number  instead  of  16,  as  in  the  single  Dove 
siren  we  have  just  described,  and  that  the  orifices  in  the  four  series 
of  the  upper  siren  are  respectively  9,  12,  15,  and  16  in  number. 
If,  therefore,  we  w^ish  to  obtain  by  the  double  siren  the  major  chord 
C"  E-  G^  and  C^  at  the  same  time,  the  series  of  orifices  8,  10  and  12 
must  be  opened  in  the  lower  siren,  and  the  series  of  16  orifices  of 
the  upper  siren,  the  air  being  allowed,  of  course,  to  pass  from  the 
bellows  through  both  sirens,  the  number  of  rotations  of  the  disks 
being  recorded  in  the  same  manner  as  already  described  by  wheel- 
work  attached  to  the  axis  common  to  the  two  sirens,  and  omitted 
for  simplicity  in  Fig.  479.  It  will  be  observed  that  the  double 
siren  is  provided  with  resonance  boxes  the  half  of  each  of  which 
has  been  removed  in  the  figure,  which  greatly  intensifies  the  funda- 
mental sound.  The  upper  siren  is  also  connected  with  a  toothed 
Avheel  and  pinion  turned  by  a  handle,  by  which  we  are  enal^led  to 
rotate  the  cylinder  of  the  upper  siren  as  well  as  the  disk,  the  handle, 
etc.,  being  so  disposed  that  if  it  be  turned  to  the  right  the  orifices 
in  the  cylinder  and  in  the  disk  will  then  pass  over  each  other  more 
quickly  than  if  the  cylinder  was  at  rest,  and  if  in  the  reverse  direc- 
tion more  slowly,  the  pitch  rising  in  the  one  case,  the  puffs  suc- 
ceeding each  other  then  more  rapidly,  and  falling  in  the  other,  fol- 
loAving  more  slowly.  The  use  of  the  dial  and  index  underneath 
the  handle  will  be  illustrated  hereafter.  It  is  needless  to  say  that 
by  doubling  all  parts  of  the  siren,  etc.,  as  done  by  Helmholtz,^  that 
many  varied  combinations  can  be  introduced,  and  that  the  general 
usefulness  of  the  instrument  has  thereby  been  greatly  increased. 

Quality  of  Sound. 

Every  fundamental  tone,  whether  produced  by  a  string,  column  of 
air,  reed,  etc. — that  is,  a  sound  due  to  the  string,  for  example,  vibrat- 
ing through  the  whole  of  its  length  (Fig.  477),  may  be  accompanied 
by  partial  tones  or  overtones  ^  due  to  the  string  vibrating  through 
the  half,  third,  fourth,  etc.,  of  its  length  (Fig.  482,  (2),  (4),  (6)), 
and  since  the  overtones,  accompanying  and  reinforcing  the  funda- 
mental tone,  due  to  the  sounding  of  the  string  of  one  instrument, 

1  On  the  Sensation  of  Tone,  transl.  by  A.  ,T.  Ellis,  p.  245.     London,  1875. 

^By  the  1st,  2d,  and  3d  overtones,  etc.,  will  be  meant  in  this  chapter,  tones  due 
to  vibrations  wliose  rates  are  twice,  three,  or  four  times  as  rapid  as  that  of  the  fun- 
damental tone. 


QUALITY  OF  SOUND. 


801 


are  not  the  same  as  those  of  another,  or  if  in  part  tlie  same,  are  then 
more  or  less  accentnated,  there  arises  in  consequence  a  difference  in 
the  character  of  the  sound  as  produced  by  the  two  instruments, 
very  appreciable,  even  by  unmusical  ears,  which  is  called  their 
quality.  Thus,  for  example,  the  sound  of  the  string  of  a  violin  may 
be  as  loud  as  that  of  the  piano,  or  of  that  of  the  vibratino;  column 
of  air  of  the  organ-pipe,  or  of  that  of  the  vibrating  reed  of  the  oboe, 
the  pitch  of  the  particular  note  emitted  by  the  four  instruments  may 
be  the  same,  the  number  of  vibrations  per  second  to  which  the  note 


Fk;.  482. 


Fig.  483. 


a        a       a       a 


(1)      (2)     (3)     (4)     (5)     (6) 


(1)     (2)     (3)     (4) 


Formation  of  nodes  and  ventral  segments.     (Tyn'dall.  )        Vibrations  of  tube.     (Tyxdall.  ) 

is  due  being  equal  in  all  four  instances,  and  yet  no  one  fails  to  ap- 
preciate the  difference  in  the  character  or  the  quality  of  the  sound, 
the  overtones  reinforcing  the  fundamental  note  being  different  in 
each  instance.  Inasmuch,  however,  as  the  thorough  understanding 
of  the  conditions,  upon  which  the  quality  of  soimd  depends  is  not 
only  important,  but  absolutely  essential,  in  comprehending  the  man- 
ner in  which  the  vowels  are  produced  by  the  larynx,  for  example, 
let  us  endeavor  to  explain  a  little  more  in  detail  how  these  partial 
vibrations,  to  which  the  overtones  are  due,  come  to  be  superim- 
po.sed  upon  the  fundamental  one,  and  how  their  presence  can  be  de- 
tected. Let  c  a  (Fig.  483)  represent  a  long  India-rubber  tube 
fixed  at  the  one  end,  and  free  at  the  other.  By  takiug  hold  of  the  free 
51 


802  PHYSIOLOGICAL  ACOUSTICS. 

end,  stretching  the  tube  a  little,  and  properly  timing  the  impulses, 
the  tube  can  be  made  to  swing  to  and  fro,  to  vibrate  as  a  whole,  as 
represented  in  Fig.  477.  Stop  the  motion,  and  now,  by  a  jerk, 
raise  a  hump  upon  the  tube,  the  hump  will  be  observed  to  run 
along  the  tube  a  b,  h  c  (Fig.  483,  (1),  (2)),  and  having  reached  the 
fixed  end  of  the  tube  c,  will  then  run  back  again,  but  in  the  re- 
verse direction.  But  just  as  the  latter  c  b  (3)  starts  at  c,  let  the 
tube  be  jerked  again,  so  as  to  start  the  hump  a  b  (3)  at  a,  then  by 
the  time  that  the  foremost  part  of  the  hump  beginning  at  c  arrives 
at  b,  that  beginning  at  a  will  also  have  reached  b,  the  effect  of  which 
M'ill  be  that  the  point  b  will  remain  at  rest.  For  the  hump  a  b  (3) 
in  moving  on  to  c  must  tend  to  move  the  point  b  to  the  right,  and  the 
hump  c  b  moving  on  to  a  must  tend  to  move  the  point  b  to  the  left, 
the  consequence  of  which  is,  that  the  point  b,  in  being  acted  upon 
by  equal  and  opposite  forces,  Avill  not  move  at  all.  Such  being  the 
case,  the  two  halves,  ab,  be  of  the  tube  b  c,  will  vibrate  as  if  they 
were  independent  of  each  other  (Fig.  483  (4)).  The  point  b  at  rest 
is  known  as  the  node,  the  vibrating  parts  a  b,  b  e  as  the  ventral 
segments,  twice  the  length  of  a  ventral  segment  constituting  a  wave, 
the  latter  being  made  up  by  both  the  hump  and  the  depression  follow- 
ing the  same.  By  experimenting  a  little,  it  will  be  soon  found  that 
the  tube  a  c  (Fig.  482)  can  be  so  swung  as  to  form  two  nodes  with 
three  ventral  segments  (4),  or  three  nodes  with  four  ventral  seg- 
ments (Fig.  482^  (6)),  and  so  on,  the  tube  vibrating  in  thirds, 
fourths,  etc.,  of  its  length,  and  a  little  reflection  will  make  it  clear 
that  the  cause  of  the  formation  of  the  nodes,  or  points  of  rest,  and 
of  the  string  in  consequence  vibrating  in  its  aliquot  parts,  is  pre- 
cisely the  same  as  that  just  given  in  the  case  of  the  formation  of 
one  node  and  two  ventral  segments.  Let  us  now  modify  the  pre- 
ceding experiment  slightly  by  encircling  the  tube  a  c  at  its  cen- 
ter (Fig.  482,  (1))  with  the  thumb  and  forefinger  of  one  hand, 
and,  taking  hold  of  the  middle  of  the  lower  lialf  of  the  tube  a  b  with 
the  other  hand,  pull  it  aside.  It  will  be  observed  that  one  node  is 
formed,  and  two  ventral  or  vibrating  segments  (2),  the  upper  halt 
of  the  tube  vibrating  as  well  as  the  lower.  Experimenting  in  this 
way,  but  encircling,  however,  the  tube  at  one-third  (3)  or  one-fourth 
(5)  of  its  length,  and  pulling  the  lower  third  (3)  or  lower  fourth  (5) 
of  the  tube  away  by  seizing  them,  respectively,  at  their  centers,  the 
tubes  will  be  oscillated,  so  that  two  nodes  with  three  ventral  seg- 
ments (4).  or  three  nodes  with  four  ventral  segments  (6),  Avill  be 
formed,  as  the  case  may  be,  the  vibrations  of  the  string  through  the 
space  encircled  by  the  thumb  and  finger,  a  distance  of  one  inch, 
acting  upon  the  upper  part  of  the  tube  exactly  as  the  hand  acted 
when  it  caused  the  tube  to  SAving  as  a  whole.  In  precisely  the  same 
manner,  by  placing  a  feather  (Fig.  484)  upon  the  center  of  the 
stretched  violin-string,  just  as  we  encircled  the  tube  with  the 
thumb  and  finger,  and  drawing  a  bow  across  the  center  of  the 
half  of  the  string  instead  of  pulling  it  aside  with  one  hand,  the 


FORMA  TIOX  OF  SODFS. 


803 


string  will  bo  made  to  vibrate  in  halves,  as  shown  by  the  little 
paper  rider  being-  thrown  off.  Similarly,  by  touching  the  string 
with  a  feather  at  a  third  (Fig.  485),  or  a  fourth  (Fig.  486)  of  its 


Fig.  484. 


Formatiiiu  of  one  node  and  two  ventral  segmeuts.     (Tyndall.) 

length,  and  drawing  the  bow  across  the  center  of  the  right  hand  third 
or  fourth  of  the  string  the  string  will  vibrate  in  thirds  or  fourths, 
two  nodes  with  three  ventral  segments,  or  three  nodes  with  four 

Fig.  485. 


Formation  of  two  nodes  and  three  ventral  segments.     (Tyndall.) 

ventral  segments  being  formed,  as  shown  by  the  two  or  three  red 
paper  riders  placed  upon  the  vibrating  parts  being  tossed  off,  and 
the  one  or  two  blue  ones  remainino;  on  the  string  being  situated 


Fig.  480. 


Formation  of  tliree  nodes  and  two  ventral  segments.     (Tyndall.) 

at  the  nodes,  or  points  of  rest.  A  beautiful  way  of  demonstrat- 
ing the  presence  of  nodes  and  ventral  segments  made  use  of  by 
the   author    in   addressing  a  larije  audience,  is  to  place   a   string 


804 


PHYSIOLOGICAL  A  CO  USTICS. 


connected  at  one  end  with  the  prong  of  a  tuning  fork,  and  at  the 
other  with  a  peg,  by  Avhich  it  can  be  loosened  or  tightened  in  front 
of  the  calcium  light  lantern,  an  appearance  such  as  that  represented 
in  Fig.  487  being  presented  when  the  fork  is  sounded,  according 


Fic.  487. 


Nodes  aud  segmeuts  of  a  vibratory  string  as  shown  by  lantern. 

to  the  extent  to  which  the  string  is  tensed.  While  the  string  may 
vibrate  as  a  whole,  or  in  halves,  thirds,  fourths,  fifths,  etc.,  sepa- 
rately, as  we  have  just  shown,  as  a  matter  of  fact,  the  string  usually 
in  vibrating  breaks  up,  so  to  speak,  into  its  aliquot  parts,  the  su- 
}>erimposing  of  which  vibrations  upon  the  fundamental  vibration  of 
the  string — that  is,  of  the  vibration   due  to  the  swinging  of  the 


Fig.  488. 


Fig.  489. 


Resonator  of  Helniholtz. 

string,  as  a  whole,  gives  rise  to 
a  resultant  vibration,  which  has 
been  shown  to  be  equal  to  the  al- 
gebraic sum  of  all  the  vibrations,' 
as    represented    in    Fig.  488    in 
which  the  lower  curve  represents 
the  compound  vibration  resulting 
from  the  blending  of  the  three  up- 
per curves,  representing,   respec- 
tively,  simple  vibrations,    whose 
ratio   is    as    1,  2,   3.     Of  course,  it  must    not   be  supposed    that 
sounds,  simple  or  compound,  are  due  to  curves  like  those  depicted 
in    Fig.  488  ;    the    latter    are   simply    graphic    representations    of 
'  Helmholtz,  op.  cit.,  p.  4o. 


Compound  waves.     (Mi(;RK(iOK  Robinson.) 


OVERTONES.  805 

waves  of  sound,  which,  as  wo  have  seen,  consist  of  condensations  and 
rarefactions  of  the  air.  That  the  tpne  due  to  the  sounding  of  a 
string  of  the  piano,  such  as  Do^,  vibrating  128  times  per  sec- 
ond, is  not  a  simple,  but  a  compound  tone,  will  be  appreciated  by  a 
trained  musician,  whose  sensitive  ear  enables  him  to  distinguish 
some  at  least  of  the  overtones  accompanying  the  fundamental  tone. 
Any  one,  however,  can  convince  himself  that  sucii  a  tone  as  that  of 
Do^  sounded  by  the  piano,  as  elicited  by  singing  the  corresponding 
note,  is  a  compound  one,  resulting  from  the  blending  of  the  funda- 
mental tone  with  overtones,  the  latter  being  due  to  the  partial  vi- 
brations of  the  string,  as  the  former  is  to  the  oscillating  of  the  string 
as  a  whole,  by  adapting  to  his  ear  in  succession  each  one  of  the 
series  of  nine  resonators,  of  which  one  is  represented  in  Fig.  489, 
devised  by  Helraholtz,'  and  so  constructed  as  to  iutensify  the  sound 
of  each  particular  overtone  accompanying  the  fundamental  tone, 
that  overtone  being  then  heard  alone.  Thus,  for  example,  the 
largest  resonator,  marked  Ut^,  being  applied  to  the  ear,  let  the 
note  Ut^  due  to  128  vibrations  a  second  be  sounded  ;  the  first  over- 
tone or  harmonic,  or  the  octave  above  Ut^,  256  vibrations  per  sec- 
ond, will  be  heard,  due  to  the  string  vibrating  in  halves,  the  sound 
distinctly  heard  with  the  resonator  being  the  same  as  if  the  note  Ut' 
had  been  sounded. 

Applying  the  next  largest  resonator,  marked  Sol'',  to  the  ear  and 
sounding  the  Ut^  string  on  the  piano  the  second  overtone,  the 
twelfth  above  the  fundamental,  or  SoP,  will  be  heard,  due  to  the 
string  vibrating  in  thirds,  the  sound  heard  being  the  same  as  if  the 
note  Sol''  had  been  sounded.  Adapting  in  succession  the  remaining 
resonators  graduallv  diminishing  in  size,  and  marked  respectively 
Ut*  Mi*,  SoP  Si*"*  Ut%  Re^  Mi^  the  3d,  4th,  5th,  6th,  7th,  8th,  and 
9th  overtones  due  to  the  string  or  harmonics  will  be  heard  vibrating 
in  fourths,  fifths,  sixths,  etc.,  the  sounds  heard  with  the  resonators 
being  the  same  as  if  the  notes  Ut*  Mi*  SoP  Si^'*  Uf'  Re''  Mi'^  had 
been  separately  sounded,  or  as  expressed  in  musical  notation  as  fol- 
lows, Do^  Ut^  being  the  fundamental  tone  : 


-7^ 


b^     :*:     i^:     ^ 


-(2 


i=: 


^m 


Ut2       rt'  Sol3        Ut<        Mi*         Sol*        SiM        Vt^        Ri-         Mi^ 

It  is  obvious,  therefore,  why  when  the  notes  Ut^  SoP  Ut*  are 
sounded  on  a  musical  instrument  at  the  same  time  with  Ut',  the  re- 
sulting sound  should  be  harmonious,  since  these  three  sounds  rein- 
force respectively  the  first,  second,  and  third  overtones  due  to  the 
string  vibrating  in  halves,  thirds,  and  fourths  respectively.  In  the 
same  way.  Mi*  SoP  Si'*  Ut^  Re'  Mi'  reinforcing  the  overtones  due 

M)}..  cit.,  p.  68. 


806 


PHYSIOLOGICA L  ACQ USTICS. 


Fig.  490. 


to  tlie  string  Ut"  vibrating  in  fifths,  sixtlis,  sevenths,  eighths,  and 
ninths,  when  sounded  with  Ut^,  will  also  give  a  harmonious  sound. 
Having  described  the  manner  in  which  partial  vibrations  are 
formed,  and  how  in  being  superimposed  upon  the  fundamental  vi- 
bration a  resultant  vibration  arises,  and  how  the  overtones  due  to 
the  partial  vil)rations  in  being  l>lended  with  the  fundamental  tone 
due  to  the  fundamental  vibration  give  rise  to  a  compound  tone,  it 
becomes  evident  without  further  explanation,  that  by  means  of  the 
Helmholtz  resonators  we  can  analyze  any  sound,  and  demonstrate 
whether  it  be  a  simple  or  compound  one,  and,  if  the  latter,  what 
overtones  are  present,  and  in  this  way  show  on  what  the  quality, 
timbre,  or  klangfarbe  of  the  sound  depends.  Thus,  for  example, 
the  quality  of  the  sound  of  the  piano,  as  compared  with  that  of  the 
violin,  depends  upon  the  fact  that  in  the  case  of  the  latter,  when 
boAved,  though  the  first  six  overtones  or  harmonics  are  present,  as 
in  the  case  of  the  piano,  they  are  so  faintly  sounded  as  to  be  over- 
])Owered  by  the  seventh,  eighth,  ninth,  and  tenth  overtones.  The 
overtones  in  the  case  of  an  open  pipe  are  not  the  same  as  in  the  case 
of  a  closed  one  ;  those  of  the  clarionet  differ  from  those  of  the  oboe, 
and  so  through  the  whole  range  of  orchestral  instruments.  Inas- 
much, however,  as  in  addressing  a 
large  audience,  from  the  nature  of  the 
case,  it  is  impossible  for  each  one  in- 
dividually to  make  use  of  the  resona- 
tors and  satisfy  himself  of  the  existence 
of  overtones  upon  which  the  quality 
of  a  sound  dejiends  ;  the  author  is  ac- 
customed to  demonstrate  the  same  by 
means  of  Koenig's  manometric  ap- 
paratus.^ The  latter  (Fig.  490)  con- 
sists of  a  frame  supporting  a  number 
of  resonators  each  of  which  leads  by  a 
narrow  India-rubber  tul)e  into  a  small 
chamber,  completely  divided  into  two, 
by  an  India-rubber  partition.  The 
posterior  part  of  the  chamber  is  in 
communication  with  the  resonator,  the  anterior  part  provided  with 
a  gas  jet  with  a  reservoir  containing  gas,  led  thither  by  an  ordinary 
gas  pipe.  Each  resonator  is  connected  in  this  way  with  its  own 
gas  chaml:)er  and  burner,  the  burners  being  all  placed  in  a  row,  one 
above  the  other.  0])posite  the  gas  burners  is  a  long  mirror  with 
four  refiecting  sides,  at  right  angles  to  one  another,  which  can  be 
revolved  on  an  almost  perpendicular  axis  by  a  toothed  w^heel  ar- 
rangement. Turning  on  the  gas,  and  lighting  it  as  it  issues  from 
the  Jets  in  the  chambers  connected  with  the  resonators,  and  revolv- 
ing the  mirror,  the  light  reflected  from  the  surfaces  of  the  latter  ap- 
pears as  continuous  bands.  If,  however,  the  air  in  any  one  of  the 
'  Kudnl])li  Kopiiio-,  Qnelqucs  Experiences  d'Acoustique,  p.  73.     Paris,  1882. 


MaiKjmetrie  apparatus.     (Koenk;.) 


RESONANCE. 


807 


resonators  be  thrown  into  vibration,  then  the  India-rubber  partition 
of  the  chamber  separating,  on  the  one  hand,  the  air  continuous  with 
that  of  the  resonator,  and,  on  the  other,  the  gas,  will  vibrate,  and 
the  gas  and  flame  thrown  into  agitation,  the  particular  band  of  light, 
the  corresponding  band  of  light,  becoming  segmented.  Let  now  a 
tuning  fork  Ut^,  vibrating  256  times  a  second,  be  sounded  in  front  of 
the  apparatus ;  at  once  the  flame  in  connection  with  the  resonator 
marked  Ut^,  will  become  segmented,  but  the  remaining  flames  will 
still  appear  as  continuous  bands  of  light,  since  if  the  tuning  fork  be 
properly  bowed  the  sound  produced  will  be  a  pure,  simple  tone,  un- 
accompanied with  overtones.  Let  now,  however,  the  Ut^  Do^  of 
the  piano,  or  an  open  organ-])ipe  two  feet  long,  giving,  therefore, 
the  same  fundamental  note,  be  sounded,  and  immediately  some  of 
the  remaining  bands  of  light  will  l)ecome  segmented,  as  well  as  the 
one  connected  with  the  resonator  marked  U'^,  since  the  air  of  the 
resonators  with  which  they  are  in  connection  has  been  thrown  into 
vibration  by  the  particular  overtones  present,  as,  for  example,  in 
Fig.  491,  a,  b,  representing  respectively  the  flames  due  to 
the  fundamental  and  octave 

above  it.     In  this  way  an  Fig.  491. 

optical  demonstration  can 
be  (yiven  of  the  fact  that 
the  quality  of  the  note  of 
a  n  y  musical  in.strument 
depends  upon  what  par- 
ticular overtones  or  har- 
monics accompany  the  fun- 
damental, and,  as  we  shall 
see  presently,  of  the  manner 

in  which  the  vowel  sounds 

are  produced  by  the  human  , ,,.u,v,  ,.i  inv, ,  .un-. 

voice.     As  it  is  important 

that  the  manner  in  which  resonators  reinforce  or  intensify  sounds 

should  be  understood,  a  brief  account  of  the  cause  of  resonance  in 

general  may  be  as  appropriately  considered  here  as  elsewhere. 

It  is  well  known  that  the  velocity  with  which  sound  travels  in  air 
at  the  freezing  temperature  is  1,090  feet  in  a  second,  the  velocity 
increasing  about  two  feet  for  every  additional  degree  of  heat  Centi- 
grade (1.8°  F.).  Let  us  suppose  that  the  temperature  of  the  sur- 
rounding atmosphere  be  ^.0°  Cent.  (47.3°  F.),  and  that  a  tuning 
fork  vibrating  256  times  per  second  be  sounded  ;  it  is  obvious  that 
if,  at  the  end  of  the  second,  the  sound  has  reached  a  distance  of 
1,101  feet,  then  each  vibration  must  have  been  52  inches  long, 
since  52  multiplied  by  256  gives  1,101  feet,  and  as  a  vibration  or 
wave  of  sound  consists,  as  we  have  seen,  of  a  condensation  and 
rarefaction,  the  condensation  and  rarefliction  must  have  been  both 
.  just  26  inches  in  length.  That  is  to  say,  as  the  prong  of  the  tuning 
fork  (Fig.  492)  moves  from   A  to   B,  a  distance  of  perhaps  the 


Fumlaiiieutal  note. 


808 


PHYSIOLOGICAL  ACOUSTICS. 


one-twentieth  of  an  inch,  it  generates  the  one-half  of  a  sonorous 
wave,  the  condensation,  the  foremost  point  of  which  reaches 
a  distance  of  twenty-six  inches,  at  the  same  instant  that  the 
proDg  of  the  fork  reaches  B,  and  as  the  prong  of  the  fork  moves 


A  B 


Fig.  492. 
-ZG  uiclics 


->c 


V 


Tuning  fork  vibrating.     (  Ty.vdall.  ) 


back  from  B  to  A,  the  other  half  of  a  sonorous  wave,  is  generated, 
the  rarefaction  or  the  part  progressing  backward  toward  B,  the 
second  condensation  progressing  forward  at  the  same  time  toward 
C.  Such  being  the  case,  let  the  tuning  fork  now  be  sounded  over 
a  jar  (Fig.  493),  of  which  the  column  of  air  within,  from  top  to 

bottom,  measures  just  thirteen  inches,  or 
'•  one-fourth  the  leng'th  of  the  vibration  or 

~ 

<*'^---rr wave  due  to  the  sounding  of  the  fork. 

It  follows  from  what  has  just  been  said, 
■■*'^^^^-- that  during  the  time  the  prong  of  the 

fork  moves  from  a  to  6,  the  conden- 
sation, the  air  which  it  produces  runs 
from  the  top  of  the  jar  to  the  bottom, 
thirteen  inches,  and  from  the  bottom  to 
the  top,  thirteen  inches,  or  twenty-six 
inches  in  all,  the  reflected  wave  reaching 
the  prong  of  the  fork  just  as  the  latter 
reaches  6 ;  and  similarly,  that  during 
the  time  the  prong  returns  to  a  from  6, 
"Q  the  rarefaction  to  which  it  gives  rise 
runs  down  from  the  top  of  the  jar  to  the 
bottom,  and  up  again,  also  a  distance,  in  all,  of  twenty-six  inches. 

The  vibrations  of  the  fork  being,  therefore,  perfectly  synchronous 
with  the  vibrations  of  the  aerial  column  within  the  jar,  the  motion 
will  accumulate  in  the  latter,  and  spreading  out  into  the  room,  the 
sound  will  be  greatly  augmented  as  everyone  will  appreciate,  when 
the  tuning  fork  is  sounded  first  at  some  distance  from,  and  then 
over  the  mouth  of  the  resonating  jar.  From  what  has  just  been 
said,  it  necessarily  follows  that  if  Ave  sound  other  tuning  forks, 
vibrating  at  different  rates,  the  length  of  the  column  of  air  must  be 
varied  accordingly  if  we  wish  to  make  use  of  the  latter  as  a  res- 
onator.    It  is  for  this  reason  that  the  resonators  made  use  of  in 


Tuning   fork    vibrating   in 
with  jar. 


QUALITY  OF  SnUXD.  809 

demonstratincr  the  presence  of  overtones  are  of  different  size,  and 
that  the  resonators  of  Koenig's  manometric  apparatus  are  so  con- 
structed, that  by  draAving  them  out  to  varying  distances,  the  sound 
that  each  resonator  will  reinforce  will  then  be  different.  It  is 
on  account  of  its  resonating  qualities  that,  in  sounding  a  bell, 
the  latter  is  often  placed  near  the  mouth  of  a  jar,  by  means  of 
which  the  intensity  of  the  sound  is  very  much  increased.  The 
ancients  were  well  acquainted  with  the  efficacy  of  such  aids  in 
intensifying  sound,  resonant  brass  vessels  being  placed,  according 
to  Yitruvius,  in  their  theatres  to  strengthen  the  voices  of  the 
actors.  It  is  on  account  of  the  resonating  properties  of  sound- 
ing boards,  that  the  latter  are  associated  with  musical  instruments, 
and  that  the  stethoscope  also  has  proved  in  the  hands  of  the  clini- 
cian such  an  aid  in  the  diagnosis  of  disease  by  auscultation. 

Having  shown  that  sounds  are  produced  by  the  vibrations  of 
plates,  bells,  strings,  pipes,  reeds,  membranes,  etc.,  and  how  the 
same  are  distinguished  by  their  intensity,  pitch,  and  quality,  let 
us  turn  now  to  the  consideration  of  the  larynx,  and  by  means  of 
the  principles  just  established,  endeavor  to  determine  what  kind  of 
an  acoustical  instrument  the  larynx  is  and  how  the  voice  is  pro- 
duced bv  it. 


CHAPTER   XLIL 


THE  LARYNX, 


AND  THE  PRODUCTION  OF  THE  VOICE 
AND  SPEECH. 


The  larynx,  the  organ  of  the  voice,  situated  at  tlie  top  of  the 
trachea  and  below  the  root  of  the  tongue  and  the  hyoid  bone,  con- 
sists of  a  framework  of  cartilages,  connected  by  ligaments,  provided 
with  muscles,  blood  vessels,  and  nerves,  and  lined  with  mucous 
membrane.  The  cartilages  of  the  larynx  are  nine  in  number,  three 
single  and  symmetrical  pieces,  the  thyroid,  cricoid,  and  epiglottic, 
and  three  pairs,  the  arytenoid,  cornicula  laryngis,  and  cuneiform ; 
the  last  two  pairs  are,  however,  very  small.     The  thyroid  (Fig.  494), 


Fig.  494. 


Fig.  495. 


Bird's-eye  view  of  laryux  from  above.  G  E 
H,  the  thyroid  cartilage,  embracing  the  rings 
of  tlie  cricoid,  r  n  X  w,  and  turning  upon  the 
axis,  X  z,  which  passes  tlirough  the  lower 
horns.  N  F,  N  F,  the  arytenoid  cartilages 
connected  bv  the  arvt<ii(ii(l(iis  transversus. 
T  V,  T  V,  the  vocal  nicnilinuies.  N  X,  the 
right  crico-arytenoideus  lateralis  (the  left  be- 
ing removed).  V  A-  /,  the  left  thyro-aryte- 
noideus  (the  right  being  removed)".  N/,  N/, 
the  crico-arytenoidei  postiei.  B,  B,  the  crico- 
arytenoid ligament.s. 


External  and  sectional  views  of  the  larynx. 
A  II  B.  The  cricoid  cartilage.  E  C  G.  The  thy- 
roid cartilage.  G.  Its  upper  horn.  C.  Its  lower 
horn,  where  it  is  articulated  with  the  cricoid. 
F.  The  arytenoid  cartilage.  K.  Crico-thyroid 
muscle. 


the  largest  of  the  cartilages  of  the  larynx  (Figs.  494,  495),  consists 
of  two  lateral  ring-like  plates  or  ahe,  continuous  in  front,  but  di- 
verging behind.  The  angular  projection  in  front,  surrounded  by  a 
deep  notch  much  more  marked  in  the  male  than  in  the  female,  and  in 
some  men  more  than  others,  is  known  as  Adam's  apple,  while  the 
blunt  processes,  into  which  the  posterior  angles  are  prolonged,  are 
called  the  superior  and  inferior  horns,  of  which  the  superior  are  the 
larger,  and  are  connected  by  ligaments  with  the  hyoid  bone.     The 


THE  CAVITY  OF  THE  LARYXX. 


811 


Fig.  490. 


cricoid  cartilage,  resemlilinu-  in  ^liape  a  seal  ring,  i.<  .sitnated  between 
the  thyroid  and  the  lirst  ring  of  the  trachea,  with  the  latter  of  which 
it  is  connected.  AVhile  quite  narrow  in  front,  the  cricoid  cartilage 
deejjens  considerably  posteriorly,  and  at  the  back  part  of  its  upper 
border,  articulates  by  means  of  two  convex  oval  prominences  with 
the  arytenoid  cartilages,  and  laterally  through  two  circular  facets 
Avith  the  inferior  horns  of  the  thyroid  cartilage.  The  arytenoid 
cartilages  are  two  three-sided  recurved  pyramids,  resting  by  their 
bases  upon  the  posterior  and  highest 
portion  of  the  cricoid  cartilage.  The 
apex  of  each  arytenoid  cartilage  is 
usually  surmounted  by  a  yellowish 
cartilaginous  nodule,  the  cornicula 
laryngis  or  cartilages  of  Santorini, 
while  the  folds  of  mucous  membrane, 
extending  from  the  summit  of  the 
arytenoid  cartilages  to  the  epiglottis, 
contain  also  two  small  yellowish 
cartilaginous  bodies,  the  cuneiform 
cartilages,  or  cartilages  of  A^'risberg. 
The  posterior  lateral  corner  of  each 
arytenoid  cartilage  presents  a  blunt 
projection  for  the  attachment  of 
muscles,  the  processus  muscularis 
and  the  anterior  lower  and  median 
part  a  surface  for  the  posterior  at- 
tachment of  the  vocal  membrane, 
the  "  processus  vocalis."  The  re- 
maining cartilages  of  the  larynx,  the 
epiglottis,  consisting  really  of  fibro- 
cartilage,  somewhat  spoon-shaped  in 
form,  while  free  at  its  broad  ex- 
tremity, is  attached  at  its  narrow  end 
l)y  a  Ijand  of  fibro-elastic  tissue  to 
the  thvroid  cartilage  within  the  en- 
tering  angle  of  its  two  halves,  and 
to  the  tongue,  hyoid  bone,  and  aryt- 
enoid cartilages  by  the  glosso-epiglot- 
tidean,  hyo-epiglottidean,  and  aryt- 
eno-epiglottidean  folds,  respectively. 
The  cavity  of  the  larynx  (Fig.  49()) 
is  divided  by  the  glottis,  or  rima 
glottidis,  that  is,  the  space  between 
the  vocal  membranes,  "  rima  vocalis,"  and  between  the  vocal  pro- 
cesses, ''  rima  respiratoria,"  into  an  upper  and  lower  compartment. 
The  upper  compartment  commencing  with  the  pharynx  by  the  su- 
perior aperture  of  the  larynx,  contains  the  ventricles  and  the  upj)er  or 
so-called  false  vocal  cords.    The  lower  compartment  passes  inferiorly 


human 
larynx,  showing  the  vocal  membranes.  1. 
Ventricle  ofthe  larynx.  2.  Superior  vocal 
membrane.  3.  Interior  vocal  membrane. 
4.  Arytenoid  cartilage.  5.  Section  of  the 
arytenoid  muscle.  6,  G.  Inferior  portion 
of  the  cavity  of  the  larynx.  7.  Section  of 
the  posterior  portion  of  the  cricoid  car- 
tilage. 8.  Section  of  the  anterior  portion 
of  the  cricoid  cartilage.  9.  Superior  hor- 
der  of  the  cricoid  cartilage.  10.  ."Section 
of  the  thyroid  cartilage.  11,  11.  Superior 
portion  of  the  cavity  of  the  larynx.  12, 
lo.  Arytenoid  gland.  14,  16.  Epiglottis. 
15,  17.  Adipose  tissue.  IS.  Section  of  the 
hvoid  bone.    19,  19,  20.  Trachea. 


<S12  THE  LARYNX. 

into  the  trachea  without  any  observable  constriction  between  them. 
The  mucous  membrane  lining  the  cavity  of  the  larynx,  continuous 
with  that  of  the  pharynx  and  trachea,  extending  from  the  epiglottis 
to  the  tongue  and  arytenoid  cartilages  as  the  glosso-arytenoid  epi- 
glottidean  folds,  descends  from  the  superior  aperture  and  is  reflected 
at  each  side  outwardly  and  upwardly  as  a  pair  of  pouches,  the  ven- 
tricles of  the  larynx,  oval  recesses  communicating  by  a  transverse 
elliptical  orifice  with  the  interior  of  the  larynx,  and  prolonged  up- 
ward and  outward  as  the  laryngeal  pouches.  The  upper  edge  of  the 
ventricle,  somewhat  prominent  through  the  presence  of  connective 
tissue,  is  known  as  the  false  vocal  cord,  since  it  is  not  concerned  in 
the  production  of  the  voice,  the  lower  edge  corresponding  with  the 
upper  border  of  tlie  vocal  membrane  or  true  vocal  cord,  as  it  is  often 
improperly  called,  and  upon  the  vibration  of  which  the  production 
of  the  voice  depends.  From  the  ventricles  the  mucous  membrane 
passes  downward,  lining  the  vocal  membrane,  cricoid  cartilage,  and 
finally  becomes  continuous  with  that  of  the  trachea.  The  mucous 
membrane  of  the  larynx  is  soft,  thin,  and  pale  red,  its  epithelium 
being  of  the  ciliated  columnar  form,  except  upon  the  so-called  vocal 
cords,  where  it  is  stratified  like  that  of  the  pharynx  and  mouth. 
That  part  of  the  mucous  membrane  situated  at  the  base  of  the 
epiglottis  being  thickened,  gives  rise  to  a  slight  prominence,  the  so- 
called  "  cushion."  While  adhering  tightly  to  the  epiglottis,  the 
vocal  membrane,  and  the  interior  of  the  cricoid  cartilage,  the  mucous 
membrane  in  other  parts  of  the  larynx  is  loosely  attached  to  the 
subjacent  parts  by  connective  tissue. 

The  vocal  membranes  (Figs.  494,  496),  15  mm.  (about  seven  lines) 
long  in  the  male  and  10  mm.  (five  lines)  in  the  female,  bounding  the 
anterior  third  of  the  aperture  of  the  glottis,  and  consisting  of  elastic 
tissue,  may  be  regarded  as  extending  from  the  front  and  sides  of 
the  upper  border  of  the  cricoid  cartilages,  upward  to  the  bases  of 
the  arytenoid  cartilages,  and  to  the  lower  part  of  the  entering  angle 
of  the  thyroid.  The  lower  portion  of  each  vocal  membrane  is  the 
strongest,  and  may  be  seen  at  the  front  of  the  larynx  in  the  in- 
terval between  the  thyroid  and  cricoid  cartilages.  The  lateral  por- 
tions are  thin  and  are  separated  by  the  thyroid  and  arytenoid  mus- 
cles from  the  alae  or  wings  of  the  thyroid.  The  upper  margins  of 
the  vocal  membranes — that  is,  the  parts  corresponding  in  position 
to  the  lower  edges  of  the  ventricles,  extending  on  either  side  from 
the  anterior  prominent  angle  of  the  base  of  the  arytenoid  cartilages 
to  the  entering  angle  of  the  thyroid,  being  somewhat  thickened, 
are  usually  described  as  the  "  true  vocal  cords,"  as  contrasted  with 
the  false  vocal  cords,  or  the  upper  edges  of  the  ventricle.  As  a 
matter  of  fact,  however,  apart  from  the  vocal  membrane,  of  which 
they  are  the  upper  thickened  edges,  no  such  organs  as  vocal 
cords  exist.  That  the  whole  vocal  membrane  consists  of  elastic 
tissue  is  readily  shown  by  the  yellowish  color  of  the  tissue  being 
distinctly  seen  through    the  overlying    mucous  membrane,  which 


ACTIO X  OF  THE  MUSCLES  OF  THE  LABYXX. 


813 


in  this  situation  is  (jaite  thin.  The  essentially  membranous  char- 
acter of  the  vibrating  portion  of  the  larynx  is  well  seen  in  the 
case  of  the  elephant,  in  which  animal  the  vocal  membranes  are 
two  elastic  bands  almost  two  inches  in  length  and  nearly  three- 
quarters  of  an  inch  in  breadth.  Inasmuch  as  the  vocal  mem- 
branes extend  from  the  arytenoid  cartilages  to  the  thyroid,  it  is 
evident  that  if  these  cartilages  approach  or  recede  from  each  other 
the  vocal  membranes  will  be  relaxed  and  tensed  accordingly,  and 
that  if  the  arytenoid  cartilages  be  rotated  backward  or  forward,  the 
vocal  membranes  will  recede  or  diverge  from  each  other,  or  will  ap- 
proach and  become  parallel.  Such  changes  in  the  tension  of  the 
vocal  membranes  and  in  the  form  of  the  glottis,  just  referred  to, 
are,  as  a  matter  of  fact,  brought  about  through  the  action  of  the 
intrinsic  assisted  by  the  extrinsic  muscles  of  the  larynx  upon  the 
thyroid  and  arytenoid  cartilages.  Thus  the  crico-thyroid  muscle 
(Fig.  495)  arising  from  the  front  and  side  of  the  cricoid  car- 
tilag:e  to  be  inserted  in  the  lower  border  of  the  thvroid  in  drawing; 
the  latter  downward  and  forward,  and  therefore  away  from  the  aryt- 
enoid, tenses  the  vocal  membrane.  On  the  other  hand,  the  thyro- 
arytenoid muscle  (Fig.  494,  V  I:  J)  arising  from  the  inner  surface  of 
the  thyroid  cartilage  to  be  inserted  into  the  outer  surface  and  base  of 
the  arytenoid  cartilage,  in  drawing  the  latter  forward  relaxes  the 
vocal  membrane. 

The  influence  exerted  by  the  crico-thyroid  and  thyro-arvteuoid 
muscles  upon  the  tension  of  the  vocal  membranes,  as  just  described, 
can  be  conveniently  illustrated  by  the  model  represented  in  Fig. 
497,  in  which  the  vertical  bar  represents  the  cricoid  cartilage,  the 
cross  piece  c  6  the  thyroid  cartilage, 
and  the  strino-  b  «  the  vocal  mem- 
brane,  and  the  cords  and  weights 
B  A  the  thyro-arytenoid  and  crico- 
arytenoid muscles  respectively.  It 
is  obvious  that  when  the  bar  6  e  is 
pulled  down  to  the  position  e  d  by 
the  weight  A,  the  elastic  band  a  b 
is  put  on  the  stretch,  and  when  ele- 
vated by  the  weight  B,  the  elastic 
band  a  6  is  relaxed. 

It  is  also  probable  that  the  vocal 
membranes  are  approximated  and 
their  form  and  thickness  modified  by 
the  contraction  of  these  muscles.  The 
effect  of  the  contraction  of  the  crico- 
thyroid muscles  in  stretching  the  vocal  membranes  is  increased  by 
the  simultaneous  contracting  of  the  arytenoid,  crico-arytenoid,  pos- 
tici,  and  sterno-thyroid  muscles,  that  of  the  thyro-arytenoid  in  re- 
laxing the  vocal  membranes  by  the  action  of  the  crico-thyroid 
lateralis  and  thyro-hyoid  muscles.     The  posterior  crico-arytenoid 


Fk;.  497 


Diagram   of  a  model    illustrating  the 
action    of  the    muscles  of    the    larynx. 

(HlXI.EY.) 


814 


THE  LARYNX. 


Fifi.  498. 


muscle  (Fig.  498),  so  called  on  account  of  its  arising;  from  the  pos- 
terior surface  of  the  cricoid  cartilages  to  be  inserted  into  the  exter- 
nal angle  of  the  l^ase  of  the  arytenoid 
cartilage,  in  rotating  the  latter  back- 
ward not  only  widens  the  glottis 
(Fig.  499),  but,  as  just  mentioned, 
also  assists  in  tensing  the  vocal  mem- 
brane. The  lateral  crico-ai'vtenoid 
muscles  (Fig.  500)  lying  under  the 
wing  of  the  thyroid  cartilage,  arising 
from  the  upper  lateral  border  of  the 
cricoid  to  be  inserted  into  the  ex- 
ternal angle  of  the  base  of  the  aryt- 
enoid cartilage,  in  contracting  rotate 
the  latter  forward  and  press  together 
their  inner  edges,  and  not  only  nar- 


row  the   glottis,   but   assist    in    re- 


Cor/i 


Larynx  from  behind  with  its  muscles. 
E.  Epiglottis,  with  the  cushion  W.  C. 
( ir)  Cartil.  Wrisbergii.  ('.  .V.  Cartil.  .san- 
torinianie.  C  c.  Cartil.  erieoidea.  Cornu 
sup.  cornu  inf.  cartilaginis  thyreoidefe. 
M.  ar.  ir.,  Musculus  arytenoideus  trans- 
versus.  Mm.  ar.  obi.  Musculi  arytenoidei 
obliqui.  M.  cr.  ari/(.  post.  Musculus  crico- 
arytcnoideus  posticus.  Pans.  cart.  Pars 
cartilaginea.  Pur.s  mr-mh.  Pars  mem- 
branacea  trachje.     (Landois.  ) 


laxing  the  vocal  membrane.  The 
arytenoid  muscle,  consisting  of  trans- 
verse and  oblique  fasciculi,  being 
attached  to  the  posterior  concave 
surface  of  the  arytenoid  cartilages, 
in  contracting  draw  the  latter  to- 
gether and  so  narrow  the  glottis. 
In  addition  to  the  muscles  just  de- 
scribed, there  are  usually  found  a 
few  muscular  fibers  passing  from  the 
epiglottis  to  the  thyroid  and  aryt- 
enoid cartilages,  known  as  the  thvro- 


FiG.  499. 


Fifi.  500. 


Lozenge  shape  of  the  glottis,  produced  by  the  action 
of  the  posterior  crico-arytenoid  muscle.   (Kuss.) 


To  illustrate  action  of  crico-arytenoid  lateralis 
muscle.     (Kuss.) 


RAXGE.OF  THE  HUMAX  JO  ICE.  815 

and  aryteno-epiglottidean  muscles,  whose  functions  appear  to  be  to 
depress  the  epiglottis,  and  compress  the  laryngeal  pouches  respec- 
tively. Such  being,  in  brief,  the  general  structure  of  the  larynx, 
it  follows,  from  what  was  said  in  the  preceding  chapter,  that  if  the 
air  expired  from  the  lungs  and  ascending  in  the  trachea  in  pass- 
ing through  the  glottis  throws  the  elastic  vocal  membranes  int(» 
vibration,  a  sound,  the  voice,  will  be  produced,  the  character 
of  which  will  depend  upon  the  tension  of  the  vocal  membranes, 
shape  of  the  glottis,  etc.,  just  as  we  can  produce  a  sound  by  forcing 
air  by  means  of  a  bellows  through  a  glass  tube,  over  the  mouth  of 
which  have  been  stretched  two  elastic  membranes.  Lest,  however, 
the  analogy  of  the  bellows  and  pipe  to  the  lungs  and  trachea  might 
suggest  the  idea  of  the  larynx  acting  as  an  organ-pipe,  or  that  the 
misnomer  vocal  cords  might  give  the  impression  that  the  larynx 
acts  as  a  stringed  instrument,  let  us  compare  the  range  of  the  voice, 
on  the  one  hand,  with  that  of  notes  as  produced  by  organ-pipes  and 
strings  on  the  other,  and  it  will  then  become  evident  that  the  larynx 
does  not  act  like  either.  The  range  of  the  human  voice  in  the  two 
sexes,  and  of  the  bass  and  tenor  voice  in  the  male  and  female,  can 
be  most  conveniently  illustrated  by  musical  notation  after  Midler,^ 
as  follows  : 


CONTRALTO 


64  vib.  SO  vib.  128  vib.  .  io24 

do  re  mi  fa  sol  la  si  do  re  mi  fa  sol  la  si  do  re  mi  fa  sol  la  si  do  re  mi  fa  sol  la  si  do     vib. 
11111      11222222233333334444444    5 


from  which  it  will  be  seen  that  the  voice  ranges  ordinarily  from  mi^ 
80  vibrations  per  second,  the  lowest  note  of  the  male 


1 


bass  voice,  to  do.  Ut.  E^zzitiE3  1,024  vibrations  per  second,  the 
highest  note  of  the  female  soprano  or  tenor,  though  it  should  be 
mentioned  that  some  bass   voices  reach  the  ia^      42.(3 


^^- 


vibratious  per  second  of  the  octave  below  the  above  scale  or  even 

lower,  and  some  soprano  voices  the  sol.  E^zii^3  l,o3()  vibrations 

'Physiology,  trans,  by  Baly,  Vol.  ii.,  p.  1030.     London,  1842. 


816  THE  LARYNX. 

per  second  above  and  even  higher.  The  human  hirynx  being  capa- 
ble, therefore,  in  the  case  of  a  man  of  emitting  ordinarily  a  note 
due  to  80  vibrations  a  second,  and  in  a  woman  of  one  due  to  1,024 
vibrations,  would  have  to  be  over  five  feet  long  and  six  inches 
long,  respectively,  if  it  acted  like  an  organ-pipe,  since  that  would 
be  the  length  of  the  pipes  giving  those  notes,  the  notes  of  an  eight- 
foot  pipe  and  six-inch  pipe  being  due  to  64  and  1,024  vibrations  a 
second,  respectively.  Similarly  no  notes  as  deep  as  those  of  the 
bass  voice  can  be  produced  by  strings  as  short  as  the  vocal  mem- 
branes, however  the  latter  may  be  relaxed. 

Further,  apart  from  the  fact  of  the  vocal  membranes  being  too 
short  to  produce  bass  notes  on  the  supposition  that  they  act  like 
strings,  the  E  string  of  the  double  bass,  for  example,  vibrating  41  ^^ 
times  per  second,  the  ratio  of  the  vibrations  of  the  vocal  membranes 
to  the  weight  extending  them  is  not  the  same.  Thus,  for  example, 
while  it  is  well  known  that  the  vibrations  of  a  string  are  doubled 
by  quadrupling  the  extending  weights,  the  number  of  vibrations 
being  proportional  to  the  square  root  of  the  weight,  the  vibrations 
of  the  vocal  membranes,  as  shown  experimentally  by  Miiller,'  are 
not  so  doubled  by  quadrupling  the  extending  weight,  the  vibrations 
not  reaching  the  octave  above,  as  in  the  case  of  a  string,  by  several 
semitones.  On  the  other  hand,  it  has  been  shown  by  Miiller  that 
the  vibrations  of  the  vocal  membranes  are  governed  by  the  same 
law  as  that  regulating  the  vibrations  of  reeds  or  tongues,  when  the 
latter  are  associated  with  pipes.  The  latter  qualification  must  be 
borne  in  mind,  since  in  reed  instruments  like  the  accordion,  con- 
certina, seraphine,  harmonium,  etc.,  in  which  the  reed  or  tongue 
vibrates  in  a  sort  of  frame  that  permits  of  the  air  passing  out  on 
all  sides  of  it  through  a  narrow  channel,  thereby  increasing  the 
strength  of  the  blast,  the  sound  produced  is  due  to  the  vibration  of 
the  reed  or  tongue  alone,  and  is  regulated  entirely  by  the  length 
and  elasticity  of  the  latter.  In  reed  instruments  like  the  clarionet, 
bassoon,  and  oboe,  however,  in  which  the  single  or  double  reeds  are 
associated  with  pipes,  the  air  setting  the  reed  in  vibration  traverses 
the  whole  length  of  the  pipe  before  escaping  into  the  atmosphere, 
and  consequently  the  soiuid  produced  is  due  to  the  vibrations  of 
both  reed  and  pipe  combined,  and  not  to  either  of  them  singly — 
the  two  sounds  accommodating  themselves  to  each  other  in  such  a 
way  that  only  one  sound  is  heard,  the  fundamental  being  neither 
always  that  of  the  reed  alone  nor  of  the  pipe  alone.  In  the  case  of 
the  clarionet,  in  which  the  reed  is  a  single  broad  tongue,  and  in 
the  oboe  and  bassoon,  in  which  the  reeds  are  double  and  somewhat 
spoon-  or  spatula-shaped,  the  difiTerent  notes  are  produced  by  clos- 
ing or  opening  a  series  of  holes,  the  position  of  which  has  been  de- 
termined by  experiment.  In  the  reed  pipes  of  the  organ,  however, 
in  which  the  reed  is  inserted  into  the  jiipe  through  a  plug,  each 
note  has  a   separate  pipe.      It   was  established  more  especially  by 

'Op.  cit.,  p.  985. 


THE  LARYNX  A  REED  INSTRUMENT.  817 

AYeber^  that  reeds  associated  M'ith  pipes,  as  in  the  case  of  the  voice 
and  of  the  instruments  just  znentioued,  ])ossess  certain  well-marked 
properties  by  which  they  can  be  at  once  distinguished  from  other 
musical  instruments,  such  as  organ-pipes,  flutes,  etc.,  and  with 
which,  in  the  case  of  the  voice,  they  may  be  confounded.  Among 
the  most  important  of  such  properties  may  be  mentioned,  1st,  that 
the  pitch  of  a  reed,  though  it  cannot  be  raised,  may  be  lowered  by 
joining  it  to  a  tube,  but  at  the  utmost  by  not  more  than  an  octave ; 
2d,  that  the  fundamental  note  of  the  reed  so  lowered  mav  be  raised 
again  to  its  original  pitch  by  a  lengthening  of  the  tube,  the  latter 
then  yielding  the  same  fundamental  note  as  the  reed  of  the  instru- 
ment without  the  tube,  whilst  by  a  further  lengthening  the  pitch  is 
again  lowered,  and  by  a  still  further  lengthening  rait^ed  again  ;  3d, 
that  the  length  of  the  tube  necessary  to  lowcn^  the  note  to  any  given 
pitch,  depends  on  the  relation  existing  between  the  rapidity  of  the 
vibrations  of  the  tongue  of  the  reed  and  those  of  the  column  of  air 
in  the  tube,  each  taken  separately.  Accepting  the  above  as  the  es- 
sential conditions  which  an  instrument  must  fulfill  in  order  to  con- 
stitute a  reed  instrument,  Miiller-  showed  that  the  larynx,  in  ful- 
filling the  same,  must  be  regarded  as  a  reed  instrument,  the  vocal 
membranes  being  comparable  to  membranous  vibrating  tongues. 
The  conclusion  just  arrived  at,  based  upon  acoustic  principles, 
that  the  larynx  is  a  reed  instrument,  is  fully  borne  out,  not  only  by 
the  fact  that  in  several  instances  persons  rendered  voiceless  by  the 
loss  of  their  larynx,  have  been  enabled  to  speak,  so  as  to  be  per- 
fectly heard  through  the  introduction  into  the  trachea  of  a  tube 
containing  a  reed,  but  also  by  observing  directly  the  larynx  during 
phonation  with  the  laryngoscope.  Among  the  first  to  investigate 
the  larynx  in  this  way  was  Manuel  Garcia,^  so  distinguished  as  a 
singing  teacher,  whose  experiments  were  made  principally  with  the 
view  of  determining  the  scientific  principles  upon  Avhich  the  teach- 
ing of  singing  should  be  based,  and  which,  up  to  that  time,  had 
been  taught  by  purely  empirical  methods.  The  difficulty  of  ob- 
serving the  vocal  membranes  during  phonation  on  account  of  the 
epiglottis  hiding  so  much  of  their  anterior  portions,  especially  in 
the  production  of  high  notes,  is  a  familiar  fact  to  those  in  the  habit 
of  using  the  laryngoscope.  The  perfect  control,  however,  possessed 
by  Garcia  over  his  own  vocal  organs,  together  with  the  skill  with 
which  he  examined  them  in  his  own  person,  enabled  him  finally  to 
determine  very  satisfactorily  the  changes  actually  undergone  by  the 
glottis  and  vocal  membranes  during  singing,  the  accuracy  of  the 
observations,  models  of  scientific  research,  being  fully  confirmed  by 
later  observers.  The  changes  in  the  glottis  during  ordinary 
breathing  (Fig.  501,  A  A')  having  been  already  described,  it  will 
be  only  necessary  in  this  connection  to  recall  the  fact,  that  during 
inspiration  the  glottis,  through  the  action  of  the  crico-arytenoidei 

'  Poggendorf,  Annalen,  xvi.,  xvii.  ^Op.  cit.,  pp.  985,  99l»,  1023. 

''Proc.  of  Roval  Society  Lond.,  18.')(i,  Vol.  vii.,  p.  399. 

52 


818 


THE  LARYNX. 


postici  muscles,  is  widely  dilated,  and  that  durino-  expiration,  the 
larynx  appearing  to  be  passive,  the  air  is  gently  forced  ont  through 
the  glottis  by  the  expiratory  movements  of  the  chest.  Garcia  hav- 
ing first  noticed  the  movements  of  the  larynx  during  his  ordinary 
breathing,  observed  next  that  just  at  the  moment  of  making  a  vocal 
effort,  his  glottis  underwent  an  entire  change,  the  arytenoid  cartil- 
ao-es  being  so  approximated  that  the  vocal  cords  were  brought 
parallel  to  each  other  (the  distance  separating  them,  it  may  be  here 

Fig.  501. 


A.  The  glottis  during  tlie  uiuission  of  a  high  note  in  singing.  B.  An  easy  or  quiet  iiilialation  of  air. 

mentioned,  not  exceeding  the  one-twelfth  of  an  inch),  the  glottis 
then  appearing  as  a  narrow  slit  (Fig.  501,  BB').  The  glottis  be- 
ing thus  prepared,  so  to  speak,  for  the  emission  of  a  note  through 
the  action  of  the  expiratory  muscles,  air  is  forced  through  the  slit 
or  chink,  the  effect  of  which  is  that  the  vocal  membranes  are  thrown 
into  vibration,  the  particular  note  emitted  being  due  essentially  to  the 
length  and  tension  of  the  latter.     Thus,  according  to  Garcia,  in  the 


production  of  the  bass  notes 


the  a'lottis  is  agitated 


by  large  and  loose  vil)rations  throughout  its  entire  extent,  the  lips 
comprehending  in  their  length  the  anterior  apophyses  of  the  aryte- 
noid cartilages  and  the  vocal  cords. 

As  the  pitch  of  the  sound  rises  through  the  gradual  apposition  of 
the  apophyses  the  length  of  tiie  glottis  is  encroached  upon,  and  with 


the  emission  of  the  sounds 


the  apophyses  touch  each 


other  throughout  their  whole  extent,  their  summits  being  solidly 


PEECISIOX  OF  MUSCULAK  COXTBACTIOX.  >^IU 

fixed  one  agaiust  the  other  at  the  notes  F^ 1-     ]~1      Witli  the 


do 


production  of  the  notes  fA^ 1 iH ,  and  so  on  upward  tu  the  eml 

of  the  register,  the  vibrations  are  due  to  the  vocal  membranes  alone, 
the  length  of  tho  glottis  diminishing,  and  the  cavity  of  the  larynx 
becoming  very  small  as  the  pitch  of  the  voice  continues  rising. 
These  changes  undergone  by  the  glottis  in  the  shape  and  size  and 
in  the  length  and  tension  of  the  vocal  membranes  in  the  production 
of  low  and  high  notes  by  the  larynx,  as  observed  by  Garcia  and 
subsequent  investigators,  become  intelligible  Avhen  it  is  remembered, 
as  shown  in  the  last  chapter,  that  the  pitch  of  the  note — that  is,  the 
number  of  vibrations  per  second — rises  as  the  leno;th  of  tlie  strinjr, 
pipe,  or  membrane  diminishes,  or  the  tension  increases,  the  change  in 
the  shape  of  the  glottis  and  of  the  tension  of  the  vocal  membranes 
being  accomplished  by  the  action  of  the  muscles,  as  already  explained. 
Thus,  men  have  deeper  voices  than  boys  and  women,  their  larynx 
being  larger,  and  their  vocal  membranes  longer.  That  the  aperture 
of  the  glottis  is  narrowed  during  the  production  of  sounds  any  one 
can  convince  himself  by  comparing  the  time  of  an  ordinary  expira- 
tion with  that  re(juired  for  the  ])assage  of  the  same  quantity  of  air 
during  a  vocal  effort,  and  that  the  size  of  the  aperture  varies  with 
the  pitch  of  the  note,  from  the  fact  of  there  being  far  less  air  ex- 
pired during  the  production  of  a  high  note  than  in  that  of  a  low 
one.  That  the  production  of  low  and  high  notes  is  due  to  varia- 
tions in  the  tension  of  the  vocal  membranes,  as  brought  about  by 
the  action  of  the  thyro-arytenoid  and  crico-thyroid  muscles,  is  made 
evident  during  the  passage  of  the  voice  from  one  extreme  of  the 
scale  to  the  other  by  the  movement  of  the  thyroid  on  the  cricoid 
cartilage,  which  is  quite  apparent  if  the  tip  of  tlie  finger  be  placed 
over  the  crico-thyroid  ligament.  As  illustrating  the  nicety  and 
precision  with  which  the  tension  of  the  vocal  membranes  is  regu- 
lated by  muscular  contraction,  let  us  suppose,  with  Miiller,^  that 
the  average  length  of  the  vocal  membrane  in  man  during  repose  is 
about  -^^'^y  of  an  inch,  and  during  the  greatest  tension  y^\,  the  dif- 
ference being,  therefore,  -^-^\^,  or  the  -I  of  an  inch,  and  that  in  the 
female  the  corresponding  extremes  are  al)Out  -f^\y  and  -^^^,  the 
difference  being  -^^q,  or  the  ^  of  an  inch,  and  that  the  natural 
compass  of  the  voice  is  about  two  octaves,  or  twenty-four  semitones. 
Such  being  the  case,  as  any  cultivated  voice  can  sing  ten  intervals 
between  the  twenty-four  semitones,  such  a  voice  can  produce  240 
sounds,  necessitating,  however,  over  240  different  states  of  tension. 
Inasmuch,  however,  as  the  available  length  of  vocal  membrane  to 
be  tensed  is  only  the  i  and  the  |  of  an  inch  in  the  sexes,  it  follows 
iQp.  cit.,  Vol.  ii.,  p.  1018. 


820  THE  LARYNX. 

that  in  tlie  production  of  eacli  of  the  240  sounds  the  vocal  mem- 
brane must  be  diminished  vohintarily  by  the  j.;^q-q  and  the  ygV-g- 
of  an  inch  in  the  case  of  the  male  and  female  sinti;er,  respectively,  and 
by  considerably  less  in  the  case  of  such  phenomenal  voices  as  those 
of  Bastardella,  Catalani,  Cruvelli,  and  Patti,  for  example,  with  a 
compass  of  three  octaves,  and  even  more.  The  remarkable  distinct- 
ness with  which  certain  voices  could  be  heard,  like  those  of  the 
celebrated  basso,  Lablache,  and  the  late  Madame  Parepa  Rosa, 
clearly  above  the  sounds  of  a  large  chorus  and  orchestra,  is  due 
rather  to  the  absolute  accuracy  with  which  the  tension  of  the  vocal 
membranes  could  be  regulated  by  those  great  singers,  to  the  purity 
of  their  tones  rather  than  to  the  mere  loudness  or  intensity.  It 
should  be  mentioned,  however,  that  the  singers  just  referred  to  were 
of  magnificent  physique,  as  might  have  been  expected,  the  power  of 
the  voice  being  due  to  the  force  with  which  the  air  is  expelled  from 
the  lungs.  As  the  action  of  tlie  diaphragm  and  abdominal  muscles 
has  already  been  considered,  it  will  be  only  necessary  in  this  con- 
nection to  recall  what  has  already  been  said,  that  the  inspiratory 
and  expiratory  acts  can  be  so  nicely  balanced  by  a  skilful  singer  as 
to  enable  him  to  produce  the  most  delicate  tones.  It  need  hardly 
be  added  that  while  sounds  may  be  uttered,  and  even  words  spoken 
during  inspiration,  that  the  true  and  natural  voice,  and,  as  we  shall 
see  presently,  articulate  speech  are  only  produced  during  expiration. 
While,  in  childhood,  the  general  character  of  the  voice  is  the  same 
in  both  sexes,  in  the  adult  condition  the  male  voice  differs  very 
much  from  that  of  the  female,  the  difference  becoming  marked  at 
the  age  of  puberty.  If  castration  be  performed,  therefore,  the  con- 
tralto, or  soprano,  voice  of  the  boy  will  be  retained  through  life, 
and  such  a  voice  being  susceptible  of  considerable  cultivation  ad- 
vantage was  cruelly  taken  of  the  fact  at  one  time  to  fill  choirs  with 
desirable  voices.  After  the  age  of  puberty,  however,  the  quality 
of  the  female  voice  remains  the  same,  except  in  gaining  strength 
and  extending  its  compass.  At  this  period,  in  the  case  of  the  male, 
however,  the  whole  character  of  the  voice  changes  through  the  de- 
velopment of  the  larynx.  While  the  intensity  of  the  voice  in  both 
sexes  depends  upon  the  force  with  which  the  air  is  expelled  through 
the  larynx,  and  the  range  or  pitch,  bass,  tenor,  contralto,  and 
soprano,  upon  the  length  and  tension  of  the  vocal  membranes,  the 
quality  of  any  particular  individual  voice,  male  or  female,  depends 
upon  the  shape,  size,  and  general  make  of  the  larynx,  and  on  the 
character  of  the  auxiliary  resonating  cavities.  In  concluding  our 
account  of  the  production  of  the  voice,  a  brief  description,  at  least, 
of  the  influence  exerted  by  the  accessory  vocal  organs,  viz.,  the 
trachea,  ventricles,  superior  vocal  cords,  epiglottis,  pharynx,  nasal 
cavities,  and  mouth,  should  be  offered.  The  tracliea  not  only  serves 
to  conduct  air  to  the  larynx,  but  through  the  vibration  of  its  own 
column  of  air  reinforces  the  sound  produced  by  the  larynx,  the 
vibration  being  perfectly  appreciable  if  the  finger  be  placed  upon  the 


PKODVCTIOX  OF  FALSETTO  VOICE.  821 

trachea  during  a  powerful  vocal  effort.  The  ventricles  probably, 
also,  intensify  the  sound,  the  homologous  parts  being  enormously 
developed  in  monkeys  and  apes  possessing  very  loud  voices,  such 
as  the  South  American  howler  (Mycetes),  the  cliimpanzee,  and 
gorilla. 

That  the  superior  or  false  vocal  cords  and  the  epiglottis  are  not 
essential  to  the  production  of  the  voice,  can  be  shown  bv  experi- 
ments like  those  (»f  Longet,^  in  which  the  above  parts  were  removed 
in  animals  without  the  voice  being  materially  affected,  and  in  man 
those  cases  in  which  the  epiglottis  had  been  lost  through  wounds  or 
disease.  The  pharynx,  mouth,  and  nasal  fossfe,  acting  as  resonating 
cavities,  modify,  however,  very  considerably  the  sounds  produced 
by  the  vocal  membranes.  Indeed,  in  the  production  of  the  natural 
voice  their  resonance  is  essential.  Thus,  Avhile  in  the  production  of 
low  notes  the  velum  palati  is  fixed,  and  the  bucco-pharyngeal  and 
naso-pharyngeal  cavities  reinforce  the  laryngeal  sounds,  in  the 
passage  upward  to  the  higher  notes  these  cavities  are  reduced  in 
size,  the  isthmus  contracting  until,  with  the  emission  of  the  highest 
notes,  the  nasal  fossse  is  shut  off  entirely,  and  the  mouth  and 
pharynx  alone  resound,  the  tongue  at  the  same  time  being  drawn 
back  into  the  mouth  with  its  base  projecting  upward  and  the  tip 
downward,  the  capacity  of  the  resounding  cavity  is  still  further 
diminished.  Such  being  the  mechanism  by  Avhich  the  chest  tones 
or  chest  register  are  produced,  it  is  only  necessary  to  add,  that  if 
the  velum  palati  lie  thrown  forward  instead  of  backward,  thereby 
cutting  off  the  mouth  from  the  pharynx,  the  resonance  being  then 
due  to  the  naso-pharyngeal  cavity,  that  we  pass  from  the  chest 
register  into  that  of  the  head  tones  or  head  register.'  According  to 
the  late  Madame  Seller,^  however,  the  head  tones  are  due  to  the 
vocal  membranes  being  firmly  approximated  posteriorly,  an  oval 
opening  being  left  with  vibrating  edges  involving  only  one-half  or 
one-third  of  the  vocal  membranes,  which  gradually  contracts  as  the 
pitch  of  the  tone  rises.  As  in  the  case  of  the  head  register,  so  in 
that  of  the  falsetto  or  middle  register  of  the  female,  a  difference  of 
opinion  still  prevails  as  to  the  exact  manner  of  its  production. 
Thus,  while,  according  to  Fournie,*  the  falsetto  is  due  to  the  tongue 
being  pressed  strongly  backward  and  the  epiglottis  forced  over  the 
larynx  ;  according  to  Seller,'  it  is  due  to  the  thin,  fine  edges  of  the 
vocal  membranes  alone  vibrating.  While  the  distinction  between 
the  chest,  falsetto,  and  head  registers  so  fiir  as  pitch  is  concerned,  is 
not  an  absolute  one,  and  while  we  find  that  every  voice  possesses  all 
three  registers,  nevertheless  the  chest  register  almost  characterizes 
male  voices  and  the  contralto  of  the  female,  the  falsetto  being  the 
most  natural  voice  of  the  soprano,  though  the  latter  voice  is  capable 

iPhysiologie,  Tomeii.,  p.  728.     Paris,  1809. 

^Fournie,  Physiologie  de  la  voix  et  de  la  parole,  p.  421.     Paris,  1866. 

3  The  Voice  in  Singing,  p.  56.     Phila.,  18(18. 

*0p.  cit.,  p.  463.  ^Op.  cit.,  p.  56. 


822  THE  LARYNX. 

of  chest  tones,  while  the  head  voice  is  particuhirly  well  developed 
in  tenors  and  in  the  female  voice.  The  falsetto  is  but  little  culti- 
vated at  the  present  day  by  tenors,  and  even  M'hen  it  or  either  of 
the  other  two  registers  is  particularly  well  developed  the  singer 
should  endeavor  to  pass  as  insensibly  as  possible  from  one  register 
to  another,  to  give  the  impression  that  his  voice  possesses  but  one. 

Speech. 

While  the  position  of  man  as  the  head  of  the  animal  kingdom 
depends  upon  the  development  of  his  intelligence,  there  can  be  no 
question  that  his  superiority  over  all  other  animals  is,  to  a  great 
extent,  due  to  his  being  able  to  convey  his  ideas  to  others  by  ex- 
pression, or  articulate  speech. 

Speech  is  made  up  of  syllables  articulated  or  jointed  together,  the 
parts  of  speech  called  words  being  formed  by  the  union  of  one  or 
more  syllables,  the  latter  consisting  usually  of  two  kind  of  sounds, 
vowels  and  consonants. 

Speech  is  voice  modulated  by  the  throat,  nose,  tongue,  and  lips. 
Voice  may,  therefore,  exist  without  speech,  and  if  the  production 
of  the  voice  be  restricted  to  reo-ular  vibrations  of  the  vocal  mem- 
branes,  it  may  be  said  that  speech  can  exist  without  voice,  since,  in 
whispering,  the  vibrations  of  the  muscular  walls  of  the  lips  replace 
those  of  the  vocal  membranes,  a  whisper  being,  in  fact,  a  very  low 
whistle.  Articulate  sounds  are  usually  divided  by  orthoepists  into 
vowels  and  consonants  :  vowels  being  continuous  sounds  due  to  the 
voice  alone,  but  modified  by  the  form  of  the  aperture  through 
which  they  pass  out ;  consonants,  interrupted  sounds  due  to  the  in- 
terruption, more  or  less,  of  the  voice,  and  sounded  with  vowels. 
This  classification  is  not,  however,  a  very  natural  one,  since  the 
sound  of  the  English  i,  being  a  diphthongal  sound,  cannot  be  pro- 
longed like  a  true  vowel  (a,  o),  while  certain  consonants  (1,  r,  f )  can  be 
pronounced  without  the  current  of  air  being  interrupted.  The  vowel 
sounds,  by  which  we  mean  u,  o,  a,  e,  are  due  to  the  reinforcing  of  the 
overtones  of  the  fundamental  tone  of  the  larynx  by  the  cavity  of  the 
mouth,  the  changes  in  the  shape  of  which  give  rise  to  so  many  reso- 
nators, each  of  which  is  adapted  to  the  reinforcing  of  the  particular 
overtone  to  which,  together  with  the  fundamental  tone,  the  partic- 
ular vowel  is  due.  The  ])resence  of  overtones  coexisting  with  the 
fiuidamental  tone  of  the  larynx  in  the  emission  of  vowel  sounds, 
and  the  determination  of  what  particular  overtone  accompanies  the 
fundamental  tone  in  the  production  of  any  particular  vowel,  can  be 
shown  by  the  Koenig  manometric  apparatus  described  in  the  last 
chapter. 

Thus  the  vowel  sound  u  is  due  to  the  fundamental  tone  being 
emitted  strong,  the  cavity  of  the  mouth  or  the  vowel  chamber  (Fig. 
o()2,  U)  being  made  as  deep  as  possible,  by  keeping  the  tongue 
down  at  the  bottom,  and  pushing  the  lips  out,  the  mouth  then  rein- 
forcing the  fundamental  tone  of  the  larynx,  and  tuned,  according  to 


PRODUCTION  OF  VOWELS. 


823 


Koenig^  to  the  pitch  of  the  note  ^7|-,,  (Fig.  ;303),  due  to  224  vibra- 
tions per  second.  The  sound  o  is  due  to  the  fundamental  note  of 
the  hirynx  being  present,  but  especially  its  first  octave  above  being 
emitted  also,  and  very  strong,  the  cavity  of  the  mouth  being  en- 


Section  of  the  parts  concerned  iu  the  formation  of  vowels.     Z.  l-..^ ^.  , „. 

Epiglottis,     fj.  Glottis.     Ii.   Hyoid  bone.    1.    Thyroid.    2,  3.    Cricoid.    4.    Arytenoid  cartilage. 
(Laxdois.  ) 


Z.  Tongue,  p.  Soft  palate. 


Ko.  of  Vib.s.,  224,         448, 

Pitch  of  vowel 


Sil 


larged  through  the  retraction  of  the  lips  so  as  to  reinforce  the  octave, 
and  tuned  to  the  pitch  of  the  note  Si\).^,  due  to  448  vibrations  per 
second.  The  sound  a,  like  the  preceding  two  vowels,  is  due  to  the 
presence  of  the  fundamental 

tone  of  the  larynx,  but  differs  Fig.  503. 

from  o  in  that  the  funda- 
mental is  accompanied  by 
the  double  octave  above,  the 
orifice  of  the  mouth  being  so 
widened  that  the  cavity  of 
the  mouth  (Fig.  502,  ^4)  is 
tuned  to  the  pitch  of  the 
note  Si\y^  due  to  896  vibra- 
tions per  second.  In  the 
production    of   the  sound   e 

the  cavity  of  the  mouth  is  still  more  retracted,  reinforcing  the  third 
octave  above  the  fundamental,  the  cavity  of  the  mouth  being  tuned 
to  the  pitch  of  the  note  Si\)r,  due  to  1,792  vibrations  per  second. 
As  the  four  vowels  u,  o,  a,  e  can  be  produced  during  one  con- 
tinuous expiration,  during  which  the  fundamental  and  overtones 
generated  by  the  vocal  membranes  remain  the  same,  by  simply 
changing  the  shape  of  the  mouth,  it  is  evident  that  the  production 
of  each  individual  vowel  will  depend,  as  already  mentioned,  upon 
which  particular  octave  or  overtone  is  reinforced  by  the  cavity  of 
the  mouth,  the  pitch  of  the  latter  depending  upon  its  shape,  and 
that  the  shape  of  the  mouth  remaining  unchanged,  the  correspond- 
ing vowel  will  be  emitted  as  long  as  the  expiration  blast  lasts. 
'Quelques:  Experiences  d' Acoustique,  p.  65.     Paris,  1882. 


b5  '^'■b« 

890,      1792,    :j.')84. 
(KOESIG.) 


824  THE  LARYNX. 

Now  while  the  vowel  i  agrees  with  the  four  vowels  just  mentioned 
in  being  due  to  the  reinforcement  of  an  overtone,  the  fourth  octave 
accompanying  the  fundamental  by  the  cavity  of  the  mouth  (Fig. 
502,  7),  which  in  this  instance  is  tuned  to  the  pitch  of  the  note  Si[^y, 
due  to  3,584  vibrations  per  second,  an  octave  higher  than  in  the 
case  of  the  vowel  e,  it  diifers  from  the  true  vowels  in  that,  the 
cavity  of  the  mouth  remaining  the  same,  if  the  expiratory  blast  be 
prolonged,  it  does  not  remain  i,  but  becomes  e.  The  vowels  are 
the  only  real  vocal  sounds,  it  being  only  on  a  vowel  that  a  note  can 
be  said  or  sung.  Speech,  however,  is  made  up  not  only  of  vowels, 
but  of  consonants — that  is,  of  sounds  that  are  sounded  in  conjunc- 
tion with  a  vowel.  While  the  distinction  between  vowels  and 
consonants,  as  already  mentioned,  is  not  an  absolute  one,  it  may  be 
said  that  while  vowels  are  due  to  the  vibrations  of  the  vocal  mem- 
branes being  modified  by  the  mouth,  consonants  are  due  to  the 
expiratory  blast  being  interrupted  in  various  ways  in  its  course 
through  the  throat  and  mouth  ;  the  vibrations  of  the  vocal  mem- 
branes, when  essentia],  being  rather  secondary  in  character.  Con- 
sonants may  be  divided,  according  to  their  manner  of  production, 
into  two  kinds,  explosive  and  continuous,  the  sound  of  the  explosive 
consonants  being  due  to  the  sudden  establishment  or  removal  of  a 
particular  interruption,  that  of  the  continuous  consonant  to  the  air 
rushing  continuously  through  some  constriction,  for  example,  ex- 
plosive consonants  are  the  labials  p,  b,  dentals  t,  d,  and  gutturals 
k,  g,  p,  t,  and  k,  being  uttered  without  the  voice,  the  so-called 
surds  b,  d,  and  g  (hard)  with  the  voice  sonants — that  is,  are  ac- 
companied by  a  vowel  sound.  In  uttering  p  the  lips  arc  first 
closed,  then  the  expiratory  blast  suddenly  opening  them,  the  sound 
is  produced.  Similarly  the  sudden  interruption  of  the  contact  of 
the  tip  of  the  tongue  with  the  hard  palate,  and  of  the  root  of  the 
tongue  with  tlie  soft  palate  gives  rise  respectively  to  the  sounds  t 
and  k.  The  continuous  consonants  are  subdivided  into  aspirates, 
resonants,  and  vibratory. 

In  certain  cases  a  brief  sound  due  to  the  sudden  opening  of  the 
closed  glottis,  the  so-called  spirited  lenis,  inaugurates  a  vowel,  the 
vibrations  of  the  vocal  membranes  immediately  following  with  the 
production  of  a  true  vowel  sound.  In  other  cases  in  uttering  a 
vowel  the  glottis  being  open  but  constricted  irregular  vibrations 
produced  by  friction  give  rise  to  the  so-called  spiritus  aspera. 

The  aspirates  include  the  labials  f,  v,  the  dentals  s,  1,  sh,  th 
(hard),  z,  zh,  th  (soft),  and  the  gutturals  ch,  gh.  Like  the  explo- 
sive consonants,  some  of  the  aspirates  are  uttered  without  the  voice, 
as  f,  s,  1,  sh,  c,  h ;  some  with  the  voice,  as  v,  z,  zh,  th,  ch.  The 
resonants  include  the  sounds  m,  n,  ng,  and  the  vibratory  the  sound 
r,  common  and  guttural.  Of  the  aspirates,  f  and  s  are  formed 
through  the  lips  and  teeth  being  brought  nearly  in  contact  respec- 
tively ;  th  through  the  placing  of  the  tongue  between  the  two  par- 
tially open  rows  of  teeth ;  1  when  the  tip  of  the  tongue  is  placed 


PRODUCTION  OF  COXSOXANTS.  825 

against  the  hard  pahite,  and  the  air  escapes  at  the  sides  ;  sh  through 
the  dorsal  surface  of  the  tongue  being  raised  toward  the  pakiti,  the 
passage-way  between  the  two  being  thereby  narrowed ;  ch  and  gh 
through  the  approximation  of  the  root  of  the  tongue  to  the  soft 
palate.  In  the  production  of  all  of  the  resonants  the  vocal  mem- 
branes vibrate  and  the  nasal  chambers  resonate,  the  closing  of  the 
lips  in  particular  giving  rise  to  m,  the  contact  of  the  tongue  with 
the  hard  palate  to  n,  and  the  approximation  of  the  root  of  the 
tongue  to  the  soft  palate  to  ng.  The  vibratory  consonants  include 
the  various  forms  of  the  sound  r,  so  called  on  account  of  being 
produced  by  the  vibration  of  the  constricted  portion  of  the  vocal 
passage  ;  thus,  the  common  r  is  due  to  the  vibrations  of  the  point 
of  the  tongue  elevated  against  the  hard  palate ;  the  guttural  r  to 
vibrations  of  the  uvula  or  other  parts  of  the  walls  of  the  pharynx. 
The  tongue,  while  an  organ  of  speech,  is  not  essential,  since  after  its 
loss  the  faculty  of  speech,  more  or  less  perfect,  remains.  Finally, 
while  the  consonant  e  is  a  breathed  aspirate,  it  diifers  from  all  other 
letters  in  being  formed  in  the  larynx  itself,  the  glottis  being  nar- 
rowed enough  to  produce  a  wind-rush,  but  not  sufficiently  to  throw 
the  vocal  membranes  into  vibration,  c  is  redundant,  producing 
the  same  effect  as  k  or  s  ;  q  is  equivalent  to  1,  being  used  only  be- 
fore the  vowel  u  ;  x  is  the  same  as  ks  at  the  end  of  a  syllable,  and 
z  when  beginning  a  word. 

While  the  limits  of  this  work  will  not  permit  of  any  further 
detailed  consideration  of  orthoepy,  or  of  any  theory  of  the  origin 
and  growth  of  language  in  general,  or  of  that  of  the  language  in 
which  this  work  is  written  in  particular,  the  above  description  will 
suffice  as  a  general  account  of  the  production  of  articulate  speech, 
a  factor  almost  as  important  as  that  of  intelligence  in  the  develop- 
ment of  civilization. 


CHAPTER    XLIII. 

THE   STRUCTURE    OF   THE   EAR,    AND    THE   SENSATION    OF 

HEARING. 

The  organ  of  hearing  is  usually  described  as  consisting  of  three 
parts,  the  external  ear,  including  the  pinna  or  auricle  and  the  ex- 
ternal auditory  meatus,  the  middle  ear  or  tympanum,  and  the  in- 
ternal ear,  including  the  labyrinth  and  the  auditory  nerve.  For 
convenience,  as  well  as  to  avoid  repetition,  the  functions  of  the 
three  parts  of  the  ear  will  be  considered  at  the  same  time  as  that 
of  the  description  of  their  structure. 

The  Structure  and  Functions  of  the  External  Ear. 

The  pinna,  auricle,  or  ear,  in  the  ordinary  sense  of  the  term — that 
is,  the  portion  projecting  from  the  head  (Fig.  504),  with  the  excep- 

FiG.  504. 


Diagram  of  organ  of  hearing  of  left  side.  1.  The  pinna.  2.  Bottom  of  ooncha.  2,2.  Meatus 
externus.  o.  Tym])amim.  Aljuve  3,  the  chain  of  o.ssieles.  :i  ()])euiiig  into  the  ma.stoid  cells.  4. 
P^u.stachiau  tube.  .1  Meatus  internus,  containing  the  facial  (uppermost )  and  auditory  nerves,  6, 
placed  on  the  vestibule  of  the  labyrinth  above  the  fenestra  ovalis.  A.  Ape.x  of  the  petrou.s  l)one. 
B.  Internal  carotid  artery.  C.  .Styloid  process.  1).  Facial  nerve,  issuing  from  the  stylo-mastoid 
foramen.     E.  Mastoid  jjrocess.     F.  Squamous  jiart  of  the  bone.     (Quaix  after  Arsoli).) 

tiou  of  the  lower  lobular  portion,  consists  of  fibro-cartilage  and  pre- 
sents certain  prominences,  the  tragus  and  antitragus  ridges,  the  helix 
and  antihelix,  which,  together  with  their  fossse,  adapt  it  to  receive 
the  aerial  viljrations  giving  rise  when  transmitted  to  the  auditory 


STBCCTUBE  OF  THE  MIDDLE  EAR.  >^'2~ 

nerve  to  the  sensation  of  stmiid.  Owing-  to  the  inimolnlity  of  the 
ear,  through  tlie  imperfect  development  of  the  attoleus,  attrahens, 
and  retrahens  auri,  as  well  as  its  intrinsic  muscles,  the  external  ear 
is  not  as  functionally  important  in  man  as  in  the  case  of  the  lower 
animals  for  the  appreciation  of  the  intensity  of  sound,  since  persons 
deprived  of  it  do  not  experience  any  sensible  change  in  their  power 
of  hearing.  That  the  auricle  is,  however,  of  use  in  enabling  us  to 
judge  as  to  the  direction  of  sounds,  any  one  can  convince  himself 
by  filling  the  convolutions  with  wax,  or  flattening  the  ear  forcibly 
against  the  side  of  the  head,  when  it  Avill  be  found  impossible  to 
determine  the  direction  from  which  the  sound  comes.  Such  is  also 
the  experience  of  those  persons  who  have  lost  the  external  ear  from 
wounds,  etc.  Indeed,  there  can  be  little  doubt  that  we  judge  as  to 
the  origin  and  direction  of  sounds  from  the  fact  that  the  sound 
waves  do  not  impinge  upon  the  ears  alike,  and  that  the  intensity  of 
the  sound  is  modified  by  the  manner  in  which  it  fiills  upon  the  ex- 
ternal ear  and  is  reflected  from  it.  Hence,  in  determining  whether 
a  sound  proceeds  from  directly  behind  or  in  front  of  us,  we  usu- 
ally incline  the  head  in  the  direction  from  which  we  suppose  it  to 
come.  The  aerial  vibrations  having  been  collected  by  the  auricle, 
are  thence  transmitted  by  the  external  auditory  meatus  from  the 
concha  or  the  deep  concavity  within  the  position  of  the  antihelix 
and  subdivided  l)y  the  helix  to  the  tympanum.  The  external  audi- 
tory meatus,  about  an  inch  aud  a  quarter  in  length,  is  directed  in- 
ward and  forward,  upward  and  downward,  and  is  narrowest  at  its 
middle  portion.  It  consists  of  two  portions,  an  iuterfibro-cartilagi- 
nous  one,  the  prolongation  of  the  auricle,  and  an  inner  osseous  one, 
a  part  of  the  temporal  bone,  both  portions  l>eing  lined  with  skin. 
The  skin  of  the  outer  portion  is  thick  and  provided  with  numerous 
hair,  sebaceous  and  ceruminous  glands.  The  latter,  small,  round, 
brownish-yellow  bodies  imbedded  in  the  subcutaneous  tissue,  and 
giving  rise  to  the  punctured  appearance  of  the  skin,  are  modified 
sudoriferous  glauds,  consisting,  like  the  latter,  of  a  narrow  tube 
coiled  upon  itself  in  the  form  of  a  ball,  and  secrete  the  cerumen  or 
ear-wax.  The  latter  is  said  to  be  composed  of  fiitty  and  albumi- 
nous matters  of  salts  of  soda  and  lime,  and  has  a  very  bitter  taste,  a 
property  which  has  been  considered  of  service  in  preventing  insects 
entering  the  ear.  The  cerumen,  which  probably  consists  of  seba- 
ceous matter  mixed  with  the  proper  secretion  of  the  ceruminous 
glands,  lubricates  the  meatus.  The  skin  of  the  inner  osseous  por- 
tion of  the  meatus  is  very  thin,  destitute  of  hairs  and  glands,  and 
at  the  bottom  of  the  meatus  is  continued  over  the  tympanic  mem- 
brane as  its  outer  investing  layer. 

The  Structure  of  the  Middle  Ear. 
The  middle  ear,  separated  from  the  external  ear  by  the  tympanic 
memlirane,  includes  tiie  tympanum  or  drum  of  the  ear,  the  ear  bones, 
with  their  ligaments,  muscles,  the  mastoid  sinuses,  aud  the  Eusta- 


828 


STRUCTURE  OF  THE  EAR. 


chian  tube.  The  tympauum,  au  irregular  cavnty  in  the  interior  of 
the  petrous  portion  of  the  temporal  bone,  is  about  half  an  inch  in 
height  and  breadth,  and  perhaps  the  sixth  of  an  inch  from  without 
inward,  is  closed  in  front  by  the  tympanic  membrane,  at  the  back 
by  the  wall  of  the  labyrinth,  and  opens  above  and  posteriorly  into 
the  sinuses  and  in  front  into  the  Eustachian  tube.  The  tympanic 
membrane  separating,  as  already  mentioned,  the  external  auditory 
meatus  from  the  tympanum,  is  about  two-fifths  of  an  inch  in  height 
and  breadth,  somewhat  funnel-shaped  in  form,  and  is  disposed 
obliquely,  making  an  angle  of  40°  with  the  floor  of  the  meatus. 
That  part  of  the  membrane  drawn  inward  by  the  tip  of  the  ma- 
nubrium of  the  malleus  and  constituting  a  central  depression  is 
called  the  umbo.  The  oblique  position  of  the  tympanic  membrane 
is  of  advantage,  since  more  sound  waves  fall  vertically  upon  it  than 
if  it  were  placed  vertically. 

The  tympanic  membrane  is  inserted  by  the  greater  part  of  its  cir- 
cumference into  a  groove  which,  while  in  the  adult  is  regarded  as 
a  portion  of  the  temporal  bone,  is  in  reality  the  only  part  visible  of 
an  originally  entirely  separate  osseous  ring,  the  homologue  of  the 

'^  Fig.  505.  B 


C* 


Bones  of  the  tyiii)i;irimn  cil'  the  left  side.  A.  Malleus.  1.  Ldiig  or  slender  process,  li.  The 
handle.  4.  Sliorl  proeess.  .l.  Head.  B.  Incus.  1.  Body.  '1.  Short  or  posterior  process.  3.  The 
long  process  with  the  orbicular  process  4.  C.  Stajies.  1.  Head.  4,5.  Crura.  6.  Base.  I).  The 
three  bones  in  their  natural  connection,  m.  Malleus,  .vc.  incus,  x.  Stajies.  C*.  Base  of  the 
stapes. 

tympanic  bone  of  the  lower  vertebrates,  but  which  in  man,  instead 
of  remaining  distinct  as  in  them,  coossifies  as  development  advances 
witli  the  tem})oral  bone,  and  grows  outwardly  as  the  osseous  external 
auditory  meatus,  its  morphological  significance  being  thereby  entirely 
lost  sight  of. 


OSSICLE,^  OF  THE  MIDDLE  EAR.  829 

At  tlie  point  Avherc  the  ring  of  bone  is  wanting  the  tympanic 
membrane  is  attached  to  the  bone  above,  and  being  less  tense  in  that 
position  even  when  thrown  into  folds  is  distingnished  as  the  mem- 
brana  flaccida.  The  tympanic  membrane,  thin  and  translncent,  is 
composed  of  a  layer  of  fibrous  tissue,  the  membrana  propria,  cov- 
ered externally  by  the  skin  of  the  external  auditory  meatus,  and 
internally  by  the  mucous  membrane  of  the  tympanum,  the  latter 
being  continuous  with  that  lining  the  Eustachian  tube.  The  fibrous 
layer  of  the  tympanum  consists  of  two  sets  of  fibers,  of  which  the 
greater  part  radiate  from  its  center,  the  remaining  ones  being  con- 
centrically disposed  at  tlic  periphery.  The  little  ear  bones  (Fig. 
505),  three  in  number,  the  malleus,  incus,  and  stapes,  are  disposed 
within  the  tympanum  from  before  backward  in  the  order  named. 
The  malleus,  so  called  on  account  of  its  resemblance  to  a  hammer, 
is  suspended  vertically  from  the  floor  of  the  tympanum  by  a  slender 
band  of  fibers,  the  suspensory  ligament,  which  passes  into  its  head, 
the  latter  articulates  through  an  oval  facet  covered  with  cartilage 
with  the  body  of  the  incus.  The  malleus  is  also  connected  Avith  the 
tympanic  membrane,  its  tapering,  slightly  twisted  manubrium  or 
handle  passing  down  into  the  fibrous  layer  of  the  latter  as  far  as  its 
center.  From  the  neck  of  the  malleus,  or  the  constricted  portion 
below  the  head,  two  processes  are  given  off. 

The  larger  process  or  processus  gracilis  projecting  at  right  angles 
and  passing  into  the  Glasserian  fissure  is  attached  by  ligament  to 
the  spinous  process  of  the  sphenoid  bone.  The  smaller  process 
gives  attachment  to  the  tensor  tympani  muscle,  so  called  on  account 
of  its  tensing  the  tympanic  membrane  and  which,  arising  from  the 
end  of  the  cartilage  of  the  Eustachian  tube,  and  the  contiguous 
surfaces  of  the  sphenoid  and  temporal  bones,  passes  through  a 
special  canal  of  the  latter  into  the  tympanum. 

The  incus  or  anvil,  situated  behind  and  articulated  with  the 
malleus  as  already  mentioned,  is  also  sustained  in  its  position  by  a 
fibrous  band,  passing  from  its  short  process  to  the  margin  of  the 
opening  leading  into  the  mastoid  cell.  The  long  process  of  the 
incus,  curved  and  tapering,  descending  nearly  parallel  with  the 
manubrium  or  handle  of  the  malleus,  terminates  in  the  so-called 
orbicular  process,  by  which  it  articulates  through  cartilage  with  the 
facet  on  the  head  of  the  stapes,  or  stirrup.  The  orbicular  process 
is  in  reality  a  distinct  bone,  being  separable  from  the  incus  even  at 
birth  ;  soon  after,  however,  it  becomes  so  ossified  with  the  latter  as 
to  be  undistinguishable  from  it.  The  stapes,  or  stirrup,  situated 
inwardly  between  the  incus  and  the  foramen  ovale  of  the  vestibule, 
is  disposed  at  right  angles  to  the  long  process  of  the  incus,  the 
crura — that  is,  the  portion  joining  its  head  and  its  base,  lying  hori- 
zontally in  the  tympanum.  By  its  annular  ligament,  the  margin 
of  the  base  of  the  stapes  is  connected  with  the  border  of  the  fora- 
men ovale  of  the  vestibule,  the  pressure  of  the  base  of  the  stapes 
against  the  oval  window  or  the  perilymph  back  of  it  being  regu- 


830  STRUCTURE  OF  THE  EAR. 

latecl  by  the  stapeclius  muscle,  which,  arising  within  the  hollow  of 
the  pyramid,  or  the  conical  eminence  projecting  from  the  back  part 
of  the  tympanum,  is  inserted  into  the  head  of  the  stirrup. 

The  mastoid  sinuses,  so  called  from  being  situated  in  the  interior 
of  the  mastoid  portion  of  the  temporal  bone,  are  irregular  cavities 
lined  with  mucous  membrane,  which  communicate  by  a  large  orifice 
with  the  upper  and  back  part  of  the  tympanum.  The  Eustachian 
tube  (Fig.  504,  e),  al)out  an  inch  and  a  half  long  and  somewhat 
trumpet-shaped  in  form,  extends  from  the  front  part  of  the  tympa- 
num obliquely  downward,  forward,  and  inward,  terminating  by  an 
oval  orifice  in  the  pharynx  on  a  level  with  the  turbinated  bone  at 
the  back  of  the  posterior  nasal  orifice.  The  Eustachian  tube  con- 
sists of  two  portions,  an  upper  osseous  portion  situated  in  the 
petrous  portion  of  the  temporal  bone  and  opening  into  the  tympa- 
num, and  a  lower  fibro-cartilaginous  portion  opening  into  the 
pharynx,  the  two  portions  being  united  within  the  angle  between 
the  squamous  and  petrous  portions  of  the  temporal  bone.  It  is 
lined  with  mucous  membrane  provided  with  ciliated  epithelium, 
continuous  on  the  one  hand  with  that  of  the  tympanum,  and  on  the 
other  with  that  of  the  pharynx.  The  existence  of  such  a  tube  as 
that  just  described,  putting  the  cavities  of  the  middle  ear  in  com- 
munication with  that  of  the  pharynx,  as  well  as  the  presence  of  a 
chain  of  bones  connecting  the  membrana  tympani  with  the  oval 
window  of  the  vestibule,  will  become  intelligible  when  the  develop- 
ment of  the  ear  is  considered. 

Functions  of  the  Middle  Ear. 

Such  being  in  general  the  structure  and  relations  of  the  tympanic 
membrane,  ear  bones,  Eustachian  tube,  etc.,  if  the  aerial  vibrations 
collected  and  transmitted  by  the  auricle  to  the  external  auditory 
meatus  throw  the  tympanic  membrane  into  vibration,  the  vibrations 
of  the  latter  will  in  turn  be  transmitted  by  the  ear  bones  through 
the  intermediation  of  the  fluids  of  the  vestibule,  etc.,  to  the  termi- 
nal filaments  of  the  auditory  nerve,  and  so  give  rise  to  the  sensation 
of  sound. 

The  importance  of  the  membrana  tympani  in  audition  is  shown 
by  the  fact  that  the  acuteness  of  hearing  is  always  more  or  less 
aflFected  in  those  cases  in  which  the  membrane  is  thickened,  per- 
forated, or  destroyed,  and  that  relief  is  obtained  by  the  wearing  of 
an  artificial  membrane  if  the  latter  can  be  tolerated.  This  becomes 
perfectly  intelligible  when  it  is  remembered,  as  shown  by  Miiller,^ 
that  while  aerial  vibrations  are  communicated  to  solid  bodies  like 
the  ear  bones  only  with  difficulty  and  Avith  considerable  diminution 
in  their  intensity,  they  are  communicated  very  readily  to  the  same, 
a  tense  membrane  like  the  tympanic  membrane  intervening,  the 
fact  of  the  membrane  being  fixed  at  the  periphery,  and  having  air 
on  both  sides  of  it  being  also  most  favorable  conditions.  That  mem- 
•  Physiology,  Vol.  ii.,  p.  1248. 


FUXCTIOXS  OF  THE  MIDDLE  EAR.  831 

branes  of  as  small  extent  as  tliat  of  tlie  m('m])i'ana  tympani  wlien 
stretched  are  readily  thrown  into  vibration,  can  be  shown  by  ex- 
periments like  those  of  Savart  ^  in  which  sand  strewed  over  their 
surface  was  cast  oif,  on  sonorous  vibrations  being  excited  in  their 
vicinity.  It  is  a  well-known  fact,  that  membranes  vibrate  more 
powerfully,  more  intensely,  when  relaxed  than  when  tensed,  hence 
the  sensitiveness  to  all  sounds  experienced  in  facial  palsy,  which  is 
due  to  the  want  of  innervation  of  the  tensor  tympanic  muscles  by 
the  filaments  of  the  paralyzed  facial  supplying  it.  It  is  also  worthy 
of  mention  in  this  connection  that  the  vibrations  of  the  mcmbrana 
tvmpani  are  more  intense  in  proportion  as  tlie  latter  approaches  a 
vertical  position,  as  accounting  to  some  extent  for  the  appreciation 
of  sounds  by  musicians,  in  some  of  whom  the  tympanic  membrane  is 
almost  vertically  disposed,  whereas  in  persons  with  but  little  car 
for  music  the  membrane  is  very  oblique  in  position.  It  has 
already  been  explained  that  sounds  not  only  differ  in  their  loud- 
ness or  intensity,  but  in  their  pitch  or  number  of  vibrations  per 
second  as  well,  and  since  we  hear  sounds  of  different  pitch,  it  is 
obvious,  therefore,  that  there  must  be  some  means  of  tuning — that 
is,  of  tightening  or  relaxing  the  tympanic  membrane,  so  that  the 
vibrations  of  the  latter  shall  be  the  same  per  second  as  those  to 
which  the  particular  note  or  notes  heard  are  due.  That  is  to  say, 
every  sonorous  aerial  wave — that  is,  a  condensation  and  a  rarefac- 
tion— bending  the  tympanic  membrane  once  in  and  once  out,  the 
rate  of  vibration  of  the  membrane  must  be  the  same  as  that  of  the 
vibration  of  the  sonorous  body  causing  it,  if  the  particular  sound 
due  to  the  latter  is  to  be  heard.  That  the  membrana  tympani  is 
relaxed  for  sounds  of  low  pitch  and  tensed  for  those  of  high  pitch, 
is  shown  by  the  insensil)ility  to  low  tones,  and  marked  appreciation 
to  high  ones,  being  proportional  to  the  extent  to  which  the  mem- 
brane is  tensed.  Thus,  if  the  mouth  and  nose  being  closed,  we  at- 
tempt to  breathe  forcibly  by  expanding  the  chest,  the  air  within 
the  tympanum  becoming  rarefied,  the  tympanic  membrane  will  be 
forced  in  by  the  external  air  and  rendered  more  tense,  the  effect  of 
which  is  that,  as  Dr.  WoUaston  -  showed,  we  become  deaf  to  low 
sounds.  A  similar  deafness  to  sounds  of  low  pitch  is  also  produced, 
the  nose  and  mouth  being  stopped  when  a  strong  effort  is  made  to 
expire,  the  increased  tension  of  the  membrane  being  due,  however, 
in  this  instance  to  the  air  being  forced  into  the  tympanum  through 
the  Eustachian  tube  instead  of  being  sucked  out  of  it  and  the  mem- 
brane being  pushed  outwardly.  A  sudden  concussion  may  produce 
temporary  deafness  in  either  of  the  al)Ove  ways — that  is,  by  forcing 
air  either  into  or  out  of  the  tympanum. 

It  is  evident,  from  the  facts  just  mentioned,  that  the  function  of 
the  Eustachian  tube  is  the  maintaining  of  equilibrium  between  the 
air  within  the  tympanum  and  the  air  without.     Hence  if  the  tube 

1  Journal  de  Physiologie,  Tome  iv.,  p.  203.     Paris,  1824. 
2Philos.  Trans.,  Lond.,  1820,  p.  300. 


832  STRUCTURE,  OF  THE  EAR. 

be  closed,  which  is  usually  the  case,  according  as  the  external  air 
becomes  denser,  as  in  descending  in  a  diving-glass,  or  rarer,  as  in 
making  high  mountain  ascents,  the  tympanic  membrane  will  be 
pushed  in  or  out  in  either  case,  will  be  rendered  more  tense  and 
pain  and  deafness  experienced,  both  of  which  can,  however,  be 
usually  relieved  by  the  act  of  swallowing,  which,  in  opening  the 
Eustachian  tube,  reestablishes  the  equilibrium  between  the  internal 
and  external  pressure.  It  may  be  mentioned,  in  this  connection, 
that  the  Eustachian  tube  is  opened  by  the  contraction  of  the  tensor 
palati,  levator  palati,  and  the  palato-pharyngeus  muscles  ;  the  tensor 
palati,  in  drawing  the  hook  of  the  cartilage  outward,  and  the  levator 
palati,  in  drawing  the  end  of  the  cartilage  upward  and  inward,  en- 
large and  Aviden  its  pharyngeal  orifice,  the  palato-pharyngeus  fixing 
the  cartilage.  With  the  relaxing  of  the  muscles  just  mentioned, 
through  the  elasticity  of  the  cartilage,  the  tube  then  closes  again 
almost  entirely,  a  narrow  chink  alone  remaining.  Since,  while  the 
Eustachian  tube  is  oj^en,  the  cavity  of  the  tympanum  is  in  commu- 
nication with  that  of  the  pharynx,  it  follows  that  if  we  swallow 
several  times  in  succession,  the  nose  and  mouth  being  closed,  that 
the  air  will  be  gradually  drawn  from  the  tympanic  cavity,  the 
membrane  being  rendered  tense  by  the  external  atmospheric  pres- 
sure, as  in  the  case  just  mentioned,  in  which  forced  inspiratory  ef- 
forts were  made,  and  an  insensibility  to  low  sounds  experienced. 
That  the  tympanic  membrane  is  tensed  for  high  sounds  is  shown 
by  the  fact  that  in  certain  individuals,^  whose  ordinary  limit  of  ap- 
preciation was  of  sounds  due  to  fifteen  hundred  vibrations  per  sec- 
ond by  voluntary  contraction  of  the  tensor  tympani  muscle,  this 
was  increased,  so  that  sounds  could  be  heard  due  to  2,500  vibrations 
per  second.  There  can  l>e  little  doubt,  then,  that  the  membrana 
tympani  is  relaxed  or  tensed,  according  as  the  sonorous  vibrations 
are  low  or  high  in  pitch,  and  that  the  variations  in  the  tension  of 
the  membrane  are  regulated  by  the  action  of  the  tensor  tympani 
muscle.  While  there  is  a  great  difference  in  individuals  as  regards 
the  appreciation  of  sounds,  some  persons  being  insensible  to  the  hum 
of  insects,  the  chirrup  of  the  sparrow,  the  squeak  of  the  bat,  others 
to  the  high  sounds  of  small  organ-pipes,  or  even  the  highest  notes 
of  the  piano,  there  is  a  limit,  nevertheless,  to  audibility  in  all,  the 
tympanic  membrane  failing  to  link  together  into  a  continuous  tone 
vibrations  succeeding  each  other  less  rapidly  than  16  a  second,  or 
more  so  than  38,000  a  second.  In  the  former  case,  we  are  con- 
scious only  of  separate  shocks ;  in  the  latter,  we  are  unconscious  of 
sound  altogether.  The  range  of  audibility  lying  within  the  above 
limits  embraces,  therefore,  about  1 1  octaves,  of  which  about  two- 
thirds,  or  7  octaves  only,  are,  however,  made  use  of  in  music.  It 
is  true  that  we  obtain  from  the  lowest  C  of  the  piano  the  note 
due  to  32  vibrations  per  second,  and  from  the  lowest  A  of  the 
new  grand  piano  that  due  to  27  vibrations  per  second,  and  from  a 
'Blake,  Trans,  of  the  Amer.  (Jtological  Soc,  Vol.  v.,  p.  77.     Boston,  1872. 


RANGE  OF  MUSICAL  SOUNDS.  833 

closed  organ-pipe  1 G  feet  long,  or  an  open  one  32  feet  long,  the 
lowest  C,  due  to  16  vibrations  per  second,  but  the  latter  sound,  and 
that  of  the  lowest  C  or  A  of  the  piano,  are  so  unmusical,  so  dull 
and  groaning  in  character,  that  they  are  ])ut  little  used.  The  deep- 
est tone  made  use  of  in  orchestral  music  being  that  due  to  the  E 
string  of  the  double  bass,  giving  41]-  vibrations,  the  highest  that  of 
the  D  of  the  piccolo  flute,  due  to  4,752  vibrations  per  second  ;  it  may 
be  said  that  practically  the  range  of  musical  sounds  is  confined  be- 
tween 40  and  4,000  vibrations  per  second,  the  highest  C  of  the 
piano  reaching  4,224  vibrations  per  second — that  is,  in  round  num- 
bers, as  just  said,  about  7  octaves.  Even  within  such  limits  the  im- 
mense number  and  kind  of  sonorous  waves  that  fall  upon  the  tym- 
panic membrane  while  listening  to  a  grand  opera  as  given  by  the 
leading  artists,  together  with  full  choral  and  grand  orchestral  ac- 
companiment, must  impress  one  with  the  remarkable  acoustic  prop- 
erities  of  the  membrana  tympani,  so  small  and  delicate,  and  yet 
so  susceptible  to  such  an  immense  number  and  variety  of  sounds. 
But  little  imagination  is  required  to  picture  to  one's  self,  during  tlie 
performance  of  an  opera,  the  sonorous  waves  flowing  across  the 
auditorium,  and  breaking  upon  the  drum  of  the  ear  like  those  of 
the  ocean  upon  some  weather-beaten  rock  or  beach,  the  long  waves, 
from  35  to  12  feet  in  length  proceeding  from  the  deep  bass  instru- 
ments and  voices  of  the  bassos  like  billows  from  the  distant  sea,  the 
short  ones  from  30.3  inches  in  length,  like  ripples  or  white  caps, 
from  the  violins,  flutes,  and  voices  of  the  tenors  and  sopranos,  with 
intermediate  ones  of  different  lengths,  and  yet  all  following  each 
other  in  such  orderly  mathematical  sequence  that,  amidst  such  a 
variety  of  sounds,  we  are  conscious  of  nothing  but  melodious  and 
harmonious  tones.  From  the  fact  of  our  being  able  to  appreciate 
the  latter,  it  is  obvious  that  the  tympanic  membrane  is  susceptible 
of  being  impressed  by  simultaneous  as  well  as  by  successive  sounds, 
and  while  the  limits  of  this  work  do  not  permit  of  any  considera- 
tion of  harmony,  discord,  of  chords,  of  consonant  intervals,  or  those 
that  give  the  ear  a  sense  of  relief,  or  dissonant  ones  that  must  be 
resolved,  etc.,  it  seems  proper  to  jioint  out  and  illustrate  the  fact  that 
the  vibrations  to  which  harmonious  sounds  are  due  are  in  a  definite 
ratio  to  each  other,  and,  that,  whatever  the  cause  may  be,  sounds 
are  harmonious  in  proi)ortion  as  the  ratio  between  the  number  of 
the  vibrations  giving  rise  to  them  is  a  simple  one. 

The  simplest  ratio  being  one  to  one,  two  sounds,  as  produced  by 
the  siren,  for  example,  will  l)e  in  perfect  union,  if  the  pitch  of  both 
be  the  same.  The  next  simplest  ratio  being  1  to  2,  a  harmonious 
sound  will  remain,  if  with  the  fundamental  its  first  overtone  above, 
or  octave,  be  at  the  same  time  given — that  is,  if  with  Do^  C^  256 
vibrations  per  second,  Do*,  C*  512  vibrations  per  second  be  also 
sounded.  The  waves,  never  interfering  with  each  other,  will  give 
rise  to  no  discord,  and  the  two  sounds  blended  into  one  may  be 
continued  indefinitely.  Proceeding  in  the  same  manner,  according 
53 


834  STRUCTURE  OF  THE  EAR. 

to  the  simplicitv  of  the  ratio,  the  next  in  order  will  be  that  of  2  to 
3,  or  C  to  G — that  is,  with  Do^  C  256  vibrations  per  second,  Sol'' 
G^  384  vibrations  per  second  may  be  sounded ;  for  there  being  for 
every  two  waves  of  C  three  waves  of  G,  there  will  be  a  coincidence 
for  every  second  wave  of  C  and  every  third  wave  of  G.  The 
next  ratio  being  that  of  3  to  4,  or  C  and  F,  C'^  and  F^  Fa\  341.3 
vibrations  per  second,  may  be  sounded  together.  Although  we 
have  already  shown  by  the  siren  that  the  sounding  of  the  notes  C  E 
G,  together,  give  rise  to  the  harmonious  major  chord,  nevertheless, 
according  to  the  law  that  the  smaller  the  ratio  of  vibration  between 
diiferent  sounds  the  more  perfect  the  harmony,  the  combination  of 
C  with  E — that  is,  in  the  ratio  of  4  to  5,  or,  as  in  the  above,  of 
256  to  320 — is  a  less  pleasing  one  than  that  of  C  to  F,  in  which 
the  ratio  is  3  to  4.  It  is  the  want  of  harmony  of  F  with  G  that 
excludes  it  from  the  cord  C  E  G  C  ;  the  cord  C  F  A  C  is,  how- 
ever, a  harmonious  one.  Continuing  the  next  ratio,  that  of  6  to  5, 
or  of  C  to  E  flat,  a  minor  third,  consistently  with  its  ratio,  being 
less  simple  than  that  obtaining  in  the  major  third,  is  a  less  harmo- 
nious one.  Finally,  as  illustrating  a  step  further  the  law  just 
enumerated,  it  may  be  mentioned,  though  well  known,  that  the  in- 
terval corresponding  to  a  tone  in  which  the  vibrations  giving  rise 
to  the  two  notes  C"  D^,  for  example,  are  in  the  ratio  8  to  9,  256  to 
288  is  a  dissonant  one,  and  that  the  interval  of  a  semitone  C  to  D 
flat,  in  which  the  ratio  ^is  15  to  16,  is  a  very  sharp,  grating,  and 
dissonant  one.  About  five  hundred  years  before  our  era^  it  was 
shown  by  Pythagoras  that  if  a  stretched  string  was  so  divided  into 
two  parts  that  one  was  twice  the  length  of  the  other,  and  the  two 
parts  of  the  string  sounded  simultaneously,  that  the  note  emitted 
by  the  short  part  was  the  octave  emitted  by  the  long  one.  Contin- 
uing to  experiment,  this  celebrated  philosopher  next  showed  that 
if  the  string  be  divided  in  the  ratio  of  2  to  3  then  the  interval  be- 
tween the  notes  emitted  would  be  that  of  a  fifth  ;  and  further,  that, 
according  to  the  ratio  in  which  the  string  was  divided,  the  remain- 
ing more  or  less  consonant  intervals  would  be  heard,  the  harmony 
of  the  two  sounds  being  proportional  to  the  simplicity  of  the  ratio 
of  the  two  parts  into  which  the  string  was  divided. 

1st, 

Note, C 

Lengths  of  the  string,       1 
Number  of  vibrations,     256     288 

This  important  law,  the  first  step  made  in  the  physical  ex})laua- 
tion  of  musical  intervals,  Pythagoras,  however,  did  not  account 
for,  it  remaining  for  later  investigators  to  show  that  the  vibrations 
of  strings  are  inversely  proportional  to  their  length.  It  has  just 
been  mentioned  that  while  the  combination  of  a  fundamental  tone 
with  its  octave,  for  example,  is  a  consonant,  pleasing  one,  giving 
'  Montucla,  Hist,  des  Matheraatiques,  Paris,  An.  vii.,  Tome  i.,  ]>.  114. 


2(1. 

yd. 

4th. 

3th. 

Gth. 

7th. 

8th. 

D 

E 

F 

G 

A 

B 

c 

J88 

4 

320 

341 

t 
384 

3 

426 

_8_ 

480 

512 

CA  USE  OF  BEA  TS.  83  5 

rise  to  no  discord,  tliat  of  the  interval  of  a  tone,  or  of  a  semitone, 
is  a  dissonant,  disagreeable,  discordant  one.  It  remains  for  us  now, 
therefore,  to  determine,  if  possible,  the  physical  cause  of  discord. 
It  will  be  remembered  that  in  the  double  siren  of  Helmholtz  there 
are  two  series  of  12  orifices,  each  common  to  both  sirens;  such  be- 
ing the  case,  if  both  these  series  of  orifices  are  opened  and  air 
forced  through  the  instrument,  the  tM'o  sounds  produced  will  be  in 
unison,  and  will  continue  so,  since  the  pitch  of  both  will  be  the 
same  however  low  or  high  the  sound  may  be.  In  describing  the 
double  siren  attention  was  also  called  to  "the  flict  that,  by  turning 
the  handle  of  the  upper  siren  the  orifices  of  the  wind  chest  will 
either  meet  or  retreat  from  those  of  its  retreating  disk,  the  pitch  of 
the  upper  siren  rising  or  falling  accordingly.  But  the  relation  of 
the  rotation  of  the  handle  to  that  of  the  upper  wind  chest  is  such 
that  if  the  handle  be  turned  through  45  degrees  the  wind  chest 
turns  through  15  degrees,  or  through  the  2V  of  its  circumference, 
which  causes  the  orifices  of  the  upper  wind  chest  to  be  closed  at 
exactly  the  same  moment  that  the  1 2  orifices  of  the  lower  wind 
chest  are  opened,  and  vice  versa,  the  effect  of  which  is  that  the  in- 
tervals between  the  pufFs  of  the  lower  siren — that  is,  the  rarefac- 
tions of  its  sonorous  waves — Avill  be  filled  up  by  the  puifs  or  con- 
densations of  the  waves  of  the  upper  one.  But  if  the  condensation 
of  the  one  set  of  sonorous  waves  coincides  with  the  rarefactions  of 
the  other  set  there  will  he  neither  condensation  nor  rarefiiction, 
upon  which  all  sound  depends,  the  fundamental  sounds  of  the 
siren  will  be  extinguished  through  the  interference  of  the  two 
sounds,  as  it  is  called,  and  absolute  silence  would  result  were  it  not 
for  the  presence  of  the  overtones  of  the  siren.  Rotating,  however, 
the  wind  chest  through  30  degrees,  or  the  -^^  of  its  circumference, 
by  turning  the  handle  through  90  degrees,  the  ])uffs  or  condensa- 
tions of  the  sonorous  waves  of  the  loAver  siren  will  coincide  with 
those  of  the  upper  one,  reinforcing  the  latter  ;  and  as  this  latter 
takes  place  once  for  each  90  degrees,  there  will  be  4  of  these  rein- 
forcings,  or  beats,  as  they  are  called,  for  every  3G0  degrees,  or  for 
one  rotation  of  the  handle. 

The  change  in  the  pitch  of  the  sound  emitted  by  the  upper  siren 
induced  by  the  rotating  of  the  handle,  the  pitch  of  the  sound  emit- 
ted by  the  lower  siren  remaining  the  same,  gives  rise  then  to  beats, 
of  which  there  will  be  four  for  every  one  rotation  of  the  handle. 
For  a  time,  however,  there  may  be  heard  twelve  or  eight  beats  ; 
when  such  is  the  case,  it  is  due  to  the  strength  of  the  second  or  first 
overtone  being  sufficient  to  overpower  the  fundamental,  which  vi- 
brating three  times  and  twice  as  rapidly  as  the  fundamental,  will, 
of  course,  give  rise  to  three  times,  or  twice  as  many  beats.  It  is 
through  the  presence  of  these  overtones  that,  though  the  tone  of  the 
fundamental  may  swell  or  sink  as  the  handle  is  turned,  sound  is 
still  heard,  even  though  the  handle  reach  the  position  at  which  the 
fundamental   sound    through    interference   is   extinguished.     Beats 


836  STRUCTURE  OF  THE  EAR. 

can  be  readily  produced  by  tuning  forks  which  are  especially  suited 
for  this  purpose,  no  overtones  being  generated  if  the  forks  be  prop- 
erly toned.  Let  us  suppose,  for  example,  that  of  two  standard 
tuning  forks  Do',  each  giving  256  vibrations  per  second,  and  whose 
sounds  are  therefore  in  unison,  one  of  which  be  weighted  just  suffi- 
ciently to  cause  it  to  vibrate  a  little  more  slowly  than  the  other, 
say  255  times.  The  two  sounds  then  emitted  will  no  longer  flow^ 
on  continuously  in  unison,  there  being  now  alternate  diminutions 
and  reinforcements  of  the  sounds  or  beats,  and  in  this  particular 
case  one  beat  per  second,  which,  it  will  be  observed,  is  exactly  the 
difference  between  the  two  rates  of  vibration  of  the  two  forks,  256 
and  255.  A  moment's  reflection  w-ill  make  it  clear  why  the  beats 
should  occur,  and  at  such  a  rate.  Since  the  one  fork  vibrates  256 
times  in  a  second,  and  the  other  255  times,  it  is  evident  that  at  the 
end  of  the  second  the  wave  of  the  latter  fork  will  be  one  vibration 
behind  that  of  the  former,  and  at  the  end  of  a  half  second  a  half  a 
Avave  behind,  the  one  fork  having  made  128  vibrations,  the  other 
Vllh,  but  at  that  moment  the  condensation  of  the  one  wave  coin- 
ciding with  the  rarefaction  of  the  other,  the  sounds  will  be  extin- 
guished through  their  complete  interference  with  each  other.  From 
the  half  of  the  second  onward,  however,  until  the  end  of  the  second, 
the  condensations  reinforce  each  other  more  and  more,  until  at  the 
end  of  the  256th  vibration  of  the  one  fork,  and  the  255th  of  the 
other,  condensation  coincides  Avitli  condensation,  and  rarefaction  with 
rarefaction,  the  full  effect  of  both  sounds  being  then  expei*ienced. 
Similarly,  from  the  half  second  where  the  interference  is  complete 
backward  to  the  beginning  of  the  second,  condensation  coincides 
more  and  more  with  condensation,  rarefaction  with  rarefaction,  until 
at  the  beginning  of  the  second,  of  course,  as  at  the  end,  the  coinci- 
dence is  complete.  Suppose,  however,  that  the  two  forks  vibrate 
240  and  234  times  a  second,  then  at  the  end  of  the  first  ^  of  a  sec- 
ond, one  fork  will  have  generated  40  sonorous  waves,  the  other  39, 
the  one  wave  being  one  vibration  ahead  of  the  other,  and  therefore, 
at  the  end  of  the  -^^  of  a  second,  half  a  vibration  ahead.  This  in- 
stant being,  however,  that  at  which  interference  is  complete,  during 
Avhich  the  sound  is  extinguished,  the  time  elapsing  on  the  one  hand 
between  it,  or  the  ^V  of  the  second,  and  the  beginning  of  the  second, 
and  on  the  other  to  the  end  of  the  ^  of  the  second,  will  be  charac- 
terized, as  in  the  preceding  case,  by  a  gradual  diminution,  followed 
by  a  gradual  augmentation  of  the  sound  or  one  beat ;  but  as  this  is 
repeated  in  this  case  six  times  during  the  second,  there  will  be  six 
l)eats,  which,  it  will  be  observed,  is  exactly  the  difference  between 
the  two  rates  of  the  forks,  240  and  234.  Experimenting  this  way 
with  forks,  pipes,  etc.,  it  can  be  proved  that  the  number  of  beats 
per  second  is  always  equal  to  the  difference  between  the  rates  of 
vibration  of  the  two  sounds  to  whose  interference  they  are  due. 
Now  it  has  been  shown  by  Helmholtz  that  if  the  beats  per  second 
succeed  each  other  less  rapidly  than  33  per  second,  the  sound  is  not 


RESULTANT  TONES.  837 

disagreeable,  but  if  at  that  rate,  the  dissonance  becomes  then  abso- 
lutely intolerable.  As  the  number  of  beats  per  second,  however,  in- 
creases, the  dissonance  diminishes,  and  when  the  beats  have  reached 
the  rate  of  132  a  second,  they  disappear  and  discord  vanishes.  Beats 
are  therefore  the  cause  of  dissonance  or  discord,  and  intervals  free 
from  them  will  be  harmonious.  Thus  the  fundamental,  due,  for 
example,  to  256  vibrations  per  second,  Avhen  continued  with  its  oc- 
tave to  512  vibrations  is  a  harmonious  one,  free  from  beats,  since 
the  difference  in  the  rate  of  vibration,  or  250,  is  too  high  to  admit 
of  them.  The  interval  of  the  fifth  C  and  G  is  still  harmonious, 
the  difference  in  the  rate  of  vibration,  384  —  256  =  128,  being  also 
too  high.  On  the  other  hand,  the  interval  of  the  fourth  C  and  F 
due  to  341  and  256  vibrations  per  second  respectively,  is  somewhat 
dissonant,  the  difference  between  the  rates  of  vibration  being  59, 
admitting,  therefore  of  that  number  of  beats  below  the  limits  at 
which  discord  vanishes ;  and  the  interval  of  C  and  E  more  disso- 
nant still,  the  diflPerencc  in  their  rates  of  vibration  being  64,  the 
notes  being  due  to  256  and  320  vibrations  per  second,  respectively. 
It  should  be  mentioned  in  this  connection,  in  order  to  avoid  any 
misconception,  that  the  ]>henomenon  of  beats  is  of  an  entirely  dif- 
ferent nature  from  that  of  the  resultant  tones  discovered  by  Sorge, 
Tartini,  and  Helmholtz.  That  resultant  tones  should  ever  have  been 
considered  as  identical  with  beats,  is  not  so  strange,  since  the  rate 
of  vibration  of  the  first  difference  tone,  or  the  loudest  resultant 
tones  like  that  of  beats,  is  equal  to  the  difference  in  the  rates  of 
vibrations  of  the  two  primary  sounds  producing  them,  which  led 
the  celebrated  Young  to  regard  resultant  tones  as  due  to  the  link- 
ing together  of  rapidly  recurring  beats.  That  a  resultant  tone  is 
not  made  up  of  beats  is  shown  by  the  fact  that  while  a  resultant 
tone  due  to  thirty-three  vibrations  per  second  is  smooth,  consonant, 
musical  beats  succeeding  each  other  at  that  rate,  as  already  men- 
tioned, are  most  dissonant. 

In  concluding  this  necessary  digression  upon  the  nature  of  mu- 
sical intervals,  discords,  beats,  resultant  tones,  etc.,  it  must  be 
observed  that  whether  they  are  caused  in  the  manner  indicated,  or 
however  they  may  be  accounted  for  physically,  hereafter,  in  any 
case,  no  explanation  whatever  is  offered  why  one  rate  of  vibration 
should  affect  us  agreeably,  and  another  rate  disagreeably — that  is,  if 
sounds  are  harmonious  through  the  absence  of  discords,  why  should 
the  presence  of  the  latter  give  rise  in  us  to  a  sense  of  discomfort, 
dissonance?  Nor  have  we  any  reason  to  hope,  judging  from  the 
past,  that  the  study  of  mere  acoustics  will  ever  throw  any  light 
upon  our  sensations  of  tone  subjectively,  or  contribute  to  the  prog- 
ress of  music  objectively.  Indeed,  it  appears  to  be  generally  for- 
gotten by  the  cultivators  of  harmony  that  the  best  music  was  com- 
posed when  acoustics  was  in  its  infancy,  to  this  day,  the  best 
illustration  of  theoretical  harmony  being  taken  from  the  works  of 
Mozart,  Handel,  Haydn,  the  science  of  sound  having  not  added  one 
cord  or  progression  that  was  not  known  to  Bach. 


838 


STRUCTURE  OF  THE  EAR. 


llemarkable  as  are  the  properties  of  the  tympanic  membrane,  and 
essential  as  it  is  undoubtedly  in  normal  hearing,  when  it  is  remem- 
bered that  it,  together  v;\i\\  the  remaining  part  of  the  middle  as 
well  as  the  external  ear,  is  only  the  intermediate  means  by  which 
the  terminal  filaments  of  the  auditory  nerve  are  excited,  it  becomes 
intelligible  why  after  the  rupture  or  eyeniibsence  of  both  mem- 
branes, hearing,  though  impaired,  and  appreciation  of  musical 
sounds  are  still  possible. 

The  innumerable  and  diiferent  kind  of  sonorous  waves  imping- 
ing upon  the  tympanic  membrane  and  throwing  it  into  vibration  to 
be  appreciated  in  consciousness  as  sounds,  must  be  thence  con- 
ducted to  the  vestibule  of  the  internal  ear.  This  is  accomplished 
by  the  chain  of  ear  bones  stretching  across  the  tympanum  from  the 
tympanic  membrane  to  the  foramen  ovale  of  the  vestibule.  The 
ear  bones,  while  three  in  number,  in  point  of  fact  may  be  regarded 
physiologically  as  being  equivalent  to  one  long  bone,  vibrating  to 
and  fro  with  the  tymj^anic  membrane.  That  such  is  the  case  is  not 
only  shown  by  the  manner  in  which  the  bones  are  articulated  with 
each  other,  but  from  the  fact  that  in  the  lower  vertebrates  the  homo- 
logue  of  the  stapes  is  a  long  rod-like  bone,  passing  from  the  tym- 
panic membrane  to  the  vestibule,  while  the  homologues  of  the  incus 
and  malleus  are  not  situated  Avithin  the  tympanum,  but  outside  of 
it,  entering  into  the  formation  of  the  lower  jaw. 

Movements  of  the  Ear  Bones. 

The  articulation  of  the  malleus  and  incus  is  such  that  w^hile  Mith 
the  outward  movement  of  the  manubrium  of  the  malleus,  the  head 
of  the  latter  moves  freely  in  the  joint,  Avith  the  inward  movement 
of  the  latter  the  malleus  and  incus  move  together  as  one  bone, 

the  lower    projecting   margins 
Fig.  506.  of   their   articulating    surfaces 

interlocking  together  like  the 
teeth  of  a  Bregnet  watch  key.^ 
The  malleus  and  incus  move 
freely  about  an  axis  («  x,  Fig. 
50(5)  one  end  of  which  passes 
through  the  anterior  ligament 
of  the  malleus,  the  other  end 
through  the  ligament  of  the 
incus. 

In  the  case  of  audition,  as 
in  that  of  vision,  the  sensation 
lasts  longer  than  the  stimu- 
lus. Hence,  when  the  interval  of  time  elapsing  between  two 
sounds  such  as  that  of  a  pendulum  beating  seconds  is  less  than 
the  yi^  of  a  second,  the  sensations  of  the  two  sounds  are  fused 
into  one  sensation.     The  ear,  like  the  eye,  experiences  also  fatigue. 

'  Ilelmlioltz,  Sensations  of  Tone,  trans,  by  Ellis,  1875,  p.  196. 


/ffe 

The  ligaments  of  the  ossicles.  The  figure  rep- 
resents a  nearly  horizontal  section  of  the  tym- 
panum, carried  through  the  head  of  the  malleus 
and  incus.  M.  Malleus.  /.  Incus.  /.  Articular 
tooth  of  incus.  Ifja,  Anterior  and  Ifje,  External 
ligament  of  the  malleus.  Uj  inc.  Ligament  of  the 
incus.  The  line  ax  represents  the  axis  of  rota- 
tion of  the  two  ossicles.     (Hensen.) 


MOVEMENTS  OF  OSSICLES  OF  EAR.  839 

Thus,  for  example,  when  the  sound  of  a  tuning  fork  becomes  in- 
audible to  one  ear,  if  the  fork  be  placed  to  the  opposite  ear,  the 
sound  will  be  heard  distinctly.  It  is  due  to  the  ear  becoming 
fatigued  that  a  person  who  has  been  listening  for  some  time 
to  a  particular  overtone  fails  to  hear  the  same  when  the  latter  is 
sounded  witli  its  fundamental  and  the  accompanying  series  of  over- 
tones. The  note  sounded  under  such  circumstances  seems  to  be  poor 
in  quality.  Difference  of  opinion  still  prevails  as  to  the  number  of 
vibrations  that  must  fall  upon  the  ear  to  give  rise  to  the  conscious- 
ness of  sound.  According  to  some  from  two  to  five  vibrations  per 
second  will  cause  a  sensation  of  sound,  a  greater  number  of  vibra- 
tions being,  however,  necessary,  as  we  have  seen,  to  produce  in  con- 
sciousness the  sensation  of  a  distinct  musical  note.  In  audition, 
as  in  the  case  of  the  other  senses,  there  is  a  minimum  stimulus 
necessary  for  the  production  of  sound.  It  is  said  that  a  pith  ball 
weighing  one  milligramme  (0.0154  grain)  falling  through  1  mm. 
(Jg  of  an  inch)  upon  a  glass  plate  will  be  heard  at  a  distance  of  91 
mm.  (3.6  inches).  The  "  constant  proportion,"  that  is  the  incre- 
ment necessary  to  cause  the  sensation  of  sound,  is  said  to  be,  as  in 
the  case  of  the  sensation  of  touch,  temperature,  one-third  of  the 
original  stimulus.  In  inward  movements  of  the  tympanic  mem- 
brane the  three  ear  bones  move  as  one  bone  around  the  axis  of 
suspension,  the  maximum  amplitude  of  the  center  of  the  tym- 
panic membrane  being  from  the  -^j  to  ^  mm.,  that  of  the  stapes, 
however,  only  from  the  Jg-  to  J^  mm.  That  the  stapes  is 
pressed  against  the  liquid  of  the  vestibule  by  the  movement  of  the 
tympanic  membrane  and  ear  bones  can  be  shown  experimentally, 
as  by  Helmholtz,  by  fitting  a  slender  glass  tube  into  the  semicir- 
cular canal  and  filling  the  vestibule  and  part  of  the  tube  ^\ith 
water,  when,  through  the  forcing  of  the  tympanic  membrane  in- 
ward, the  water  will  be  seen  to  rise  nearly  a  millimeter  {-^^  of  an 
inch). 

In  outer  movements  of  the  tympanic  membrane,  while  ordinarily 
the  articulating  processes  appear  to  be  retained  in  apposition  by  the 
elastic  reaction  of  the  ligament  and  the  stapedial  attachment  of 
the  incus,  in  cases  where  the  tympanic  membrane  is  abnormally 
forced  outward  the  malleus  leaves  the  incus  behind,  alone  complet- 
ing its  outward  motion.  By  this  provision  of  nature  the  stapes 
escapes  being  torn  out  of  the  oval  Avindow. 

The  movement  upon  the  tympanic  membrane  and  ear  bones  can 
be  graphically  studied  and  recorded,  as  by  Koenig,^  by  attaching  a 
style  to  the  incus  or  malleus,  the  tympanic  membrane  being  thrown 
into  vibration  by  two  organ-pipes,  and  the  sound  of  the  latter  rein- 
forced by  a  resonator. 

Inasmuch  as  the  distance  from  the  tip  of  the  manubrium,  where 
the  aerial  waves  fall,  that  is,  the  point  of  the  application  of  the 
pressure  to  the  axis  of  rotation,  is  one  and  a-half  times  the  distance 
1  Quelques  Experiences  d'acoustique,  1882,  p.  29. 


840 


STBUCTURE  OF  THE  EAR. 


to  the  long  process  of  tlie  incus.  Where  the  effect  is  produced  the 
amount  of  movement  of  the  stapes  is  only  two-thirds  that  of  the  tip 
of  the  manubrium,  the  force  exerted  by  the  stapes  is  one  and  a-half 
times  as  great  as  that  exerted  by  the  tip  of  the  manubrium.  In  other 
words,  the  parts  involved  are  so  disposed  as  to  constitute  a  lever  with 
unequal  arms,  the  long  arm  carrying  the  light  weight  representing 
the  distance  from  the  maniibrium  to  the  axis  of  rotation,  the  short 
arm  carrying  the  heavy  weight  the  distance  from  the  axis  to  the 
stapes.  Such  being  the  mechanical  relation  of  the  parts  it  follows 
that  a  motion  of  large  amplitude  but  of  little  force,  such  as  falls 
upon  the  tympanic  membrane,  becomes  a  motion  of  small  amplitude 
but  of  great  force,  falling  upon  the  fluid  of  the  vestibule  at  the  oval 
window.  It  is  in  this  way  that  aerial  waves,  falling  upon  the 
tympanic  membrane,  are  transformed  into  the  water  waves  of  the 
vestibule. 

Structure  of    the  Internal  Ear. 

The  internal  ear  includes  the  labyrinth  and  the  auditory  nerve. 
The  labyrinth,  so-called  on  account  of  its  highly  complex  structure, 
consists  of  the  vestibule,  semicircular  canals,  and  cochlea.  Though 
these  parts  are  imbedded  in  the  petrous  portion  of  the  temporal 
bone,  their  osseous  walls  are  independent  of  the  bony  structure  of 
the  latter.     This  is  well  seen  at  birth,  when  the  whole  labvrinth  can 


Fig.  507. 


1,  2,  3.  Turns  of  cochlea.    4.  Feuestra  rotunda.     5.  Fenestra  ovalis.    8,  9,  10.  Posterior  semicir- 
cular canal.    11.  Superior  semicircular  canal.     12.  External  or  horizontal  semicircular  canal.  _, 

be  readily  excavated  from  the  surrounding  loose  osseous  substance. 
The  vestibule,  situated  between  the  tympanum  and  the  internal 
auditory  meatus,  is  a  somewhat  oval-shaped  cavity  about  5  millime- 
ters (I  of  an  inch)  in  diameter,  passing  postero-externally  into  the 
semicircular   canals,   and   antero-internally   into   the   cochlea,    and 


MEMBILiXO US  LAB YPxINTH. 


841 


communicatintr  with  the  tympanum  by  the  foramen  ovale.  The 
semicircidar  canals,  so-called  ou  account  of  theii'  form,  are  three  in 
number  and  are  named  from  their  position  superior,  posterior,  and 
inferior,  or  external,  the  two  former  being  disposed  vertically,  the 
latter  horizontally.  Each  semicircular  canal  expands  at  one  ex- 
tremity into  a  bottle-like  dilatation,  the  ampulla,  Avhich  communi- 
cates with  the  vestibule.  Of  the  undilatcd  extremities  two  unite, 
and  then  with  the  remaining  one  also  open  into  the  vestibule.  The 
three  semicircular  canals  thus  communicate  with  the  vestibule  by 
five  orifices.  The  vestibule,  semicircular  canals,  and  cochlea,  as 
well,  are  lined  throughout  with  a  thin  periosteal  membrane,  which 
in  passing  over  the  foramen  ovale  and  foramen  rotundum  thereby 
close  these  orifices.  Within  the  cavity  of  this  membrane  is  found 
a  serous-like  fluid,  the  liquor  cotungii  or  perilymph  of  Breschet,  an 
appropriate  name  on  account  of  its  surrounding  the  membranous 
labyrinth  also  containing  a  similar  fluid,  the  endolymph  of  Breschet 
or  lic|Uor  of  Scarpa.  The  membranous  labyrinth,  so  called  on 
account  of  its  membranous  structure,  and  receiving  the  terminal 
filaments  of  the  internal  auditory  nerve,  floats  in  the  perilymph 
within  the  bony  labyrinth,  with  the  walls  of  which  it  is  more  or 
less  connected  by  delicate  fibrous 

bands.      The  membranous  laby-  Fic;.  508. 

rinth,  like  the  osseous,  consists  of 
three  parts,  vestibule,  semicircu- 
lar canals, .  and  cochlea.  The 
membranous  vestibule  (Fig.  508), 
however,  is  composed  of  two  dis- 
tinct sacs  or  pouches,  the  utriculus 
(U)  and  sacculus  (S),  the  former 
of  which,  the  larger,  occupies  the 
hemi-elliptical  fossa  of  the  bony 
vestibule,  and  gives  off  three 
membranous  semicircular  canals, 

the  latter,  the  smaller,  occupies  the  hemispherical  fossa  and  gives 
off  through  a  narrow  duct,  the  membranous  cochlea. 

The  sacculus  and  utriculus,  while  not  communicating  directly,  do 
so  indirectly  through  the  membranous  aqueduct  (A)  of  the  vesti- 
bule, the  latter  being  formed  through  union  of  the  small  ducts  pro- 
ceeding from  the  sacculus  and  utriculus,  respectively.  Adhering 
to  the  inner  surface  of  both  the  utriculus  and  sacculus,  may  be  seen 
white,  discoidal  masses,  consisting  of  minute  crystalline  particles  of 
calcium  carbonate,  the  so-called  otoliths  or  otoconia.  The  mem- 
branous, semicircular  canals,  about  one-third  of  the  diameter  of  the 
osseous  ones,  in  the  perilymph  of  which  they  float,  resemble  the 
latter  in  form  and  general  disposition,  being  three  in  number,  dis- 
posed superiorly,  vertically,  and  horizontally,  expanding  into 
ampulhe,  and  communicating  with  the  membranous  vestibule  by 
five  orifices.     The  membranous  vestibule  and  semicircular  canals, 


Membranous  labyrinth.  Cs.  Semicircular 
canals,  t'.  L'triculus.  S.  Sacculus.  A.  A(jue- 
duct  of  vestibule.  Cr.  Ductus  reuniens.  Co. 
Cochlea. 


842 


STRUCTURE  OF  THE  EAR. 


Fig.  509. 


consisting  of  three  layers,  an  outer  fibrous,  an  inner  epithelial,  and 
an  intermediate  niembrana  propria,  receive,  as  already  mentioned, 
the  terminal  filaments  of  the  vestibular  branch  of  the  internal  audi- 
tory nerve.  The  latter  divides  at  the  bottom  of  the  internal  audi- 
tory meatus  into  three  branches,  the  first  of  which,  passing  through 
the  pyramidal  eminence  of  the  l^ony  vestibule  at  the  superior  cribri- 
form spot,  is  distributed  to  the  utriculus  and  ampulhe  of  the  superior 
and  inferior  or  horizontal  semicircular  canals  ;  the  second,  passing 
through  the  hemispherical  fossa  at  the  middle  cribriform  spot,  is 
distributed  to  the  sacculus ;  and  the  third  through  the  ampulla  of 
the  bony  posterior  semicircular  canal  at  the  inferior  cribriform  spot, 
to  the  ampulla  of  the  membranous  posterior  semicircular  canal. 
Just  in  those  situations  where  the  nerve  fibers  penetrate  the  mem- 
branous vestibule  (macula  acustica)  and  the  membranous  semicircu- 
lar canals  (crista  acustica),  their  outer  or  fibrous  layer  is  intimately 
associated  through  connective  tissue  with  the  bony  wall  of  the 
vestibule  and  canals,  the  perilymph  being  here  absent.'  The  ul- 
timate nerve  fibers  having 
passed  through  the  membran- 
ous vestibule  and  canals, 
finally  terminate  in  what  may 
be  called  the  auditory  epi- 
thelium, Avhich  appears  to 
consist  essentially  of  colum- 
nar cells  intermixed  w  i  t  h 
spindle-shaped  ones  support- 
ing long,  firm  bristles,  the 
auditory  hairs  (Fig.  509), 
which  penetrate  into  the  en- 
dolymph  and  support  the  oto- 
liths. The  otoliths,  otocrania, 
or  ear  stones,  are  small,  rhom- 
bic or  octohedral  crystals  con- 
sisting of  calcium  carbonate 
with  traces  of  other  salts  and 
organic  matter.  The  function 
of  the  otoliths  is  very  obscure. 
By  some  they  are  regarded  as 
adjuvants,  by  others  as 
dampers  of  sound  waves. 
They  have  also  been  supposed 
to  aid  in  some  way  the  appre- 
ciation of  the  direction  and 
extent  of  our  movements. 
Up  to  the  present  moment,  in  order  to  prevent  confusion,  we 
have  purposely  avoided  mentioning,  except  incidentally,  the  bony 

'  M.  V.  Lenhossek,  Beitriige  zur  Ilistologie  des  Nervensystems  vuid  der  Sinnes- 
organe,  1894,  s.  1. 


Diagram  of  the  auditory  epitlieliuui,  and  the  mode 
of  termination  of  tlie  nerves  of  the  ampullie.  6. 
Spindle-shaped  cells,  each  supporting  an  auditory 
hair  (8).  7.  Basal  sujjporting  cells.  .3,  4.  Nerve 
fiber  passing  through  the  tunica  propria  to  join  the 
plexus  in  the  epithelium.     (M.  Schultze.) 


STRUCTURE  OF  THE  COCHLEA. 


843 


or  membranous  cochlea,  and  yet  it  will  be  found  that  the  cochlea, 
though,  at  first  sight,  resembling  but  little  a  semicircular  canal, 
consists,  like  the  latter,  of  a  bony  tube  enclosing  and  attached  to  a 
membranous  one,  the  latter  floating  in  perilymph  and  containing 
endolymph.  For  simplicity  sake,  k't  us,  in  considering  tlie  struc- 
ture of  the  cochlea,  begin  by  disabusing  our  minds  of  it  being  a 
coiled  tube,  and  regard  it  as  a  straight  one,  as  it  is  throughout  its 
whole  length  in  birds,  and  at  its  commencement  in  man  ;  and  fur- 
ther, let  us  begin  our  description  of  its  structure  by  supposing  that 
we  are  viewing  the  cochlea  at  its  commencement  in  transverse  section, 
and  endwise,  as  represented  in  Fig.  510.     Looking  at  the  cochlea 


Fig.  510. 


Section  through  one  of  the  coils  of  the  cochlea,  diagrammatic.  Mag.  ;]0.  .ST.  Scala  tympaDi. 
.SI'.  .Scala  vestibuli.  CC.  CanalLs  cochleae.  1.  Membrane  of  Keissuer  forming  it.s  vestibular  wall. 
a.  Limbus  laminae  spiralis,  b.  Sulcus  spiralis.  2.  Cochlear  nerve.  3.  Lamina  spiralis,  /hc.  Mem- 
brana  tectoria.    mh.  Membrana  basilaris.     de.  Rods  of  Corti.     4.  Ligameutum  spirale. 

from  such  a  point  of  view,  it  will  be  seen  to  consist  of  a  bony  tube, 
divided  by  a  septum  partly  bony  (lamina  o.ssea),  partly  membranous, 
into  an  outer  and  inner  space,  the  latter  communicating  through 
the  foramen  rotundum  M'ith  the  tympanum,  and  called,  therefore, 
the  scala  tyrapani  ;  the  former  continuous  with  the  bony  cavity  of 
the  vestibule,  and  communicating,  therefore,  indirectly  through  the 
foramen  ovale  with  the  tympanum,  and  called  the  scala  vestibuli. 
This  may  be  at  once  .shown  by  readjusting  the  cochlear  portion  of  the 
section  that  we  have  just  been  considering  to  the  remaining  portion 
of  the  bony  labyrinth,  and  passing  bristles  througli  the  foramen 
rotundum  and  ovale,  supposing  the  membrane  passing  across  this 
opening  and  the  stapes  be  removed.  Conceiving,  however,  that 
the  cochlea  be  a  straight  tube,  and  supposing  it  to  be  divided  longi- 
tudinally, it  will  be  found  that  the  bony,  membranous  partition 
(Fig.  oil)  is  absent  at  the  end  of  the  cochlea  (helicotrema),  the  end 


844 


STRUCTUEE  OF  THE  EAR. 


opposite  to  the  vestibule,  the  consequence  of  which  is  that  the 
bristles  just  passed  through  the  foramen  ovale  from  the  tympanum, 
if  continued  onward,  after  traversing  the  scala  vestibuli,  will  pass 
at  the  end  of  the  cochlea  into  the  scala  tympani,  and  thence,  through 
the  foramen  lotundum,  reach  the  tympanum.  Such  being  the  rela- 
tions of  the  scala  vestibuli  and  scala  tympani  to  each  other  and  to 
the  vestibule  on  the  one  hand,  and  to  the  tympanum  on  the  other, 
on  the  supposition  that  the  cochlea  is  a  straight  tube,  it  is  obvious 

Fig.  511. 


I)iagrammatic  view  of  the  relative  position  of  the  parts  of  the  ear.  EM.  External  meatus. 
T.v^r.  Tympanic  iiiembraue.  Ty.  Tympanum.  ^I.  ^lalleus.  I.  Incus.  S.  Stapes.  li.  Round 
window.  ().  Oval  window.  SG.  Semicircular  canal.  U.  Utriculus.  S.  Sacculus.  V.  Vestibule. 
SV.  Scala  vcstibula.  ST.  Scala  tympani.  MC.  Membranous  cochlea.  LS.  Lamina  ossea.  E«. 
Eustachian  tube.     AN.  Auditory  nerve. 

that  if  the  latter  be  turned  two  and  a-half  times  upon  itself  around 
an  axis  or  modiolus  from  right  to  left  in  the  right  ear,  and  the  re- 
verse in  the  left,  the  apex  being  situated  downward,  forward,  and 
outward,  that  the  above  relations  will  not  in  any  way  be  essentially 
changed.  From  an  inspection  of  Fig.  510,  representing  the  cochlea 
in  transverse  section,  it  will  be  observed,  however,  that  the  mem- 
branous portion  of  the  septum  dividing  the  interior  of  the  cochlea 
into  the  scala  vestibuli  and  scala  tympani,  and  attached  to  the 
osseous  wall  by  the  ligamentum  spirali,  consists  of  two  layers,  a 
basilar  membrane,  and  a  tectorial  membrane,  a  space  intervening 
between  the  two,  and  that  just  at  the  point  where  the  tectorial  mem- 
brane is  attached  to  the  osseous  lamina,  which  in  the  coiled  tube  is, 
of  course,  spirally  disposed,  a  third  membrane,  the  membrane  of 
Reissner,  passes  obliquely  across  to  the  outer  osseous  wall. 

As  a  matter  of  fact,  however,  as  both  ends  of  the  cochlea 
are  covered  in  by  membrane,  the  vestibular  scala  is  separated 
from  the  tympanic  scala  by  a  membranous  tube  which  is  given 
off  by  the  membranous  sacculus  (Figs.  508,  511)  through  the 
ductus  rcuniens  just  as  the  membranous  semicircular  canals  are 
given  off  by  the  utriculus,  the  other  end  of  the  membranous 
cochlear  tube  being  attached  by  its  pointed  blind  extremity  to 
the  wall   of  the    cupola,   the   latter    partly  bounding   the    helico- 


RODS  OF  CORTI. 


845 


trenia.     And   just    as    the   membrauoiis  seniicircular  canal,   filled 
with   endolymph   and    floating  in  perilymph,   is    attached    to   the 


Fig.  o12. 


Fi,. 


Cr. 


'  Diagrammatic  view  of  the  osseou.s 
cochlea  laid  open.  1.  Modiolus  or  ceutrai 
pillar.  2.  Placed  on  three  turns  of  the 
lamina  spiralis.  .3.  Scala  tympani.  4. 
Scala  vestibuli. 

wall  of  the  bony  semicircu- 
lar canal,  so  is  the  mem- 
branous cochlea,  filled  with 
endolymph  and  floating  in 
perilymph,  attached  to  the 
wall  of  the  bony  cochlea, 
the  membranous  cochlea, 
however,  being  spirally  dis- 
posed like  the  bony  cochlea 
enclosing  it  (Fig-  512). 
The  membranous  cochlea 
differs,  however,  from  the 
membranous  semicircular 
canal,  not  only  in  being 
coiled  upon  itself,  but  in  the 
highly  complex  character  of 
the  structures  lying  in  the 
space  intervening  between 
the  basilar  and  tectorial 
membranes,  known  as  the 
rods  of  Corti,  which  receive 
the  terminal  filaments  of  the 
cochlear  branch  of  the  in- 
ternal auditory  nerve. 

The  rods  of  Corti  are 
stiff",  rod-like  bodies,  dis- 
posed in  two  sets,  an  inner 
set  and  an  outer  set ;  the  in- 
ner numbering  about  6,0(  »0, 
the  outer  about  4,500.  The 
inner  rods  being  inclined 
outwardly,  and  the  outer 
rods  inwardly,  the  two  sets 
of  rods  meet  at  their  heads, 
the  space  between  the  rods- 
basilar  membrane — being  kno 


^m^ 


LO 


U, 


V 


Scmi-diagramniatic  view  of  part  of  the  basilar  mem- 
brane and  tunnel  of  Corti  of  the  rabbit,  from  above 
and  the  side.  Much  maguiticd.  /.  Linibus.  Cr.  Kx- 
treniity  or  crest  of  limbus  witli  teeth-like  projections. 
bh.  Ba.silar  membrane,  p.  I'erl'oratiou.s  lur  transmis- 
sion of  nerve  fibers  -V,  which  are  lepresented  at  the 
lower  part  of  the  figure,  but  omitted  for  the  sake  of 
clearness  in  the  upjier.  h:  l-ilteen  of  the  inner  rods 
of  Corti.  /li.  Their  flattened  heads  seen  from  above. 
cr.  Nine  outer  rods  of  Corti.  Ac.  Their  heads,  with 
the  phalangeal  processes  extendingoutward  from  them 
and  forming,  with  the  two  rows  of  phalanges,  the 
lamina  reticularis.  Ir.  The  fibers  of  the  outer  rods 
are  seen  to  be  continued  into  the  striation  of  the  basi- 
lar membrane,  through  which  the  connective  tissue 
fibers  and  nuclei  of  the  undermost  layer  are  seen. 
Portions  of  a  few  of  the  basilar  processes  of  the  outer 
hair-cells  remain  attached  to  the  membrane.  (liiAiN 
und_Sii.\RiM:v. ) 

-that  is,  between  the  latter  and  the 
wn  as  the  canal  of  Corti,     The  inner 


846  STRVCTUliE  OF  THE  EAR. 

rods  support  on  their  inner  surfoce  one  row  of  epitlielial  cells,  the 
inner  hair  cells,  so  called  on  account  of  their  terminating  in  short, 
stiff  hairs  ;  the  outer  rods  on  their  outer  surface  three  or  four  rows 
of  siruilar  cells,  though  somewhat  more  elongated  than  the  outer 
hair  cells.  The  hairs  of  the  latter  pass  through  ring-like  structures, 
the  reticulum,  attached  to  the  heads  of  the  outer  rods.  Both  the 
outer  and  inner  hair  cells,  in  all  probability,  receive,  directly  or  in- 
directly, the  terminal  filaments  of  the  cochlear  nerve  (Fig.  513). 
The  latter,  after  passing  through  the  foramina  of  the  spiral  tract  at 
the  bottom  of  the  internal  auditory  meatus,  ascend  through  the  axis 
of  the  cochlea,  and  thence  traversing  the  lamina  ossea  spiralis  perfo- 
rate the  basilar  membrane,  and  so  reach,  by  intermediate  filaments, 
the  hair  cells.  Bearing  in  mind  that  the  base  of  the  stapes  is  adher- 
ent to  the  periosteum  lining  the  vestibule  and  covering  the  foramen 
ovale ;  it  is  evident  that  the  vibrations  of  the  tympanic  membrane, 
in  being  transmitted  through  the  ear  bones  to  the  perilymph  filling 
the  bony  labyrinth,  will  throw  into  vibration  the  endolymph  filling 
the  membranous  labyrinth  and  the  hairs  projecting  into  it,  and 
consec{uently  the  auditory  nerve,  regarding,  as  we  do,  the  hairs  as 
the  terminal  filaments  of  the  vestibular  and  cochlear  nerves,  into 
which  the  auditory  nerve  divides  in  the  meatus,  whence  the  vibra- 
tions, in  being  further  transmitted,  more  especially  by  the  fibers 
of  the  cochlear  nerve,  to  the  temporo-sphenoidal  convolutions 
of  the  cerebrum,  give  rise  to  the  sensation  and  jierception  of  the 
sound.  With  reference  to  the  function  of  the  membrane  cover- 
ing the  foramen  rotundum,  the  membrana  secondaria,  which  con- 
sists on  the  tympanic  side  of  the  mucous  membrane,  and  on  the 
cochlear,  of  the  periosteal  layer  lining  the  scala  tympani  of  the 
cochlea ;  while  nothing  is  positively  known,  in  all  probability  it  is 
pushed  outward,  as  the  stapes  is  pushed  inward,  which  would  ob- 
viously be  of  advantage  in  absorbing  some,  at  least,  of  the  super- 
fluous sonorous  wave  motion.  Such  being,  in  general,  the  disposi- 
tion and  relation  of  the  parts  of  which  the  internal  ear  is  composed, 
and  the  manner  in  Avhich  the  auditory  nerve  is  distrilmted  to  it,  is 
thrown  into  vibration,  it  is  to  be  expected  that  such  a  complexity 
of  structure  is  correlated  with  a  corresponding  differentiation  in 
function.  As  a  matter  of  fact,  however,  little  has  been  definitely 
estaldished  as  regards  the  specific  functions  of  the  vestibule,  semi- 
circular canals,  and  cochlea,  which  is  due,  no  doubt,  to  any  experi- 
mental investigation  being  so  ditficult  on  account  of  the  nature  of 
the  case,  and  from  the  pathological  and  clinical  data  on  the  subject 
being  so  meagre  and  unreliable  in  character.  In  the  absence  of 
such  evidence  the  facts  of  comparative  anatomy  have  been  appealed 
to  as  a  means  of  elucidating  the  functions  of  the  internal  ear.  It 
is  w^ell  known  to  anatomists  that  the  organ  of  hearing  exists  in  the 
lower  animals  in  a  very  rudimentary  condition  ;  thus,  in  certain  of 
the  Crustacea,  for  example,  the  ear  consists  of  an  invagination  of  the 
tkin,  a  cutaneous  pit  lined  with  hairs,  situated  in  the  basal  joint  of 
she  internal  antennae,  which  may  remain  open  and  contain  particles 


COMPARATIVE  ANATOMY  OF  EAR.  847 

of  sand,  or  may  be  closed  and  enclose  calcareous  otoliths.  A 
similar  vesicle,  lined  with  ciliated  epithelimn,  and  containing 
otoliths,  is  also  found  in  the  mollusca  situated  upon  the  infra- 
oesophageal  portion  of  the  nervous  collar  surrounding  the  alimentary 
canal.  On  the  supposition  that  the  vesicle  just  described  as  occur- 
ring in  the  Crustacea  and  mollusca,  and  even  in  lower  forms  of  life, 
as  in  the  annelida,  hydrozoa,  etc.,  is  a  rudimentary  organ  of  hear- 
ing, its  functions  must  be  limited  almost  entirely  to  the  appreciation 
of  the  intensity  or  loudness  of  sounds — at  least  it  is  difficult  to  con- 
ceive of  animals,  relativelv  so  IomIv  oriranized,  being;  affected  to  anv 
very  great  extent  by  ditference  in  pitch  and  quality.  If  such  is  the 
case,  and  it  be  admitted  that  this  vesicle,  or  otocyst  of  the  lower 
animals,  is  the  homologue  of  the  vestibule  of  the  higher,  which  the 
study  of  the  development  leads  us  to  suppose,  then  it  follows  that 
the  function  of  the  vestibule  in  man  is  the  appreciation  of  the  in- 
tensity of  sound.  In  passing  from  the  invertebrata  to  the  verte- 
brata,  and  more  particularly  to  the  fishes,  we  find,  with  the  excep- 
tion of  the  amphioxus,  in  which  the  ear  is  absent  altogether,  that 
the  organ  of  hearing  becomes  more  complex  as  avc  ascend  through 
the  successive  forms  of  piscine  life.  Thus,  in  the  myxine,  the  ear 
consists  of  a  vestibule  with  one  semicircular  canal ;  in  the  lamprey 
of  a  vestibule  with  two  semicircular  canals ;  and  in  the  teleosts  of 
three  with  a  rudimentary  cochlea  as  well.  Xow,  Avhile  it  is  evident 
that  it  would  l)e  of  advantage  to  fishes  to  be  able,  not  only  to  dis- 
tiusruish  loud  from  low  sounds,  but  also  the  direction  from  which  the 
sounds  proceed,  the  appreciation  of  melodious  and  harmonious  ones 
would  be  of  but  little  use,  and  since  the  homology  of  the  semicircular 
canals  of  the  lower  vertebrates  with  those  of  the  higher  ones  is  un- 
doubted it  is  still  held  by  some  physiologists  that  our  appreciation  of 
the  direction  of  sounds  is  connected  in  some  way  with  these  struc- 
tures. However  that  may  be,  experiments  upon  animals  and  clinical 
and  pathological  observation  in  man  already  referred  to  have  shown 
conclusively  that  the  maintenance  of  equilibrium  depends,  to  a  certain 
extent,  at  least,  upon  the  integrity  of  the  semicircular  canal. 

To  what  extent  the  inability  in  maintaining  equilibrium  in  such 
cases  is  due  to  the  hearing  being  impaired,  and  how  much  to 
the  transmission  of  the  afferent  impressions  to  the  cerebellum 
being  interfered  with,  upon  wliich  the  maintenance  of  equilibrium 
partly  depends,  is  difficult,  if  not  impossible,  to  determine  ex- 
actly. By  a  method  of  exclusion,  then,  the  inference  is  rather 
forced  upon  us,  that  our  sensation  of  tone  dejiends,  in  some  way, 
upon  the  cochlea,  the  structure  of  which  undoubtedly  suggests  that 
its  function  is  rather  concerned  with  the  appreciation  of  the  quality 
of  sound,  a  sort  of  universal  resonator,  than  with  that  of  pitch  or 
intensity.  Regarding  the  rods  of  Corti,  and  the  hair  cells  lying 
upon  them,  as  so  many  piano  keys  and  strings  appropriately  tuned,  it 
is  obvious  that  it  would  analyze  sounds,  like  a  series  of  resonators. 

The  objection  offered  to  the  above  ingenious  view  of  Helmholtz, 
that  the  rods  of  Corti  being  absent  in  the  rudimentary  cochlea  of  birds, 


848 


STRUCTURE  OF  THE  EAR. 


cannot  be  essential  for  the  recognition  of  tones,  is  not  a  necessarily 
fatal  one,  since,  thongh  many  birds  can  sing,  it  does  not  follow  that 
their  sensations  and  ideas  of  melody  and  harmony  should  be  as  de- 
veloped as  that  of  man ;  on  the  contrary,  in  the  absence  of  a  com- 
plex brain,  it  is  difficult  to  comprehend  how  they  should  have  any 
considerable  appreciation  of  musical  sound. 

A  more  important  objection  than  that  just  mentioned  is  that  the 
length  and  disposition  of  the  rods  of  Corti  do  not  vary  to  the  extent 
that  the  hypothesis  of  Helmholtz  demands.  It  has  been  suggested, 
therefore,  that  it  is  the  basilar  membrane  present  in  birds  as  well  as 
mammals  that  vibrates  sympathetically  rather  than  the  rods  of  Corti, 
the  basilar  membrane  being  regarded  as  consisting  of  parallel  strings 
of  different  lengths,  tensed  radially,  but  relaxed  longitudinally,  con- 
ditions which  are  consistent  with  the  mechanical  theory  involved. 
It  would  appear,  therefore,  that  the  so-called  auditory  nerve  con- 
sists really  of  two  different  nerves,  the  cochlear  nerve,  the  auditory 
nerve  proper,  the  pathway  for  the  impulses  giving  rise  to  hearing, 
and  the  vestibular  nerve  transmitting  the  impulses  upon  which  the 
maintenance  of  equilibrium  depends  and  possibly  those  by  which 
we  appreciate  the  direction  of  sounds.  In  accordance  with  this 
view  the  cochlear  and  vestibular  nerves,  as  might  be  expected,  pass 
by  different  routes  from  the  periphery  to  the  cortex.  The  fibers  of 
the  cochlear  nerve  appear  to  arise  from  cells  in  the  spiral  ganglion 
and  from  the  anterior  auditory  nucleus  of  the  cerebellum,  and  pass 
thence  by  the  tuljcrclc  acusticum  and  by  the  strife  medullares,  into 
the  lemniscus  of  the  opposite  side,  and  so  to  the  posterior  quad- 
rigeminal  and  internal  geniculate  bodies  of  that  side  into  the 
internal  capsule  ^  to  terminate  in  the  first  and  second  temporal  con- 
volutions of  the  cortex  (Fig.  514).      The   vestibular   nerve  lying 

ventrally  to  the  cochlear  nerve 
passes  between  the  restiform 
body  and  the  descending  root 
of  the  fifth  nerve  to  terminate 
in  three  distinct  nuclei  situated 
in  the  floor  of  the  fourth  ven- 
tricle and  known,  respectively, 
as  the  chief  nucleus,  the  nucleus 
of  Deiters,  and  the  nucleus  of 
Bechterew.  In  all  probability 
the  fibers  of  the  vestibular 
nerve  terminate  in  a  distinct 
cortical  center,  situated  in  the 
temporal  lobe  in  the  neighborhood  of  that  of  the  cochlear  nerve.^ 

In  conclusion,  it  must  not  be  forgotten  that  whatever  function  be 
assigned  to  tlie  different  parts  of  the  internal  ear,  that  the  cause  of 
the  sensation  of  sound,  like  that  of  color,  is  psychical,  and,  in  its 
subjective  aspect,  is  as  little  understood  in  the  one  case  as  the  other. 

lEdinger,  op.  cit.,  s.  360.  Rauber,  op.  cit.,  Band  ii.,  s.  830.  Obersteiner,  op. 
cit.,  8.  412. 


Fig.  514. 


Position  of  the  auditory  ceutcr  in  the  first  tem- 
jjoral  convolution.     (Goweks.) 


CHAPTER    XLIV. 

IRRITABILITY,  CONDUCTIVITY,  AND  CONTRACTILITY 

OF  MUSCLE. 

Ix  consideriug  the  subject  of  nervous  irritability,  it  will  be  re- 
membered that  the  contraction  of  a  muscle  following  stimulation 
of  the  nerve  supplying  it,  was  taken  as  an  indication  and  measure 
of  the  changes  occurring  in  the  latter.  The  changes  undergone  by 
the  muscle  itself,  however,  during  its  contraction  remain  still  to  be 
described.  Muscles  are  of  two  kinds,  striped  and  unstriped,  of 
which  the  former  will  be  first  studied.  Striped  muscles,  such  as 
the  skeletal  muscles,  heart,  diaphragm,  etc.,  consist  of  fasciculi  or 
bundles  of  fibers  separated  by  connective  tissue,  the  latter  being- 
prolonged  from  the  outer  envelope  or  perimysium  covering  the 
muscle.  Each  muscular  fiber  is  a  more  or  less  cylindrical  tube 
from  3  to  4  cm.  (1.2  to  1.6  of  an  inch)  in  length,  and  between  ^ 
and  Jj  of  ^  ^^-  (ion  ^^^^^   eFo  ^^  ^^^  inch^  in  diameter,  and  con- 

FiG.  .J15. 


/'c  -  i^ 


A.  Portion  of  a  medium-sized  human  muscular  fiber  (magnified  nearly  SOO  diameters).  B. 
Separated  bundles  of  fibrils,  equally  magnified.  </,  a.  Larger,  and  ft,  b,  Smaller  collections,  c. 
Still  smaller.    </,</.  The  smallest  wliich  could  be  detached.    Kirkes.) 


sists  of  three  parts,  the  sarcolemma-  or  sheath,  the  sarcous  substance, 
and  the  nuclei  or  muscle  corpuscles.    The  sarcolemma  is  the  elastic, 

54 


850  IRRITABILITY,  ETC.,   OF  MUSCLE. 

transparent,  structureless,  and  colorless  sheath  enclosing  the  sarcous 
substance.  The  latter,  being  marked  transversely  by  alternating 
light  and  dark  bands,  is  said  to  be  transversely  striate.  If  fresh 
muscular  fiber  be  examined  in  its  own  juice,  not  only  the  light  and 
dark  bands  just  referred  to  will  be  seen,  but  it  will  be  observed 
(Fig.  515)  that  the  light  band  is  divided  into  two  by  what  looks 
like  a  line,  the  so-called  line  of  Krause,  Dobie  or  sarcoplasm,  the 
portion  of  the  fiber  intervening  between  the  latter,  constituting 
the  sarcous  substance  or  sarco-styles.  The  sarcous  substance  ap- 
pears to  consist  of  a  broad,  dim,  doubly  refracting  or  anisotropous 
contractile  disk,  both  ends  of  which  are  capped  by  a  layer  of  clear, 
homogeneous,  single  refracting  (isotropous),  soft  or  fluid  substance. 
The  nuclei  or  muscle  corpuscles  lie  immediately  under  the  sarco- 
lemma,  their  long  axis  being  in  the  long  axis  of  the  fiber,  and  in 
all  probability  generate  the  sarcous  substance.  As  already  men- 
tioned, muscles  being  active  organs  are  well  supplied  with  blood, 
and  with  sensory  as  well  as  motor  nerves ;  the  sensibility  of  mus- 
cles is  relatively,  however,  but  slight.  The  second  variety  of 
muscle,  the  non-striped  or  smooth,  occurring  among  other  situations 
in  the  alimentary  canal,  arteries,  ureter,  etc.,  consists  of  fusiform  or 
spindle-sliaped  cells  with  tapering  ends,  varying  in  length  from  gV 
to  Jg-  of  a  millimeter  (gi^  to  -jJ- ^  inch)  and  in  breadth  from  ^\-^  to 
_i_  of  a  millimeter  (g  qIq-q  to  ^J-^-^  inch).  Within  each  cell  may 
be  seen  after  the  addition  of  acetic  acid,  a  solid,  oval,  elongated  nu- 
cleus, containing  one  or  more  nucleoli,  in  which  the  motor  nerves 
derived  from  the  sympathetic  and  consisting  of  both  mcdullated  and 
non-medullated  fil)ers,  appear  to  terminate.  Non-striped  muscle, 
while  freely  supplied  with  blood,  is  not,  however,  so  vascular  as  the 
striped  variety.  Striped  muscle  or  ordinary  flesh  is  either  neutral 
or  slightly  alkaline  in  reaction,  and  consists  chemically  by  weight, 
of  three-fourths  water  and  one-fourth  nitrogenous,  non-nitrogenous 
matters,  and  salts.  Of  the  nitrogenous  matters  the  most  impor- 
tant is  the  coagulable  substance  that  becomes  in  dead  rigid  muscle 
myosin,  tliough  albuminates,  creatin,  xanthin,  hypoxanthin,  taurin, 
inosic  and  uric  acids  are  also  present.  Among  the  non-nitrogen- 
ous matters  may  be  mentioned  paralactic  (sarcolactic)  acid,  muscle 
sugar,  glycogen,  dextrine,  and  glucose.  Of  the  salts,  the  principal 
ones  are  the  alkaline  phosphates,  potassium  and  sodium  chloride. 
But  little  is  known  of  the  chemical  composition  of  unstriated  mus- 
cular tissue  beyond  the  fact  of  it  consisting  of  Avater,  nitrogenous 
and  non-nitrogenous  bodies. 

Let  us  turn  now  to  the  consideration  of  some  of  the  more  im- 
portant properties  of  muscle,  many  of  which,  such  as  irritability, 
conductivity,  and  contractility,  have  already  been  incidentally  re- 
ferred to  in  the  consideration  of  the  nervous  system.  The  irritability 
of  muscle,  like  that  of  nerve,  is  excited  by  sudden  blows,  pinching, 
cuts,  etc.  ;  by  sudden  and  extreme  changes  in  temperature,  and  is 
altered  by  solutions  of  all  kinds,  except  those  resembling  in  their 


RESISTAyCE  OFFERED  BY  MUSCLE.  851 

composition  serum  and  lymph.  The  irritability  of  muscle  is  also 
influenced  like  that  of  nerve  by  the  strength,  density,  rate  of  change 
in  intensity,  duration,  and  angle  of  application,  of  the  electrical 
current. 

It  will  be  remembered,  that  by  attaching  a  lever  to  a  muscle  and 
connecting  the  pen  of  the  same  with  the  recording  cylinder  or  the 
plate  of  the  pendulum  myograph,  that  we  obtained  a  trace,  the  mus- 
cle curve,  and  that  by  means  of  suitjible  chronographic  apparatus 
we  determine  the  latent  period,  the  moment  of  the  beginning,  maxi- 
mum, and  end  of  the  muscular  contraction. 

It  may  be  also  mentioned  in  this  connection  that  the  excitement 
developed  through  the  stimulation  of  a  muscle  Avith  a  galvanic  cur- 
rent begins  with  a  closing  current  at  the  kathode  and  spreads 
thence  through  the  muscle,  whereas  that  developed  with  an  opening 
one  begins  at  the  anode,  and  that  such  is  the  case,  Avhether  the 
current  is  a  descending  or  an  ascending  one.  As  in  the  case  of  the 
injured  nerve,  so  also  in  that  of  the  injured  muscle,  it  can  be  shown 
by  means  of  the  galvanometer  that  a  difference  of  electrical  poten- 
tial exists  between  the  longitudinal  uninjured  surface  and  the  trans- 
verse cut,  one  giving  rise  to  a  "  current  of  rest,"  the  direction  of 
which  is  from  the  longitudinal  to  the  transverse  surface.  The 
electro-motive  force  of  the  current  of  rest  of  muscle,  as  determined 
by  the  round  compensator,  amounts  to  the  0.0G9  of  a  Daniel  ele- 
ment. The  resistance  offered  l)y  muscle  to  the  transmission  of  an 
electrical  current  in  a  longitudinal  direction,  as  compared  with 
mercury,  is  in  the  ratio  of  2,00(3,000  to  1,  and  in  a  transverse  one 
in  the  ratio  of  13,103,000  to  1.'  The  "  current  of  rest "  of  muscle, 
like  that  of  nerve,  undergoes  also  during  its  activity  a  "  negative 
variation,"  exhibits  a  current  of  action  which  travels "  at  the  rate 
of  3  meters  (9.8  feet)  per  second,  with  a  Avave-length  of  10  mm.  {.^^ 
of  an  inch),  accompanied  by  a  visible  contraction  wave,  which  travels 
at  about  the  same  rate,  but  with  a  wave-length  of  from  200  to  40(1 
mm.  (8  to  10  inches),  and  shorter.  If  a  portion  of  living  irritable 
muscle  of  an  insect,  that  of  Telephorus,  for  example,  be  viewed 
under  the  microscope,  the  contraction  waves  observed  passing  along 
the  fibers  may  be  fixed  by  appropriate  treatment  with  osmic  acid, 
and  so  compared  with  the  remaining  portion  of  the  fiber  at  rest. 
By  such  method  of  investigation,  it  has  been  shown,  that  while  the 
dark  and  light  bands  so  characteristic  of  striated  muscle  at  rest  are 
still  observable  in  the  muscle  when  contracted,  the  relation  of  the 
two  is  reversed,  that  is  to  say,  the  dark  band  in  the  contracted 
muscle  corresponds  to  the  light  band  in  the  quiet  one,  and  rice 
versci,  the  distinction  between  light  and  dark  bands  not  being 
observable,  however,  during  the  intermediate  stage  between  rest  and 
contraction.     AYhile  there  is  still  some  difference  of  opinion  as  to 

'H.  C.  Chapman  c*c  A.  P.   Erubaker,  Eesearches  upon  the  General  Plivsiologj' 
of  Nerve  and  Muscle,  Proc.  Acad,  of  Nat.  Science,  Phila.,  188S,  pp.  lOG,  loo. 
^Bernstein,    Untei-suchuniren,  >;.  o8.     Heidelberi?,  1871. 


852  IRRITABILITY,  ETC.,   OF  MUSCLE. 

the  interpretation  of  all  of  the  appearances  of  such  a  preparation, 
the  same  makes  very  evident  the  swelling  and  shortening  of  the 
fibers,  which  is  brought  out  even  better  if  the  object  be  viewed  by 
polarized  light. 

In  describing  the  induction  apparatus  of  Du  Bois  Reymond,  it 
will  be  remembered  that  the  secondary  coil  can  be  removed  as  de- 
sired from  the  primary  and  the  strength  of  the  stimulus  thrown  into 
the  nerve  or  muscle  in  this  way  varied.  Beginning  with  a  very 
weak  stimulus  and  gradually  increasing  the  same,  the  correspond- 
ing contraction  will  be  found  to  increase,  at  first  rapidly,  then  more 
slowly,  until  a  maximum  is  reached,  then  to  diminish  until  contrac- 
tion finally  ceases  through  the  muscle  being  flitigued  from  repeated 
stimulation.  If  the  distance  through  which  the  secondary  coil  be 
slid  along  be  laid  down  as  the  abscissa  line  and  the  extent  of  con- 
traction as  the  ordinates,  the  curve  obtained  will  be  the  graphic 
representation  of  the  contraction  considered  as  a  function  of  the 
stimulus.  It  should  be  mentioned,  in  this  connection,  that  M'hile 
muscles  in  the  body,  where  they  are  on  tlie  stretch  after  contraction, 
return  at  once  to  their  initial  length,  out  of  the  body  they  fail  to  do 
so  either  as  completely  or  as  quickly,  the  rapidity  and  extent  of  the 
return  appearing  to  depend  upon  the  nutrition  of  the  muscle.  Sup- 
pose that  instead  of  varying  the  electrical  stimulus,  as  in  the  case 
just  mentioned,  we  maintain  it  as  constant  as  possible,  but  that  we 
place  in  the  little  scale  pan  suspended  from  the  lever  attached  to 
the  muscle  successively  10,  20,  30,  40,  and  50  grammes — that  is, 
we  gradually  increase  the  weight  the  muscle  has  to  lift  to  increase 
the  resistance  that  it  has  to  overcome.  Contrary  to  what  might 
naturally  be  expected,  the  resistance  oflPered  to  the  contraction,  for 
a  time  at  least,  increases  the  contraction,  then  with  a  continued  in- 
crease of  weight,  the  contraction  having  reached  a  maximum, 
gradually  diminishes  until  finally  it  ceases  altogether.  If  the 
Aveio-hts  be  rerarded  as  the  abscissas  and  tlie  extent  of  contraction 
as  the  ordinates,  then  the  curve  obtained  will  represent  the  contrac- 
tion regarded  as  a  function  of  the  resistance.  It  will  be  observed, 
in  experimenting  with  weights,  that  a  stretched  muscle  reaches 
quickly  its  initial  length  after  the  extending  cause  has  been  re- 
moved, the  elasticity  not  being  very  great  but  j)erfect.  Contrary, 
however,  to  Avhat  miglit  have  been  expected,  the  extensibility  is 
not  diminished  during  contraction  but  increased,  so  that  the  muscle 
has  to  overcome  the  resistance  due  to  its  extensibility  before  it  can 
raise  any  weight.  Thus,  suppose  that  a  muscle  be  extended  a  given 
extent  by  a  weight  of  say  40  grammes  during  rest,  and  tlien  that  it 
be  unloaded  and  thrown  into  a  state  of  tetanus  and  then  again 
loaded  with  the  same  weight,  the  extension  in  the  latter  case  will 
be  greater  than  in  the  former.  It  will  also  be  learned,  l)y  experi- 
menting with  gradually  increasing  weights,  that  finally  the  elonga- 
tion of  the  muscle  due  to  its  elasticity  is  exactly  compensated  by 
the  shortening  due  to  its  contraction,  such  a  contractioji  of  static 


WOBK  DONE  BY  MUSCLE. 


equilibrium  being  reached  in  the  case  of  the  frog,  the  transverse 
section  being  one  stjuare  centimeter  and  the  weight  G92  grammes, 
and  in  man  the  muscles  being  those  of  the  calf  of  the  leg,  and  the 
weight  8  kilogrammes  (17.B  lti>.). 

The  work  done  by  a  muscle,  like  all  work,  is  estimated  by  the 
height  through  which  a  weight  is  raised.  Thus,  if  5  grammes  (77.1 
grains)  are  raised  27  millimeters  (1.08  inch)  by  the  muscle  of  a 
frog,  then  27  x  •"),  or  135  grammes  millimeters  (83  grain  inch) 
work  is  done  by  such  a  muscle.  By  gradually  increasing  the 
weights  and  noting  the  heights  through  wliich  they  are  raised,  it 
will  be  found  that  the  work  done  gradually  increases  as  the  Aveight 
increases  until  a  maximum  is  reached,  after  which  there  is  a  gradual 
diminution  until  the  muscle,  as  in  the  former  instances,  ceases  to 
contract.      Tlio   fatigue  experienced  by   nnisclc  (hiring  prolonged 

Fig.  516. 


Helmholtz's  myophonc.     f .  Button  to  be  placed  on  muscle. 

luLut  to  tulophone. 


ir.  Wires  :or  attach- 


contraction,  which  sooner  or  later  brings  the  latter  to  an  end,  ap- 
pears to  be  due  to  the  accumulation  of  the  waste  effete  products  in- 
cidental to  its  activity.  Within  certain  limits  such  matters  are 
eliminated  as  rapidly  as  formed  and  new  materials  for  the  repair  of 
the  muscle  are  at  the  same  time  supplied.  If,  however,  the  con- 
tractions follow  each  other  very  rapidly,  sufficient  time  is  not^  al- 
loAved  for  the  accomplishing  of  these  processes,  and  the  equilibrium 
between  disassimilation  and  assimilation  is  no  longer  maintained. 
While  the  cohesion  and  irritability  of  muscle  are  diminished  by 
fatigue,  the  elasticity  is  but  little,  if  at  all,  affected.  The  latent 
period  is,  however,  lengthened.     During  fatigue  the  extent  of  con- 


854  IRBITABILITY.  ETC.,   OF  MUSCLE. 

traction  is  smaller  and  tlie  latter  lasts  longer  than  when  the  muscle 
is  fresh,  the  return  to  the  initial  length  is  also  slower.  As  might  be 
expected,  a  muscle  is  fatigued  much  sooner  when  it  does  work  than 
than  when  it  simply  contracts  without  doing  work.  If  a  stetho- 
scope or  myophone  (Fig.  5 1(5)  l>e  applied  over  a  powerfully  con- 
tracting muscle,  the  biceps,  for  example,  a  deep,  low  tone  will  be 
heard,  the  pitch  of  which  is  about  40  vibrations  a  second,  and 
whicli  is,  without  doubt,  due  to  the  successive  shortenings  which 
make  up  a  muscular  contraction,  the  latter  caused,  in  all  probabil- 
ity, by  40  nervous  impulses  being  transmitted  to  the  nerve  centers 
along  the  motor  nerves  to  the  muscle.  We  say  that  the  pitch  of 
this  muscular  sound  or  tone  is  40  vibrations  per  second  and  caused 
by  40  nervous  impulses,  because  that  is  the  note  actually  heard, 
and  l)ecause  we  can  produce  such  a  note  experimentally  out  of  the 
body  by  stimulating  the  nerve  that  number  of  times. 

It  should  be  mentioned,  however,  that  according  to  most  physi- 
ologists, the  muscular  sound  heard  when  the  biceps  contracts,  while 
due  to  40  vibrations  per  second  is  really  the  first  overtone  or  first 
octave  above  the  fundamental,  the  latter  being  due  to  20  vibrations 
per  second.  If  such  be  the  case,  then  the  muscle  contracts  only 
20  times  a  second,  the  pitch  of  the  muscular  sound  produced  is  20 
vibrations  a  second,  and  the  nerve  is  stimulated  20  times  a  second. 
AMiether  the  muscular  sound  heard  be  the  fundamental  note  or  the 
octave  above,  in  either  case,  however,  the  mechanism  of  its  produc- 
tion is  the  same — that  is,  due  to  muscular  vibration.  It  will  be 
remembered  that  in  accounting  for  the  first  sound  of  the  heart,  mus- 
cular contraction  was  assigned  as  one  of  the  causes,  and  while  there 
is  no  doubt  that  it  is  an  clement  in  the  production  of  the  first  sound, 
it  must  be  admitted  that  it  is  difficult  to  understand  how  the  con- 
traction of  the  heart,  if  a  simple  one,  can  give  rise  to  a  muscular 
sound,  which  we  have  just  seen  is  produced  by  numerous  contrac- 
tions. Facts  of  this  kind,  as  Avell  as  peculiarities  in  the  muscular 
structure  of  the  heart  itself,  lead  one  to  suppose  that  possibly  the 
contraction  of  the  heart  during  its  ventricular  systole  is  rather  of 
a  tetanic  than  simple  cliaracter,  as  is  usually  supposed.  The  mus- 
cle sound  or  muscle  tone  due  to  successive  muscular  contractions 
nuist  not  be  confounded  with  what  is  unfortunately  called  muscular 
tonus  or  muscular  tonicity,  by  whicli  is  meant  the  state  of  tension 
due  to  the  muscles  in  the  living  body  being  more  or  less  stretched 
between  their  attachments.  Sucli  being  the  case,  when  a  muscle 
is  divided  transversely  it  contracts,  the  two  parts  receding  from 
each  other.  The  sphincter  muscles,  however,  do  not  appear  to  be 
stretched  during  repose,  but  only  when  they  are  dilated.  On  the 
other  hand,  by  the  term  muscular  tone,  as  understood  more  espe- 
cially by  neurologists,  is  meant  the  firmness  or  tone  of  muscle  due 
to  continued  nervous  excitement  emanating  from  the  spinal  cord. 
By  some  physiologists,  however,  it  is  denied  that  the  spinal  cord 
exerts  any  such  tonic  influence  upon  the  muscles,  and  yet  it  is  well 


MYOSIN.  855 

known  that  a  decapitated  frog  will  remain  in  a  sitting  posture 
as  long  as  the  spinal  cord  is  intact,  but  that  with  its  removal  the 
limbs  fall  apart.  Further,  the  limbs  of  a  decapitated  turtle,  and, 
to  a  certain  extent,  those  of  a  decapitated  rabbit,  also  retain  their 
firmness,  tone,  but  with  the  removal  of  the  spinal  cord  become  lax, 
flaccid.  Such  facts  are  incomprehensible  unless  it  be  supposed 
that  the  muscles  are  maintained  firm,  elastic,  resilient  through  the 
influence  of  the  spinal  cord.  As  the  influence  exerted  hj  heat, 
blood  supply,  etc.,  upon  the  activity  of  the  muscle  is  essentially 
the  same  in  the  case  of  muscle  as  in  that  of  nerve,  it  will  not  be 
necessary  to  dwell  further  upon  the  same  in  this  connection.  If 
living  contractile  frog's  muscle,  freed  as  much  as  possible  from 
blood,  be  frozen  and  then  minced  and  rubbed  up  in  a  mortar  with 
four  times  its  weight  of  snow  containing  1  per  cent,  of  sodium  chlo- 
ride, a  mixture  will  be  obtained,  which  at  about  0°  Cent.,  can  be 
filtered.  The  filtrate  so  obtained,  or  muscle  plasma,  at  first  fluid, 
becomes,  at  ordinary  temperature,  jelly-like,  and  then  se):>arates  into 
a  clot  and  serum,  the  action,  M'hich  before  coagulation  was  neutral, 
or  slightly  alkaline,  now  l)eing  distinctly  acid.  The  serum  contains 
albumin  and  extractives ;  the  clot  consists  of  myosin,  a  substance 
intermediate  in  character  between  fibrin  and  globulin.  It  will  be 
observed  as  in  the  case  of  the  fibrin  of  the  blood,  that  myosin  does 
not  exist  as  such  in  living  contractile  muscle,  but  that  it  is  devel- 
oped during  the  coagulation  of  the  same  out  of  some  preexisting 
albuminous  element  or  elements.  The  myosin  so  developed  from 
living  muscle  does  not  diflcr  at  all  from  the  myosin  obtained  by  ap- 
propriate chemical  manipulation  from  dead  muscle.  Indeed,  the 
passage  of  a  muscle  into  the  condition  of  rigor  mortis,  character- 
ized by  loss  of  its  irritability,  softness,  translucency,  extensibility, 
and  elasticity  may  be  regarded  as  being  essentially  due  to  the  co- 
agulation of  its  muscle  plasma,  to  the  development  of  myosin  out 
of  its  preexisting  albuminous  elements.  Since  living  muscle  dur- 
ing its  contraction  becomes  distinctly  acid  from  having  been  pre- 
viously faintly  alkaline  or  neutral,  from  a  considerable  amount  of 
lactic  and  sarcolactic  acid  being  set  free,  as  in  the  condition  of 
rigor  mortis,  from  the  fact  of  the  muscle,  as  in  the  latter  distinc- 
tion, becoming  rigid,  it  might,  at  first  thought,  be  supposed  that 
the  changes  occurring  during  the  contraction  of  the  living  muscle 
arc  essentially  the  same  as  those  occurring  in  rigor  mortis,  due 
to  the  oxidation  of  some  complex  albuminous  material  elaborated 
and  stored  up  in  the  muscle  during  its  periods  of  repose.  That  the 
phenomenon  of  muscular  contraction  is  not,  however,  identical  with 
that  of  rigor  mortis,  is  shown  by  the  important  fact  that  during 
muscular  contraction  no  myosin  is  developed,  upon  the  formation 
of  which  the  phenomenon  of  rigor  mortis  depends,  and  that  during 
contraction  the  extensibility  of  the  muscle  is  increased,  instead  of 
being  diminished,  and  that  it  does  not  lose  its  translucency. 

But  little  is  positively  known  as  to  the  physical  and  chemical 


856 


IRRITABILITY.   ETC. .   OF  MUSCLE. 


changes  imdergoue  by  uiistriatcd  muscular  fiber  during  death  or 
contraction  ;  from  what  has  been  established,  however,  we  are  led 
to  believe  that  the  processes  going  on  in  unstriated  muscle  fiber  dif- 
fer in  degree  rather  than  in  kind  from  those  just  described  as  oc- 
curring in  striated  muscle.  While  the  limits  of  this  work  do  not 
permit  of  any  discussion  of  general  muscular  movements  which 
Mould  involve  a  detailed  description  of  the  muscles  and  joints  and 
the  consideration  of  animal  mechanics,  a  brief  account  of  how  or- 
dinary movements  are  performed  does  not  appear  inappropriate  in 
concluding  this  chapter.  The  greater  part  of  the  skeletal  muscles 
may  be  regarded  as  so  many  sources  of  power  for  moving  the  bones 
viewed  as  levers.  The  levers  are  of  three  kinds  or  orders  accord- 
ing to  the  relative  position  of  the  power,  the  weight  to  be  moved, 
and  the  axis  of  motion  or  fulcrum.  In  a  lever  of  the  first  kind, 
as  in  Fig.  517,  A,  the  power  (P)  is  at  one  end,  the  weight  (W)  at 
the  other,  and  the  fulcrum  (F)  in  the  middle.     As  a  familiar  ex- 


A 


Tllustratiou  of  lever  of  fir>;l  order.     (Kirkes.  ) 


ample  of  the  first  kind  of  lever,  occurring  in  the  human  body,  may 
may  be  mentioned  the  raising  of  the  body  from  the  stooping  posture 
by  the  action  of  the  hamstring  muscles  attached  to  the  tuberosity  of 
the  ischium  (Fig.  517,  B).  In  a  lever  of  the  second  kind  (Fig. 
518,  A),  the  power  is  at  one  end,  the  fulcrum  at  the  other,  and  the 
weight  in  the  middle.  The  de])ression  of  the  lower  jaw  in  the 
opening  of  the  mouth  is  an  illustration  of  a  lever  of  the  second  kind 
(Fig.  518,  B),  in  which  the  tension  of  the  muscles  elevating  the 
jaw  represents  the  weight.  In  a  lever  of  tlie  third  kind  (Fig.  519, 
A),  while  the  fulcrum  and  weight  are  at  either  end,  the  power  is  in 
the  middle.  The  flexing  of  the  forearm  by  the  action  of  the  biceps 
muscle  (Fig.  519,  B)  is  an  instance  of  this  form  of  lever  in  the 
body.     The  different  movements  of  the  foot  offer  an  illustration  of 


ACTIOX  OF  MUSCLES  AS  LEVERS. 


o< 


all  three  kinds  of  level's  :  of  the  first  kind  when  tlie  foot  is  raised 
and  the  toe  tapped  upon  the  ground,  the  ankle  joint  being  the  ful- 


FiG.  olS. 


Band 


Illustration  of  lever  of  .second  ordiT.     ( K  irkes.) 

crnm  (Fig.  520, 1);  of  the  second  when  the  body  is  raised  upon  the 
toes,  the  ground  being  the  fulcrum  (Fig.  520,  II) ;   of  the  third 

Fig.  519. 


Illustration  of  lever  of  third  order.     (Kikkes.) 

kind,  Avhen  one  dances  a  weight  np  and  down  by  moving  only  the 
foot,  the  fulcrum  being  the  ankle-joint  (Fig.  520,  III).     As  a  gen- 


FiG.  520. 


II  III 

Illustration  of  levers  of  all  three  orders. 
W.  Weight  of  resistance.    F.  Fulcrum.    P.Power.     (Ill" -\  ley.) 

eral  rule,  in  the  human  body,  the  poAver  is  so  disposed  with  refer- 
ence to  the  fulcrum,  that  while  a  greater  range  of  motion  is  acquired 


858  IRRITABILITY,  ETC.,   OF  MUSCLE. 

the  power  is  diminished.  Thus,  in  the  case  of  the  action  of  the 
biceps,  it  is  evident  that  a  great  amount  of  force  must  be  put  forth 
to  move  the  forearm,  but  that  a  considerable  range  of  movement  is 
obtained  through  a  rehitively  slight  shortening  of  the  muscular 
fibers.  In  the  act  of  standing,  as  accomplished  by  muscular  action, 
the  body  is  in  a  vertical  position  of  equilibrium,  a  line  drawn  from 
the  center  of  gravity  of  the  body  falling  within  the  feet  placed  upon 
the  ground.  The  head  is  firmly  fixed  upon  the  vertebral  column 
by  the  cervical  muscles  pulling  from  the  latter  upon  the  occiput, 
and  the  vertebral  column  itself  being  fixed  by  the  longissimus  dorsi 
and  quadratus  lumborum  muscles.  In  the  sitting  position  the  head 
and  trunk,  together  constituting  an  immovable  column,  are  supported 
upon  the  tubera  ischii.  In  the  forward  posture  the  line  of  gravity 
passes  in  front,  in  the  backward  posture  behind,  and  during  the 
erect  posture  between,  the  tubera  ischii.  In  walking,  the  two  legs 
act  alternately,  the  one  leg,  the  active  or  supporting  leg,  carrying  the 
trunk,  the  other  leg  being  inactive  or  passive.  The  act  of  walking, 
for  convenience  of  description,  may  be  considered  as  made  up  of  two 
acts.  Act  1st  (Fig.  521) :  the  active  leg  being  vertical  and  slightly 
flexed  at  the  knee,  alone  supports  the  center  of  gravity  of  the  body, 

Fig.  521. 


Phases  of  walking.  The  thick  lines  represent  the  active,  the  thin  the  passive,  leg.  h.  The  hip- 
joint.  A-,  a.  Knee.  /,  h.  Ankle,  c,  d.  Heel,  m,  e.  Ball  of  the  tarso-metatarsal  joints,  z,  y.  Point 
of  great  toe.     (Landois.) 

the  passive  leg  touching  the  ground  with  the  tip  of  the  great  toe  (2) 
only.  At  this  moment  the  position  of  the  leg  corresponds  to  a 
right-angle  triangle  in  which  the  active  leg  and  ground  represent 
the  two  sides,  the  passive  leg  the  hypothenuse.  Act  2d  :  the  active 
leg  being  inclined,  moves  forward  to  an  oblique  position,  the  trunk 
moves  forward,  the  active  leg  being  at  the  same  time  lengthened 
that  the  trunk  may  remain  at  the  same  height.  The  latter  is  ac- 
complished by  extension  of  the  knee  (3,  4,  5)  and  the  lifting  of  the 
heel  from  the  ground  (4,  5,),  until  the  foot  finally  rests  upon  the 
ground  by  the  point  of  the  great  toe.     As  the  active  leg  is  extended 


WALKING,    RUNNING,   ETC.  859 

and  moves  forward  the  tips  of  the  toes  of  the  passive  le^  leave  the 
ground  (3),  and  being  slightly  flexed  at  the  knee-joint  perform  a 
pendulum-like  movement  (4,  5),  the  passive  foot  passing  as  far  in 
front  of  the  active  leg  as  it  was  previously  behind  it.  The  foot  being 
then  placed  flat  upon  the  ground,  the  center  of  gravity  is  transferred 
to  what  now  becomes  the  active  leg,  the  latter  being  slightly  flexed 
at  the  knee  and  placed  vertically.  The  first  act  is  then  repeated, 
and  so  on.  It  will  be  observed  that  during  walking  the  trunk 
leans  toward  the  active  leg  and  inclines  somewhat  forward,  the  ef- 
fect of  which  is  to  overcome  resistance  of  the  air,  and  that  it  slightly 
rotates  on  the  head  of  the  active  femur.  Running  differs  from 
rapid  walking  in  that  at  a  particular  moment,  both  legs  not  touch- 
ing the  ground,  the  body  is  raised  in  the  air,  the  necessary  impetus 
being  given  to  the  body  l>y  the  forcil>le  extension  of  the  active  leg. 


CHAPTER   XLV. 

REPRODUCTION. 

Spontaneous  Generation.     Fissiparous,    Gemmiparous,   and    Sexual 

Generation. 

At  an  immensely  remote  period  the  earth  must  have  been  en- 
tirely destitute  of  life,  at  least  the  physical  conditions  of  the  azoic 
period  of  geologists,  and  the  seons  preceding  it  were  such  as  to 
make  the  existence  of  life,  as  we  are  acquainted  with  it,  impossible. 
Whether  the  nebular  hypothesis  of  the  earth  having  been  cast  off 
from  the  sun  be  accepted  or  not,  there  can  be  no  doubt  that  at  an 
inconceivably  distant  period  the  earth  was  in  a  fluid  or  semi-fluid 
molten  condition,  and  its  temperature  so  high  as  to  render  life  im- 
possible, or  even  to  admit  of  the  union  of  the  chemical  elements 
composing  it,  the  latter  existing  then  separately,  as  they  do  in  all 
probability  now,  in  the  sun,  as  shown  by  spectral  analysis.  The 
basalts,  prophyries,  and  lavas  entering  into  the  formation  of  the 
igneous  rocks,  the  volcanic  action  constantly  going  on  at  the  pres- 
ent day  in  many  parts  of  the  world,  the  seismic  disturbances,  the 
high  temperature  of  mines,  etc.,  not  only  prove  that  originally 
the  world  was  but  little  else  than  a  ball  of  fire,  but  also  that  the 
fire,  far  from  being  extinguished,  is  only  now  restricted  to  the  inner 
subterraneous  regions  lying  under  the  crust  of  the  earth.  If  specu- 
lation be  admitted,  we  can  conceive  how  with  the  loss  of  heat  and 
the  lowering  of  the  temperature  through  the  combination  of  hydro- 
gen and  oxygen  the  water  was  formed,  and  that  gradually  through 
the  combination  of  the  chemical  elements  the  binary  and  ternary 
salts  entering  into  the  formation  of  the  rocks  constituting  the 
crust  of  the  earth  were  next  produced,  and  finally,  the  physical 
conditions  being  suitable,  that  the  combination  of  carbon,  hydro- 
gen, oxygen,  nitrogen,  and  phosphorus  or  sulphur  atoms,  resulted 
in  the  development  of  protoplasm,  or  the  simplest  kind  of  life. 
While  it  is  true  that  there  is  no  evidence  whatever  that  life 
now  is  ever  generated  otherwise  than  from  preexisting  life,  soli- 
tary ta])eworms,  maggots,  etc.,  often  cited  by  the  uneducated  as 
instances  of  animals  spontaneously  generated,  offering  no  exception 
to  the  rule,  being  in  reality  reproduced,  like  all  life,  by  preexisting 
animal  life,  that  the  first  life  appearing  upon  the  face  of  the 
earth  was,  nevertheless,  s])ontaneously  generated,  developed  inde- 
pendently of  preexisting  life  must  be  admitted,  since  there  was  no 
antecedent  life  during  the  azoic  period  to  give  rise  to  it.  As  to  the 
inconceivability  of  how  spontaneous  generation  Avas  brought  about, 
of  how  protoplasm,  with  its  remarkable  properties,  was  ever  de- 


SPONTANEOUS  GENERATION.  801 

veloped  through  the  combination  of  chemical  elements  possessing 
different  properties,  it  may  be  said  that  it  is  just  as  difficult  to 
comprehend  how  the  combination  of  acid  and  base  will  give  rise  to 
a  salt  exhibiting  properties  possessed  by  neither,  or  how  two  gases 
like  oxygen  and  hydrogen  in  combination  produce  a  liquid,  water, 
different  from  either.  In  either  case  we  must  suppose  that  the  prop- 
erties of  the  substance  formed,  however  remarkable,  are  the  sum  of 
the  properties  of  the  elements  entering  into  combination  and  giving 
rise  to  the  substance,  whatever  is  true  of  tlie  inorganic  in  tliis  re- 
spect being  true  of  the  organic  as  well,  the  question  in  either  case 
being  one  of  the  redistribution  of  matter  and  energy  only.  Admit- 
ting that  life  originated  spontaneously,  there  is  little  reason,  how- 
ever, to  hope  that  the  physical  conditions  which  obtained  when  life 
first  appeared  upon  the  face  of  the  earth  can  ever  be  realized  ex- 
perimentally so  as  to  enable  one  to  generate  life  (h  novo.  Still 
it  must  not  be  forgotten  that  what  appears  impossible  to  one  age 
becomes  perfectly  so  to  a  succeeding  one.  Life  having  once  ap- 
peared upon  the  face  of  the  earth,  however  produced,  there  is  no 
reason  to  suppose  that  it  has  ever  been  entirely  absent,  since  catas- 
trophies,  such  as  volcanic  eruptions,  earthquakes,  floods,  climatic 
changes,  etc.,  which  are  so  destructive  to  life,  are  relatively  local 
in  action.  Further,  the  first  life,  out  of  which  all  life  has  since 
been  gradually  developed,  must  have  been  of  the  simplest  kind  ; 
indeed,  so  simple  as  to  make  it  difficult,  if  not  impossible,  to 
say  whether  such  life  should  be  regarded  as  animal  or  vegetable, 
its  characters  being  intermediate  between,  and  partaking  of  the 
nature  of  both  plants  and  animals.  The  latter,  judging  from 
their  remains  as  presented  in  the  Cambrian  and  Silurian  rocks,  or 
such  as  immediately  overlie  the  azoic  strata,  were  also  at  first  of 
a  simple  kind.  Thus  among  the  plants  and  animals  living  in 
these  early  ages  of  the  primary  period  of  geologists  may  be 
mentioned  seaweeds,  jelly  fish,  coral-making  polyps,  crinoids, 
brachiopods,  various  kinds  of  mollusca,  trilobites,  etc.  Passing 
on  through  the  later  ages  of  the  primary  period,  the  life  becomes 
more  varied  and  complex  ;  fishes,  ganoids,  and  sharks,  and  land 
plants,  pine-like  lepidodendrons,  and  ferns  making  their  ap])ear- 
ance  during  the  Devonian  age,  or  that  of  the  sandstone,  and  rc])- 
tiles  in  the  carboniferous  age,  or  that  of  the  coal  period,  remark- 
able also  for  the  richness  of  its  cryptogamous  plants.  As  the  ages 
rolled  on,  during  which  the  Jura  rocks  were  deposited  in  SNA-itzer- 
land,  the  chalk  cliffs  in  England,  the  marls  in  New  Jersey, 
phanerogamous,  or  flowering  plants,  palms  and  trees  like  those  of 
our  own  forests,  oaks,  dogwoods,  poplars,  beeches,  appeared,  wliile 
among  the  animals  that  lived  during  these  ages  may  be  mentioned 
fishes  resembling  those  of  the  present  day,  gigantic  reptiles,  birds, 
and  probably  a  few  marsupial  mammals. 

During  the  tertiary  period  that  followed,  the  flowering  plants  and 
trees  then  flourishing  resembled  closelv  those  of  the  forests  of  the 


862 


REPRODUCTION. 


present  day,  the  invertebrate  forms  of  life  differed  bnt  little  from 
those  existing  now,  the  fishes  and  reptiles  were  similar  to  those 
found  in  our  rivers,  oceans,  and  forests  ;  while  herbivorous  animals, 
resembling  the  tapir,  peccary,  camel,  deer,  horse,  rhinoceros,  and 
elephant,  roamed  in  herds  over  the  continents,  hippopotami  wallowed 
in  the  streams ;  while  beasts  of  prey  were  also  numerous,  being 
represented  by  animals  closely  allied  to  the  lion,  tiger,  hyena,  dog, 
and  panther  of  the  present  day.  During  the  close  of  the  Tertiary, 
or,  rather,  of  the  post-Tertiary  period,  the  general  aspect  of  tlie 
world  differing  but  little  from  that  presented  by  it  now,  man  ap- 
peared but  in  a  condition  of  development  probably  far  lower  than  that 
of  the  lowest  existing  savage,  and  the  process  of  civilization  began. 
The  idea  of  reproduction  is  usually  associated  with  that  of  the 
difference  of  sex ;  the  production  of  offspring  naturally  suggesting 
the  idea  of  two  parents.  Many  plants  and  animals,  however,  are 
reproduced  entirely  independently  of  sexual  intercourse,  by  what  is 
known  as  fission  or  gemmation  ;  and  as  many  of  the  structures  of 
the  body  are  developed  by  these  processes,  it  is  essential  that  they 
should  be  at  least  briefly  illustrated.  By  the  process  of  fission  is 
meant  the  division  of  the  single  parent  organism  into  two  or  more 
parts,  each  of  whicli  will  become  a  new  being,  similar  in  form,  in- 
heriting the  properties  of  the  parent.  Reproduction  by  the  process 
of  fission  may  be  observed  in  many  of  the  lower  cryptogamous 
plants,  and  among  animals  in  the  infusoria,  annelida,  etc.     AVhat 


Fig.  r>22. 


Fig.  523. 


Division  of  blood  cells  in  embryo  of 
stag.     (Frey.) 


interests    us   in    this  connection, 

however,  as  regards  fission  is,  that 

the  segmentation  of  the  vitellus 

of  the  egg,  the  development  of  the 

embryonic  blood  corpuscles  (Fig. 

522),  the  proliferation  of  the  cells 

constituting  morbid  growths,  etc.,  are  accomplished  by  this  process. 

On  the  other  hand,  by  gemmation  is  understood  the  reproduction 

of  the  new  being  by  a  process  of  budding,  as  seen  in  ordinary  flower- 


HydroiJ  colony.    Eudendrium  ramosum. 
(Gegenbaue.  ) 


FEMALE  GENERATIVE  ORGANS. 


8«J3 


ing  plants,  and  among  animals  in  the  hydra,  actinia,  etc.,  each  bud 
becoming  a  new  animal.  In  certain  cases  of  gemmiparous  repro- 
duction, however,  the  buds,  instead  of  being  cast  oif  as  produced, 
remain  attached  to  the  parent  stock,  and  so  give  rise  to  a  colony, 
as  in  the  hydroids  (Fig.  528),  each  member  of  Avhich  is  in  commu- 
nication, directly  or  indirectly,  with  each  other.  Such  a  mode  of 
reproduction  in  the  humau  body  is  seen  in  the  development  of  a 
compound  gland  (Fig.  524),  through  the  division  and  subdivision 
of  a  simple  follicular  gland. 
The  reproduction  of  man 
and  most  animals,  however, 
is  accomplished  by  the  union 
of  a  spermatozoon  and  an 
ovum,  both  male  and  female 
generative  organs  co-exist- 
ing, however,  in  the  same 
individual  in  many  inverte- 
brates. In  the  tapeworm, 
for  example,  which  is  a  hermaphrodite,  reproduction  is  accom- 
plished even  by  self-impregnation.  The  ova  and  spermatozoa  are 
specialized  products  of  the  male  and  female  generative  apparatus 
respectively,  which,  while  elaborated  by  a  process  of  fission,  unlike 
the  products  of  the  latter,  must  fuse  together  in  order  to  give  rise 
to  a  new  being,  neither  spermatozoon  nor  ovum,  by  themselves 
being  capable  of  further  development.  Further,  it  will  be  observed 
that  since,  in  the  production  of  a  new  being  by  sexual  generation, 
the  union  of  the  spermatozoSn  and  ovum  is  indispensable,  the  quali- 
ties of  the  parents  must   be  transmitted  to  their  offspring.     The 


Itiagrammatic  view  of  devclopnKiit  of  glands. 


Fig.  525. 


Sketch  of  the  uterus  and  its  appendages.  1.  Uterus,  with  its  peritoneal  covering  partially 
retained.  2.  Its  fundus.  3.  Its  neck,  with  the  forepart  of  the  attachment  of  the  vagina  removed. 
4.  Mouth  of  the  uterus.  5.  Interior  of  the  vagina.  6.  Broad  ligament,  roniDved  on  the  opposite 
side.  7.  Position  of  the  ovarv  behind  the  broad  ligament.  8.  lioiiinl  huament.  ".».  Oviduct,  or 
Fallopian  tube.  10,  Its  fimbriated  e.\treinitv.  11.  Ovary.  12.  Ovarian  ligament.  13.  Process 
connecting  the  fimbriated  extremity  with  the  ovary.  14.  Cut  border  ot  the  broad  ligament. 
(WiL.soN.; 

female  generative  organs,  situated  partly  Avithin  and  partly  without 
the  pelvis,  consist  of'  the  uterus,  Fallopian  tubes,  vagina,  ovaries, 
the  external  and  internal  labia,  clitoris,  etc.     The  uterus  (Fig.  525), 


864  REPRODUCTION. 

or  womb,  is  a  pyriform,  hollow  muscular  organ,  lying,  in  the  un- 
impregnated  condition,  within  the  pelvis,  between  the  rectum  and 
the  bladder,  and  maintained  in  position  by  its  attachment  to  the 
vagina  by  the  recto-  and  vesico-uterine  peritoneal  folds,  and  the 
round  and  broad  ligaments.  Its  upper  broad  extremity  is  known  as 
the  fundus,  or  base,  the  narrow  extremity  the  cervix,  or  neck,  and 
the  intervening  portion  as  the  corpus,  or  body.  The  uterus  is 
about  three  inches  in  length,  two  inches  in  breadth,  and  one  inch 
in  thickness. 

The  walls  of  the  uterus  consisting  of  unstriated  muscular  tissue, 
being  about  one-half  an  inch  in  thickness,  its  cavity  is  but  a  narrow 
space.  The  latter  is  lined  with  a  thin,  soft,  smooth,  and  ciliated 
mucous  membrane  of  a  pale  red  color,  containing  numerous  tubular 
glands  adhering  closely  to  the  underlying  muscular  tissue,  there 
being  no  intermediate  fibrous  or  submucous  tissue,  which  becomes 
continuous  with  the  mucous  membrane  of  the  Fallopian  tubes  and 
that  of  the  neck  of  the  uterus.  The  mucous  membrane  of  the 
latter  is  of  the  squamous  character,  thicker  and  less  soft  than  that 
of  the  body  of  the  uterus,  its  glands  being  of  the  simple  follicular 
kind  and  secreting  a  tenacious  mucus,  the  latter  in  an  inspissated 
condition,  ffivin";  rise  to  the  so-called  ovula  Nal)othi.  The  uterine 
mucus,  both  of  the  fundus  and  cervix,  is  alkaline  in  reaction.  The 
Fallopian  tubes,  or  the  horns  of  the  uterus,  are  trumpet-shaped 
tubes  about  four  inches  in  length,  extending  from  the  fundus  out- 
wardly above  and  beyond  the  ovary.  The  outer  free  extremity 
opening  into  the  abdominal  cavity  expands  into  a  funnel-shaped 
orifice,  the  pavilion,  the  margin  of  which,  being  fringed  with  a  num- 
ber of  irregular  processes,  gives  rise  to  its  name  of  fimbriated  ex- 
tremity. One  of  the  largest  of  these  fringed  processes,  doubled  so 
as  to  include  a  furrow,  extends  along  the  edge  of  the  broad  ligament 
to  be  attached  to  the  ovary.  The  Fallopian  tube  is  lined  with 
ciliated  mucous  membrane,  continuous  through  its  interim  or  uterine 
orifice  with  that  of  the  cavity  of  the  fundus,  and  disposed  in  a  lon- 
gitudinal manner  or  as  narrow  folds.  The  tube  itself  consists  of 
fibrous  intermixed  with  unstriated  muscular  tissue,  loosely  invested 
by  peritoneum.  The  small  sac,  often  absent,  attached  by  a  long 
pedicle  close  to  the  fimbriated  extremity,  is  the  remains  of  the  duct 
of  ]\Iiiller  of  the  embryo,  as  we  shall  see  presently.  The  vagina  is 
a  cylindrical  canal  about  four  inches  in  length  and  an  inch  and  a 
quarter  in  breadth  (in  the  virgin  adult),  extending  from  the  uterus, 
the  neck  of  which  projects  into  it,  to  the  vulva.  The  vagina  con- 
sists of  three  coats,  an  outer  fibro-elastic,  a  middle  unstriated  mus- 
cular, and  an  inner  mucous  ;  the  epithelium  of  the  latter  is  of  the 
squamous  kind,  and  is  provided  with  numerous  minute  conical 
papillae.  In  the  virgin  condition  the  lower  orifice  or  entrance  of 
the  vagina  is  constricted  by  a  crescentic  or  zone-like  fold  of  the 
lining  of  the  membrane,  the  so-called  hymen.  The  latter  is  usually 
obliterated  by  sexual  intercourse,  childbirth,  etc.  ;  in  some  instances, 


GRAAFIAN  FOLLICLES  AND  OVA. 


865 


however,  it  is  so  strong  that  even  impregnation  may  occur  without 
its  being  ruptured.  Its  presence  cannot,  therefore,  be  taken  as  an 
evidence  of  virginity,  or  its  absence  of  the  contrary.  The  inner 
surface  of  the  anterior  and  posterior  walls  of  the  vagina  is  rough- 
ened by  folds,  the  wart-like  eminences  into  which  they  are  divided 
more  particularly  at  the  entrance  of  the  vagina  being  known  as  the 
carunculie  myrtiformes.  While,  as  just  mentioned,  the  uterine 
mucus  is  alkaline  in  reaction,  that  of  the  vagina  is  decidedly  acid. 
The  two  ovaries  are  compressed  ovoid  bodies,  situated  behind  the 
broad  ligament  and  enclosed  by  a  pouch  of  the  latter  about  an  inch 
from  the  uterus,  to  which  they  are  attached  by  the  ovarian  liga- 
ment. The  ovary  consists  of  a  reddish  spongy  fibrous  stroma,  en- 
closed in  a  dense  fibrous  tunic,  the  tunica  albug-inea.  AVithin  the 
stroma  of  the  ovary  are  found  numerous  vesicular-like  bodies, 
varying  from  a  microscopical  size  to  the  fourth  of  an  inch  in 
diameter,  the  Graafian  follicles  or  vesicles,  so-called  after  Kegnerus 
de    Graaf,  their  discoverer.^     These    vesicles  (Fig.    526),    which 


Ovum,  Graafian  follicle,    a.  Ovum.     b.  L>iscus  imdiserus.    <•.  >rembiaiia  granulosa.    </.  Fibrous 

layer.    (Haeckel.) 

are  especially  abundant  at  the  peripheral  portion  of  the  stroma 
of  the  ovary,  consist  of  an  outer  fibro-vascular  layer  or  tunic, 
a  middle  basement  membrane  or  membrana  propria,  and  an  inner 
layer  of  polyhedral  granular  epithelial  cells,  the  membrana  granu- 
losa. At  the  side  of  the  Graafian  follicle  lying  next  the  surface  of 
the  ovary,  the  cells  of  the  membrana  granulosa  are  heaped  uji,  con- 
stituting the  discus  proligerus,  within  which  is  found  the  ovum  or 

iDe  Mulieiurn  Organis  Generationi  insLTvientibu-;  Tractatus   Xovus,    p.   177. 
Lugd.  Batav.,  1672. 
55 


866 


BEPRODVCTIOX. 


G^g,  only  discovered  as  recently  as  1827  by  Von  Baer.^  The  re- 
maining portion  of  the  Graafian  follicle — that  is,  the  part  not  oc- 
cupied by  the  discus  proligerus  with  the  enclosed  egg — is  filled 
with  a  serous  liquid  containing  granules,  nuclei  cells  apparently 
detached  from  the  merabrana  granulosa.  The  ovum  or  egg,  as  just 
discharged  from  the  follicle,  has  usually  adhering  to  it  the  cells  of 
the  discus  proligerus  and  shreds  of  epithelium ;  the  latter  being  re- 
moved, the  egg  can  then  be  seen  with  the  naked  eye  on  a  perfectly 
clean  piece  of  glass  as  a  very  minute  speck,  averaging  in  length  the 
-|-  of  a  millimeter  {^),-q  of  an  inch)  in  diameter.  Under  the  micro- 
scope the  ovum  or  egg  (Fig.  527)  appears  as  a  spheroidal  body,  ex- 

FiG.  527. 


The  human  ovum.      -.  Zona  pclhicida.     '.  Vitellus.      G.  Germinal  vesicle,      g.  Germinal  spot. 

(II.VECKEL. ) 

hibiting  the  characters  of  an  organic  cell  as  already  described.  Thus, 
it  con.sists  of  a  cell  Avall,  an  elastic  membrane,  the  zona  pellucida 
or  vitelline  membrane,  measuring  about  ^i-jj  of  a  millimeter  (0-5^0 
of  an  inch)  in  diameter,  and  which,  while  apparently  a  clear  pellu- 
cid meml)rane,  is  in  reality  striated,  the  strite  being  possibly  canals 
through  which  the  spermatozoa  pass  into  the  Qgg. 

The  cell  contents,  yelk  or  vitellus,  enclosed  within  the  zona  pel- 
lucida, consist  of  a  soft  or  semi-fluid  protoplasm  or  cytoplasm  con- 
taining oil  globules  and  yolk  granules,  among  which  may  be  clearly 
seen  a  micleus  and  nucleolus.  The  yolk  granules,  or  deutoplasm, 
being  found  in  the  greatest  quantity  in  the  middle  of  the  ovum,  are 

•  De  Ovi  maramalium  et  hominis  generi,  Lip.suc,  1827.  Ueber  Entwicklungs 
Geschichte  der  Thiere,  Konigsberg,  1828. 


ATTRACTION  SPHERE. 


><»37 


often  described  as  constitutiDg  the  so-called  deutoplasmic  zone  as 
distingnislied  from  the  clearer,  more  peripheral  portion,  the  proto- 
plasmic zone.  The  food,  yolk,  or  deutoplasm  exists  only  in  small 
amount  in  the  human  ovum  as  the  latter,  being  developed  within 
the  bodvof  the  mother  and  deriving;  its  nourishment  from  the  blood 
of  the  latter,  but  little  is  required  for  the  early  stages  of  gro^^•th. 
In  this  respect  the  ovum  of  the  bird  diifers  markedly  from  that  of 
the  human  female,  since  the  bird,  being  developed  outside  of  the 
body  of  the  mother,  depends  entirely  upon  the  food  yolk  for  its 
growth,  hence  the  great  amount  present.  The  nucleus,  or  germinal 
vesicle,  as  it  is  called,  in  the  ovum  discovered  in  maimnals  by 
Coste/  in  1834,  and  usually  situated  near  the  surface  of  the  egg 
is  a  clear,  spheroidal  vesicle,  measuring  about  the  77V  of  a  milli- 
meter {^\-^j  of  an  inch)  and  consists  of  protoplasm  within  which  is 
found  the  nucleolus,  macula,  or  the  germinal  spot.  The  latter,  dis- 
covered by  AVagner  -  in  1835,  measures  about  the  -^^  of  a  millimeter 
(seVo  ^^^*^^^)  i'^  diameter.  It  may  be  mentioned  in  this  connection 
that  there  is  also  found  in  most  mammalian  ova  in  the  ])rotoplasm 
ii  peculiar  liody,  the  so-called  attraction  sphere  within  which  lies 


^-^^ 

^?^ 

'^'ft 

- 

'm-^ 


'"'^I^^M'M 


Vertical  section  through  the  ovarv  of  a  newborn  female,  a.  Ovarium  epithelium,  h.  Egg 
string,  c.  Young  ova.  d.  Egg  string,  with  follicles,  e.  Follicles.  /.  Mngle  follicle.  <7.  Blood 
vessel.    (Waldeyer.) 

a  single  or  double  centrosome  and  which  appears  to  initiate  the 
karyokinetic  division  of  the  ovum  to  be  presently  descril>cd.  It 
is  a  fact  of  profound  significance  that  the  human  ovum,  or  first  cell, 
from  which  all  the  cells  composing  the  body  are  developed,  should 
be  practically  undistinguishable,  morphologically  at  least,  from  the 

1  Eecherches  sur  la  generation  des  Mammiferes  par  Delpech  et  Coste.    Paris,  1834. 
^Miiller,  Archiv,  1835.     Prodroniiis  historiie  generatioub.     Lips.,  1836. 


868  EEPRODVCTION. 

ova  of  the  ordinary  mammalia  ;  that  the  first  or  transitory  egg-stage 
through  which  man  passes,  should  be  permanently  retained  through 
life  in  many  of  the  lower  plants  or  animals,  such  beings  never  pass- 
ing beyond  the  unicellular  stage,  and  that  the  very  lowest,  as  well 
as  the  highest  forms  begin  life  in  exactly  the  same  way  as  masses  of 
protoplasm  ;  the  zona  pellucida  being  a  secondary  formation.  The 
ova  are  developed  from  the  germinal  epithelium  (Fig.  528),  a 
covering  of  the  primitive  ovary.  Through  the  inward  growth  of 
this  epithelium  into  the  substance  of  the  ovary,  cords  of  cells  {b  d) 
are  formed,  which  become  divided  into  compartments  through  the 
encroachment  of  the  fibrous  stroma.  Of  the  cells  witliin  these 
compartments  the  largest  become  ova  ;  the  smallest,  the  cells  of  the 
membrana  granulosa  of  the  Graafian  follicle  (e  /),  the  wall  of 
which  is  continuous  with  the  stroma.  As  development  advances, 
fluid  accumulates  between  the  growing  cells,  the  follicle  assumes 
the  shape  of  a  vesicle,  the  egg  lying  eventually  to  its  inner  wall. 
With  the  ripening  of  the  ovum,  the  Graafian  follicle  comes  to  the 
surface  of  the  ovary,  the  wall  of  which  as  w^ell  as  that  of  the  follicle 
becoming  at  the  same  time  thinner  and  thinner,  until,  finally,  they 
are  ruptured,  and  so  permit  of  the  escape  of  the  egg.  From  the 
fact  of  the  egg  or  embryo  being  found  in  the  Fallopian  tube  or 
uterus,  except  in  the  unusual  case  of  abdominal  pregnancy,  it  is 
evident  that  the  Fallopian  tube  must  be  so  disposed  with  reference 
to  the  Graafian  follicle  that  at  the  moment  of  its  rupture  a  tem- 
porary passage-way  is  usually  formed  from  one  to  the  other.  As  a 
matter  of  fact,  it  is  not  positively  known  how  the  egg  passes  from 
the  Graafian  follicle  to  the  Fallopian  tube.  It  may  be  supposed, 
however,  that  the  fimbriated  extremity  affixes  itself  to  the  ovary 
at  the  moment  of  rupture  of  the  follicle,  or  that  the  egg,  dropping 
into  the  furrow  of  the  long  fimbriated  process  situated  at  the  edge 
of  the  broad  lig^ament  and  attached  to  the  ovary,  is  transferred  bv 
ciliary  action  into  the  orifice  of  the  tube,  and  thence  by  the  same 
kind  of  action  through  the  Fallopian  tube  into  the  uterus.  The 
ecrp-  havino;  arrived  in  the  cavitv  of  the  latter,  if  not  in  the  mean- 
time  impregnated,  sooner  or  later  decomposes  and  disappears.  Be- 
fore describing,  however,  the  manner  in  which  the  ovum  is  impreg- 
nated, certain  changes  undergone  by  the  Graafian  follicle  and  the 
mucous  membrane  of  the  uterus,  incidental  to  the  maturation  and 
escape  of  the  ovum  from  the  follicle,  M'hether  the  ovum  be  impreg- 
nated or  not,  must  be  first  considered. 

Corpus  Luteum  of  Menstruation  and  Pregnancy. 

It  is  impossible  to  convey  by  words  any  idea  of  tlie  extent  of  the 
congestion  of  the  internal  generative  apparatus  of  the  female  during 
the  period  of  the  maturation  and  escape  of  the  ovum  from  the 
Graafian  follicle.  The  author  can  only  say  that  in  making  post- 
mortem examinations  of  females  dying  while  menstruating,  he  was 
impressed  with  the  fact  that  the  blood  vessels,  arteries,  capillaries. 


CORPUS  LUTEUM.  800 

and  veins  were  distended  to  an  extent  never  accomplished  by  an 
artificial  injection,  however  successfully  performed.  Such  hQuv^ 
the  case  (as  might  be  expected)  with  the  rupture  of  the  Graafian 
follicle,  there  being  quite  an  abundant  hcniorrliage,  tlie  cavity  of 
the  follicle  fills  with  blood.  The  hitter  soon  coagulating,  as  it 
would  do  if  extravasated  elsewhere,  the  clot  remains  enclosed  within 
the  walls  of  the  follicle  (Fig.  529),  having  no  organic  connection, 
however,  with  the  latter,  but  simply  hing 
loose  in  the  cavity  of  the  follicle,  out  of  Avhich  Fk;.  529. 

it  can  be  readily  turned  by  the  handle  of  a 
scalpel.  The  clot,  which  at  this  moment  is 
large,  soft,  and  gelatinous,  soon  begins  to  eon- 
tract,  and  the  serum  exuded  being  absorbed 
by  the  adjacent  parts,  it  becomes  smaller  and 
denser.  The  coloring  matter  of  the  clot  at  c— 
the  same  time  undergoing  the  usual  changes 
incidental  to  extravasation,  and  being  to  a 
great  extent  absorbed  Avith  the  serum,  a  dimi- 
nution in  its  color  becomes  quite  perceptible. 
During  this  period,  about  two  weeks,  the  lin- 
ing membrane  of  the  follicle,  which  at  the  oraafian  f„iiicie,  reeentiv 
moment  of  rupture  i)resents  a  smooth,  trans-     yiM't'^ed  (Uiring  i.icnstriia- 

II  ■  tliiii,  aim  filled  Willi  a  lilcHiily 

parent,   vascular  aiuiearance,  becomes    much     cuKuium ;  shown  in  \<mn\- 

■|-,   .    1  ,  ,  '  ',  ,  '   ,  ,        ,  tuUinul  section,     n.    Ti.ssue 

thickened  and  convoluted,     i  hrough  the  con-     of  the  ovary,  i.  Membraue 

,•1  -I  ,.  _f       1    i  1     ii  •    1         •  of  the  vesicle,     r.  Point  of 

tinned   condensation   of    clot   and   thiclvenmg     rupture,    (d.vi.tox.) 
of  the  lining  membrane,  as  just  described,  the 

follicle  has  become  so  altered  in  its  appearance  that  by  the  end  of 
three  weeks  it  can  be  no  longer  recognized  as  such,  and  is  hence- 
forth known  as  the  corpus  luteum,  though  its  color  can  scarcely  be 
said  as  yet  to  be  distinctly  yellow,  xit  this  period  the  corpus  lutemn 
may  be  described  as  a  rounded  tumor,  about  four-fifths  of  an  inch 
(twenty  millimeters)  in  length,  situated  in  the  stroma  of  the  ovary, 
and  projecting  from  the  surflice  of  the  latter,  the  surface  of  the 
<!orpus  presenting  a  minute  cicatrix,  the  mark  of  the  rupture  of  the 
follicle. 

If  such  a  corpus  luteum  be  divided  longitudinally  (Fig.  530),  it 
will  be  found  to  consist  of  a  central  clot  and  the  convoluted  wall, 
and  it  will  be  observed  that,  while  the  clot  and  the  convoluted  wall 
lie  in  contact  with  each  other,  there  is  neither  any  organic  connec- 
tion between  the  convoluted  wall  and  the  clot,  on  the  one  hand,  nor 
the  surrounding  ovarian  tissues,  on  the  other.  From  this  time  on, 
the  corpus  luteum  undergoes  a  retrograde  metamorphosis.  By  the 
end  of  the  fourth  week  it  is  diminished  to  about  half  of  tiie  size  at- 
tained at  the  end  of  the  third  week,  the  central  clot  has  been,  to  a 
great  extent,  absorbed,  the  convoluted  wall  is  with  difficulty  separ- 
ated from  the  central  clot  and  the  peripheral  ovarian  tissue,  and  its 
color,  instead  of  having  faded,  like  that  of  the  clot,  is  now  a  bright 
yellow.     After  this  ]-,(>riod   it  will  be  found  impossible  to  .separate 


870 


REPRODUCTION. 


the  yellowish  convoluted  wall,  cither  from  the  ovarian  tissue  or  the 
central  clot,  and  by  the  end  of  two  months  the  whole  corpus  luteum 
will  be  found  to  be  reduced  to  the  condition  of  a  greenish,  cicatrix- 
like  spot  (Fig.  531),  about  6  millimeters  (one-fourth  of  an  inch)  in 


Fig.  530. 


Fig.  531. 


Iliiiiian  (>\ai\  cut  open,  showing  a  corpus 
lutmni,  (li\  idcd  lougitudinally,  three  weeks 
iit'tci  mciii.triiation.  From  a  girl,  twenty  years 
of  age,  dead  of  hsemoptysis.     (I.)alton.) 


Ovary, Kh.iwiiigeorjius  luteum,  nine  weeks 
after  menstruation.  From  a  girl  dead  of 
tubercular  meningitis.    (Dalton.) 


diameter.  At  the  end  of  six  months  the  corpus  luteum  has  usually 
disappeared.  It  may,  however,  be  sometimes  found,  though  in  a 
very  atrophied  condition,  even  seven  or  eight  months  after  the  rup- 
ture of  the  follicle.  Such,  in  brief,  is  the  manner  in  which  the 
corpus  luteum  of  menstruation  is  developed  out  of  the  ruptured 
Graafian  follicle  from  which  the  ovum  has  escaped,  at  least  as  ob- 
served by  the  author  in  a  number  of  females  dying  from  natural 
causes  or  violent  deaths,  and  which  does  not  differ  essentially  from 
the  process  so  admirably  described  by  Dalton.^  As  during  preg- 
nancy far  more  blood  flows  to  the  female  generative  apparatus  than 
during  menstruation,  it  might  necessarily  be  supposed  that  while 
the  production  of  the  corpus  luteum  would  be  essentially  the  same 
in  both  conditions,  the  corpus  luteum,  being  better  nourished, 
would  grow  larger  and  persist  longer  than  the  corpus  luteum  of 
menstruation.  That  such  is  the  case  there  can  be  no  doubt,  a  cor- 
pus luteum  being  present  at  the  end  of  pregnancy  even,  and  meas- 
vu'ing  as  much  as  half  an  inch  in  diameter.  While  marked  differ- 
ences exist,  therefore,  between  the  corpus  luteum  of  menstruation 
and  that  of  pregnancy,  nevertheless,  as  these  differences  arc  of  de- 
gree, and  not  of  kind,  and  since  the  corpus  luteum  of  menstruation 
during  the  first  three  weeks  increases  in  size,  but  that  of  pregnancy 
after  the  first  six  months  diminishes,  it  can  be  readily  conceived 
that  at  a  particular  moment  the  corpus  luteum  of  menstruation 
might  be  of  the  same  size  as  that  of  pregnancy,  and  that  if  the  color 
of  the  clot  and  convoluted  wall  in  the  two  were  not  well  marked, 


^  Trans,  of  the  American  Med.  Assoc.,  Vol.  iv.,  p, 
ology,  7th  ed.,  p.  608.     Pliila.,  1882. 


547.     Pliila.,  1851.     Tliysi- 


MENSTE  UA  TION.  871 

the  two  corpora  lutca  might  bo  undistinguisliablo.  At  least  such 
has  been  the  experience  of  the  author,  in  conij)aring  numerous  cor- 
pora lutea  of  menstruation  of  various  ages  with  those  of  pregnancy. 
Further,  that  the  presence  or  absence  of  a  corpus  luteum  <'ainiot  be 
accepted  as  positive  evidence  of  imjiregnation  haviug  taken  phice  is 
shown  by  the  fact  that,  altliough  in  several  instances  in  making 
post-mortem  examinations  a  fletus  was  removed  from  the  uterus  by 
the  author,  not  a  trace  of  a  corpus  luteum  could  be  found  in  either 
ovary,  and,  on  the  other  hand,  in  more  than  one  instance  a  well- 
developed  corpus  luteum  being  present  several  months  after  the 
last  menstruation,  there  was  not  the  slightest  reason  to  believe  that 
during  that  period  there  had  been  a  foetus  in  the  uterus,  at  least  the 
relatives  of  the  deceased  had  no  object  in  concealing  the  fact  of  im- 
pregnation, if  such  had  really  occurred. 

Menstruation. 

Coincident  with  the  maturation  and  escape  of  the  ovum  from  the 
Graafian  follicle,  the  mucous  membrane  of  the  uterus  undergoes 
several  well-marked  changes.  Thus,  while  in  the  ordinary  condi- 
tions it  measures  only  about  18  millimeters  (^^^  of  an  inch)  in  thick- 
ness, at  this  period  it  becomes  twice  or  even  three  times  as  thick. 
It  is  also  much  softer  and  more  loosely  attached  to  the  underlying 
part  than  ordinary,  being  somewhat  rugose  in  character.  The 
glands  are  very  much  enlarged,  and  the  surface  of  the  membrane 
smeared  with  blood.  The  latter  is  due  to  a  kind  of  disintegration 
set  up  in  the  mucous  membrane  involving  the  blood  vessels,  by 
which  the  capillaries  are  ruptured.  The  hemorrhage  so  caused  con- 
stituting the  menstrual  flow,  or  the  menses,  catamenia,  etc.,  appears 
monthly  in  the  healthy  female,  and  lasts  upon  the  average  from 
four  to  five  days.  It  appears  to  be  pure  arterial  blood  mixed  with 
desquamated  utero-vaginal  epithelium ;  the  amount  of  the  latter 
would  appear  from  the  observations  of  the  author  to  be  greater 
than  usually  supposed.  The  menstrual  blood  is  kept  from  coagu- 
lating by  the  vaginal  mucus.  As  might  be  expected  from  the 
nature  of  the  case,  it  is  impossible  to  say  how  much  blood  is  dis- 
charged during  the  menstrual  period,  for,  apart  from  the  difficulty 
experienced  in  collecting  it,  women  vary  very  nuich  in  respect  to 
the  amount  of  blood  lost.  From  100  "to  200  c.c.  (4  to  8  ounces) 
may  be  accepted  as  an  approximate  estimate  of  the  total  flow  during 
the  menstrual  period.  ]\[enstruation  is  sometimes  regarded  as  the 
effect  of  ovulation,  the  two  being  so  intimately  associated.  Since 
menstruation,  however,  occurs  without  ovulation  in  the  absence  of 
ovaries,  and  ovulation  without  menstruation,  it  is  evident  that  the 
two  phenomena  are  not  related  as  cause  and  effect,  but  should  be 
considered  as  the  effects  of  a  common  cause,  the  general  prepa- 
ration of  the  system  for  impregnation.  Indeed,  the  thickening 
and  shedding  of  the  mucous  membrane  of  the  uterus,  an(l  hemor- 
rhage during  menstruation,  differ  only  in  degree,  not  in  kind,  from 


872  REPRODUCTION. 

the  changes  undergone  by  the  mucons  membrane  dnring  pregnancy 
and  ])artiirition,  the  decidna  menstraalis  being  the  forernnner  of  the 
decidua  graviditatis.  That  the  menstrual  flow  is  the  eifect  of  a  deep- 
lying  cause,  the  fitting  of  the  mucous  membrane  for  tlie  reception 
of  the  ovum,  though  not  due  to  the  production  of  the  latter,  is 
shown  by  the  constitutional  disturbance  experienced  by  the  female 
when  the  menses  first  appear,  and  ever  afterward  with  their  monthly 
reappearance,  though  then  to  a  less  extent.  The  menses  usually 
appear  between  the  age  of  thirteen  and  fifteen  years  and  much 
earlier  in  warm  climates.  At  this  period,  the  age  of  puberty,  there 
is  a  general  development  of  the  body,  the  limbs  become  fuller  and 
rounder,  hair  appears  on  the  mons  veneris,  the  mammary  glands 
enlarge,  ova  maturate,  and  the  disposition  changes.  Just  before 
the  establishment  of  the  flow,  either  in  the  case  of  its  first  appear- 
ance or  in  after-recurring  ones,  for  about  two  days  a  feeling  of  gen- 
eral malaise  is  experienced,  particularly  a  sense  of  weight  and  ful- 
ness in  the  pelvic  organs,  the  vaginal  mucus  is  increased  in  amount 
and  becomes  rusty  in  color,  and  gives  rise  to  the  odor  so  perceptible 
in  certain  females,  the  breasts  also  enlarge,  showing  the  sympathy 
existing  between  the  latter  and  the  generative  organs.  With  the 
establishing  of  the  flow,  the  disagreeable  feelings  and  uneasiness 
usually  pass  aAvay,  and  by  the  end  of  the  fourth  day,  though  the 
time  varies,  the  flow  ceases,  and  the  mucous  membrane  returns  to 
its  normal  condition.  At  about  forty-five  years  of  age  the  menses 
become  irregular  in  their  recurrence  and  usually  cease  altogether  at 
fifty.  The  phenomenon  of  the  menses  is  not  restricted  to  the 
human  female,  as  is  often  supposed,  the  heat  or  rut  of  the  lower 
domestic  animals,  such  as  that  of  the  mare,  cow,  bitch,  being  essen- 
tially the  same  process,  only  recurring  at  diiferent  intervals.  In- 
deed, in  monkeys  and  apes  there  is  a  monthly  discharge,  as  in  the 
case  of  the  human  female.  It  is  a  significant  fact  that  the  female 
of  animals,  except  monkeys,  only  receive  the  male  during  the  rut- 
ting or  menstruating  period. 

The  Male  Generative  Apparatus. 

The  male  generative  apparatus  consists  of  the  testicles,  the 
spermatic  ducts,  the  seminal  vesicles,  prostate  and  suburethral 
glands,  and  the  penis.  The  testicles  (Fig.  532),  secreting  the 
spermatic  fluid,  are  tAVo  glandular  bodies  suspended  by  the  sper- 
matic cords  Avitliin  the  scrotum.  Tiie  latter  is  essentially  a  musculo- 
cutaneous pouch,  divided  into  two  recesses  by  a  septum  for  the  re- 
ception of  the  two  testicles.  Each  testicle  consists  of  an  anterior 
oval  portion  of  the  body,  or  testis  proper,  and  a  posterior  elongated 
portion  clas])ing,  as  it  were,  the  former,  the  e[)ididymis.  The  up- 
per portion  of  the  epididymis  is  known  as  the  head,  or  globus  major, 
the  lower  part  as  the  tail,  or  globus  minor,  wliicli,  in  turning  upward 
upon  itself,  becomes  the  spermatic  duct.  The  testes  are  covered 
with  a  dense  white  fibrous  membrane,  the  tunica  albuginea,  which 


MALE  GENERATIVE  APPARATUS. 


873 


Fk;.  532 


at  the  back  of  the  testes  forms  a  process,  the  niediastimim.  The 
Latter,  being  prolonged  as  fibrous  Ixmds  to  be  inserted  into  the  in- 
ner surface  of  the  tunica  albuginea,  serves  as  a  sort  of  scaffolding 
to  support  the  delicate  glandular  substance  within.  The  testicle 
proper  is  made  up  of  about 
two  hundred  lobules,  each 
lobule  in  turn  consistins:  of 
from  one  to  six  seminiferous 
tubules,  of  which  there  are 
perhaps  eight  hundred  in  all. 
The  seminiferous  tubules 
at  the  narrow  end  of  the 
lobule  assume  a  straight 
course,  being  then  known  as 
the  vasa  recti.  The  latter 
entering  the  mediastinum, 
constitute  together  the  plexus 
retiformis,  from  which  emerge 
about  a  dozen  efferent  canals, 
or  vasa  efferentia,  to  pass  out 
to  the  head  of  the  epididymis. 
Within  the  latter  these  ef- 
ferent canals  form  the  sper- 
matic cones,  wdiich  finally 
^ive  rise  to  one  convoluted 
tube,  constituting  the  body 
and  tail  of  the  epididymis, 
the  latter  of  which,  as  just 
mentioned,  becomes  the  sper- 
matic duct.  The  spermatic 
duct  passing  through  the  in- 
guinal canal,  leaves  the  latter 
-at  the  internal  abdominal 
ring,  and  descending  backward  and  do^vnward,  passes  forward  to 
form,  together  with  the  duct  of  the  seminal  vesicle,  the  ejaculatory 
duct,  the  latter  terminating  in  the  prostatic  urethra.  The  seminifer- 
ous tubules,  about  thirty  inches  in  length  Avhen  unravelled,  and  the 
.j-i^  of  an  inch  in  diameter,  consist  of  a  fibro-membranous  wall  lined 
with  a  delicate  layer  of  soft  polyhedra  nucleated  cells,  the  sperm 
cells,  which  elaborate  the  spermatic  or  seminal  licjuid,  of  which  about 
half  a  drachm  is  emitted  during  the  orgasm.  The  latter  is  a  faintly 
alkaline  liquid,  slightly  heavier  than  water,  becoming  jelly-like 
first,  and  then  hardening  after  emission.  The  semen  consists  chem- 
ically of  82  per  cent,  water,  serum,  albumin,  alkali  albuminate, 
nuclein,  lecithin,  cholesterin,  fats,  phosphorized  fats,  alkaline,  and 
earthy  phosphates,  sulphates,  carbonates,  nnd  chloride,  and  an 
odorous  body,  the  so-called  "spermatin,"  the  nature  of  which  is 
unknown. 


Testicle  aud  epididymis  of  the  hiiuiaii  suliject.  (t. 
Testicle,  b.  Lobules  of  the  testicle,  c.  Vasa  recta. 
il.  Uete  testis.  i>.  \'asa  etfereiitia.  /.  Cones  of  the 
globulus  major  of  the  epididymis.  ;/.  Kpididymis. 
/i.  Vas  deferens.  /.  Vas  aberrans.  ;«.  Branches  of 
the  spermatic  artery  to  the  testicle  and  epididymis. 
;'.  Ramification  of  the  artery  upon  the  testicle  and 
epididymis,  n.  Deferential  artery,  p.  Ana.stomosis 
of  the  deferential  with  the  s])ermatic  artery.     (  Kol- 

LIKEK.  ) 


874 


REPRODUCTION. 


Fig.  533. 


V^ 


Physiologically  the  essential  portion  of  the  spermatic  fluid,  upon 
which  its  fecundating  powers  without  doubt  depend,  are  the  sper- 
matozoa that  it  contains.  Indeed,  if  the  seminal  liquid  be  deprived 
of  its  spermatozoa,  it  is  rendered  entirely  inoperative  as  regards 
impregnation. 

The  spermatozoa  are  developed  out  of  the  nuclei  of  the  daughter 
cells  of  the  parent  cells,  which  lie  near  the  outer  wall  of  the 
seminiferous  tubule,  the  nucleus  assuming  the  form  of  a  spermatozoon, 
which  is  set  free  by  the  deliquescence  of  the  cell  wall  enclosing  it. 
The  spermatozoa  appear  first  at  the  age  of  puberty,  and  afterAvard 
till  the  end,  life  being  found  in  the  semen  of  healthy  men  of  ninety 
years  of  age.  The  spermatozoa  (Fig.  533),  measur- 
ing the  2V  of  ^  millimeter  {-q\-q  inch)  in  length,  dis- 
covered by  A-^on  Hammen,  in  1677,  and  described 
by  Leeuwenhock,  resemble  the  flagellate  animal- 
cule for  which  they  were  first  taken.  A  sperma- 
tozoon consists  of  an  ovoidal  head,  measuring 
■g^^Q-  of  a  millimeter  (g^Vo^  of  an  inch)  containing 
chromatin  and  of  a  filamentary  appendage  or  tail 
measuring  0.050  mm.  (-5  J-jj  of  an  inch)  which  vibrates 
with  astonishing  rapidity.  The  tail  of  the  spermato- 
zoon is  usually  described  as  consisting  of  three  parts, 
the  middle,  main,  and  end  pieces.  The  middle  piece 
or  the  thickest  part,  that  nearest  the  head,  is  said 
to  contain  an  axial  thread  and  exhibits  a  very  fine 
spiral  thread  running  around  it.  The  movements  of 
the  spermatozoa  are  arrested  by  water  and  cold,  re- 
tarded by  acids,  and  favored  by  alkalies.  The 
spermatic  fluid,  with  the  spermatozoa,  passes  from 
the  testicles  by  the  spermatic  ducts  to  the  seminal 
vesicles,  wdiere  it  becomes  mixed  with  the  secretion 
of  the  latter,  the  nature  and  use  of  which  are,  how- 
ever, doubtful,  as  no  secreting  glands  are  found  in 
these  vesicles ;  its  use  may  be  to  dilute  the  mixed 
spermatic  fluid.  The  spermatic  fluid,  having  ac- 
cumulated in  the  seminal  vesicles,  is  thence  introduced  during 
coition,  still  further  mixed  with  the  secretion  of  the  prostate 
gland,  of  the  glands  of  Cowper,  and  of  the  urethra,  the  use  of 
which  is  not  known,  by  an  ejaculatory  efl'ect,  into  the  vagina  of  the 
female,  the  spermatozoa  by  their  vibrating  movements  passing 
up  into  the  Fallopian  tubes,  and  even  the  ovaries,  as  shown  by 
the  development  of  the  ovum  in  those  situations  in  cases  of  extra- 
uterine pregnancy.  The  spermatozoa  have  been  found  moving  in 
the  uterus  even  eight  days  after  emission,  the  rate  of  movement 
being  probably  from  between  1.2  to  3.6  mm.  ])er  minute.  In  order 
that  coition  should  be  accomplished,  it  is  essential  that  the  penis 
should  be  erect.  This  is  brought  about  through  its  blood  supply 
being  very  much  increased  by  the  stimulation  of  the  vaso-dilator 


Human  sperma- 
tozoiin.  h.  Head. 
//*.  Middle -piece. 
I.  Tail.  e.  End- 
piece.    (RETZII'S.) 


INTERNAL  SECRETION  OF  TESTICLE.  875 

fibers  of  the  nervi  eri^entes,  the  later  arising  probably  from  the 
second  sacral  nerves.  The  center  of  erection,  sitnated  in  the  cord, 
can  be  reflexlj  stimulated  either  by  impressions  made  u])un  the 
ijenital  organs  or  upon  tlie  mind.  Tlie  cjacidatory  effort  is  due  to 
the  simultaneous  contraction  of  the  bulbo  urethrie,  iscliio-cavernous, 
and  transverse  perinaius  muscles,  due  to  the  reflex  stimulation  of 
the  ejaculatory  center  of  the  spinal  cord,  situated  in  the  lumbar 
region. 

Recent  researches '  render  it  probable  that  the  testicles,  in  addi- 
tion to  secreting  the  spermatic  fluid,  elaborate  an  "  internal  secre- 
tion," spermin,^  having  a  chemical  composition  represented  by  the 
formula  CHj^N^,  and  which,  passing  into  the  blood,  increases  the 
mental  and  physical  vigor  of  the  aged,  and  benefits  those  afflicted 
with  general  prostration  and  neurasthenia.'^ 

1  Brown-Seciuard,  Arcliives  de  Pliysiologie  normalc  et  pathologique,  1889,  92. 
^Poehl,  Zeitschrift  fiir  klinische  raedecin,  Band  2(3,  1S94,  s.  13.S. 
3Zoth,  PHiiger's  Arcliiv,  Band  62,  1896,  s.  335.     Preyer,  Ibid.,  s.  379. 


CHAPTER  XLVI. 

EEPRODUCTION.— (Co/ic/»f^^J.) 


Impregnation  of  the  Ovum  and  Development  of  Embryo. 

As  a  matter  of  fact,  nothing  is  known  as  to  the  manner  in  which 
the  ovum  is  impregnated  in  the  human  female,  or  of  the  early  stages 
of  the  development  of  the  embryo.  Since  the  primitive  ova  of  all 
animals  are  more  or  less  alike  and  the  spermatozoa  diifer  from  each 
other  unessentially,  it  is  to  be  inferred  that  the  process  of  impreg- 
nation in  the  human  female  is  the  same  as  that  observed  in  animals. 
Further,  as  the  human  foetus  of  about  three  weeks  old  (Fig.  534) 


Fig.  534. 


Fig.  535. 


1,1 


Embryo  of  man.  Embryo  of  rabbit. 

«.  Eye.    m.  Mid-braiu.    o.  Ear.    r.  Spiual  marrow,    tc.  Vertebral  column,    k.  Visceral  arches. 

(Haeckel.) 

differs  but  little  from  that  of  the  rabbit  at  about  ten  days  (Fig. 
535),  there  can  be  little  doubt  that  the  stages  intermediate  between 
that  of  the  e^g  and  that  of  three  weeks  old,  through  which  the 
human  embryo  passes,  are  essentially  tlie  same  as  the  corresponding 
stages  through  wliich  the  rabbit  embryo  passes  from  the  stage  of  the 
e^^  to  that  represented  in  Fig.  535,  or  the  corresponding  stages 
in  the  development  of  the  dog,  hog,  etc.,  or  even  bird,  reptile,  or 
fish.  Assuming,  then,  that  the  development  of  man,  in  the  early 
stages,  is  the  same  as  that  of  a  rabbit,  for  example,  we  will  describe, 
as  illustrating  the  former,  the  development  of  the  animal  ^  up  to 
the  period  that  it  begins  to  diifer  from  that  of  man,  basing  our  ac- 
count of  impregnation,  however,  upon  the  manner  in  which  that 
process  is  said  to  take  place  in  the  Ascaris  mcgalocephala,^  a  large 
Avorm  found  in  the  alimentary  canal  of  the  horse. 

^BisclioffJ  Entwicklungs  Geschichte  des  K:ininclien-Eies.  Braunschweig,  1842. 
E.  Van  Jk'neden,  La  Maturation  dc  I'tcuf,  etc.,  d'apres  des  recherches  faites  cliez  le 
lapin.     Bruxolles,  1875. 

^  Van  Beneden  ot  Neyt,  Nouvelles  recherches  sur  la  fecondation  et  la  division 
mitosique  chez  I'ascaride  megalocephale,  Bullet,  de  I'acad.  royalo  des  sciences  de 
Belgique,  3ser.,  T.  xiv.,  1887. 


MATURATJOX  OF  OVUM, 


'i^ll 


Either  before  or  immediately  after  its  escape  from  the  Graafian 
follicle  the  ovum  undergoes  a  change  known  as  ''  maturation,"  a  pro- 
cess preparatory  to,  but  independent  of  fertilization.  This  consists 
in  the  extrusion  by  the  germinal  vesicles  of  two  minute  spherical 
bodies,  the  "  polar  globules "  or  "  directive  corpuscles,"  so-called 
on  account  of  it  being  supposed  by  some  embryologists  that  their 
presence  determinates  the  pole  at  which  the  first  segmentation  will 
take  place  in  the  event  of  the  ovum  being  impregnated.  The  polar 
globules  are  formed  in  the  ovum  of  the  Ascaris  megalocephala  ^  in 
the  following  manner : 

The  germinal  vesicle  approaches  the  periphery  of  the  vitellus, 
becomes  indistinct  in  outline,  and  is  transformed  into  a  spindle  of 
fibers,  at  the  equator  of  wdiich  are  situated  eight  chromatin  parti- 
cles (Fig.  .)36),  The  latter  shortly  separate  into  two  sets,  consist- 
ing of  four  chromatin  particles  each  (Fig.  5o7).     One  set  of  four 


Fir..  537 


The  ovum,  with  the  germinal  vesical  transformed 
into  a  spindle  of  achromatic  fibrils  ;  from  the  poles 
of  the  spindle  other  tibrils  radiate  into  the  proto- 
plasm. At  the  equator  of  the  spindle  eight  por- 
tions of  chromatin  are  visible.  C.V.  Head  of  a 
spermatozoon  which  has  previously  entered  the 
ovum,  and  is  becoming  transformed  into  the  male 
pronucleus,  m.  Gelatinous  membrane  of  the 
ovum.     (QuAis.) 


The  chromatin  particles  are  seen  separated 
into  two  sets.  The  achromatic  tibrils  are 
not  shown  in  this  preparation.  The  ovum 
is  considerably  shrunken.     (Qcais.) 


chromatin  particles,  together 
with  part  of  the  proto})lasm, 
is  extruded  into  the  peri-vitel- 
line  space  as  the  first  polar  globule  (Fig.  538),  while  the  other  set 
of  four  chromatin  particles  remains  in  the  vitellus  situated  upon 
the  equator  of  the  second  spindle  into  which  the  remainder  of  the 
germinal  vesicle  has  been  transformed  (Fig.  .");3J)).  Soon  two  chro- 
matin particles  are  extruded  from  the  spindles  as  the  second  polar 
globule  (Figs.  540,  541),  while  the  other  two  chromatin  particles 
remain  in  the  vitellus  and  constitute,  with  the  remainder  of  the 
germinal  vesicle,  the  female  pronucleus.  The  act  of  impregnation 
in  the  rabbit,  and  in  all  animals  in  which  impregnation  has  been 
observed,  consists  in  the  passage  of  one  or  more  spermatozoa  (Fig. 
542)  through  the  vitelline  membrane  of  the  e^g  into  the  peri-vitel- 
line  space,  though  one  spermatozoon  alone  normally  enters  the  vitel- 

1  Gehuchten  Xouvelles  observations  siir  la  vesicule  gerniinative  et  les  globules 
polaires  de  r  Ascaris  Megalocephale,  Anat.  Anz.,  1887. 


878 


REPRODUCTION. 


lus  to  form  the  male  pronucleus,  the  union  of  which  with  the  female 
pronucleus  gives  rise  to  the  new  being. 


Fig.  538. 


Half  of  the  germiual  vesicle  is  extruded  into 
a  peri-vitelliue  space,  and  aloug  with  a  portion 
of  the  protoplasm  is  becoming  separated  oft" 
from  the  ovum  as  a  polar  globule.  The  ex- 
truded half  includes  four  of  the  chromatin 
particles  ;  the  other  four  remain  in  the  ovum. 
m'.  Membrane  dividing  the  polar  globule  from 
the  ovum.     (Quais.) 


The  remainder  of  the  germinal  vesicle  (after 
extrusion  of  the  first  globule  .7')  has  again 
become  transformed  into  a  spindle  of  achro- 
matic fibrils,  with  the  four  remaining  chromatin 
particles  at  the  equator  of  the  spindle.    (Quain.  ) 


It  has  also  been  shown  that  the  head  of  the  spermatozoon,  which 
is  the  part  that  is  transformed  into  the  male  pronucleus,  contains 
only  two  chromatin  particles,  the  other  two  having  been  thrown  off  in 


Fig.  540. 


Fig.  541. 


The  spindle  p,  now  irregularly  Y-shajted, 
is  seen  approaching  the  surface  of  the  ovum. 
I/'.  First  polar  globule,  ns.  Male  pronucleus 
'which  has  become  formed  from  a  sperma- 
tozoon.    (QUAIN.) 


Completion  of  the  process.  The  second  polar 
globule,  g-,  is  now  separated  from  the  ovum  ;  it 
containstwoof  thechroiuatin  particles.  Theother 
two  remain  in  what  is  left  of  the  germinal  vesicle. 
«3.  Which  now  forms  the  female  pronucleus,  ns. 
Male  pronucleus.  </i.  First  polar  globule.  (Quain.) 


the  "  maturation  "  of  the  spermatozoon  during  its  development  from 
the  nucleus  of  the  daughter  cell  of  the  parent  cell  of  the  seminiferous 
tubule.     It  would  appear,  therefore,  that  through  the  formation  of 


CON  JUG  A  TION  OF  PRONUCLEI. 


879 


Fig.  542. 


the  polar  globules  as  just  described,  room  is  made,  so  to  sjioak,  for  the 
reception  by  the  female  pronucleus  of  the  two  chromatin  particles 
brought  to  it  by  the  male  pronucleus, 
the  original  number  of  chromatin  par- 
ticles, viz.  four,  being,  therefore,  re- 
stored by  the  union  of  the  female  and 
male  pronucleus.  However  that  may 
be,  the  formation  of  the  polar  globules 
appears  to  be  an  indispensable  condi- 
tion to  the  impregnation  and  further 
segmentation  of  the  ovum.  The  two 
chromatin  particles  of  each  of  the  two 
pronuclei  are  now  transformed  into  a 
skein  (Fig.  543),  the  two  pronuclei 
being  separated  by  the  two  so-called 
"  attraction  bodies  "  which  appear  at 
this  stage  of  development.  The  skeins 
eventually  assume  the  shape  of  four  V-shaped  loops  or  filaments 
(Fig.   544),  and  Avhich  are  distinctly  visible   even  after  the  con- 


Passage  of  speriuiitozoa  into  ovum. 

(llAlUKEI..) 


Fig.  543. 


Fig.  544. 


The  chromatin  filaments  of  the  pronuclei 
have  become  transformed  into  skeins.  Two 
attraction-spheres,  each  with  a  central  par- 
ticle, united  by  a  spindle  of  achromatic  fibers, 
have  made  their  ajjpearauce  near  the  pro- 
nuclei. The  male  pronucleus  has  the  remains 
of  the  body  of  the  spermatozoon  adlieriug  to 

it.      (QUAIN.) 

Fig.  545. 


The  V-shaped  filaments  are  splitting  longi- 
tudinally. The  attract i(iM-siilieres  and  ach- 
romatic spindles,  although  present,  are  not 
shown.     UiL-.\ls.) 


Fig.  546. 


Equatorial  arrangement  of  the  four  chromatin 
loops  in  the  middle'of  the  now  elongated  ovum  ; 
the  achromatic  substance  forming  a  spindle- 
shaped  system  of  granules  with  fibrils  radiating 
from  thepoles  of  the  spindle  (attiaction-sphcresj 
into  the  protojjlasm,  commencing  division  of 
the  ovum  into  two  cells.     (ijiAlx. ) 


Further  separation  of  the  chromatin  fila- 
ments. K.ich  of  the  central  particles  of  the 
attraction-spheres  has  divided   into    two. 


jugation  or  union  of  the  two  pronuclei.     As  development  ^advances 
the  V-shaped  chromatin  particles  split  longitudinally  (Fig.  545), 


880 


REPRODUCTION. 


Fig.  547. 


and  dispose  them.selves  for  a  time  along  the  equator  of  the  spindle- 
shaped  nucleus,  four  of  the  chromatin  filaments  pa.ssing  soon  up- 
wards towards  one  pole  and  four  towards  the 
other  (Fig.  546).  Finally  the  chromatin  fihi- 
ments  are  transformed  into  the  skeins  of  the 
daughter  nuclei  developed  through  segmenta- 
tion, each  attraction  sphere  dividing  at  the 
same  time  into  two  (Fig.  547).  The  process 
of  segmentation,  that  is  the  cleavage  or  fur- 
rowing of  tlie  vitellus,  begins  shortly  after  the 
formation  of  the  new  nucleus,  the  division  of 
the  vitellus  (which  has  shrunk  away  from  the 
vitelline  membrane)  into  two  new  spheres, 
being  preceded  by  the  formation  of  a  spindle- 
shaped  system  of  achromatic  fibrils,  such  as 
take  place  in  the  karvokinesis  or  mytosis  of 
an  ordinary  cell.^  The  two  spheres  (Fig. 
548,  a),  so  formed  by  fission,  subdividing  into 
four  (Fig.  548,  6),  and  the  four  into  eight,  the  eight  into  sixteen 
(Fig.  548,  c),  and  so  on,  the  original  single  vitellus  becomes  finally 


The  daughter  nuclei  ex- 
hibit a  chromatin  uet- 
worlv.  Each  of  the  attrac- 
tion-spheres has  divided 
into  two,  which  are  joined 
by  achromatic  libers,  and 
are  connected  -with  the 
periphery  of  the  cell  in 
the  same  manner  as  the 
parent  sphere.     (Quaix.  ) 


Fig.  548. 


First  stages  of  segmentation  of  a  mammalian  ovum  ;  semi-diagrammatic,  r.  p.  Zona  pellu- 
cida.  p.  ;//.  Polar  globules,  a.  Division  into  two  segments,  ii.  Larger  and  clearer  segment.  /. 
.Smaller,  more  granular  segment,  h.  Stage  of  four  segments,  c.  d.  Succeeding  stages  of  segmen- 
tation showing  the  more  rapid  division  of  the  clearer  segments  and  the  enclosure  of  the  darker 
.segments  by  them.     (Qi  ain.) 


^  It  may  be  mentioned  in  this  connection  tliat,  according  to  the  modem  investiga- 
tions of  Buttcldi,  Ilertwig,  Strasburger.  etc.,  cells  appear  to  be  generally  reproduced 
by  karvokinesis  ratlier  than  by  simple  fi.ssion. 


GASTRVLA. 


881 


transformed  into  a  mnlherry-like  mass  of  vitelline  spheres 
(Fig.  548,  d),  the  vitelline  membrane  remaining,  however,  nn- 
divided.  These  cells  are  not  of  the  same  size  and  are  differently 
affected  by  reagents.     The  larger 

cells   arrange   themselves  in  the  Fig.  549. 

center,  the  smaller  ones  at  the 
periphery  and  in  a  single  row,  the 
latter  enclosing  the  former,  as  a 
cup,  its  contents.  The  e^^  now 
reaches  its  gastrnla  stage  (Fig. 
549).  Shortly  afterward,  hoM- 
ever,  through  one  of  the  larger 
inner  cells  being  drawn  inward, 
the  mouth  (o)  of  the  gastrnla  dis- 
appears, and  the  latter  now  forms 
a  ball  consisting  of  large  cells 
within  and  covered  by  a  single 
layer  of  small  vesicles  without. 
Fluid,  formed  probably  through 
the  deliquescence  of  some  of  the  cells,  appears  between  the  inner 
cells  and  the  layer  of  outer  ones ;  the  latter  is  expanded  into  a 
one-layered  globular  vesicle,  the  inner  cells  remaining  as  a  ball  of 
cells  adhering  to  the  outer  layer  at  a  point  where  the  mouth  of  the 
gastrnla  was  situated.  The  inner  cells  now  lose  their  ball-like  form, 
and  becoming  flattened,  assume  a  discoidal  shape,  spreading  them- 
selves out.  The  gastrnla,  so  modified,  is  now  known  as  the  blasto- 
dermic vesicle  (Fig.  550),  and  consists,  as  shown  in  section,  of  the 
original  zona  pellueida  or  cell-wall  («)  which  we  shall  henceforth 


GastruUi  ol"  rabbit,  in  longitudiual  section. 
(Haixkel.  ) 


Fig.  550. 


Fig.  551. 


Blastodermic  vesicle  of  rabbit,  seen  in  section. 
(Haeckel.) 


Blastodermic  vesicle  of  rabbit,  seen  from 
surface.     (KOllikkk,  after  Bi.schoff.) 


designate  as  the  chorion,  of  a  single  layer  of  cells  (b)  lying  next  to 
the  chorion  and  constituting  the  wall  of  the  blastodermic  vesicle,  of 
a  heap  of  cells  {c)  adhering  to  the  inner  surface  of  the  wall.  The 
latter  beins:  darker  in  color  thau  the  cells  forming  the  wall  of  the 


56 


882  REPRODUCTION. 

vesicle,  looks  like  a  dark  mass  when  the  blastodermic  vesicle  is 
viewed  from  the  surface,  the  cells  of  the  wall  then  appearing  like 
a  mosaic  (Fig.  551). 

The  changes  just  described  by  which  the  Qgg  is  transformed  into 
the  blastodermic  vesicle  appear  to  take  place  as  the  egg  passes 
through  the  Fallopian  tube. 

Formation  of  Blastodermic  Membrane. 
The  blastodermic  vesicle  does  not  remain,  however,  long  a  one- 
layered  vesicle,  but  soon,  through  the  extension  of  the  disk-like 

dark  cells  around  to  the  opposite  pole 
Fig.  552.  of  the  egg,  a  two-layered  vesicle  ;  and 

further,  through  development  of  a  third 
layer  intermediate  between  the  external 
and  internal  one,  a  three-layered  ves- 
icle (Fig.  552),  not  including,  of 
course,  the  chorion  (Z)  or  the  original 
zona  pellucida  of  the  Qgg,  which  now 
presents  here  and  there  over  its  outer 
surface  little  wart-like  i  villous  pro- 
cesses. The  three  layers  of  which  the 
blastodermic  vesicle  now  consists  (1, 
2,  3,  Fig.  552)  are  known  from  with- 
out inward  as  the  external,  middle, 
and  internal  blastodermic  membranes, 
or,  more  briefly,  as  the  epiblast,  mesoblast,  and  hypoblast. 

Development  of  Primitive  Organs. 
Shortly  after  the  development  of  these  three  layers  through  the 
thickening  of    the    two    outer  ones  (Fig.   553,  h),  there  appears 


Diagrammatic  view  of  ovum  of  rabbit, 
consisting  of  chorion,  enclosing  three- 
layered  blastodermic  vesicle. 


Fig.  553. 


Fi(i.  554. 


Diagrammatic  view  of  ovum  of  rabbit  to  show  for- 
mation of  germ  sliioUl  b. 


Germ    shield    of    rabbit    {h).    Primitive 
groove  (a).    Area  pellucida  (c).    Area  opaca 


DEVELOPMENT  OF  PBrMiriVE  ORGANS. 


883 


within  tolerably  well-defined  limits  an  opaque  oval-like  body,  the 
so-called  "  double  shield,"  ^  "  embryonic  area,"  -  or  ^erm  shield  ^ 
and  which  indicates  the  rudiment  more  particularly  of  the  dorsal 
portion  of  the  body  of  the  future  embryo,  the  remaining  portions 
of  the  blastodermic  membranes  not  entering  into  the  formation  of 
the  body  of  the  em])ryo,  but  aj^projiriated,  as  we  shall  see  presently, 
for  the  formation  of  the  true  and  false  amniotic  folds  and  umbilical 
vesicle.  If  the  blastodermic  vesicle  be  viewed,  not  in  section,  but 
from  the  surflice,  the  germ  shield  will  be  seen  (Fig.  554,  6)  as 
an  oval-like  structure,  lying  in  the  center  of  a  pellucid  area  (e),  so 
called  on  account  of  the  latter  being  surrounded  by  an  opac^ue  area 
(d),  the  whole  area  extending  from  edge  to  edge  of  the  area  opaca 
(d),  being  known  as  the  area  germinativa,  Avhicli  at  this  period, 
while  oval-shaped,  is  at  its  first  appearance  round  in  form. 

Shortly  after  the  development  of  the  germ  shield  there  ap- 
pears along  its  central  line  a  delicate  white  streak,  the  primitive 
streak  *  or  axis  plate,'  due  to  the  coalescence  of  the  three  blastoder- 
mic membranes  along  the  middle  line,  as  shown  by  section  (Fig. 
555,  B),  and  with  further  development  within  the  latter  a  delicate 
groove  or  furrow,  the  primitive  groove,  which,  however,  soon  dis- 
appears.    Its  function  is  unknown. 

Shortly  after  the  development  of  the  primitive  groove  there  ap- 
pears a  second  groove  (Fig.  556,  ft)  situated  in  front  of  the  former,  the 
medullary  groove,  so  called  on  account  of  it  giving  rise  through  the 
closing  in  of  its  walls,  or  the  medullary  folds,  along  the  middle  line 
to  the  primitive  medullary  tube,  or  central  nervous  system.     As  the 


Fig.  555. 


Diagrammatic  view  of  ovum  of  rabbit 
to  show  formation  of  primitive  streak  (B) 
bv  fusion  of  blastodermic  membranes. 


Lvre-shaped  germ  shield  of  rabbit,  a. 
Medullary  groove.  6.  (i  erni  shield,  c.  Area 
pellucida!    </.  Area  opaca. 


lEemak,  Untersuchungen  iiber  die  entwickeluns'  der  Wirbelthiere,  s.  7.  Berlin, 
1855.    ^F.  M.  Balfour,  Treatise  upon  Comparative  Enibrvolotfv,  Vol.  ii.,  1881,  p.  180. 

^Haeckel,  Anthropoffenie,  Yierte  Auflage,  1891,  s.  '285. 

*  Von  Baer,  Ueber  Entwickelungs  Geschiclite  der  Thiere.  Zweiter  Theil.,  s.  69, 
s.  190.     Konigsberg,  1887.  5j>e,jmk^  ^ip_  ^.[^^  g   7_ 


884 


BEPROD  UCTION. 


medullary  groove  (o)  deepens,  the  germ  shield  (6)  and  area  pel- 
lucida  (c)  lose  their  oval  shape  and  Ijecorae  lyre-  or  sole-shaped^ 
the  area  opaca  {d),  however,  reassumes  its  original  round  shape. 
Returning  now  to  the  consideration  of  the  embryo  as  more  ad- 
vanced in  development,  it  will 
Fig.  557.  be  seen  that  not  only  the  me- 

dullary groove  or  furrow  (Fig. 
557)  is  much  deepened,  but 
that  the  external  blastodermic 
membrane  rises  up  into  folds 
(Irt),  which,  arching  over  the 
dorsal  surface  of  the  embryo, 
coalesce  in  the  middle  line  and 
form  the  amnion,  the  remain- 
ing portion  of  the  external 
blastodermic  membrane  reced- 
ing from  the  amnion  proper  as 
the  false  amniotic  folds  (/'), 
until  they  finally  fuse  with  the 
inner  surface  of  the  chorion. 
It  will  also  be  observed  that 
the  middle  blastodermic  mem- 
brane or  mesoblast  has  split 
into  two  layers  (Fig.  558,  hf  and  df),  of  which  hf,  the  skin  fibrous 
layer,  unites  with  the  skin  sensory  layer  h,  to  form  the  somato- 
pleure  or  the  parietes  of  the  body,  while  the  intestinal  fibrous 
layer  df,  in  adhering  to   the  liypoblast  dd,  forms  the  splanchno- 


Diagi'ammatic  view  of  ovum  of  rabbit  to  show 
medullary  furrow,  amniotic  folds,  splitting  of 
mesoblast. 


Fig.  558. 


In  all  the  figures  the  letters  indicate  the  same  parts,  h.  Skin  sensory  layer.  ;«)•.  Spinal  tube. 
/(/.  Skin  fibrous  layer,  w.  Primitive  vertebra;,  ch.  Xotoehord.  c.  Body-cavity  {crrloma).  df. 
Intestinal  fibrous  layer,  ilil.  Intestinal  glandular  layer,  d.  Intestinal  cavity,  nh.  I'mbilical  or 
vitelline  vesicle.     (Hakckei,.  ) 


pleure,  or  the  fibro-muscular  wall  of  the  primitive  alimentary  canal 
and  umbilical  vesicle,  the  space  between  the  two  layers  of  the  meso- 
blast C  becoming  eventually  the  crelom  or  primitive  body  cavity, 
while  the  internal  blastodermic  membrane,  or  the  intestinal  glandu- 


DEVELOPMENT  OF  ORGANS. 


885 


lar  layer  d  d,  giving  rise  only  to  the  mucous  membrane  lining  the 
same.  An  inspection  of  these  different  sections  will  show  also  that 
just  as  the  primitive  neural  canal,  or  spinal  cord,  is  developed 
through  the  medullary  groove  {inr)  being  transformed  into  a  tube, 
which  later  becomes  entirely  separated  from  the  external  blasto- 
dermic membrane,  the  latter  giving  rise  to  the  epithelium  or  epi- 
dermis of  the  skin,  so  through  the  deepening  of  the  furrow  (d)  in 
the  internal  blastodermic  membrane  the  primitive  alimentary  canal 
is  formed,  the  uml)ilical  vesicle,  originally  part  of  the  same,  being 
constricted  off  Ijy  the  bending  downward  and  inward  of  the  parietes 
of  the  body. 

An  inspection  of  Fig.  ooS  will  also  show  that  as  the  medullary 
groove  or  spinal  tube  (mr)  of  the  external  blastodermic  memljrane  is 
formed  there  is  developed  within  the  internal  blastodermic  memljrane 
a,  rod  of  cartilage  (cA),  the  notochord,  or  chorda  dorsalis,  which 
represents  the  axis  around  which  will  be  developed  the  bodies 
of  the  future  vertebrae,  the  neural  canal  being  finally  enclosed 
by  a  bony  spinal  canal,  through  ossification  of  that  portion  of  the 
mesoblast  lying  above  and  on  either  side  of  the  notochord.  The 
embryo  of  the  rabbit  consists  at  this  period,  then,  apart  from  the 
enveloping  chorion  (Fig.  558,  E),  of  two  tubes,  a  neural  one 
above,  an  alimentary  tube  below,  separated  by  a  rod  of  cartilage,  and 
enclosed  by  the  walls  of  the  body,  the  space  between  the  two  layers 
of  the  mesoblast  representing  the  ccelom,  or  body  cavity.  Eesiuning 
what  Ave  have  just  endeavored  to  describe,  it  will  be  seen  that 
through  the  process  of  segmentation  the  vitellus  is  transformed  into 
a  mass  of  cells,  that  these  cells  dispose  themselves  as  three  mem- 
branes or  layers,  that  the  three  layers  give  rise  to  the  primitive 
organs  of  tlie  bodv,  out  of  which  the  remaining  organs  are  devel- 
oped,  as  follows  : 


Membranes  and  Layers  of  Embryo  and  Organ? 

FROM  Them. 


Developed 


Membranes. 

External  blasto- 
dermic membrane 
or  epiblast, 


Middle  blasto- 
dermic membrane  ■{ 
or  mesoblast. 


Internal  blasto- 
dermic membrane 
or  hypoblast, 


Skin, 
sensory, 


Skin, 
fibrous, 


Intestinal 
fibrou.-, 


Intestinal 
oflandulur, 


Organs. 

(  Epidermis. 

■    Central  nervous  system. 

(  Primitive  kidneys. 

(  Dermis. 

I   Peripheral  nervous  system. 

<^   Os.>;eous  " 

I   Mu.^cular  ••  " 

[  Testes. 

(  Vascular  system. 

I   Mesentery. 

■{   Wall  of  alimentary  canal 

I       and  appeudajres. 

[  Ovaries. 

(  Epithelium  of  alimentary 
<       canal  and  appendages, 
i   Notochord. 


886 


EEPEODVCTION. 


Development  of  Amnion,  AUantois,   and  Umbilical  Vesicle. 

It  has  already  been  mentioned  that  that  portion  of  the  external 
blastodermic  membrane  not  entering  into  the  formation  of  the  em- 
bryo rises  np  into  folds  (Fig.  559)  at  the  sides,  head,  and  tail  ends 


Fig.  561. 


a.  Umbilical  vesicle. 
6.  Amniotic  cavity,  c. 
Allantois.    (Daltox.) 


Fecundated  egg,  with  allan- 
tois fully  formed,  a.  Umbilical 
vesicle,  b.  Amnion,  c.  Allan- 
tois.    (Daltox.) 


Fecundated  egg,  with  allantois 
nearly  coinplete.  a.  Inner  lamina 
of  amniotic  fold.  h.  Outer  lamina 
of  ditto,  c.  Point  where  the  am- 
niotic folds  come  in  contact.  The 
allantois  is  seen  penetrating  be- 
tween the  inner  and  outer  laminae 
of  the  amniotic  folds.     (Dalton.) 

of  the  latter,  and  arching  over  its  back,  and  coalescing  in  the  middle 
line,  form  the  amnion  (a),  the  remaining  peripheral  portions  of  the 
extensive  blastodermic  membranes  not  giving  rise  to  the  amnion 
receding  as  the  false  amnion  (h)  from  the  trne  one  (Fig.  5(30),  un- 
til it  reaches  the  inner  surface  of  the  chorion,  with  which  it  ulti- 
mately fuses.  It  will  also  be  seen  from  Fig.  559,  that  during  the 
formation  of  the  amnion  (6)  there  buds  out  as  an  outgrowth  of  the 
posterior  portion  of  the  intestine  a  vesicle,  the  allantois  (c),  which, 
growing  outward,  gradually  extends  itself  (Fig.  560),  around  the 
entire  inner  surface  of  the  chorion,  the  cavity  of  the  vesicle  being 
finally  ol)literate(l  by  the  fusion  of  its  outer  and  inner  layers  (Fig. 
561).  The  chorion,  covered  with  villous  processes  (Fig.  562,  5  di  2) 
at  this  stage  will  consist,  then,  from  without  inward,  of  the  original 
zona  pellucida  of  the  false  amnion,  tlie  allantois.  As  the  allantois 
develops,  blood  vessels  make  their  appearance  in  it,  derived  from 
the  vessels  of  the  foetus,  as  we  shall  see  presently,  which,  in  extend- 
ing into  the  villous  processes  of  the  chorion,  serve  to  convey  to  the 
foetus  the  nutritive  material  introduced  by  osmosis  from  the  uterine 
blood  of  the  mother,  the  allantois  constituting,  in  fact,  the  foetal 
part  of  the  placenta.  With  the  establishing  of  the  allantois,  and 
the  consequent  nourishing  of  the  fietus  by  the  mother,  the  um- 
bilical vesicle  (Fig.  562,  d  s),  which,  uj)  to  this  time,  through  its 
vessels,  nourished  the  same,  begins  now  to  diminish  in  size,  and 
finally  disappears  altogether.  As  the  human  embryo,  at  the  ear- 
liest period  of  its  existence,  so  far  as  observed — that  is,  from  about 
twelve  to  fourteen  days  old — consists,  essentially,  of  the  same  primi- 
tive organs  and  appendages  as  that  of  the  rabbit,  there  can  be  no 


DEVELOPMENT  OF  MAMMALIAN  EMBRYO. 


887 


cIonl)t  that  the  still  earlier  stages  of  its  development,  not  vet  actu- 
ally seen,  are  essentially  the  same  as  those  just  described  as  taking 
place  in  the  rabbit. 


Fig.  502. 


Diagrammatic  figures,  illustrating  the  development  (if  the  nianimnlinn  embryo  and  the  ftetal 
membrane.  1.  The  blastodermic  vesicle  invested  in  the  zona  pclhieida,  and  showing  at  its  upper 
pole  the  embryonic  area.  2.  Shows  the  j)inching  oft"  the  embryo  from  the  yolk-sac,  and  the  lor- 
mation  of  the  "amnion.  3.  Further  development  of  amnion,  and  commencement  of  allantois.  4. 
Completion  of  amnion,  and  growth  of  allantois.  Chorion  gives  off  villous  processes.  5.  The 
allantois  has  grown  all  round  the  vesicle,  and  gives  oil'  i)rocesses  into  the  villi  which  are  much 
hirger  than  before.  The  yolk-sac  is  greatly  reduced  in  size.  u.  Epiblast  of  embryo,  a'.  Kpiblast 
of  non-embryonic  part  of  blastodermic  vesicle,  al.  Allantois.  aw.  Amnion,  ch.  Chorion,  ch'l. 
Chorionic  villi.  </.  Zona  pcllucida.  </'.  Processes  of  zona.  (/(/.  Kmbryonie  hyj)obla,st.  (If.  Area 
vasculosa.  f/17.  Yolk-stalk.  </.?.  Yolk-sac.  c.  Kmbryo.  /(A.  Pericardial  cavity.  /.  Xon-embryonlc 
hypoblast,  ili.  Cavity  of  blastodermic  vesicle,  ks.  Ucad-fold  of  amnion,  m.  ICmbryonic  meso- 
bfast.  n.  Non-embryonic  mesoblast.  r.  Space  between  true  and  false  amnion,  sh.  Chorion. 
x.t.  Veil-fold  of  amnion,  st.  Sinus  termiualis.  si.  Processes  of  zona  jiellucida.  vl.  Ventral  body- 
wall  of  embryo.      (KOLI.IKKR.) 


888 


BEPEODUCTIOX. 


Development  of  the  Nervous  System. 

The  primitive  nervous  system  cousists,  as  already  meutioued,  of 
a  tube  lying  between  the  external  blastodermic  membrane  and  the 


Fig.  o()3. 


Fig.  o64. 


-•IMiJ' 


Primitive  brain  and  spiniil  tulieof  man, 
with  sixteen  pairs  of  primitive  vcrtebrse. 
The  brain  has  divided  into  five  bladders. 
r.  Fore-brain.  ::.  Twixt-braiu.  vi.  Mid- 
brain. //.  Hind-brain.  ?i.  After-brain. 
«.  Eye-bladders.  //.  Ear- vesicles,  c. 
Heart,  ilr.  Yolk-veins,  mp.  Medullary 
plates,  iiir.  Primitive  vertebrie. 
(Haeckel.  ) 


Md 


Mo ^ 


Diagrammatie  horizontal  section  of  a  vertebrate 
brain.  The  figures  serve  both  for  this  and  the 
next  diagram.  Mh.  Mid-brain:  what  lies  in  front 
of  this  is  the  fore-,  and  what  lies  behind,  the 
hind-brain.  IJ.  Lamina  terminalis.  Ozf.  Olfae- 
tory  lobes.  JIiiiji.  Hemispheres.  Th£.  Thala- 
mencephalon.  I'n.  Pineal  gland.  Pi/.  Pituitary 
body.  F.V.  Foramen  of  Monro,  is.  Corpus  stria- 
tum. T/i.  Optic  thalamus.  CC.  Crura  cerebri : 
the  mass  lying  above  the  canal  represents  the 
corpora  quadrigemina.  Cb.  Cerebellum.  / — JA'. 
The  nine  pairs  of  cranial  nerves.  1.  Olfactory 
ventricle.  2.  Lateral  ventricle.  3.  Third  ven- 
tricle. 4.  Fourth  ventricle.  +  Iter  a  tertio  ad 
quartum  ventriculum.     (Huxley.) 


notochord,  and  ruiminti:  from  one  end  of  the  body  to  the  other.  As 
development  advances,  however,  the  anterior  portion  of  the  primi- 
tive neural  tube  separates,  and  subdivides  into  three  vesicles  :  the 
anterior,  middle,  and  posterior  cerebral  vesicles  ;  while,  through 
the  further  subdivision  of  the  anterior  vesicle  into  two,  and  of  the 
posterior  vesicle  into  two  also,  soon  five  vesicles  are  developed  (Fig. 
563),  which  are  known,  from  l)efore  backward,  as  the  prosen- 
cephalon, thalamencephalon,  mesencephalon,  epenccphalon,  and 
metencephalon,  or  as  the  fore-brain,  between  brain,  mid-l)rain, 
hind-brain,  and  after-brain.  Through  the  development,  anteriorly 
and  laterally,  of  two  vesicles  (Figs.  564,  505)  from  the  anterior 
primary  vesicle  the  future  olfactory  l)ulbs  and  optic  cups  are 
formed;    while  the  thickening  and  inward  growth  of  the  walls  of 


DEVELOPMEy'T  OF  THE  yERVOUS  SYSTE.V. 


HSd 


tlie  vesicles  give  rise  to  the  hemispheres  aucl  the  ganglia  of  the 
brain,  the  intervening  passage-ways — tliat  is,  tlie  remnant  of  the 
-cavities  of  the   original  cerebral   vesicles   remaininof   from  before 


f  1.   Prosencephalou, 


Longitudinal  and  vertical  diagianimatic  section  of  a  vertebrate  lirain.    Letters  as  before.    Lauiiiia 
terminalis  is  represented  by  the  strong  black  line  joining  Pit  and  Pi/.     (IIvxlev.) 

backward  as  the  lateral  and  third  ventricles,  tlie  avmv  from  the  third 
to  the  fourth  ventricle  ;  the  cavity  of  the  spinal  portion  of  the 
primitive  neural  tube,  persisting  as  the  canal  of  the  spinal  cord  of 
the  adult. 

Cerebral  Vesicles  and  Parts  of  Brain  Developed  out  of  Them. 

I  Cerebral  hemispheres,  corpora 
J  striata,  corpus  callosum,  for- 
]  nix,  lateral  ventricles,  olfae- 
l^      tory  bulb  (Rhinencephalon). 

(  Thalami  optici,  Pineal  gland, 
pituitary  body,  third  ventricle, 
optic  nerve  (primarily). 

(  Corpora     (juadrijiemiua,      crura 
cerebri,  aqueduct  of  Sylvius, 
(       optic  nerve  (secondarily). 

f  Cerebelkun.  pons  Varolii,  an- 
(       terior  part  of  fourth  ventricle. 

I  Medulla  oblongata,  fourth  ven- 
(       tricle,  auditory  nerve. 


II. 


Anterior,  j 

Primary,  <j 

Vesicle,  j 

I 

Middle.  ) 

Primai-y 

Vesicle, 


i 


2.  Thalamen- 

cephalon 
(Diencephalon),    ( 

3.  Mesencephalon 

4.  Epencephalon, 


III.  Posterior,  I 
Primary,  i 
Vesicle,       [  5.  Metencephalon, 


At  an  early  period  of  devolopiuent  the  five  different  parts  of  the 
brain  developed  out  of  the  primary  vesicles  may  be  nu^re  or  less 
seen  through  the  membranous  head  of  the  embryo.  Just  as  we  have 
seen,  however,  that  through  ossification  of  the  mesoblast  aromul 
and  above  the  chorda  dorsalis,  the  primitive  sjiinal  neural  canal 
becomes  enclosed  in  a  bony  one,  the  sjiinal  column,  so  through  the 
os.siticatiou  of  the  mesoblast  forming  the  in-iiuordial  craniuiu  sur- 
rounding the  primitive  cerebral  vesicles,  the  latter,  ov  the  future 
brain,  comes  to  be  enclosed  in  a  bony  cavity,  the  skull.  There  are 
three  marked  differences  though,  to  be  noticed  in  the  development 
of  the  skull,  as  compared  with  that  of  the  si>inal  eolumiL  First,  the 
uotochord  does  not  extend  entirelv  through  the  head  end  of  the  em- 


890  BEPEOD  UCTION. 

bryo  bnt  stops  short  in  a  tapering;  point  at  the  pituitary  fossa.  Sec- 
ond, the  mesoblast  does  not  split  into  the  skin  fibrous  and  intestinal 
fibrous  layers.  Third,  the  primordial  cranium  never  exhibits  any 
trace  of  segmentation  into  segments  or  vertebrre.  That  the  embryo 
skull  does,  nevertheless,  consist  of  segments  of  modified  vertebrse, 
though  not  in  the  sense  held  by  Goethe,^  the  presence  of  visceral  or 
l)ranchial  arches  clearly  proves,  since  the  latter  are  morphologically 
cranial  ribs  bearing  the  same  relation  to  diiferent  parts  of  the  skull 
that  the  thoracic  ribs  bear  to  the  vertebrae  to  which  they  are  attached. 
As  the  primordial  cranium  of  man,  however,  shows  no  trace  of  such 
segmentation,  gives  no  evidence  of  having  ever  consisted  of  ver- 
tebra?, it  is  evident  that  the  fusion  or  coalescence  of  the  same  must 
liave  taken  place  at  such  an  early  period  in  the  development  of  the 
vertebral  type  that  no  trace  of  the  primitive  segmentation  of  the 
skull  is  ever  seen  in  the  transitory  condition  through  which  it  passes, 
even  in  the  earliest  condition  of  the  embryo.  The  study  of  the 
embryonic  or  adult  skull  in  man  will  not  enable  us,  therefore,  to 
determine,  even  approximately,  the  number  of  the  primitive  vertebrse 
through  the  fusion  of  which  it  has  been  developed.  The  researches 
of  Gegenbaur  -  go  to  show,  however,  that  the  skull  of  the  shark  retains 
to  some  extent  the  primordial  type  of  segmentation,  in  the  fact  of 
there  being  eight  or  nine  branchial  arches,  and  that  the  nerves 
emanating  from  the  brain,  excepting  the  olfactory  and  optic,  bear 
to  the  latter  the  same  relation  that  the  spinal  nerves  bear  to  the 
spinal  cord.  If  the  latter  be  the  case,  and  the  branchial  arches  be 
regarded  as  homological  with  so  many  ribs,  then  the  primitive 
cranium,  in  the  shark,  at  least,  must  have  been  developed  through 
the  coalescence  of  so  many  vertebne.  Keturning  from  this  brief 
digression  upon  the  nature  of  the  primordial  cranium  in  man  to  the 

Fig.  566.  Fig.  567. 


1 
Visceral  arches  iu  man. 


thread  of  development,  let  us  consider  what  becomes  of  these 
branchial  arches.  The  visceral  or  branchial  arches  resembling 
those  of  fishes,  the  intervening  spaces  between  them  being  per- 
forated by  gill-like  openings  or  slits,  as  in  the  latter  animals,  are 
four  in  number  in   man,  and  symmetrically  disposed  (Fig.   566),. 

'  \'iivli()w,  Goethe  als  Xatnrforsclier,  1861,  s.  103. 
^  Das  Kopfskelet  der  Selachier,  1872. 


DEVELOPMENT  OF  SKULL. 


891 


and  are  called  from  before  backward  the  first  or  mandibular  (u),  tlie 
second  or  liyoid  (h),  the  third  or  thyro-liyoid  (d),  the  fourth  or  mh- 
hyoid  (r)  arches  respectively.  Through  the  fusion  at  the  middle 
line  of  the  distal  ends  of  the  first  visceral  arches  (Fi*r.  560,  u),  the 
rudimentary  lower  jaw  (Fig.  567,  a)  is  developed,  the  permanent 
jaw  being  developed  by  ossification  {mi,  Fig.j  568)  around  the 
cartilages  of  Meckel  (J/), 
or  the  rod  of  cartilage 
that  early  a]>pcars  within 
this  first  arch,  the  proxi- 
mal part  of  the  cartilages 
of  jNIeckel  not  related  to 
the  formation  of  the  lower 
jaw  becoming  eventually 
the  malleus  (w)  and  incus 
(«')  of  the  middle  ear.  It 
may  be  mentioned  in  this 
connection  that  the  stapes 
is  not  derived  from  either 
the  mandibular  or  hyoid 
cartilages,  being  devel- 
oped as  an  ossification  of 
the  membrane  closing  the 
fenestra  oval  is. 

In  addition  to  the 
changes  just  described, 
there  grows  from  the  root 
of  each  of  the  first  or  man- 
dibular arches,  forward  and  inward,  a  process  (Fig.  566,  o),  the  su- 
perior maxillary,  from  which  are  developed  the  superior  maxillary 
and  malar  bones,  and  a  pair  of  cartilaginous  rods  Avhich  ultimately 
become  the  pterygoid  plate  of  the  sphenoid  an<l  the  ])alate  bones, 
which  lie  parallel  with  the  trabecuke  cranii.  The  latter  are  two 
elongated  bands  of  cartilage  at  the  base  of  the  cranium,  connected 
with  the  i)rimitive  auditory  capsuli>,  which  diverging  to  enclose  the 
pituitary  body  unite  beneath  the  anterior  end  of  the  primordial 
cranium  to  form  the  septum  of  the  nose. 

The  basis  of  the  cranium  consists,  therefi)re,  at  an  early  i)eriod  of 
development,  of  cartilage  surrounding  the  notochord,  and  continuous 
where  the  latter  ends  with  the  trabecukv  cranii,  in  which  the  basi 
occipital,  basi  sphenoid,  and  presphenoid  bones  are  develoju'd  from 
three  centers  of  ossification,  respectively;  the  vault  of  the  skull, 
however,  witli  the  exception  of  the  squamo-occipital — that  is,  the 
frontal,  parietal,  and  squamous  jiortion  of  the  temporal  bones — 
being  developed  directly  out  of  membrane,  instead  of  out  of  cartil- 
age. During  the  develoi)nient  of  tiie  su^terior  maxillary  process 
from  the  first  or  mandibular  arch,  as  just  described,  there  grows 
downward,  between  the  primitive  oH'actory  grooves,  later,  the  nos- 


2.  The  zygomatic  arch.  nia.  The  mastoid  process,  tiii. 
Portiou.s  of  the  h)\verjaw.  M.  Tlie  cartihige  of  Meckel  of 
the  rifjht  side,  and  a  small  jiart  of  that  of  the  left  side, 
joining  the  left  cartilage  at  the  symphysis.  T.  The  tym- 
pauic  ring.  »(.  The  malleus.  (.  The  ineus.  .«.  The  stapes. 
sla.  The  sta])eilius  muscle,  s/.  The  styloid  jirocess.  p,h, 
g.  The  stylo-]ilKuynt;eus,  styln-hydid,  and  stylo-glossus 
muscles,  sti.  Stylo-hy(jid  lit^ameiit  attaclied  to  the  lesser 
coriiu  of  the  hyoid  bouc.  //*/.  The  hyoid  boue.  th.  Thy- 
roid cartilage."    (Quais.  ) 


892  REPRODUCTION. 

trilg,  the  naso-frontal  process  (Fig.  567,  m)  or  the  termination  of 
that  ])art  of  the  investment  of  the  head  situated  beneath  the  fore- 
l^rain  (v).  In  this  way  a  large  cavity  is  foi'med,  bounded  by  the 
naso-frontal  process  above,  the  superior  maxillary  process  at  the 
sides,  and  the  primitive  lower  jaw  below,  which  later,  through  the 
inward  growth  and  coalescence  of  the  palatine  plates,  is  subdivided 
into  a  mouth  below  and  a  nasal  cavity  above,  the  latter  being  fur- 
ther subdivided  into  two  by  the  growth  of  the  septum  nasi — the 
congue  growing  from  the  inner  surface  of  the  center  of  the  first  gill 
arch.  The  second  visceral  arches,  or  hyoid  arches  (Fig.  566,  h), 
growing  downward,  and  fusing  on  the  middle  line,  give  rise  to  the 
lesser  cornua  of  the  hyoid  bone,  the  stylo-liyoid  ligament  (Fig. 
568,  stl),  and  styloid  process  {st).  The  third  visceral  arches,  the 
thyro-hyoid  (Fig.  566,  d),  are  transformed,  through  fusion,  into  the 
body  and  greater  cornua  of  the  hyoid  bone.  The  fourth  visceral 
arches,  or  the  subhyoid  (Fig.  566,  r),  do  not  appear  to  be  developed 
into  any  particular  organ,  being  situated  in  that  part  of  the  embryo 
which  in  the  adult  becomes  the  neck,  and  which  is  absent  in  the 
fnetus.  It  has  just  been  mentioned  that  the  branchial  arches  in 
man  resemble  those  of  fish,  in  that  the  intervening  spaces  are  per- 
forated by  slit-lilce  openings  or  clefts,  through  which  the  water 
passes  by  which  the  vascular  gills  attat'hed  to  the  arches  are  bathed 
and  the  blood  aerated  in  the  latter  animals.     Apart,  however,  from 


Development  of  the  internal  ear.     (]Iai;<  kkl.  ) 

the  fact  of  the  branchial  arches  in  man  never  l)eing  fringed  with 
gills,  as  in  the  fish,  the  same  present  another  striking  difference,  in 
that  these  clefts  all  close  up,  save  the  first  one,  or  that  intervening 
between  the  mandibular  and  hyoid  arches,  which  persists  as  the 
tympano-Eustachian  tube — the  latter  being  finally,  in  the  adult,  cut 
off  from  the  exterior  by  the  growing  across  it  of  the  tympanic  mem- 
brane. Thus,  through  the  transformation  of  the  proximal  ends  of 
the  first  and  second  visceral  arches,  and  of  the  cleft  between  them, 
the  ear  bones,  meatus,  tympanic  membrane,  tympanum,  and 
Eustachian  tube  are  formed,  the  external  car  l)eing  developed  from 
the  integument  near  the  first  and  second  arches  ;  the  rudimentary 
internal  car  through  the  invagination  of  that  part  of  the  epiblast 
situated  immediately  above  the  upper  or  proximal  ends  of  the  second 
arch,  which,  in  time  closing  (Fig.  569,  A  fl,  B  h'),  becomes  a  vesi- 
cle.    The  latter,  the  rudimentary  vestibule,  in  giving  off  succes- 


DEVELOPMENT  OF  ALIMENT ARY  CANAL. 


SO  3 


Develoiiiiient  of  the  eye.     (Remak.  ) 


sivelv  the  tliree  semicircular  canals  (Fig.  5(39,  C,  D,  E,  c,  cp,  est), 
and  the  cochlea  (c),  originally  a  straight  tube,  develops  into  the 
internal  ear  of  the  adult.  It  will  be  remembered,  in  speaking  of 
functions  of  the  ear,  it  was  mentioned  that  the  transitory  stages 
through  whi<'h  it  passes  in  its  development  in  man  are  permanently 
retained  as  such  in  the  organ  of  hearing  in  the  hnver  animals. 
Like  the  ear,  the  eye — at 
least  the  anterior  part  of 
it — appears  first  as  an  in- 
vagination of  the  epiblast 
(Fig.  570,  A,  3),  which  in 
closing  up  (Fig.  570,  B,  2) 
and  separating  from  the 
same  gives  rise  to  the  crys- 
talline lens  (2).  On  the 
other  hand,  through  the 
invagination  of  the  optic 
cup  or  vesicle  —  that  is,  the  peripheral  portion  of  the  optic 
nerve — by  the  indenting  into  it  of  the  lens,  the  inner  surface  of 
the  cup  becomes  the  retina  (4),  the  outer  the  tapetum  nigrum  of 
the  choroid  (5),  the  vitreous  humor  being  developed  through  the 
insertion  of  the  mesoblast  from  below  between  the  lens  and  the 
retina.  The  remaining  portions  of  the  eye  are  also  developed  out 
of  the  mesoblast,  through  the  latter  growing  around  the  ball  of  the 
eye  as  a  fibrous  capsule,  Avhich,  splitting  into  an  anterior  and  a  pos- 
terior layer,  gives  rise  to  the  sclerotic  and  cornea,  and  choroid  and 
iris,  respectively.  Though  the  brain  and  spinal  cord  arc  developed 
out  of  the  epiblast,  the  cranial  nerves,  with  tlie  exception  of  the 
olfactory  and  optic,  which  are  outgrowths  of  the  anterior  cerebral 
vesicle,  as  well  as  the  spinal  nerves  and  sympathetic,  are  developed 
out  of  the  mesoblast. 

Development  of  Alimentary  Canal  and  its  Appendages. 

The  primitive  alimentary  canal,  like  the  neural  canal,  extending 
as  a  straight  tube  from  one  end  of  the  body  to 
the  other,  is  formed,  as  already  mentioned, 
through  the  pinching  off  of  the  internal  blas- 
todermic membrane  and  the  intestinal  fiV)rous 
layers  of  the  middle  blastodermic  membrane 
covering  it,  and  by  the  bending  inward  and 
downward  of  the  parietes  of  the  body,  the 
upper  portion  persisting  in  the  adult  as  the 
alimentary  canal,  the  lower  portion  remaining 
onlv  temporarily  in  the  embryo  as  the  umbil- 
ical vesicle  (Fig.  571).  At  first  the  alimen- 
tarv  tube  is  closed  at  the  ends,  but  as  develop- 
ment proceeds  the  skin  at  both  its  extremities 
invaginating,  deep  furrows  are  formed,  which,  gradually  growing 


Fig 


Human  embryo,  with  um- 
bilical vesicle ;  about  the 
fifth  week.     (Dalton.) 


894  BEPRODUCTION. 

toward  the  blind  ends  of  the  intestinal  tube,  finally  break  into  the 
latter,  and  so  give  rise  to  the  mouth  and  anus.  Such  being  the 
manner  in  whicii  these  apertures  are  formed,  it  is  evident  that  their 
lining  membrane  differs  from  that  of  the  remaining  portion  of  the 
alimentarv  canal  in  being  developed  out  of  epiblast  instead  of  hypo- 
blast. The  mucous  membrane  of  the  mouth  being  then  invaginated 
skin,  the  salivary  glands,  developed  through  the  division  and  sub- 
division of  its  follicular  glands,  must  be  regarded  as  being  essentially 
the  same  kind  of  glands  as  the  sudoriparous  and  sebaceous  glands — 
that  is,  as  epidermal  in  origin.  Hence,  also,  the  fact  of  the  teeth  of 
certain  fishes  resembling  so  closely  their  dermal  spines  that  at  the 
border  of  the  mouth  it  is  difficult  to  say  where  the  one  ends  and  the 
other  begins.  Indeed,  teeth  are  simply  calcified  mucous  membrane, 
the  invaginated  oral  ejaithelium,  giving  rise  to  the  enamel,  the  sub- 
nmcous  papilla  below  to  the  dentine,  the  pulp  being  made  up  of  a 
matrix  of  connective  tissue  supporting  blood  vessels  and  nerve  fibers. 
The  alimentary  canal  does  not  remain  long  in  the  human  embryo 
a  simple  straight  tul)e  ;  its  al^dominal  portion  soon  expands  into  the 
stomach,  while  through  the  elongation  and  coiling  of  the  part  im- 
mediately succeeding  the  latter  the  small  intestine  is  differentiated 
from  the  large  one.  It  has  been  mentioned  that  the  (glandular 
structures  of  the  alimentary  canal  are  developed  out  of  the  hypo- 
blast or  its  lining  membrane.  This  is  accomplished  through  the 
invagination  of  the  latter  into  the  wall  of  the  alimentary  canal, 
formed,  it  will  be  remembered,  out  of  the  intestinal  fibrous  layer  of 
the  mesoblast.  The  simple  follicular  glands  so  formed  either  re- 
main as  such,  or,  through  elongation,  become  simple  tubular  glands, 
or,  through  segmentation,  peptic  or  racemose  glands.  The  liver 
and  pancreas  arise  in  a  similar  manner,  the  only  essential  difference 
being  that  these  glands  eidarge  enormously  and  recede  to  a  consider- 
able extent  from  the  alimentary  canal,  with  which  they  remain, 
however,  through  life  in  communication  through  their  ducts.  In 
the  case  of  the  liver,  as  already  mentioned,  the  cells,  like  those  of 
the  remaining  alimentary  canal,  are  hypoblastic  in  origin,  the  fi- 
brous capsule  and  vessels  mesoblastic,  the  bile  ducts  beginning  as 
spaces  between  the  cells. 

Development  of  the  Vascular  System. 

The  heart,  like  the  glands  just  mentioned,  is  also  an  appendage 
of  the  alimentary  canal,  but  differs  from  the  latter  in  l)eiug  devel- 
oped only  out  of  the  mesoblastic  wall  of  the  same.  Tiie  heart  is 
originally  a  mass  of  cells,  but,  through  liquefaction  of  the  latter,  or 
the  primitive  blood  corpuscles,  is  soon  transformed  into  a  muscular 
sac  or  tube,  which  remains  for  a  short  time  connected  by  a  mesen- 
tery (Fig.  572,  hg)  Avith  the  wall  of  the  alimentary  canal,  of  which 
it  is,  as  just  said,  an  outgrowth.  Coincidently  with  the  develop- 
ment of  the  heart,  as  just  described,  and  in  connection  with  it,  there 


DEVELOPMENT  OF  THE  VASCT'LAR  SVSTE^f.  895 


appears,  apparently  tlirough  fission  of  the  Inner  and  outer  parts  of 
the  intestinal  fibrous  mesoblastic  wall  of  the  alimentary  canal,  the 
two  primitive  aortte  and  the  two  primitive  cardinal  veins,  respec- 
tively.      The    two    primitive 

aortfe     uniting     then     divide  Fk;.  ■')7l'. 

^gain,  the  two  branches  pass- 
ing along  the  inner  surface  of 
the  first  visceral  arches  and, 
curving  around  the  anterior 
portion  of  the  alimentary  canal, 
unite  anteriorly  and  pass  as  one 
tube  into  the  heart.  At  first 
there  are  but  one  pair  of  vas- 
cular arches  encircling  the  ali- 
mentary canal ;  in  time,  \vm- 
ever,  five  such  are  developed 
(Figs.  573-576),  three,  how- 
ever, onlv  coexisting  at  one 
period. 

The  primitive  aorta  further 
gives  oif  lateral  branches,  of 
which  two,  passing  to  the  um- 
bilical vesicle,  are  known  as 
the  vitelline  or  omphalo-mes- 
enteric  arteries,  while,  through 
the  t"\visting  of  the  heart  into 
nu  S-like  shape,  the  auricles 
become  uppermost,  the  ventricles  lowermost.  Two  veins,  similarly 
named,  return  from  the  uml)ilical  vesicle  to  the  body  of  the  foetus. 


niagraniniatic  transverse  section  tbrougli  the 
head  of  an  eruliryonie  mauiiual.  A.  Epidermis- 
plate,  m.  Medullary  tube  (braiu-bladder).  inr. 
Wall  of  the  latter.  /.' Dermis-plate.  .«.  Rudinieu- 
tary  skull,  c/i.  Xotochord.  /;.  Gill-arch.  mjj. 
Muscle-plate,  r.  Heart-cavity,  anterior  part  of 
the  body-cavity  (rr('/o;;/«).  </.  intestinal  tube.  rf</. 
Intestinal  glandular  layer,  df.  Intestinal  muscle- 
plate,  /if/.  Heart-mesentery,  hw.  Heart-wall. 
hk.  Ventricle,  ah.  Aorta-arches,  a.  Transverse 
section  through  the  aorta.     (H.\eckel.) 


Fig. 


Fig.  574. 


Fig. 


Fig.  o7t). 


Metamorphosis  of  the  five  arterial  arches  in  the  human  embryo,  ta.  Arterial  stalk.  1.2,3,4, 
5.  The  arterial  arches  from  the  first  to  the  fifth  pair.  a<l.  Main  stem  of  the  aorta,  air.  Roots  of 
the  aorta.  In  Fig.  573,  three  of  the  arterial  arches  are  given  ;  in  Fig.  574.  the  whole  five  (those 
indicated  by  dots  are  not  vet  developed);  in  Fig.  575,  the  first  two  have  again  disappeared;  in 
Fig.  57(>,  the  permanent  arterial  stems  are  represented.  The  dotted  parts  disappear.  .«.  .Sub- 
.clavian  artery,  r.  Vertebral  artery,  ax.  Axillary  artery,  c  Carotid  artery  ((-',  outer  ;  c",  inner 
carotid),    p.  "Pulmonary  artery  (lung-artery).     (Ratuke.  ) 

and  pass  as  a  single  trunk,  the  sinus  venosus,  into  the  heart.  Such 
being  the  disposition  of  the  heart  and  the  primitive  vessels,  it  follows 
that  the  nutritive  material  of  the  umbilical  vesicle  pasr^es  by  the 


896 


REPRODUCTION. 


Fig.  577. 


vitelline  veins  to  the  heart,  and  thence  throngh  the  vascnlar  arches 
to  the  primitive  aorta  and  so  to  the  l)ody  generally,  the  circulation 
being  completed  by  the  vitelline  arteries.  Neither  the  heart,  aortic 
trunk,  nor  vascular  arches  remain,  however,  long  in  the  condition 
in  which  they  have  just  been  described,  Tlie  heart  soon  subdivides 
into  a  right  and  left  heart  through  the  growtli  of  a  longitudinal 
septum,  and  further  into  auricles  and  ventricles  (Fig.  577)  through 
the  growth  of  transverse  septa,  the  septum 
between  the  auricles  remaining,  liowever,  in- 
complete until  after  birth,  the  opening  so 
caused  being  known  as  the  foramen  ovale. 
Coincidently  with  the  development  of  the 
cavities  of  the  heart  through  the  growth  of  a 
longitudinal  septum  in  the  common  arterial 
trunk,  the  latter  subdivides  into  aorta  and 
pulmonary  artery,  tlie  aorta  finally  being  dis- 
posed to  the  right,  the  pulmonary  artery  to 
the  left.  Finally  through  the  transformation 
of  the  third,  fourth,  and  fifth  vascular  aortic 
arches,  the  first  and  second  having  disap- 
peared, the  aorta  and  its  first  main  branches 
and  the  pulmonary  artery  are  developed,  the 
change  being  brought  about  through  the 
atrophy  or  hypertrophy  of  these  arches  re- 
spectively. Thus,  for  example  (Figs.  578— 
576),  of  the  left  fifth  arch  (5),  the  internal 
half  becomes  the  pulmonary  artery  (p),  the 
external  half  the  ductus  arteriosus,  the  right 
fifth  arch  disappearing,^  The  left  fourth  arch 
(4)  becomes  the  permanent  aorta  and  gives  off  the  left  subclavian 
artery  (.s).  The  right  fourth  arch  develops  into  the  innominate 
dividing  into  the  right  subclavian  and  right  common  carotid,  the 
left  common  carotid  being  given  oif  by  the  aorta.  The  third  left 
arch  (3)  on  both  sides  enters  more  into  the  formation  of  the  internal 
carotid  than  of  the  external  one,  its  outer  connecting  portion,  as 
well  as  that  of  the  fourth  arch,  disappearing. 

With  the  establishing  of  the  allantois,  however,  and  the  dwindl- 
ing away  of  the  umbilical  vesicle,  the  allantoic  or  second  circula- 
tion gradually  re])laces  the  vitelline  or  first  one.  The  allantoic  or 
umbilical  veins,  (jriginally  two  in  number,  appear  to  be  developed 
as  branches  of  the  vitelline  veins,  which,  extending  themselves 
through  the  allantois,  finally  pass  into  the  villous  processes  of  the 
(;horion.  Shortly  after  the  apj)earance  of  the  umbilical  veins,  the 
right  one  disappears,  and  with  it  the  right  vitelline  vein  and  that 
part  of  the  left  vitelline  outside  of  the  body  of  the  embryo.  The 
mesenteric  portion  of  the  latter,  or  left  omphalo-mesenteric  vein 
(Fig,  578,  M),  enlarges,  however,  while  the  remaining  portion  (O), 
'  The  embiyo  is  supposed  to  be  lying  upon  its  dorsal  surface. 


Heart  and  head  of  an  eiu- 
liryonic  dog,  from  the  front. 
(/.  Fore-brain.  6.  Eyes.  c. 
Mid-brain,  d.  Primitive 
lower  jaw.  i'.  Primitive 
upper  jaw.  //'.  Gill-arches. 
;/.  Right  auricle.  /(.  Left 
auricle.  /.  Left  ventricle. 
k .    Right    ventricle. 

(  BlSCIIOFF. ) 


DEVELOPMENT  OF  THE  VASCULAR  SYSTEM. 


807 


that  returning  from  the  unilMlical  vosiolo,  atrophies.  At  the  same 
time  the  left  umbilical  vein  (Fig.  578,  U)  becomes  very  much  en- 
larged, and  as  it  is  a  branch  of  the  omphalo-mesenteric  vein  it  will, 


Fig.  o7<s. 


Fig.  o79. 


Diagram lu at ic  view  of  portal  ami  iimliilical  eir- 
culatious. 


Diagrammatic  vic\r  of  portal  and  umbilical 
circulations  more  advanced. 


with  the  mesenteric  branch  of  the  same,  pass  as  one  trunk  (P  D)  to 
the  sinus  venosus  (S),  and  so  reach  the  heart  (H).  The  continuity, 
however,  of  this  trunk  due  to  the  union  of  the  umbilical  and  om- 
phalo-mesenteric vein  is  interrupted  by  the  development  of  the 
liver  (L)  as  an  investing  mass  around  it,  and  by  the  appearance  of 
the  inferior  vena  cava.  The  latter  may  be  regarded  as  the  back- 
ward prolongation  of  the  sinus  venosus  (S),  and  in  dividing  poste- 
riorly into  two  branches  gives  rise  to  the  two  iliac  veins.  AVith  the 
growth  of  the  liver  the  common  trunk  (Fig.  579,  P),  which  may 
now  Ijc  called  the  portal  vein,  gives  oft'  capillaries  (C  C),  wliich, 
ramifying  through  the  liver,  pass  into  the  vena  cava  by  a  distinct 
vessel,  the  hejiatic  vein  (Fig.  ")7JI,  H).  The  amount  of  blood  cir- 
culating through  the  hepatic  capillaries  (c  c)  at  this  period  is,  how- 
ever, but  small,  since  little  blood  comes  from  the  intestines  through 
the  mesenteric  vessel  (M),  while  of  the  blood  j)assing  through  the 
umbilical  vein  (U)  the  greater  part  Hows  directly  through  wliat 
may  be  now  called  the  ductus  venosus  (D)  into  the  inferior  vena 
(Ivc),  very  little  mixing  with  the  blood  of  the  portal  vein  (P).  It 
w'ill  be  remembered  that  the  single  aorta  formed  through  the  union 
of  the  vascular  or  branchial  arches,  passing  from  the  heart  along 
the  inner  surface  of  the  visceral  arches,  soon  divides  into  the  two 

57 


898 


REPRODVCTIOX. 


primitive  aortse  that  run  aloug  toward  the  posterior  eucl  of  tlie  body 
on  either  side  of  the  notochord.  As  development  proceeds,  the 
point  of  division  of  tlie  a<»rta  is  carried  much  further  back,  its  two 
branches  becominsj-  the  iliac  arteries. 


Fig.  580. 


Fk;.  581. 


Further  clevelojiment  of  the  venous  system. 
The  cardinal  veins  (C)  are  diminished  in  size. 
The  canal  of  Cuvier  ( I) )  on  left  side  much  atro- 
phied. Primitive  left  innominate  vein  (Li), 
and  primitive  vena  azygos  minor  vein  (c)  ai> 
pearing.  J.  Jugular  vein.  S.  .Subclavian  vein. 
(Daltox.) 


Adult  condition  of  venous  system.  1.  Right 
auricle  of  heart.  2.  Vena  cava  superior.  3,  3. 
Jugular  veins.  4,  4.  Subclavian  veins.  5. 
Vena  cava  inferior.  6,  6.  Iliac  veins.  7. 
Lumbar  veins.  8.  Vena  azygos  major.  9. 
Vena  azygos  minor.  10.  Superior  intercostal 
vein.     (Dalton.  ) 


P^rom  the  internal  part  of  the  latter,  that  which  becomes  later 
the  internal  iliac  arteries,  two  vessels  are  given  off,  which,  passing 
to  the  allantois,  give  rise  to  the  umbilical  or  hypogastric  arteries. 
In  the  meantime  the  primitive  cardinal  veins  (Fig.  580,  C  C ), 
uniting  with  the  jugular  veins  (J  J),  pass  into  the  sinus  vcnosus, 
and  so  to  the  heart,  there  lacing  at  this  period  then  two  superior 
vense  cavie,  a  disposition  which  is  retained  during  life  in  the  ele- 
phant, manatee,  rodents,  monotremes,  and  birds.  This  condition, 
however,  is  only  a  transitory  one,  since  a  vessel  {Ja,  Fig.  580)  is 
given  off  from  the  point  of  union  of  the  left  jugular  and  sub- 
clavian veins,  which,  uniting  with  the  corresponding  vessel  of  the 
right  side,  forms  the  superior  vena  cava  (2,  Fig.  581),  the  left 
primitive  superior  vena  cava  almost  entirely  disappearing,  being 
only  represented  in  the  adult  by  the  coronary  sinus  and  a  fibrous 
band  descending  obliquely  on  the  left  auricle.  Such  being  the 
disposition  of  the  venous  system  Avith  the  establishment  of  the 
allantois,  or,  as  we  shall  see  presently,  of  the  placenta,  the  heart 
in  the     meantime    having  become    four-chambered,  the    allantoic 


DEVELOPMENT  OF  THE  GENITO-URINARY  ORGANS.     899 

or  second  circulation  will  be  as  follows  :  The  blood  returning 
from  the  head  and  upper  extremities  will  pass  to  the  rijrht 
auricle  of  the  heart  by  the  superior  vena  cava,  thence  by  the 
right  ventricle  and  ductus  arteriosus  to  the  aorta,  and  so  to  the 
lower  extremities,  and  to  the  allantois  by  the  umbilical  arteries. 
The  latter  being  nourished  by  blood  that  has  circulated  through  the 
head,  etc.,  will  be  relatively,  therefore,  poorly  nourished.  On  the 
other  hand,  the  blood  of  the  umbilical  vein  returning  directlv  from 
the  allantois  or  placenta  laden  with  nutritive  material  and  oxygen 
absorbed  from  the  maternal  blood  will  pass  with  little  or  no  admix- 
ture from  the  portal  blood  into  the  right  auricle,  whence  guided  by 
the  Eustachian  valve  it  will  pass  through  the  foramen  ovale  into 
the  left  auricle,  thence  into  the  left  ventricle,  and  so  by  the  aorta 
to  the  head,  lience  the  fact  of  the  latter  being  so  much  better  de- 
veloped than  the  rest  of  the  body.  But  little  blood  passes  through 
the  lungs  in  the  foetus,  aeration  being  effected  by  the  placenta  ;  on 
the  other  hand,  a  very  large  amount  traverses  the  liver,  which  may 
be  accounted  for  on  the  supposition  that  the  liver  acts  as  a  decar- 
bonizer of  the  blood,  supplementing  in  this  way  the  want  of  action 
of  the  lungs.  At  all  events,  with  the  establishing  of  the  pulmo- 
nary respiration,  the  liver  becomes  smaller,  relatively,  while  in 
animals,  generally,  the  lungs  and  liver  are  in  an  inverse  ratio  as 
regards  size  and  functional  importance.  With  the  replacing  of  the 
second  or  allantoic  circulation  by  the  adult  pulmonic  and  systemic 
circulations  the  foramen  ovale  closes,  the  ductus  arteriosus,  umbili- 
cal vein,  and  umbilical  arteries  being  shrivelled  up  into  cords.  The 
internal  portion  of  the  latter  remains,  however,  ])ervious,  and  persists 
in  the  adult  as  the  superior  vesical  arteries,  while  the  part  of  the 
allantois  remaining  within  the  body  becomes  the  urinary  bladder 
and  urachus. 

Development  of  Eespiratory  Organs. 

The  respiratory  organs  may  be  regarded  as  appendages  of  the 
alimentary  canal,  since  the  trachea  and  oesophagus  are  originally 
one  and  the  same  tube.  As  development  advances,  the  trachea 
separates  itself  from  the  cesophagus,  the  upper  portiou  becoming 
the  larynx,  the  lower  subdividiug  into  the  two  bronchi,  the  latter, 
by  a  process  of  fission  and  segmentation,  giving  rise  to  the  bron- 
chial tubes  and  pulmonary  lobules. 

Development  of  the  Genito-urinary  Organs. 

The  genito-urinarv  organs  are  so  intimatclv  associated  iu  their 
development  that  it  will  be  found  conv-enient  to  study  them  to- 
gether. In  describing  the  structure  of  the  kidney,  it  was  men- 
tioned that,  however  complex  in  structure  the  organ  may  aj)j)ear  to 
be,  it  consists  essentially  of  a  tube,  open  at  oue  end,  from  which  are 
given  off  diverticula  terminating  in  blind  globular-like  expausions. 


5)00 


REPEODVCTION. 


Such  a  primitive  type  of  structure  is  presented  tlirough  life  in  the 
kidneys  of  the  myxinoid  fishes,  and  as  a  transitory  condition  in 
man  in  the  early  period  of  development.  The  common  duct  (Fig. 
o82,  ?'•),  running  from  end  to  end  of  the  body  on  either  side  of  the 
notochord,  which  gives  off  the  primitive  nrine 
Imi;.  ">S-.  tubes  (Fig.  '"i'^^,  u),  is  known  as  the  Wolffian 

duct  and  appears  to  be  developed  out  of 
the  skin  sensory  layer  (583,  u)  by  invagina- 
tion and  constriction,  precisely  as  the  spinal 
cord  is  developed,  the  duct,  however,  receding 
(Fig.  084,  /()  farther  from  the  general  surface 
of  the  body  than  the  cord,  and  terminating  in 
the  cloaca  or  lower  portion  of  the  alimentary 
canal.  Coincidently  with  the  development 
of  the  Wolffian  duct  and  its  diverticula,  or  the 
])rimitive  kidneys,  there  appears  in  the  meso- 
blast  just  at  that  part  where  the  latter  splits 
into  the  intestinal  fibrous  layer  (Fig.  584,  c/), 
and  the  skin  fibrous  layer  (//  f),  the  so-called 
indifferent  gland,  the  cells  of  which  differ  in 
many  respects  from  those  of  which  the  latter 
layers  consist,  and  out  of  which  the  germinal 
epithelium  (Fig.  585,  g)  giving  rise  to  either 
ova  or  spermatozoa,  as  the  case  may  be,  ap- 
pears to  be  developed.  Such  a  condition  of 
the  urinary  apparatus  does  not,  however, 
remain  long,  there  being  developed  out  of 
the  posterior  portion  of  the  AVolffian  duct  near 
where  it  passes  into  the  cloaca  a  secondary 
duct,  the  primitive  ureter,  A\hich  gradually 


o  f   ;i 
'J'  li  e 


Primitive  kidney 
human  embryo :  ii. 
urine  tubes  of  tlie  primitive 
kidney,  ir.  Wolffian  duct. 
w'.  Upper  end  of  tlie  latter 
(Morgagni'.s  hydatid),  m. 
MUllerlan  duet,  m' .  Upper 
of  the  latter  (Fallopian  hy- 
datid), fi.  Hermaphrodite 
gland,  becoming  either  tes- 
ticle or  ovary.     (Koiselt. ) 


^IG.  583. 

yn^n   /P 

^          ^^^/    3^ 

Lj^^v^"" 

f- 

j^€^-y=E_:^  y>^ 

C\ 

V 

Fig.    r)84. 


//.  Skill  sensory  l;iyer.  n.  SpiiKil  tulic. 
n.  ijegiiiiiiiij;  of  tVoiffian  body.  .'■.  Noto- 
chord. '■.  l5ody  cavity.  /."  Intestinal 
tibrou.s  layer,  il.  Intestinal  glandular 
hiver.     (/.   Intestinal  tube.     (IlAiifKKL. } 


)i.  I'riiuitivc  spinal  cord.  /■.  Xotocliord.  ///.Skin 
filirous  layer,  ir.  Vertebra-.  ./'.  Skin  sensory  layer,  riii. 
Dorsal  muscles,  hiii.  \'eiitral  muscles,  i/.  Mesentery. 
III.  Indiireicnt  se.xual  ^laiid.  <l.  Intestinal  fibi-oiis 
layer.    /.    Intestinal   glandular  layer      (IIaeckkl.) 


DEVELOI'MEXT  OF  GEXITO-J'RISARy  ORGAXS. 


901 


elongates  and  gives  off  diverticula,  wliicli  become  the  renal  tubules, 
and  disposed  witli  reference  to  the  blood  vessels  precisely  as  the 
diverticula  of  tlie  ^^'olffian  duet  were.  The  urine  excreted  by  the 
former,  however,  passes  into  the  posterior  part  of  the  stalk  of  the 
allantois,  or  the  urachus,  which,  dilating,  is  retained  in  the  body  as 
the  primitive  bladder.  The  latter  in  time  separates  both  from' the 
cloaca  and  that  part  of  the  allantois  which  comes  away  as  the  um- 
bilical cord  and  the  fetal  portion  of  the  placenta. 

In  this  manner  the  permanent  kidneys  grow  out  of  and  replace 
the  primitive  ones  developed  out  of  the  Wolffian  duct.     Tlie  latter, 

Fig.  585. 


Transverse  section  through  the  pelvic  region  and  the  hind  limbs  of  a  chick  on  the  fourth  day 
of  incubation  (about  forty  times  the  natural  size),  h.  Skin  sensory  layer,  u:  Medullary  tube. 
/(.  .Spinal  canal,  n.  Wolifiau  body  or  primitive  kidneys,  r.  Chorda,  e.  Uind  limbs.  /<.' .\llan- 
tois  canal  iu  the  ventral  wall.  /.  Aorta,  r.  Cardinal  veins.  «.  Uitestine.  <L  Intotinal-glandu- 
lar  layer.  /.  Intestinal  tibrous  layer,  hf.  .Skin  muscle  layer,  y.  Oerm-epilhelium.  r.  Dorsal 
muscles,     c.  Body  cavity  (f<p/o/rt«;."    (Waloeyer.) 

however,  do  not  di-sajipear,  but  split  (Fig.  586)  into  two  distinct 
tubes,  the  outer  still  called  the  AA'olffiau  duct  (»•),  the  inner  the  Miil- 
lerian  duct  (//)).  The  Wolffian  du(!t,  as  just  mentioned,  for  a  time 
carries  off  the  urine  excreted  by  its  tubules  from  the  blood,  but,  as 
this  office  is  transferred  to  the  ureter  and  permanent  kitlneys,  it 
gradually  is  transformed,  if  the  individual  becomes  a  male,  into  the 
epididymis  and  vas  deferens,  and  will  hereafter  carry  to  the  uretlira 
the  spermatozoa  developed  by  the  hitherto  indifferent  body  (ot), 
now,  therefore,  a  testicle  ;  the  Miillerian  ducts,  at  their  lower  distal 
united  portion,  persisting  as  the  sinus  poculari.'*,  the  homologue  of 
the  vagina  ;  the  upper  proximal  portions  as  the  so-called  hydatid 
of  Morgagni.      On   the   other   hand,  if  the  individual    becomes   a 


902 


SEPRODUCTION. 


Fig.  586. 


female,  the  gland  (of)  produces  eggs,  and  is  henceforth,  therefore, 
an  ovary.  The  Miillerian  ducts  fuse  together  from  below  upward 
and  become  the  vagina,  uterus,  and  Fallopian  tubes  ;  the  Wolffian 
ducts  persisting  in  an  atrophied  condition,  in  the  human  female,  as 

the  parovarium,  or  the  M'hite 
tortuous  tubes  in  the  broad 
ligament  of  the  uterus  ;  and 
in  that  of  certain  animals, 
the  pig,  as  the  ducts  of 
Gaertner  opening  into  the 
vagina.  At  an  early  period 
of  intrauterine  life  the  con- 
joined Wolffian  and  Miil- 
lerian  ducts  pass  as  the  gen- 
ital cord  (Fig.  oHG,go)  into 
the  expanded  stalk  of  the 
allantois,  or  urogenital  sinus 
(ug)  ;  the  latter,  in  time, 
emptying,  together  with  the 
alimentary  canal  (/),  into  the 
cloaca  (el),  or  cavity  com- 
mon to  both.  As  develop- 
ment advances,  however,  the 
rectum  separates  from  the 
cloaca,  and  if  the  individual 
becomes  a  female  a  further 
differentiation  takes  place, 
in  that  the  lower  united  por- 
tion of  the  Miillerian  ducts, 
or  the  vagina,  terminates  in 
an  opening  distinct  from 
that  of  the  urethra,  or  the 
passage-way  from  the  bladder.  The  latter,  in  the  case  of  the  indi- 
vidual Ijeing  a  female,  will  pass  beneath  the  clitoris,  or  female  penis, 
the  two  adjacent  folds  of  skin  becoming  the  labia  minora,  the  two 
lateral  external  ones  the  labia  majora,  the  ovaries  lying  within,  in  the 
body  cavity.  On  the  other  hand,  if  the  individual  be  a  male,  the 
urethra  passes  through  the  elongated  penis  ;  the  under-skin  of  which 
is  formed  bv  the  coalescence  in  the  middle  line  of  what,  in  the  female, 
constitute  the  labia  minora ;  the  scrotum  l)eing  formed  through  the 
fusion  along  the  future  raphe  of  the  parts  corresponding  to  the  labia 
majora,  into  Avhich  the  testicles  descend  by  passing  through  the  in- 
guinal canal,  the  peritoneum  consequently  pushed  in  front  of  them 
becoming  the  tunica  vaginalis  testis.  Such  being  the  manner  in 
which  the  external  generative  organs  are  developed  in  the  two  sexes, 
it  will  be  readily  understood  why,  in  those  male  individuals,  on  the 
one  hand,  in  which  development  is  arrested  at  the  stage  at  which  the 
external  generative  organs  in  the  two  sexes  are  alike  ;  and  in  the 


Diagram  of  the  Wultiiaii  IhwUi-s.  Miilleriau  ducts, 
and  adjaceut  parts  previDUs  X'<  -ixiial  distiuction,  as 
seeu  from  before,  sr.  The  sviinarinal  Imdies.  r.  The 
kidueys.  ot.  Common  blastema  (jf  ovaries  or  testicles. 
W.  Wolffian  bodies,  w.  Woltfian  ducts,  m,  m. 
Miillerian  ducts,  ffc.  Genital  cord.  ug.  Sinus  uro- 
geuitalis.    i.  Intestine,    cl.  Cloaca.     (Quain.) 


DEVELOPMENT  OF  EXTREMITIES.  903 

other,  in  those  female  ones  in  which  the  clitoris  is  much  elongated, 
that  such  should  be  regarded  by  the  vulgar  as  hermajjlirodites,  though 
in  neither  case  is  hermaphroditism  really  present.  Bearing  in  mind 
what  has  just  been  said  as  to  the  development  of  the  uterine  gener- 
ative organs,  it  is  readily  conceivable,  also,  that  if  one  of  the  indif- 
ferent bodies  of  early  intra-uterine  life  became  a  testicle,  and  the 
other  an  ovary,  and  both  functionally  active,  or  if  two  ovaries  and 
two  testicles  were  developed  through  the  subdivision  of  the  indif- 
ferent bodies,  which  consisted,  probal^ly,  of  both  male  and  female  ele- 
ments ;  and  further,  that  the  Wolffian  ducts  became  vasa  deferentia, 
and  the  ^liillerian  ducts  the  vagina,  uterus,  and  Fallopian  tulje  or 
tubes  ;  that  the  same  individual  might  produce  ova  and  sperma- 
tozoa, and  that  an  egg  might  be  developed  in  the  uterus  of  the  in- 
dividual producing  it  after  fecundation  by  its  own  spermatozoa,  or  by 
those  of  a  similar  or  normal  male  individual.  In  such  a  hypothet- 
ical case  there  would  Ijc,  however,  either  a  penis  or  clitoris,  but 
not  both,  and  either  a  scrotum  or  labia  majora,  but  not  both. 
While  a  condition,  like  that  just  described,  is,  therefore,  within  the 
limits  of  possibility,  it  is  extremely  doubtful  Avhether  such  a  case 
ever  actually  existed  in  a  human  being,  though  hermaphroditism 
obtains  in  many  of  the  lower  animals,  mollusca,  worms,  etc.,  and 
in  numerous  plants  ;  the  stamens  and  pistil  of  a  iloMcr  constituting 
the  male  and  female  generative  organs  respectively.  The  onlv 
true  test  of  sex  being  the  power  of  producing  ova  or  spermatozoa, 
it  is  obvious  that  however  nuich  the  external  or  internal  organs  in 
any  one  individual  may  reseml>le  those  of  the  normal  nuile  or  female 
as  due  to  either  hypertrophy  or  arrest  of  development,  that  such 
modified  organs  cannot  be  taken  alone  as  an  evidence  of  sex. 

Development  of  Extremities. 

The  limbs  first  appear  as  bud-like  protuberances  from  the  sides 
of  the  body  (Fig.  585,  e),  those  giving  rise  to  the  upper  extremi- 
ties being  developed  first.  While  covered  by  the  outer  or  skin 
sensory  layer,  the  limbs  are  developed  more  especially  out  of  the 
deeper  or  skin  fibrous  layer,  through  its  cells  becoming  first  carti- 
lage, with  after-ossification  of  the  same.  As  development  advances, 
the  primitive  limb-bud  recedes  from  the  body,  and  expanding  at  its 
distal  extremity,  segments  the  divisi<ms  so  arising,  becoming,  here- 
after, the  fingers  and  toes — the  characteristic  bones  with  the  corre- 
lated muscles  being  gradually  developed  in  the  same. 

Resume  of  Development  of  Foetus. 

On  the  supposition  that  the  ontogeny  or  development  of  the  in- 
dividual is  the  ej)itomized  ])hylogeny  or  history  of  the  race,  we 
have  some  explanation  of  the  fact  that  the  various  changes  through 
which  the  embryo  passes  re])res6nt  morphologically  the  permanent 
condition  of  lower  forms  of  life.     The  principal  changes  undergone 


904  REPBODUCTION. 

by  the  embryo  during  its  development,  which  we  have  just  endeav- 
ored to  describe  and  account  for,  may  be  synoptically  resumed 
about,  as  follows  : 

At  the  twelfth  day,  the  ovum,  about  5  millimeters  (^  of  an  inch) 
in  length,  consists  of  the  zone  pellucida  beset  with  small  villi, 
and  enclosing  a  two-layered  vesicle,  the  blastodermic  vesicle. 

At  the  fifteenth  day  the  embryo,  about  2  millimeters  (the  J^"  of 
an  inch)  in  length, exhibits  the  primitive  groove,  amnion,  allantois, 
and  umbilical  vesicles ;  the  heart,  though  still  onc-chambcred,  is 
present,  and  the  first  or  vitelline  circulation  is  established,  and  the 
rudiments  of  the  Wolffian  duct  indicated. 

At  the  twentieth  day  the  embryo,  about  3  millimeters  (|  of  an 
inch)  in  length,  presents  the  visceral  arches  and  perforated  clefts. 

At  the  twenty-first  day  the  embryo,  about  4  millimeters  (^  of 
an  inch)  in  length,  has  developed  rudimentary  eyes,  ears,  mouth, 
three  cerebral  vesicles,  and  the  heart  has  become  four-chambered. 

At  the  end  of  the  first  month  the  embryo  has  attained  a  size  of 
12  millimeters  [h  an  inch),  and  is  characterized  by  the  presence  of 
distinct  rudimentary  limbs,  the  whole  ovum  measuring  about  17 
millimeters. 

At  the  end  of  the  second  month  the  embryo  is  about  25  milli- 
meters (1  inch)  in  length,  and  weighs  about  4  grammes  (|  of  an 
ounce),  the  whole  ovum  measuring  about  7  centimeters  (2.4  inches). 
By  this  time  the  vitelline  vessels  and  right  umbilical  vein  are  ob- 
literated, the  future  fingers  and  toes  are  indicated,  the  outer  ear  has 
appeared,  nose  and  eyelids  are  present ;  the  umbilical  cord  is  about 
16  millimeters  (|  of  an  inch)  in  length,  and  ossification  has  begun 
in  the  lower  jaw,  clavicle,  ribs,  vertebral  bodies  ;  permanent  kid- 
neys present,  but  sex  still  indistinct. 

At  the  third  mfmth  the  fcetus  is  about  10  centimeters  (4  inches) 
in  length,  weighs  about  20  grammes  (|  of  an  ounce) ;  a  difference 
of  sex  is  indicated  by  the  external  genitals,  the  umbilical  cord  is  7 
centimeters  (2.8  inches),  and  the  placenta  begins  to  be  formed. 

At  the  fourth  month  the  foetus  is  17  centimeters  (7  inches)  long, 
weighs  120  grammes  (4  ounces);  umbilical  cord  is  19  centimeters 
(7  inches)  long,  and  weighs  80  grammes  (2.6  ounces). 

At  the  fifth  month  the  foetus  is  about  20  centimeters  (8  inches) 
in  length,  and  weighs  284  grammes  (9  ounces)  ;  the  hair  of  the 
head  and  of  the  body,  or  lanigo,  is  quite  distinct,  and  covered  with 
the  vernix  caseosa  ;  the  umbilical  cord  is  about  31  centimeters  (12 
inches)  long,  and  the  placenta  weighs  178  grannnes  (6  ounces). 

At  the  sixth  month  the  foetus  is  28  centimeters  (11  inches)  long, 
and  Aveighs  634  grammes  (20  ounces),  and  meconium  appears  in 
the  intestines. 

At  the  seventh  month  the  fiotus  is  about  35  centimeters  (14 
inches)  long,  and  weighs  1,218  grammes  (2J  pounds)  ;  the  eyes  are 
open,  one  testicle  has  descended  into  the  inguinal  canal,  and,  if 
l)orn  at  this  period,  is  viable. 


DEVELOPMEXT  OF  THE  I'LACEXTA. 


IMIO 


At  the  eighth  month  the  foetus  is  42  centimeters  (l(j  inches)  in 
length,  and  weighs  between  1  and  2  kilos.  (2.2  t(.  4.4  poundsj  ;  one 
testicle  has  descended  into  the  scrotum. 

At  the  end  of  the  ninth  month,  or  at  full  term,  the  foetus  isah.mt 
51  centimeters  (20  inches)  in  length,  and  weighs  3^-  kilos.  (7  pounds). 

Development  of  the  Placenta. 

Up  to  the  present  moment  notliing  has  heen  said  as  to  the  changes 
undergone  liy  the  mucous  membrane  of  the  uterus  after  the  ovum 
impregnated  has  passed  into  the  cavity  of  the  same.  These  changes, 
which  must  now  be  at  least  briefly  considered,  appear  to  differ 
rather  in  degree  than  in  kind  from  those  exhibited  by  the  mucous 
membrane  during  menstruation,  the  essential  difference  being  that 
the  mucous  membrane  during  pregnancy  is  hypertrophied  to  a  far 
greater  extent,  and  more  of  it  is  finally  cast  off  than  during  men- 
struation. As  the  fecundated  egg  passes  through  the  Fallopian 
tube,  the  mucous  membrane  of  the  uterus  becomes  tumefied,  vas- 
cular, and  rugose,  ])rojecting  as  rounded  eminences  into  the  cavitv 
of  the  uterus  (Fig.  587),  the  uterine  tubules  at  the  same  time  clon- 


FrG.  o87. 


Fig.  588. 


Impregnated  uterus,  with  projecting  folds  of 
decidua  growing  up  around  the  egg.  The 
narrow  opening,  where  the  edges  of  tbe  folds 
approach  each  other,  is  seen  over  the  most 
prominent  portion  of  the  egg.     (Dalton.  ) 


Impregnated  uterus  :  sbowing  conncctiou  be- 
tween villosities  of  chorion  and  decidual  nicm- 
braue.     (Dalton.) 


gating  and  expanding  to  such  an  extent  that  their  open  mouths  be- 
come perceptible  at  the  surface.  The  nuicous  membrane  so  motlitied 
is  a  thick,  soft,  velvety,  vascular  lining,  quite  different  from  that  vi' 
the  unimpregnated  condition  ;  indeed,  st)  much  so  that  the  decidua 
vera,  as  the  membrane  is  now  called,  was  supposed  at  one  time  to 
be  of  new  formation. 

The  decidua  vera  is,  however,  only  the  hyj)ertropliied  mucous 
membrane  of  the  uterus,  its  cells  being  derived  from  the  connective 
tissue  cells  of  the  latter,  and  is  continuous  at  the  orifices  of  the 
Fallopian  tubes  with  the  mucous  membrane  lining  the  latter,  and 
at  the  OS  internum  with  that   lininu'  the  cervix.      It  should  also  l)e 


906 


REPRODUCTION. 


mentioned  that  at  this  period  the  cavity  of  the  latter  becomes  so 
filled  with  a  viscid-like  mucus  that  the  passage-way  to  the  vagina 
is  blocked  up,  the  ovum  within  the  cavity  of  the  uterus  being 
thereby  protected  from  external  influences.  The  impregnated  e^g 
having  reached  the  uterine  orifice  of  the  Fallopian  tube,  passes 
through  the  latter  into  the  cavity  of  the  uterus  and  is  caught,  as 
it  were,  between  a  pair  of  the  folds  of  the  decidua  vera,  and  re- 
tained there  by  the  growing  downward  and  around  of  the  latter 
until  the  ovum  is  completely  inclosed  by  the  same.  The  reflected 
folds  so  developed  are  known  as  the  decidua  reflexa(Fig.  5.88),  that 
portion  of  the  decidua  vera  lying  between  the  ovum  and  the  wall  of 
the  uterus  as  the  decidua  serotina.  It  has  already  been  mentioned 
that  the  chorion  or  vitelline  membrane  of  the  ovum  at  an  early 
period  of  intrauterine  life  is  covered  with  small  villous-like  pro- 
cesses, which  in  time  become  vascular  through  being  penetrated  by 
the  blood  vessels  of  the  allantois.  The  villi,  when  examined  by 
the  microscope  (Fig.  589),  present  such  a  very  characteristic  ap- 


FiG.  589. 


Fig.  590. 


Compound  villosity  of  human  chorion,  ramified 
extremity.  From  a  three  months'  IVetus.  Magni- 
fied thirty  diameters.     (D altos.) 


Extremity  of  villosity  of  chorion,  more 
highly  magnified;  showing  the  arrangement 
of  blood  vessels  in  its  interior.     (Dalton.  ) 


pearance  that  their  presence  may  be  accepted  as  positive  proof  of 
the  existence  of  a  fretus,  as  much  so,  indeed,  as  if  the  foetus  it- 
self had  been  found.  The  general  appearance  of  a  villus  is  like 
that  of  a  seaweed,  originating  in  the  chorion  by  a  trunk,  which 
divides  and  subdivides  into  filamentous  branches,  swollen  here 
and  there  and  terminating  in  rounded  extremities,  and  consisting 
internally  of  a  finely  granular  substance  containing  nuclei.  At 
first  the  villous  processes  of  the  chorion  are  without  vessels,  but 
Avith  the  establishment  of  the  allantois  they  Ix'come  vascular  through 


DEVELOPMENT  OF  THE  PLACENTA, 


IKI7 


prolongation  of  the  terminal  allantoic  vessels,  which  (Fig.  500)  are 
disposed  in  loops.  As  development  advances,  however,  the  chorion 
loses  its  villi,  except  at  that  part  of  it  in  contact  with  the  decidna 
serotina  (Fig.  591),  but  here  the  villi  are  much  developed,  dividing 


Fig.  591. 


Fig.  .092, 


Preguant  uterus  :  showing  the  for- 
matiou  of  the  placenta  bv  the  local 
development  of  tlie  decidiia  and  the 
chorion.     (  Dalton.  ) 


Pregnant  human  uterus  and  its  contents,  about  the 
end  of  the  seventh  month  :  showing  the  relations  of 
the  cord,  placenta  and  membrane.  1.  Decidua  vera.  2. 
Decidua  rellexa.    :i.  Chorion.  4.  Amnion.    (Daltox.) 


and  subdividing  and  insinuating  themselves  as  they  grow  into  the 
mucous  mem])rane  or  decidua  serotina  of  the  uterus.  The  latter 
in  the  meantime  hypertrophies,  grows  downward,  around,  and  be- 
tAveen  the  villous  processes  of  the  chorion  (Figs.  593,  594,  v),  its 
capillaries  (fc)  at  the  same  time  becoming  enormously  dilated,  being 
finally  transformed  into  sinu.scs  into  and  from  which  pass  a  uterine 
artery  ('/a)  and  vein  ("'•).  The  wall  of  the  sinus  eventually  fusing 
with  that  of  the  villous  process  of  the  chorion  (r),  and  the  latter  with 
the  wall  of  the  capillary,  eventually  the  maternal  blood  in  the  sinus 
(vc)  is  separated  from  tiie  fcetal  blood  in  the  villous  process (/V) by  a 
memlirane  so  thin  as  not  to  exceed  the  rj-,^.^  of  a  millimeter  (^yto-q-  inch) 
in  thickness,  which  readily  permits  of  the  osmosis  of  nutritive  mate- 
rials and  oxygen  from  the  mother's  bloo<l  into  that  of  the  foetus, 
and  of  effete  materials  from  the  blood  of  the  ftetus  into  that  of  the 
mother,  though  at  no  time  is  there  any  connection  between  mater- 
nal and  ffctal  vessels.  The  organ  so  formed,  with  nutritive  and 
respiratory  functions,  is  called  the  placenta,  and  evidently  consists 
of  two  parts,  foetal  and  maternal,  the  allantois  and  decidua  serotina, 
which,  however,  become  so  intimately  united  that  eventually  they 
are  inse])arable,  and  are  cast  off  as  such  during  labor  as  the  "after- 
birth."    As  development  proceeds,  the  amnion  becoming  distended 


908 


REPRODUCTION. 


with  the  fluid  given  off  by  the  foetus,  consisting  principally  of 
water,  some  urea  and  alkaline  salts,  comes  in  contact  about  the  hlth 
month  of  pregnancy  with  the  chorion  and  adheres  more  or  less 
to  the  latter  by  a  gelatinous  layer  of  tissue,  the  tunica  media  ot 
Bischoff. 


Fig.  593. 


'un',1    -<l^ 


Fro.  594. 


Fig.  595. 


ua.  Uterine  artery,   nc.  Uterine  capillary.    -"■^:^:%J^^f'  ^'"•'"'"='-     '''■  ''""°°- 
■v.  Villous  processes  ol  chonou.    Jv.  iMi'tal  \c!m>o!s.     (.Imicolani.; 

The  decidua  reflexa,  fusing  in  turn,  about  the  seventh  month  of 
pregnancy  with  the  decidua  vera,^  it  so  comes  that  at  the  end  ot 

1  It  sh..ukl  be  mentioncHl,  however,  that  acconling  to  many  f ^brvologi^ts  the 
aecidm  retlexa  l.oLnns  to  atrophv  about  the  tilth  month  of  gestation,  and  being 
gra(Uially  absorbed  finally  disappears  between  the  sixth  and  seventh  months. 


RUPTURE  OF  MEMB RAXES.  909 

pregnancy  the  foetus,  suspended  from  the  phu-enta  bv  the  umbilical 
cord,  floats  in  the  amniotic  fluid,  the  enclosing  sac  of  which  con- 
sists of  the  layers  just  mentioned. 

With  the  rupture  of  the  latter  and  the  escape  of  tlie  water,  etc., 
the  child  is  born,  and  that  life  begins  which  it  has  been  the  object 
of  this  work  to  endeavor  to  describe. 


INDE 


A  BSOEPTIOX,  159 
J\.    bv  intestines,  170 

of  oxygen,  383 

by  stomach,  170 

by  veins,  16<S 
Accommodation,  767 

changes  in  form  of  lens  in,  708 
Achrodextrin,  49,  99 
Acid,  amid  ethyl  sulphonic,  15 

amido-caproic,  65 

aspartic,  65,  138 

benzoic,  51,  65 

carbolic,  51 

carbonic,  47 

cholalic,  143 

dibasic,  50 

ethereal  sulphuric,  67 

fermentation,  50 

glucuronic,  49,  67 

glycocholic,  143 

hippuric,  65,  471 

hydrochloric,  production  of,  IIS 

indoxyl  sulphuric,  151 

isobutyl  amid  acetic,  65 

lactic,  44 

methyl  guanidin  acetic,  66 

monobasic,  50 

oleic,  53 

oxalic,  54,  473 

oxj-fatty,  44 

paired,  118 

palmitic,  53 

phenyl  acetic,  65 

skatoxyl  sulphuric,  151 

stearic,  52 

succionic,  50 

taurocholic,  143 
Acidity  of  muscle,  50 
Adenin,  67 

Adenoid  or  cytogenous  tissue,  193 
Aerotonometer,  381 
Agraphia,  675 
Air,  amount  of,  inspired  in  24  hours,  387 

complemental,  378 

exhalation  of  ammonia  in,  406 
of  nitrogen  in,  406 
of  organic  matters  in,  406 

expired,  temperature  of,  405 

pure,  per  cent,  of  carbon  dioxide  in, 
407 

reserve  or  supplemental,  378 

residual,  379 

tension  of  gases  in,  383 

tidal,  378 
Albumin,  61 

crude  coagulation  of,  61 


'  Albumin,  serum,  61 
Albuminate,  coagulation  of,  62 

acid,  62 

alkali,  62 
Albuminoids,  64 

Albuminous  bodies,  composition  of,  60 
Albumoses,  ()2 
Alcohol,  79 

aldehyde,  45 

hexatomic,  45 

ketone,  45 

methyl,  47 

oxidization  and  excretion  of,  80 

triatomic  derivatives,  66 
Aldehyde  alcohol,  45 

formic,  47 

glycerine,  45 
Aldose,  45 

Alimontarv  canal,  development  of,  894 
Alkali  albuminate,  62 
Alkaline  ethereal  sulphates,  51 
Allantoic  circulation,  896 
Allantois,  formation  of,  886 
Alveo-dental  periosteum,  89 
Alveoli,  tension  of  gases  in,  383 
Alvergniat  gas  pump,  223 
Amid  ethyl  sulplionic  acid,  65 
Amides,  65 
Amido-acetic  acid,  65 

caproic  acid,  65 
Amines,  65 

Ammonia,  exhalation  of,  in  air,  406 
Ammoniacal  fermentations,  42 
Ammonium  magnesium  phosphate,  42 
Amnion,  composition  of  fluid  of,  908 

formation  of  lavers  of,  884 
Am<eba,  30 
Araylodextrin,  49 
Amylolytic  ferment,  100 
Amylopsin,  13S 
Anacrotic  pulse,  273 
Anastomoses  of  veins,  329 
Anatomy,  relation  of  physiology  to,  19 
Anelectrotonus,  54r) 
Angular  gyrus,  735 
Animal  heat,  413 
Apiiasia,  675 
Apn<i'a,  408 
Aqueous  liumor,  751 
Area  germinativa,  883 

opaca.  S83 

pellucida,  883 
Argutinsky,  experiments  of,  467 
Argyll  Robertson  pupil,  772 
Arterial  pressure,  294 
Arteries,  259 


912 


INDEX. 


Arteries,  caliber  of,  dailv  variations  in, 
274     _ 

contractility  of,  263 

influence  of,  265 

elasticity  of,  261 

enlargement  of,  266 

structure  of,  261 
.Articulation,  temporo-maxillary,  89 
Artificial  respiration,  371 
Ascaris,  development  of,  32 
Aspartic  acid,  65,  138 
Asphj'xia,  410 
Astigmatism,  765 
Atmospliere,  composition  of,  386 
Atmosplieric  pressure,  influence  of,  401 
Attraction  bodies,  879 
Aubert-Heringtheorj'  of  color  sensations, 

784 
Auditory  nerve,  846 

Auricular  branch  of  tenth  nerve,  func- 
tions of,  620 

diastole,  236 

\entriiular  systole,  237 
Axis  cylinder,  480 
Axon,  478 

1)ArTP:RirM  termo,  58 
)     Basic  substances,  65 
Bassow,  experiments  of,  111 
Baths,  Russian,  424 

Turkish,  424 
Beats,  835 

cause  of,  836 
Benzol  derivatives,  67 
Benzoic  acid,  51,  65 
Benzo-pyrol,  67 
Bernstein's  differential  rheotome,  536 

method  of  using,  537 
Bi-concave  lenses,  754 
Bi-convex  lenses,   754 
Bile,   140 

composition  of,  141 

functions  of,  146 
Biliary  acids,  142 

pigments,  144 

salts,  142 
Bilirubin,  144 
Biliverdin,  144 
Binocular  vision,  774 
Blastodermic  membranes,  882 

vesicle,  881 
Blondlot,  experiments  of.  111 
Blood,  171) 

alkalinity  of,  179 

amount  of  water  in,  211 

arterial,  absorption  bands  of,  218 

circulation  of,  230 

greater  or  sj-stemic,  230 
lesser  or  pulmonary,  230 

coagulation  of,  201 

color  of,  180 

composition  of,  208 

condition  in  whicli   oxygen,   carbon 
dioxide  and  nitrogen  exist  in,  222 

corpuscles,  181 

composition  of,  212 


Blood,  corpuscles,  red,  182 

effect  of  electricity  on,  185 
of  heat  on,  185 
of  water  on,  185 
functions  of,  189 
influence  of  altitude  upon, 

184 
method  of  determining,  183 
mnnl)er  of,  182 
origin  of,  189 
shape  of,  182 
size  of,  186 

average  human,  188 
specific  gravitv  of,  183 
white,  191 

composition  of,  191 
functions  of,  192 
origin  of,  192 
size  of,  191 
dry,  composition  of,  210 
fatty  matters  of,  226 
flow  of,  in  capillai'ies,  315 
laky,  213 

method  of  obtaining  gases  of,  222 
of    transferring     from     living 
animal  to  vessel,  224 
moist,  composition  of,  210 
odor  of,  179 
opacity  of,  179 
plates,  199 

functions  of,  200 
pressure,  275 

in  arteries,  299 
in  capillaries,  322 
in  cat,  291 
in  dog,  293 
in  frog,  292 
in  horse,  283 
in  man,  287 
in  rabbit,  290 
in  renal  arteries,  455 
in  turtle,  292 
in  veins,  330 
proteids  of,  226 
quantity  of^,  180 
specific  gravity  of,  179 
supply  of,   to  lungs,  341 
salts  of,  227 

importance  of,  227 
taste  of,  179 
temperature  of,  179 
tension  of  gases  in,  382 
transfusion  of,  229 
venous,  absorption  bands  of,  218 
velocity  of,  in  arteries,  303 
in  capillaries,  318 
determined  l\v  stromuhr,  306 
in  veins,  331 
Bodv,  general  structure  of,  28 
Bolus,  101 
Bones,  intermaxillary,  89 

maxillary,   88 
Bowman's  glands,  726 
Breatliing  capacity,  376 
Bronclii,  345 
Bronchial  tubes,  346 


INDEX. 


913 


B runner's  glands,  129 
Bufty  coat,  202 
Biuret  test,  61 
Burdach,  columns  of,  569 

/1.ECUM,  152 
V     Calcium  carbonate,    41 
chloride,  39 
oxalate,   50 

phosphate,  quality  of,  -40 
of  urine,  474 
Capillaries,  311 

capacity  of,  314 
of  diflerent  tissues,  313 
flow  of  blood  iu,  315 
blood  in,  conditions  influencing,  319 
efl'ects  of  irritants  upon,  320 
presence  of,  322 
velocity  of,  318 
number  of,  314 
Capillary  force,  325 
Capillarity,   174 
Capsule,  external,  648 

internal,  648 
Carbohydrates,   44 

as  a  fattening  diet,  55 
Carbolic  acid,  51 

Carbon  dioxide,  amount  of,  exhaled  in  24 
houi-s,  387 
amount  of,  expired,  393 

by  man  in  24  houre,  394 
exhalation  of,  384 
per  cent,  of  pure  air  in,  407 
monoxide,  spectrum  of,  219 
and  nitrogen  equilibrium,  73 
Carbonic  acid,  47 
Cardiac  curves,  291 

cycle  or  revolution,  238 
impulse,  244 
pressure,  294 
Cardinal  points,  756 
Cardiograph,  245 
(  ardiometer,  294 
Cardiophone,  251 
Cardio-pneumatic  movement,  256 
Casein,  64,  117 
Caseinogen,  117 
Catalysis,  100 
Cells,'  central,  114 
columnar,  113 
general  structure  of,  29 
goblet,  113 
specific  action  of,   in  production  of 

osmosis,  178 
taste,  731 
wandering,  191 
Central  cells,  114 
Center  of  audition,  677 
cortical,  673 
of  erection,  875 
of  general  sensation,  677 
of  gustation,  677 
of  intellection,  677 
of  olfaction,  677 
of  speech,  676 
of  organic  sensations,  677 
58 


Center  (jf  tactile  sense,  677 
of  vision,  677 

of  voluntary  movements,  677 
Cerebellum,  functions  of,  656 

structure  of,  653 
Cerebral  licmispheres,  659 
cortex  of,  659 
axons  of,  660 
cells  of,  659 
gyri  of,  (561 
sulci  of,  661 
localization,  672 
vesicles,  development  of,  889 
Cerebrin,  67 

Ccrebro-olivary  system,  654 
Ccreljro-spinal  fluid,  •'>64 
Cervical  ganglia  of  sympathetic,  684 
Chiasma,   735 
Cholalic  acid,  143 
Cholesterin,  56,  145 
Cliolin,  65 

Chorda  tymjjani  nerve,  609,  611 
Chorda'  tendinea',  2:54 
Chorion,  884 

villous  processes  of,  906 
Choroid,  737 

Chyle,  causes  of  flow  of,  167 
composition  of,  167 
coi-pasclcs,  194 
molecular  base  of,  167 
Chyme,  107 

Cileo-spinal  center,  691,  742 
Ciliary  ganglion,  740 
muscle,  739 
nerves,  740 
processes,  738 
Circle  of  AVillis,  663 
Circulation,   allantoic,  896 
of  blood,  230 
capillary,  in  twins,  324 
length  of  time  nf  entire,  335 
portal  dcveloi)ment  of,   897 
Classification  of  sciences,  IS 
COj  condition  influencing  the  production 
of,  395 
formation  of,  in  tissues,  408 
Coagulation  of  blood,  2<tl 

conditions  modifying,  203 

during  life,  207 

influence  of  calcium  salts  upon, 

206 
theories  as  to  causes,  204 
time  of,  202 
of  muscle,  50 
Cochlea,  functions  of,  848 
structure  of,  843 
membranous,  844 
Coffee,  78 
Collagen,  64 
Colliculus,  745 
Colloids,  175 
Colon,  154 

sigmoid  flexure  of,  155 
Colostrum,  711 
Columnar  cells,  113 
Compensator,  round,  526 


914 


INDEX. 


Compensator,  detei'mining  resistance  by, 

528 
Compensatory  pause,  626 
Composition  of  albuminous  bodies,  60 
of  atmosphere,  386 
of  bile,  141 
of  blood,  208 

corpuscles,  212 
dry,  210 
moist,  210 
chemical,  of  nervous  tissue,  485 
of  chyle,  167 
of  crystalline  lens,  751 
of  f?eces,  156 
of  fluid  of  amnion,  908 
of  food,  70 
of  gastric  juice,  112 
of  liEematin,  220 
of  hiiemoglobin,  214 
of  Ivmph,  163 
of  liiilk,  710 
of  pancreatic  juice,  135 
of  semen,  873 
of  sweat,  713 
of  urine,  462 
Compound  waves,  804 
Cough  center,  635 
Condiments,  82 
Conjugate  sulphates,  473 
Consonants,  production  of,  824 
Convolutions,  continuity  of,  662 

fibers  of,  663 
Cornea,  736 
Corpora  araylacea,  48 
arantii,  235 
quadrigemina,  652 
Corpus  luteum,  869 

of  menstruation,  870 
of  pregnancy,  870 
striatum,  effects  of  destruction  of,  649 
of  stimulation  of,  649 
structure  of,  648 
(_'orti,  organ  of,  845 
Cortical  areas,  effects  of  destruction  of,  674 

center,  673 
Creatin,  66 
Creatinin,  66 

amount  and  origin  of,  472 
Crest,  dicrotic,  273 
Crura  cerebri,  647 

effects  of  division  of,  647 
Crusta  petrosa,  88 
Crystalline,  751 
lens,  750 

composition  of,  751 
minute  structure  of,  750 
Crystalloids,  175 
Cuneus,  735 
Current  of  action,  534 

of  rest,  534 
Cuticula,  701 
Cyst  in,  66 


1) 


ALTOXISM,  784 
Daniell  element,  487 

electro-motive  force  of,  490 


Decidua  reflexa,  906 
serotina,  907 
vera,  905 
Defecation,  157 
Deglutition,  101 

action  of  anterior  half  arches  in,  101 
of  azygos  uvulpe  in,  102 
of  digastric  muscles  in,  102 
of  epiglottin  in,  102 
of  fauces  in,  101 
of  geno-hvoid  muscle  in,  102 
of  glottis  in,  102 
of  hard  palate  in,  101 
of  hyoglossi  muscles  in,  101 
of  larynx  in,.  102 
of  mylo-hyoid  muscles  in,  102 
of  cpsophagus  in,  102 
of  pharynx  in,  102 
of  posterior  ludf  arches  in,  102 
of  posterior  naresin,  102 
of  stylo-glossi  muscles  in,  101 
of  stylo- liy old  muscle  in,  102 
of  stvlo-pharvngeal   muscle  in, 

102 
of  tensor  palati  muscle  in,  102 
of  tongue  in,  101 
of  uvula  in,  102 
of  velum  in,  102 
stages  of,  104,  105 
time  of,  104 
Demilune  cells,  97 
Dendron,  478 
Dental  fibers,  87 
tubules,  86 
Dentine,  86 
Dermis,  697 

Development   of  alimentary    canal    and 
appendages,  894 
of  cerebral  vesicles,  889 
of  ear,  892 

of  external  genitalia,  902 
of  extremities,  903 
of  eye,_  893  _ 

of  genito-urinary  organs,  900 
of  heart,  895 

of  mammalian  embryo,  887 
of  nervous  system,  888 
of  placenta,  905 
of  portal  circulation,  897 
of  respiratory  organs,  899 
of  urinarv  organs,  900 
of  uterus,'  902 
of  vagina,  902 
of  vascular  system,  895 
of  venae  cavje,  898 
Dextrose,  45 
Dialysis,  175 
Diaphragm,  352 

action  of,  353 
Dibasic  acid,  50 
Dicrotic  crest,  273 
notch,  273 
pulse,  273 
Diet,  71 

and  alimentary  canal  of  man,  74 
in  arctic  regions,  74 


INDEX. 


U]r> 


Diet,  mixed  bread  and  moat,  72 
(|uantity  of,  71,  74 

restricted  to  carbohydrates,  7'.', 
to  fat,  73 
to  meat,  73 

in  troi)ical  regions,  74 
Digastric  muscles,  action  of,  92 

in  deglutition,  lf>2 
Digestion,  duration  of,  123 

influence  of  exercise  upon,  124 

intestinal,  126 

resume  of,  157 
I)ioxyacetone,  4-'> 
Dioxybcnzol,  ol 
Disacchiirides,  45 
Discord  and  harmony,  834 
Distilled  li(]Uors,  81 
Du  Bois  Kcvmond's  kev,  4ii5 
Ducts  of  Miiller,  901 
Dulcite,  45 

Dulong,  calorimeter  of,  430 
D^'spnoea,  408 

EAR,  S26 
bones  of,  828 

movements  of,  838 

comparative  anatomy  of,  847 

development  of,  892 

external,  functions  of,  827 

internal,  S40 

middle,  functions  of,  830 
Elasticity  of  arteries,  2(51 
Elastin,  64 
Electrotonus  in  man,  552 

secondary,  546 
Eleventh  nerve,  640 

Embryology,  relation  of  physiology  to,  22 
Enamel,  87 

Encephalon,  weight  of,  ()()5 
Endosmosis,  171 
Endosmotic  equivalent,  172 
Enzvme,  100 
Epiblast,  882 
Epidermis,  699 

Ejiiglottis,  action  of,  in  deglutition,  102 
Epithelium  of  stomacii,  113 

of  villi,  166 
Erythroblasts,  190 
p:rythrodextrin,  49,  99 
Erythrose,  45 

Ethereal  sulphuric  acid,  67 
Ethei-s  of  glycerin,  52 
Ethylene,  66 
Kupnica,  408 

Excitability  and  conductivity,  546 
I^xcreta,  ratio  of  carbon  to  nitrogen  in,  72 
Exosmosis,  171 
Expiratory  center,  1)1)3 
Extra-cardiac  accelcratory  centei-s,  631 

inhibitory  center,  628 
Extremities,  development  of,  903 
Eye,  734 

development  of,  893 

cardinal  points  of,  759 

protective  appendages  of.  788 
Eyeball,  736 


I      origm  of,  54 
use  of,  55 
i  Ficces,  155 
I  amount  of,  156 

j  composition  of,  156 

Feces,  nitrogen  of,  4()4 
Fermentation,  58,  68,  99 
acid,  50 

of  urine,  475 
alkaline  of  urine,  475 
annufjniacal,  42 
Ferments,  67 
j  amylolytic,  100 

organized,   68 
unorganized,  ()7 
Ferratin,  42 
Ferric  chloride,  42 
Ferrous  sulphiile,  42 
!  Filjere,  geminal,  571 
j  Fibrinogen,  205,  226 
coagulation  of,  62 
Fick  and  \\'isliccnus,  experiment^  of.  465 
Fifth  nerve,  599 
Fn'tus,   size  and  weight  of,   at  diferent 

ages,  904 
Food,  69 

conii)osition  of,  70 
I  plastic,  71 

l)rinciplcs,  69 
(pialitv  of,   71 
stuHs,"69 
uses  of,  77 
Foot,  movements  of,  85" 
Foramen  of  Majendic,  664 
j  Formic  aldehyde,  47 
,  Fourth  nerve,  598 
Franklin,  experiments  of,  42.5 

GALACTOSE,  45 
(jalvanometer,  512 
Thomson's,  515 
Ganglion,  l)asal,  functions  of,  651 
ciliary,  740 
geniculate,  605 
(lastric  digestion,  aljsence  of  putn-faction 
during,  122 
juice,  acid  reaction  of,  112 
action  of  food  upon,  119 
amount  of,  123 
coni|iosilion  of,  112 
production  of,  118 
preparatory  action  of,  125 
!-ecretioii  of,  115 
s])ecitic  gravity  of,  112 
tidndes,  114 
Gastrula,  881 
(ieminal  libers,  571 
Generation  appar.itus,  female,  864 
male,  872 
sjjontaneous,  860 
tTcniculate  ganglion,  605 
(Jenitalia,  external,  development  of,  902 
(ieno-hvoid  nniscle.  action  of,  in  degluti- 
tion, 102 
Glands,  Eowman's,  726 


916 


INDEX. 


Glands,  Brunner's,  129 

laclirvmal,  788 

Lieberkiihn's,  130 

lymphatic,  193 

mammary,  70!) 

Meibomian,  788 

mucous,  97 

parotid,  95 

sebaceous,  707 

serous,  97 

solitary,  193 

sublingual,  96 

submaxillary,  96 

sudoriferous,  711 

termination  of,  483 
Globidin,  1213 
Glomeruli,  453 

Glosso-labial  laryngeal  paralysis,  644 
Glosso-pharvngeal  nerve,  615 
Glottis,  81 1" 

action  of,   in  deglutition,  102 
Glucose,  45,  99 
Glucoside,  45 
Glucuronic  acid,  49 
Glycerides,  52 
Glycerin,  52 

aldehyde,  45 

ethers  of,  52 
Glycerose,  44 
Glycocholic  acid,  143 
Glycocol,  51,  66 
GlycocoU,  65 
Glycogen,  49 

functions  of,  149 
Glycose,  44 

(jlycuronic  acid,  49,  67 
Gmelin's  test,  144 
Goblet  cells,  113 
Goll,  columns  of,  569 
Graafian  follicles,  865 
Graham's  law  of  ditflisibility  of  gases, 

380 
Guanidin,  ()6 
Guanin,  67 
Gustation,  730 
Gustatory  nerves,  731 

HJi:MADYNAMOMETEE,  285 
Ha-matin,  144,  213 

composition  of,  220 
method  of  obtaining,  220 
Hsematacliometer,  307 
Hsematogen,  42 
Hjematoidin,  144 
Hicmocliromogen,  213 
Hsemodromograpli,  308 
Ha-modromometer,  304 
Haemoglobin,  63,  213 

absorption  of  oxygen  by,  221 
compcjsition  of,  214 
method  of  determining  amount  of, 
216 
of  ol)taining,  213 
molecular  weiglit  of,  215 
])hysical  charactei-s  of,  214 
Il£ematopoiesis,  190 


Hairs,  704 

function  of,  706 
structure  of,  705 
Hamberger's  apparatus,  359 
Hard  palate,  action  of,  in  deglutition,  101 
Heart,  231 

beat  of,  influence  of  age  on,  252 
of  exercise  on,  254 
of  sex  on,  252 
of  temperature  on,  255 
changes  in  form  of,  247 
development  of,  895 
duration  of  movements  of,  in  horse, 
239 
in  man,  242 
of  svstole,  methods  of  determin- 
ins,  243 
flow  of  blood  and  contractile  force 

of,  332 
frequency  of  action  of,  253 
hardening  of,  24(5 
innervation  of,  622,  623 
insensibility  of,  258 
muscular  fibers  of,   232 
nutrition  of,  257 
sensibility  of,  632 
shortening  of,   246 
sounds  of,  249 
causes  of,  250 
duration  of,   250 
fii-st,  249 
second,  249 
tricaspid  valve  of,   233 
twisting  of,   246 
work  done  by  the,  248 
Heat,  animal,  production  of,  423 

determination  of  production  of  from 

analysis  of  excreta,  440 
expenditure  of,  442 
and  mechanical  work,  444 
production  of,  by  burning  food,  438 
in  diabetes,  465 
by  human  being,  436 
tipon  mixed  diet,  441 
by  muscle,  439 
ratio  of,  to  muscular  work,  443 
Heller's  test,  61 
Hemianopsia,  735 
Hemispheres,  cerebral,  659 
Hempel  apparatus,  385 
Hepatin,  42 
Hermaplirodism,  903 
Hexatomic  alcoliol,  45 
Hexose,  45 

Hippuric  acid,  51,  65,  471 
Histology,  relation  of  physiology  to,  23 
Histio-hicmatin,  t)3,  220 
Homoiotliermal  and  poikilothcrmal,  413 
Horoi)ter,  77(5 

Haughton,  Flint,  experiments  of,  466 
Human  voice,  range  of,  815 
Hyaloid  tunic,  750 
Hydrocarbons,  66 

Hvdrochloric  acid,  production  of,  118 
Hydrolysis,  99 
Hydroquinone,  51 


INDEX. 


01 


Hvtlrostatic  bellows,   2S1 
Ilvpermetropia,  Tfili 
Hypoblast,  S82 

Hypoglossal  muscle,  action  of,   in  deglu- 
tition, 101 
nerve,  042 
Hypo-xanthin,  (i7 

TLP:0-C.1:(AL  valve.  l-)2 
1     Imbibition,  173 
Imides,  (i(> 
Imido-saivin,  (37 
xanthin,  (57 
Impressions,  labyrinthine,  inHnence 

of,  (;.')7 

tactile,  inrtuence  of,  6o(i 

visual,  influence  of,  6oG 
Indican,  lol,  473 
Indiffo  blue,  473 
Indol,  ol,  07,  lol 
Indoxyl  sulphuric  acid,  151 
Induction  apparatus,  494 
Inosite,  44,  51 
Insalivation,   '.•5 
Inspiration,  muscles  of,  356 
Inspiratory  center,  033 
Interglobular  spaces,  87 
Intermaxillary  bone,  89 
Intestinal  branches  of  pneumogastric 
nerve,  039 

digestion,  120 

juice,  action  of,  upon  food,  132 
in  animals.  130 
in  man,  131 
Intestine,  absorption  by,  170 

large,  151 

contents  of,  15S 

micro-organisms  of,  151 

mucous  membrane  of,  152 

peristaltic  movement  of,  120 

putrefactive  processes  of,  151 
Intracardiac  centers,  t)23 

inhibitory  center,  027 

nerves,  (523 
Intrapulmonary  pressure,  349 
Intrathoracic  pressure,  349 

and  blood-pressure,  309 
Iodine,  42 
Iris,  739 

functions  of,  743 

nmscular  tibei-s  of,  740 
Iron,  42 
Irradiation,  787 
Iso-butyl-amid  acetic  acid,  05 
Iso-dynamic  etiuivalent,  71 
Iso-maltose,  49 
Isotonic  solution,  37 

KARYOKINESIS,  190 
on  melosis,  880 
Katacrotic  pulse,  273 
Katelectrotonns,  540 
Keratin,  (54 
Ketone,  45 

alcohol,  45 
Ketose,  45 


Kidneys,  primitive,  901 

structure  of,  450 
Knee-jerk,  589 

Koenig's  manonietric  apparatus,  800 
Kries's  apparatus,  323 
Kymogra|)h,  Ludwig's,  289 

mercurial,  289 

spring,  301 

T  ABYRIXTH,  mcmbnmous,  841 
1j     Ladirymal  <;lands,  788 
Lactic  acid,  44 

derivatives,  (50 
Lacto-albumin,  01 
Lactose,  46 
Laky  l)l..(.d,  213 

Landx-rt's  method  of  studying  colors,  782 
Laryngeal  bran<lu's  of  teiuh  nerve,  func- 
tions of,  020,  (521 
Laryngosc'ope,  production  of  voice  studied 

bv,  817 
Larynx,  810 

action  of,  in  deglutition,  1(I2 

fimctions  of,   in  I'esjiiration,  342 

as  a  reed  instrument,  81(5 
Lavoisier,  experiments  of,  428 
Lecithin,  (55 

Ix'gallois,  exj>eriments  of,  412 
Lenses,  bi-concave,  754 

lii-convex,  754 
Leucin,  05,  138 
Leucocytes,  04,  192 
Leucomaines,  (50 
Levden  jar,  532 
Lieberkiiini's  glands,  130 
Ligamentum  jiectinatum  iridis,  736 
Lijipmann's  capillary  electrometer,  520 
Liquids,  pressure  of,  27(5 
Litpior  sant^ninis,  181 
Liipiors,  distilled,  81 

malt,  81 
Liver,  140 

production  of  glycogen  by,  147 
of  urea  by,  15(» 
Lumbar  ganglia  of  sympathetic,  687 
Lungs,  capacity  of,  .347 

elasticity  of,  3(5(» 

innervatiim  of,  (532 

sui)ply  of  blood  to,  .347 

tension  of  gases  in,  382 
Luxus,  71 
Lymph,  194 

amount  of,  1(53 

causes  of  How  of,  1(54 

composition  of,  10.3 

corpuscles,  103,  194 

method  of  obtaining,  1(52 
Lymphatic  glands,  193 
Lymphatics,  structure  of,  1(51 

valv&<  of.  1(54 
Lysatin,  (5(5 
Lysjitinin,  (50 
J^ysin,  (55 


M 


ACri.A  lutea,  745 
Magnesium,  41 


018 


INDEX. 


Ma.ant'siiun  phospliate  of  urine,  474 

^lajendie,  foramen  of,  664 

IMalphijj^ian  corpuscle,  action  of,  458 

Malt  liquors,  81 

Maltose,  46,  99 

JNIanimalian  embryo,  development  of,  887 

Mammary  glands,  709 

development  of,  709 
^Manometer,  difierential,  300 

frog,  298 

maximum,  296 

minimum,  296 
Marey,  experiments  of,  240 
Mastication,  83 

nniscles  of,  90 
Maxillary  hones,  88 
Medicine,  relation  of  physiology  to,  26 
Medulla  oblongata,  562 

reflex  action  of,  587 
centers  of,  644 
Medullary  nerves,  594 
Meibomian  glands,  788 
Meltzer's  experiments,  105 
Membrana  ebonis,  88 
Memlu-anes,    rupture    of,    during    labor, 

909 
Meningeal  brani-Jies  of  tenth  nerve,  func- 
tions of,   620 
Menstruation,  871 
Mesoblast,  882 
Methiemoglobin,  220 
Methyl  alcoiiol,  47 

guanidin,  (ii't 

guanidin  acetic  acid,  W) 

indol,  67 
Meti'onome,  365 
Micturition,  459 
Milk,  clotting  of,  46 

composition  of,  710 

curdling  of,    1 1 7 

secretion  of,  710 

souring  of,  50 

-sugar,  46 
Mitral  valve,  234 
Molecules,  electro-motor,  531 
Monobasic  acid,  50 
Mucin,  63,  99,   113 
Mucoids,  63 

ciu)ndro,  63 
Mucous  glands,  97 
MuUer,  ducts  of,  901 
Muscle,  acidity  of,  50 

coagulation  of,  50 

curve,  graphic  representation  of,  508 

digastric  action  of,  92 
in  deglutition,   102 

fatigue  of,  853 

geno-hvoid,  action  of,  in  deglutition, 
102  ■ 

livpoglossal,  action  of,  in  deglutition, 
'JOI 

irritability  of,  851 

as  levers,  action  of,  856 

of  mastication,  90 

mvlo-livoid,  action  of,  in  deglutition, 
"102  ■ 


Muscle,  ocular,  777 

papillary,  234 

respiratory,  wori<  done  by,  375 

reaction  of,  during  contraction,   855 

sound,  854 

striped,  849 

stvlo-glossal,  action  of,  in  deglutition, 
"101 

stvlo-hvoid,  action  of,  in  deglutition, 
'102  ' 

stylo-pharyngeal,  action  of,  in  deglu- 
tition, 102 

temporal  masseter,  91 

tensor  palati, action  of,  in  deglutition, 
102 

termination  of,  482 

unstriped,  850 

work  done  l)v,  853 
Muscular  contraction,  law  of,  551 

fibers  of  heart,  232 

sense,  722 
Mvlo-hvoid  muscle,  action  of,  in  degluti- 
tion,'l02 
Myo-albumin,  (U 
Myo-ha^matin,  63 
^lyopia,  765 
Myosin,  855 
Myrmecophaga  jubata,  96 

NASMYTH'S  cement,  88 
membrane,  87 
Needles,  astatic,  514 

Oereted,  512 
Nerves,  481 

auditory,  846 
cells,  477 
ciliary,  740 

chorda  tympani,  609,  611 
functions  of,  611 
depressor,  630 
electrical  currents  of,  523 
electro-motive  force  of,  525 
eleventh,  or  spinal  accessory,  640 
branches  of,  (i40 
functions  of,  640 
origin  (if,  640 
eflfect  of  direct  current  upon,  549 
of  indirect  current  upon,  550 
excitability  of,  electrotonic  moditiea- 

tion  of,  547 
facial,  effects  of  paralysis  of,  615 
libers,  meduUated,  480 
non-meduUated,  481 
termination  of,  482 
fifth,  599 

nuclei  of,  origin  of,  6(10 
roots  of,  long,  000 
short,  600 
fourtli,  598 

functions  of,  599 
nucleus  of,  origin  of,   598 
gustatory,  731 

impidse,  raj)iditv  of,  propagation  of, 
509 
velocity  of,  propagation  of,    in 
frog,  505 


INDEX. 


rno 


^"erves,   velocity  of,   ])r()j)afjation  of,   in 
motor  and  sensory,  in  man,  507 
laryngeal,  inferior,  functions  of,  G22 
maxillary,  snjjerior,  WW 
medullary,  ')!I4 
muscle,  preparation  of,  oOO 
ninth,  or  filossopliaryngeal,  G15 

branches  of,  (ilfl 

functions  of,  (ilT 

origin  of,  (ilo 
olfactory,  72() 
optic,  735 

pneumogastric,  hranciics  of,  intesti- 
nal, t);iil 

branches  of  (I'sophageal,  ((37 

effects  of  division  of,  (53-4 

inhibitorv  fibers  of,   origin    of, 
629  _ 
resistance  of,  to  electrical  current,  529 
respirator}',  afferent,  (133 

efferent,  ()3() 
secretory  and  trophic,  ()14 
seventh,  t)03,  ()()5 
seventh,  functions  of,  608 

nucleus  of,  origin  of,  605 
sixth,  599 
spinal,  565 

anterior  l)ranchcs  of,  566 

roots  ol',  functionsof,  567 

posterior  bi'anches  of,  5()() 

roots  of,  functions  of,  568 
ganglion  of,  568 

recurrent  sensil)ility  of,  568 
sympatlietic,  682 

cervical  ganglia  of,  684 

functions  of,  ()89 

influence  of,  upon  nutrition,  695 

lumbar  ganglia  of,  687 

structure  of,  682 

thoracic  ganglia  of,  685 
tenth,  or  pneumogastric,  618 

branches  of,  ()19 

functions  of,  ()19 

origin  of,   (US 
third,  594 

function  of,  597 

nuclei  of,   origin  of,  595 

situation  ot,  59() 
transmission    of,    electrical    currents 

through,  546 
trifacial  or  trigeminus,  599 
twelfth,  or  hypoglossal,  642 

branches  of,  64.'> 

functions  of,  644 

origin  of,  642 
ulnar,    application  of  current    over 

in  man,  553 
iminjured,  currents  of  action  in,  542 
vaso-dilator,  691 
vaso-motor,  264,  689 

constrictor,  (')9() 

reffcx,  excitation  of,   694 
vestibular,  functions  of,  848 
Nervous  system,  development  of,  888 

structure  of,  477 
tissue,  chemical  composition  of,  485 


•ing  colors,  7^2 


Xeurin,  65 

Neuroblasts,  479 

Neurokeratin,  64 

Neuron,  477 

Neutral  or  indifferent  point,  548 

Newton's  methoil  of  studying  col 

Nintii  nerve,  ()15 

Nitrogen,  exhalation  of,  in  air,  40(i 

imj)ortance  of,  57 
Nitrogenous  j)roximatc  principles,  43 
Nodal  point,  756 
Nodes,  S02 
Non-nitrogenous    proximate    principles, 

44 
Nonose,  45 
Nose,  725 
Notch,  dicrotic,  273 

predicrotic,  273 
Nuclein,  ()4 
Nucleo-alliumin,  42 
Nucleo-hLston,  64 
Nussbaum,  experiments  of,  458 

OCULAR  muscles,  action  of,  777 
Odont(jblastic  cells,  87 
Qi><ophageal    branches  of  pneumogastric 

nerve,  673 
(Esophagus,  action  of,   in  deglutition,  102 
Ohm's  law,   491 
Oletines,  ()5 
Oleffne  amines,  65 
( )leic  acid,  53 
Olein,  52 
Olfaction,  72(5 

center  of,  727 
Olfactory  nerves,  726 

region,  726 
Ophthalmometer,  762 
Ophthalmoscope,  773 
Optic  lobes,  652 

functions  of,  653 
nerves,  735 
Organic  mattei-s,   exhalation  of.    in    air, 

406 
Organ  of  Corti,  845 

formation  of,  885 
general  structure  of,  29 
Osmosis,  171 

in  living  body,  17() 
Osmotic  current,  173 

equivalent,  61 
Overtones,  805 
Ovum,  865,  866 

chromatin  of,  877 
develoi)ment  of,  868 
impregnation  of,  in  animals,  S76 

in  ascaris,  876 
maturation  of,  S76 
Oxalic  acid,  50 

amount  and  origin  of,  473 
Oxyfatty  acid,  44 
Oxygen,  al)sor{)tiou  of,  ;>S3 
tissues  by,  408 
amount  of,  absorlwd  by  moutli,  389 
absorbed  in  24  houi-s,  387 
Oxy-myoha-matin,  (jiZ 


920 


INDEX. 


PAIN,  sense  of,  724 
Piilmitic  acid,  53 
Palmitin,  52 

Pancreas,  internal  secretion  of,  130 
Pancreatic,  fistula,  135 
juice,  133 

composition  of,  135 
method  of  obtaining,  134 
production  of,  135 
Papilla^,  698 

circumvallate,  730 
fungiform,  730 
Papillary  muscles,  234 
Paracasein,  117 
Paraglobulin,  205,  22() 
Paranuclein,  64 
Parotid  gland,  95 

Pathology,  relation  of  physiology  to,   20 
Pendulum  myograph,  506 
Penta  methyl  diamin,  65 
Pepsin,  116 
Peptones,  120 
Pericardium,  232 
Peritoneum,  194 
Perspiration,  713 
Pettenkofer' s  respiration  apparatus,   387 

test,  143 
Phacoscope,  769 
Pharnyx,  constrictors  of,  103 
Phenaceturic  acid,  65 
Phenol,  51 
Phenoloxybenzol,  51 
Phenyl-acetic  acid,  65 
Physiological  acoustics,  791 

optics,  752 
Physiology,  definition  of,  17 
method  of  study,  19 
order  of  study  of,  27 
relation  of,  to  anatomy,  19 

to  comparative  anatomy,  21 
to  emijryology,   22 
to  histology,  23 
to  medicine,  26 
to  patliology,  20 
to  vivisection,  24 
Pituitary  body,  677 

internal  secretion  of,  677 
Placenta,  development  of,  905 
Plasma,  181 
Plethvsmograph,  320 
Pleura,  194 

Pneumogastric  nerve,  618 
Pneumograpli,  363 
Polar   globules,   or  directive    corpuscles, 

877 
Polycrotic  pulse,  273 
Polysaccharides,  47 
Pons  Varolii,  646 

functions  of,  647 
structure  of,  646 
Portal  circulation,  development  of,  897 
Porus  opticus,  745 
Potassium  carbonate,  38 
cldoride,  38 

j)hos])hate  of  urine,  474 
sulphate,  3S 


Predicrotic  iiotcli,  273 
Presbyopia,  770 
Press  sound,  103 
Primitive  groove,  883 

kidneys,  901 

streak  on  axis  plate,  883 

trace,  882 
Principal  plane,   75t) 

points,  756 
Pronuclei,  conjugation  of,  879 
Pronucleus,  female,  877 

male,  878 
Propylene,  (Ui 
Protagon,  67 
Proteids,  classification  of,  60 

coagulated,  63 

combined,   63 

chromo-,  63 

glyco-,  63 

nucleo-,  63 
Proteoses,  62 

Protococcus,  development  of,  33 
Protophyta,  31  ■ 

Protozoa,  31 

Proximate  principles,  28,  33 
fii-st  class,  34 

nitrogenous,  43 

non-nitrogenous,  44 

organic  origin  of,  43 
third  class,  57 
Pseudo-colloid,  63 
Ptomaines,  ()5 
Ptyalin,   99 

Pulmonary  lobules,  346 
Pulse,  anacrotic,  273 

dicrotic,  273 

cause  of,  273 

katacrotic,   273 

as  modified  by  disease,  274 

polycrotic,  273 

production  of,  266 

tricrotic,  273 

volume,  248 

wave,  rate  of  propagation  of,  272 
number  of,  ])er  second,  272 
Punctum  ciecum,  749 

proximum,  770 

remotum,  770 
Pupil,  bilateral  reflex,  743 

constrictor  center,  741 

dilator  center,  742 
Purkinje,  experiment  of,  748 
Putrefaction,  58,  ()8 
Putrescin,  65 
Pyramidal  tracts,  crossed,  560 

direct,  560 
Pyrocatechin,  51 

REAUMUR,  experiments  of,  109 
Eectum,  155 
Eed  blood  corpuscles,  182 
Refraction,  753 

index  of,  753 
Eegnault  and  Reiset's  respiration  appa- 
ratus, 388 
Regurgitant  venous  pulse,  331 


INDEX. 


921 


Renal  portal  system,  457 
Rennin,  116 
Reproduction,  860 
Resonance,  cause  of,  S()8 
Respiration  in  animals,  .'538 

artificial,  371 

canula  used  in,  372 

in  frog,  340 

functions  of  larynx  in,  :!42 

influence  of  dress  upon,  362 

inhiV)ition  of,  635 

internal,  408 

in  man,  340,  343 

muscles  of,  351 

nasal,  341 

number   of,    conditions   influencing, 
374 

physics  of,  348 

in  plants,  338 

in  vertebrates,  339 
Resj^iratory  center,  632 

curves,  291 

expiration,  358 

muscles,  work  done  by,  375 

organs,  development  of,  899 

pulse  of  Majendie,  357 

quotient,  402 

conditions  influencing,  404 
upon  a  fat  diet,  40:! 
upon  a  meat  diet,  403 
upon  a  starcli  diet,  403 
upon  a  vegetable  diet,  404 
Resistance  box,  491 
Rete  mucosum,  700 
Retina,  744 

cones  of,  747 

layei"s  of,  746 

rods  of,  747 
Retinal  image,  size  of,   762,  780 
Rheocord,  long,  539 
Rheoscope,  phvsiological,  524 
Ribs,  354 

influence  of  respiration  on  curvature 
of,  355 
Ritter-Valli  law,  556 
Rivinus'  ducts,  96 
Rubner,  experiments  of,  467 
Running,  859 

OACCHAROMYC'ES  cerevisite,  68 
0     Sacral  nerves,  577 
Saliva,  amount  secreted,  101 

composition  of,  99 

secretion  of,  9S 
Salivary  diastose,  99 

glands,  nerves  supplving,  612 

reflex,  613 
Salt  solution,  physiological,  37 
Saponification,  53 
Sciences,  classification  of,  18 
Sclerotic,   736 
Sebaceous  glands,  707 

fmu'tions  of,  708 
Semen,  composition  of,  873 
Semilunar  valve,  234 
Seminal  intensitv,  721 


Sense  of  pressure  or  weight,  720 
Sensory  fil)ei-s,  561 

organs,  termination  of,  4S3 
Serous  glands,  97 
Serum  albumin,  61,  226 

gloljulin,  62 
Seventh  nerve,  f)03,  605 
Sight,  perception  of,  785 

sensation  of,  778 
Silicic  acid,  42 
Silicon,  42 
Sixth  nerve,  599 
Skatol,  51,  67,  151 
Skatoxvl  sulphuric  acid,  151 
Skin,  696 

absoq)tion  by,  717 

cuticle  of,  701 

dermis  of,  697 

ei)iderniis  of,  699 

extent  of,  697 

general  functions  of,  69(> 
strnctiii-e  of,  696 

papilla-  of,  698 

rete  mucosum  of,  700 

structure  of,  703 
Sleep,  679 

amount  of,  680 

causes  of,  679 
Smell,  sense  of,  acuteness  of,  728 
Sodium  cliloride,  36 
of  urine,  474 

glycocliolate,  ^\'^,  142 

oleate,  53 

plios})liate,  38 

of  urine,  474 

sulphate,  38 

taurocliolate,  65,  142 
Solar  ])lexiis,  (iSC. 
Solitary  glands,  193 
Somatopieure,  884 
Sorbite,  45 
Sounds,  appreciation  of,  832 

musical,  range  of,  833 

pitch  of,  796 

propagation  of,  792 

quality  of,  800 

wave,  intt'iisity  of,  794 
Spaces,  interglobular,  S7 
Spectrum  analysis,  217 
Speech,  822 

center  of,  ()76 

influence   of   tongue    in    production 
of,  825 
Spermatozoa,  874 
Spermatozor>n,  maturation  of,  878 
Sphygmograpii,  267 

method  of  adjusting  of  natunil  pulse, 
268 

tracings  taken  by,  269 

of  artificial  pulse,  270 
of  natural  pulse,  influence  of  aire 
on,  271 
Spinal  accessory  nerve,  640 
Spinal  cord,  557 

automatic  functions  of,  592 
cells  of,  559 


922 


INDEX. 


Spinal  cord,  sensorv  impulses  in  pathway 
of,  572  ■_ 
effect  of  division  of  upon  respi- 
ration, 636 
fibers  of,  559 
general  structure  of,  558 
neuroblasts  of,  559 
reflex  action  of,  585 
centers  of,  591 
inhibition  of,  591 
tactile  impulses  in,  pathway  of, 
573 
nerves,  565 

anterior  branches  of,   functions 

of,  576 
posterior  branches  of,  functions 
of,  576 
system,  general  anatomy  of,  579 
Spirometer,  377 
Splanciinopleure,  884 
Spleen,  195 

rhythmical  contractions  of,  196 
variations  in  size  of,  196 
Spontaneous  generation,  860 
Squint  sound,  103 
Stanuius,  experiments  of,  624 
Starch,  48 

origin  of,  48 
Starvation,  75 

loss  of  tissue  in,  76 
Steapsin,  53,  138 
Stearic  acid,  52 
Stearin,  52 
Steno's  duct,  95 
Stercobilin,  155 
Stereoscope,  jjrinciples  of,  775 
Stetliometer,  366 
Stethoscope,  809 
Stevens,  experiments  of,  110 
Stomach,  106 

absor]jtion  by,  170 
digestion  of,  after  fleatli,  121 
epithelium  of,  113 
muscular  hbers  of,  107 
temperature  of,  124 
Stromuhr  or  rheometer,  305 
Stylo-glossal  muscle,  action  of,   in  deglu- 
tition, 101 
Stvlo-hvoid  muscle,  action  of,  in  degluti- 
tion,'l02 
Stylo-pharyngeal    muscle,    action    of,    in 

deglutition,  102 
Sublingual  gland,  i)6 
Sulimaxillarv  gland,  i>6 
Succinic  acid,  50 
Sudoriferous  glands,  711 

development  of,  712 
number  of,  712 
Sugar,  47 
milk,  46 
tests  for,  46 
Sulphates,  alkaline  ethereal,  51 

conjugate,  151 
Sulphuric  acid  of  urine,  474 
Superior  maxillary  nerve,  603 
Suprarenal  (capsules,  197 


Suprarenal   capsules,    internal   secretion 
of,  197 

Sweat,  composition  of,  713 

Sympathetic  fibers,  distribution  of,  683 
excitability  of,  684,  686 
functions  of,  in  man,  694 
sensibility  of,  684,  686 
nervous  system,  682 

Syntonin,  62 

Systolic  plateau,  296 

IWCTILE  sensibility,  719 
i     Taste  cells,  731 

pore,  731 
Taurocholic  acid,  143 
Tea,  78 

Teal's,  secretion  of,  789 
Teeth,  83 

ivoiy,  86 
Temperature  of  animals,  413 

average  of  human  body,  417 
conditions  modifying,  417 
constancy  of,  in  blooded  animals,  445 
effects  of  atmospheric  moisture  on, 
447 
baths  upon,  446 
clothes  upon,  446 
size  of  body  on,  447 
sense  of,  723 
Temporal  masseter  muscles,  91 
Temporo-maxillary  articulation,  89 
Tensor  palati  muscle,  action  of,  in  deglu- 
tition, 102 
Tenth  nerve,  618 

branches  of,  auricular,  functions  of, 
620 
laryngeal,  inferior,  functions  of, 
^  627 
superior,  functions  of,  620 
meningeal,  functions  of,  620 
Test,  Biuret,  61 
Heller's,  61 
xantho-proteic,  61 
Testicle,  internal  secretion  of,  875 

structure  of,  873 
Tetanus,  curve  of,  502 
Tetra  metliyl  diamin,  65 
Tetrose,  45 

Thalmi  optici,  effects  of  lesions  of,  650 
Thalnuis  opticus,  649 
Thermo-electric  needles,  416 
Tliermogenesis,   or  heat  production,  448 
Thermo-inhibitorv  and   accelerator  cen- 
ters, 449 

nerves,  449 
Thermolysis,  or  heat  dissii)ation,  448 
Thermometer,  melastatic,  415 
Thermotaxis,  or  heat  regulation,  448 
Third  nerve,  594 
Thoracic  duct,  161 

ganglia  of  sympathetic,  685 
Thyroiodin,  198 
Thymus  gland,  199 

internal  secretions  of,  199 
Thyroid  body,  197 

internal  secretion  of,  198 


INDEX. 


923 


Tissues,  general  structure  of,  29 

tension  of  gases  in,  382 
Tobacco,  79 
Tongue,  729 

action  of,    in  deglutition,  101 

influence  of,  in  production  of  speech, 
82o 
Tonsils,  194 
Tooth  pulp,  88 
Touch,  sense  of,  718 
Toxincs,  05 
Trachea,  344 

cilia  of,  action  of,  344 
Tniube's  curves,  370 
Triatoniic  alcoiiol  derivatives,  06 
Tricalcium  phosphate,  39 
Tricrotic  pulse,  273 
Tricuspid  valve  of  heart,  233 
Trifacial,  or  trigeniinus  nerves,  599 
Trimethyl  oxyethyl  ammonium  hydrox- 
ide, 65 

vinyl  amnioiiium  hydroxide,  05 
Triose,  45 
Troramer's  test,  45 
Trypsin,  137 
Trvpsinogen,  136 
Trvptophan,  138 
Twelfth  nerve,  642 
Tympanic  membrane,  829 
vibrations  of,  831 
Tyrosin,  51,  05,  138 

UMBIIJCAL  vesicle,  formation  of,  886 
Units,  electro-magnetic,  489 
of  resistancee  or  ohm,  490 
Urea,  65,  462 

amount  of,  Davy's  method  of  deter- 
mining, 463 
of  nitrogen  in  Kjeldahl's  method 
of  determining,  403 
creatin  and  creatinin  as  antecedents 

of,  468 
excretion  of,   conditions  influencing, 
464 
upon  difierent  diets,  4()4 
and  exercise,  405 
origin  of,  467 
metiiod  of  obtaining,  462 
production    of,   iuHuenced  by  extir- 
paticjn  of  kidney,  469 
Uric  acid,  469 

amount  of,  Ilaycraft's  method  of  de- 
termining, 470 
metiiod  of  i)l)taining,  469 
origin  of,  470 
Urinary  organ,  development  of,  900 
Urine,  acid  fermentation  of,  475 
acidity  of,  459 

alkaline  fermentation  of,  475 
amount  of  excreted  in  24  hours,  474 
calcium  phosphate  of,  474 
color  of,  459 
composition  of,  4()2 
excretion  of,  454 

excretion  of,  influence  of  blood'pres- 
sure  on,  455 


Urine,  excretion  of,  influence  of  nervous 
system  on,  455 

inorganic  coastituents  of,  474 

magnesium  ])hosphate  of,  474 

potassium  phosphate  of,  474 

l)ressure  of,  in  ureter,  455 

quantity  excreted  daily,  460 

conditions  intiiiencing,  401 

sodium  chloride  of,  474 

phosphate  of,  474 

specific  gravity  of,  460 

sulphuric  acid  of,  474 
Uriniferous  tubules,  45] 
action  of,  458 
structure  of,  452 
Urinometer,  4<t() 
Urobihn,   145 
Urogenital  sinus,  902 
Uteras,  development  of,  902 

structure  of,  864 
Uvea,  739 
Uvula,  action  of,  in  deglutition,  102 

VAGINA,  development  of,  902 
Valentin  and  Brunnei-'s  respiration 
ajiparatax,  384 
Valsalva,  sinus  of,  236 
Valves,  insufficiency  of,  237 
Vascular  system,  development  of,  895 
Vaso-constrictor  nerves,  690 
Vaso-dilator  nerves,  691 
Vaso-motor  constrictor  center,  691 
dilator  center,  692 
nerves,  2t)4,  689 
Veins,  326 

absoqjtion  Ijv,  168 

air  in,  death  frf)m,  334 

anastomosis  of,  329 

capacity  of,  328 

flow  of  Idood  in,  conditions  influenc- 
ing, 333 

pressure  of  blood  in,  330 

structure  of,  328 

valves  of,  327 

velocity  of  l)loo<l  in,  331 
Velum,  action  of.  in  deglutition.  102 
Vena-  cava^  develo|tment  of  S9S 
Ventilation  of  buildings,  408 
Ventricle,  fouilh,  504 

left,  area  of,   in  hoi-se,  284 

in  man,  2S4 
Ventricidar  systole,  237 
Vermiform  api>endix,  153 
Vestibular  nerves,  functions  of,  S48 
Vibrator,  240 
Villi,  105 

epithelium  of.  KiO 
Visceral  arciies,  890 

modiflcation  of,  891 
Vision,  acuteness  of,  7t>2 

center  of,  077 
Visual  angle.  7(il 
Vital  ca])acity.  3S(» 

conditions  aflecting,  380 
Vitellin,  04 
Vitelline,  formation  of,  886 


924 


IXDEX. 


Vitellus,  se.ffmentation  of,  880 
Vitreous  humor,  7oO 
Vivisection,  relation  of  physiology  to,  24 
Vocal  membranes,  812 
tension  of,  819 
organs,  influence  of  accessory,  820 
Voit's  respiration  apparatus,  390 
Vowels,  production  of,  823 

WALKING,  8.)8 
Wandering  cells,  191 
Water,  35 

amount  of,  exhaled  from  system,  404 

formed  in  system,  404 
equivalent,  435 

exhalation  of,  conditions  influencing, 
404 


Whai-ton's  duct,  9.5 

Whippe,  the,  504 

Wliite  blood  corpuscles,  191 

Willis,  circle  of,  663 

Wine,  81 

Wolffian  bodies,  901 

VANTHIX,  64,  67 

A.     Xantho-proteic  test,  61 

VEAST,  6S 

I      Young-IIelmlioltz    tlie;)ry    of   color 
sensations,  784 

ZIXX,  zone  of,  750 
Zone  of  Zinn,  750 
Zymogen,  100 


